Merge branch 'develop' of https://bitbucket.hdfgroup.org/scm/~koziol/hdf5 into develop

10 files changed, 8575 insertions, 12 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4106515..2b693bd 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -227,11 +227,14 @@ set (H5FD_SOURCES
     ${HDF5_SRC_DIR}/H5FDcore.c
     ${HDF5_SRC_DIR}/H5FDdirect.c
     ${HDF5_SRC_DIR}/H5FDfamily.c
+    ${HDF5_SRC_DIR}/H5FDhdfs.c
     ${HDF5_SRC_DIR}/H5FDint.c
     ${HDF5_SRC_DIR}/H5FDlog.c
     ${HDF5_SRC_DIR}/H5FDmpi.c
     ${HDF5_SRC_DIR}/H5FDmpio.c
     ${HDF5_SRC_DIR}/H5FDmulti.c
+    ${HDF5_SRC_DIR}/H5FDros3.c
+    ${HDF5_SRC_DIR}/H5FDs3comms.c
     ${HDF5_SRC_DIR}/H5FDsec2.c
     ${HDF5_SRC_DIR}/H5FDspace.c
     ${HDF5_SRC_DIR}/H5FDstdio.c
@@ -243,11 +246,14 @@ set (H5FD_HDRS
     ${HDF5_SRC_DIR}/H5FDcore.h
     ${HDF5_SRC_DIR}/H5FDdirect.h
     ${HDF5_SRC_DIR}/H5FDfamily.h
+    ${HDF5_SRC_DIR}/H5FDhdfs.h
     ${HDF5_SRC_DIR}/H5FDlog.h
     ${HDF5_SRC_DIR}/H5FDmpi.h
     ${HDF5_SRC_DIR}/H5FDmpio.h
     ${HDF5_SRC_DIR}/H5FDmulti.h
     ${HDF5_SRC_DIR}/H5FDpublic.h
+    ${HDF5_SRC_DIR}/H5FDros3.h
+    ${HDF5_SRC_DIR}/H5FDs3comms.c
     ${HDF5_SRC_DIR}/H5FDsec2.h
     ${HDF5_SRC_DIR}/H5FDstdio.h
     ${HDF5_SRC_DIR}/H5FDwindows.h
@@ -1142,6 +1148,7 @@ if (BUILD_SHARED_LIBS)
   add_library (${HDF5_LIBSH_TARGET} SHARED ${common_SRCS} ${shared_gen_SRCS} ${H5_PUBLIC_HEADERS} ${H5_PRIVATE_HEADERS} ${H5_GENERATED_HEADERS})
   target_include_directories (${HDF5_LIBSH_TARGET}
       PRIVATE "${HDF5_SRC_DIR};${HDF5_BINARY_DIR};$<$<BOOL:${HDF5_ENABLE_PARALLEL}>:${MPI_C_INCLUDE_DIRS}>"
+      PUBLIC "$<$<BOOL:${HDF5_ENABLE_HDFS}>:${HDFS_INCLUDE_DIR}>"
       INTERFACE "$<INSTALL_INTERFACE:$<INSTALL_PREFIX>/include>"
   )
   target_compile_definitions(${HDF5_LIBSH_TARGET}
diff --git a/src/H5FDhdfs.c b/src/H5FDhdfs.c
new file mode 100644
index 0000000..e3e11b2
--- /dev/null
+++ b/src/H5FDhdfs.c
@@ -0,0 +1,2070 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Read-Only HDFS Virtual File Driver (VFD)                                  *
+ * Copyright (c) 2018, The HDF Group.                                        *
+ *                                                                           *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * NOTICE:                                                                   *
+ * All information contained herein is, and remains, the property of The HDF *
+ * Group. The intellectual and technical concepts contained herein are       *
+ * proprietary to The HDF Group. Dissemination of this information or        *
+ * reproduction of this material is strictly forbidden unless prior written  *
+ * permission is obtained from The HDF Group.                                *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Programmer: Jacob Smith
+ *             2018-04-23
+ *
+ * Purpose:    Provide read-only access to files on the Hadoop Distributed
+ *             File System (HDFS).
+ */
+
+/* This source code file is part of the H5FD driver module */
+#include "H5FDdrvr_module.h"
+
+#include "H5private.h"      /* Generic Functions        */
+#include "H5Eprivate.h"     /* Error handling           */
+#include "H5FDprivate.h"    /* File drivers             */
+#include "H5FDhdfs.h"       /* hdfs file driver         */
+#include "H5FLprivate.h"    /* Free Lists               */
+#include "H5Iprivate.h"     /* IDs                      */
+#include "H5MMprivate.h"    /* Memory management        */
+
+#ifdef H5_HAVE_LIBHDFS
+#include "hdfs.h"
+#endif
+
+/* toggle function call prints: 1 turns on */
+#define HDFS_DEBUG 0
+
+/* toggle stats collection and reporting */
+#define HDFS_STATS 0
+
+/* The driver identification number, initialized at runtime */
+static hid_t H5FD_HDFS_g = 0;
+
+#if HDFS_STATS
+
+/* arbitrarily large value, such that any reasonable size read will be "less"
+ * than this value and set a true minimum
+ * not 0 because that may be a valid recorded minimum in degenerate cases
+ */
+#define HDFS_STATS_STARTING_MIN 0xfffffffful
+
+/* Configuration definitions for stats collection and breakdown
+ *
+ * 2^10 = 1024
+ *     Reads up to 1024 bytes (1 kB) fall in bin 0
+ * 2^(10+(1*16)) = 2^26 = 64MB
+ *     Reads of 64MB or greater fall in "overflow" bin[BIN_COUNT]
+ */
+#define HDFS_STATS_BASE         2
+#define HDFS_STATS_INTERVAL     1
+#define HDFS_STATS_START_POWER 10
+#define HDFS_STATS_BIN_COUNT   16 /* MUST BE GREATER THAN 0 */
+
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Calculate `BASE ^ (START_POWER + (INTERVAL * bin_i))`
+ * Stores result at `(unsigned long long *) out_ptr`.
+ * Used in computing boundaries between stats bins.
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ */
+#define HDFS_STATS_POW(bin_i, out_ptr) {                       \
+    unsigned long long donotshadowresult = 1;                  \
+    unsigned           donotshadowindex  = 0;                  \
+    for (donotshadowindex = 0;                                 \
+         donotshadowindex < (((bin_i) * HDFS_STATS_INTERVAL) + \
+                              HDFS_STATS_START_POWER);         \
+         donotshadowindex++)                                   \
+    {                                                          \
+        donotshadowresult *= HDFS_STATS_BASE;                  \
+    }                                                          \
+    *(out_ptr) = donotshadowresult;                            \
+}
+
+/* array to hold pre-computed boundaries for stats bins */
+static unsigned long long hdfs_stats_boundaries[HDFS_STATS_BIN_COUNT];
+
+
+/***************************************************************************
+ *
+ * Structure: hdfs_statsbin
+ *
+ * Purpose:
+ *
+ *     Structure for storing per-file hdfs VFD usage statistics.
+ *
+ *
+ *
+ * `count` (unsigned long long)
+ *
+ *     Number of reads with size in this bin's range.
+ *
+ * `bytes` (unsigned long long)
+ *
+ *     Total number of bytes read through this bin.
+ *
+ * `min` (unsigned long long)
+ *
+ *     Smallest read size in this bin.
+ *
+ * `max` (unsigned long long)
+ *
+ *     Largest read size in this bin.
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes: None
+ *
+ ***************************************************************************/
+typedef struct {
+    unsigned long long count;
+    unsigned long long bytes;
+    unsigned long long min;
+    unsigned long long max;
+} hdfs_statsbin;
+
+#endif /* HDFS_STATS */
+
+/* "unique" identifier for `hdfs_t` structures.
+ * Randomly generated by unweighted dice rolls.
+ */
+#define HDFS_HDFST_MAGIC 0x1AD5DE84
+
+
+/***************************************************************************
+ *
+ * Structure: hdfs_t
+ *
+ * Purpose:
+ *
+ *     Contain/retain information associated with a file hosted on Hadoop
+ *     Distributed File System (HDFS). Instantiated and populated via 
+ *     `H5FD_hdfs_handle_open()` and cleaned up via `H5FD_hdfs_handle_close()`.
+ *
+ *
+ *
+ * `magic` (unisgned long)
+ *
+ *     Number to indicate that this structure is of the promised
+ *     type and should still be valid; should be HDFS_HDFST_MAGIC throughout
+ *     the lifespan of the structure. Upon deletion of the structure, the
+ *     programmer should set magic to anything but HDFS_HDFST_MAGIC, to
+ *     indicate that the structure is to no longer be trusted.
+ *
+ * `filesystem` (hdfsFS)
+ *
+ *     A libhdfs file system handle.
+ *
+ * `fileinfo` (hdfsFileInfo*)
+ *
+ *     A pointer to a libhdfs file info structure.
+ *
+ * `file` (hdfsFile)
+ *
+ *     A libhdfs file handle.
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *             May 2018
+ *
+ * Changes: None
+ *
+ ***************************************************************************
+ */
+typedef struct {
+    unsigned long  magic;
+#ifdef H5_HAVE_LIBHDFS
+    hdfsFS         filesystem;
+    hdfsFileInfo  *fileinfo;
+    hdfsFile       file; 
+#endif
+} hdfs_t;
+
+#ifdef H5_HAVE_LIBHDFS
+
+/*--------------------------------------------------------------------------
+ * Function:   H5FD_hdfs_handle_open
+ *
+ * Purpose:    Create a HDFS file handle, 'opening' the target file.
+ *
+ * Return:     Success: Pointer to HDFS container/handle of opened file.
+ *             Failure: NULL
+ *
+ * Programmer: Gerd Herber
+ *             May 2018
+ *
+ * Changes:    None.
+ *--------------------------------------------------------------------------
+ */
+static hdfs_t *
+H5FD_hdfs_handle_open(
+        const char    *path,
+        const char    *namenode_name,
+        const int32_t  namenode_port,
+        const char    *user_name,
+        const char    *kerberos_ticket_cache,
+        const int32_t  stream_buffer_size)
+{
+    struct hdfsBuilder *builder   = NULL;
+    hdfs_t             *handle    = NULL;
+    hdfs_t             *ret_value = NULL;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "called H5FD_hdfs_handle_open.\n");
+#endif
+
+    if (path == NULL || path[0] == '\0') {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "path cannot be null.\n")
+    }
+    if (namenode_name == NULL /* || namenode_name[0] == '\0' */ ) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "namenode name cannot be null.\n")
+    }
+    if (namenode_port < 0 || namenode_port > 65535) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "namenode port must be non-negative and <= 65535.\n")
+    }
+    if (stream_buffer_size < 0) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "buffer size must non-negative.\n")
+    }
+
+    handle = (hdfs_t *)H5MM_malloc(sizeof(hdfs_t));
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, NULL,
+                    "could not malloc space for handle.\n")
+    }
+
+    handle->magic      = (unsigned long)HDFS_HDFST_MAGIC;
+    handle->filesystem = NULL; /* TODO: not a pointer; NULL may cause bug */
+    handle->fileinfo   = NULL;
+    handle->file       = NULL; /* TODO: not a pointer; NULL may cause bug */
+
+    builder = hdfsNewBuilder();
+    if (!builder) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "(hdfs) failed to create builder")
+    }
+    hdfsBuilderSetNameNode(builder, namenode_name);
+    hdfsBuilderSetNameNodePort(builder, (tPort)namenode_port);
+    if (user_name != NULL && user_name[0] != '\0') {
+        hdfsBuilderSetUserName(builder, user_name);
+    }
+    if (kerberos_ticket_cache != NULL && kerberos_ticket_cache[0] != '\0') {
+        hdfsBuilderSetKerbTicketCachePath(builder, kerberos_ticket_cache);
+    }
+    /* Call to `hdfsBuilderConnect` releases builder, regardless of success. */
+    handle->filesystem = hdfsBuilderConnect(builder);
+    if (!handle->filesystem) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "(hdfs) could not connect to default namenode")
+    }
+    handle->fileinfo = hdfsGetPathInfo(handle->filesystem, path);
+    if (!handle->fileinfo) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "hdfsGetPathInfo failed")
+    }
+    handle->file = hdfsOpenFile(
+            handle->filesystem, 
+            path,
+            O_RDONLY,
+            stream_buffer_size,
+            0,
+            0);
+    if (!handle->file) {
+        HGOTO_ERROR(H5E_VFL, H5E_CANTOPENFILE, NULL,
+                    "(hdfs) could not open")
+    }
+
+    ret_value = handle;
+
+done:
+    if (ret_value == NULL && handle != NULL) {
+        /* error; clean up */
+        HDassert(handle->magic == HDFS_HDFST_MAGIC);
+        handle->magic++;
+        if (handle->file != NULL) { 
+            if (FAIL == (hdfsCloseFile(handle->filesystem, handle->file))) {
+                HDONE_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, NULL, 
+                            "unable to close hdfs file handle")
+            }
+        }
+        if (handle->fileinfo != NULL) { 
+            hdfsFreeFileInfo(handle->fileinfo, 1);
+        }
+        if (handle->filesystem != NULL) { 
+            if (FAIL == (hdfsDisconnect(handle->filesystem))) {
+                HDONE_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, NULL, 
+                            "unable to disconnect from hdfs")
+            }
+        }
+        H5MM_xfree(handle);
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_handle_open() */
+
+
+/*--------------------------------------------------------------------------
+ * Function:   H5FD_hdfs_handle_close
+ *
+ * Purpose:    'Close' an HDFS file container/handle, releasing underlying
+ *             resources.
+ *
+ * Return:     Success: `SUCCEED` (0)
+ *             Failure: `FAIL` (-1)
+ *
+ * Programmer: Gerd Herber
+ *             May 2018
+ *
+ * Changes:    None.
+ *--------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_handle_close(hdfs_t *handle)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "called H5FD_hdfs_close.\n");
+#endif
+
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle cannot be null.\n")
+    }
+    if (handle->magic != HDFS_HDFST_MAGIC) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has invalid magic.\n")
+    }
+
+    handle->magic++;
+    if (handle->file != NULL) { 
+        if (FAIL == (hdfsCloseFile(handle->filesystem, handle->file))) {
+            HDONE_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, FAIL, 
+                        "unable to close hdfs file handle")
+        }
+    }
+    if (handle->fileinfo != NULL) { 
+        hdfsFreeFileInfo(handle->fileinfo, 1);
+    }
+    if (handle->filesystem != NULL) { 
+        if (FAIL == (hdfsDisconnect(handle->filesystem))) {
+            HDONE_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, FAIL, 
+                        "unable to disconnect hdfs file system")
+        }
+    }
+
+    H5MM_xfree(handle);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_close() */
+#endif /* H5_HAVE_LIBHDFS */
+
+
+/***************************************************************************
+ *
+ * Structure: H5FD_hdfs_t
+ *
+ * Purpose:
+ *
+ *     H5FD_hdfs_t is a structure used to store all information needed to 
+ *     maintain R/O access to a single HDF5 file in an HDFS file system.
+ *     This structure is created when such a file is "opened" and 
+ *     discarded when it is "closed".
+ *
+ *
+ * `pub` (H5FD_t)
+ *
+ *     Instance of H5FD_t which contains all fields common to all VFDs.
+ *     It must be the first item in this structure, since at higher levels,
+ *     this structure will be treated as an instance of H5FD_t.
+ *
+ * `fa` (H5FD_hdfs_fapl_t)
+ *
+ *     Instance of `H5FD_hdfs_fapl_t` containing the HDFS configuration data 
+ *     needed to "open" the HDF5 file.
+ *
+ * `eoa` (haddr_t)
+ *
+ *     End of addressed space in file. After open, it should always
+ *     equal the file size.
+ *
+ * `hdfs_handle` (hdfs_t *)
+ *     
+ *     Instance of HDFS Request handle associated with the target resource.
+ *     Responsible for communicating with remote host and presenting file 
+ *     contents as indistinguishable from a file on the local filesystem.
+ *
+ * *** present only if HDFS_SATS is flagged to enable stats collection ***
+ *
+ * `meta` (hdfs_statsbin[])
+ * `raw` (hdfs_statsbin[])
+ *
+ *     Only present if hdfs stats collection is enabled.
+ *
+ *     Arrays of `hdfs_statsbin` structures to record raw- and metadata reads.
+ *
+ *     Records count and size of reads performed by the VFD, and is used to
+ *     print formatted usage statistics to stdout upon VFD shutdown.
+ *
+ *     Reads of each raw- and metadata type are recorded in an individual bin
+ *     determined by the size of the read.  The last bin of each type is
+ *     reserved for "big" reads, with no defined upper bound.
+ *
+ * *** end HDFS_STATS ***
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes: None.
+ *
+ ***************************************************************************
+ */
+typedef struct H5FD_hdfs_t {
+    H5FD_t            pub;
+    H5FD_hdfs_fapl_t  fa;
+    haddr_t           eoa;
+#ifdef H5_HAVE_LIBHDFS
+    hdfs_t           *hdfs_handle;
+#endif
+#if HDFS_STATS
+    hdfs_statsbin     meta[HDFS_STATS_BIN_COUNT + 1];
+    hdfs_statsbin     raw[HDFS_STATS_BIN_COUNT + 1];
+#endif
+} H5FD_hdfs_t;
+
+/*
+ * These macros check for overflow of various quantities.  These macros
+ * assume that HDoff_t is signed and haddr_t and size_t are unsigned.
+ *
+ * ADDR_OVERFLOW:   Checks whether a file address of type `haddr_t'
+ *                  is too large to be represented by the second argument
+ *                  of the file seek function.
+ *
+ */
+#define MAXADDR (((haddr_t)1<<(8*sizeof(HDoff_t)-1))-1)
+#define ADDR_OVERFLOW(A)    (HADDR_UNDEF==(A) || ((A) & ~(haddr_t)MAXADDR))
+
+/* Prototypes */
+static herr_t  H5FD_hdfs_term(void);
+static void   *H5FD_hdfs_fapl_get(H5FD_t *_file);
+static void   *H5FD_hdfs_fapl_copy(const void *_old_fa);
+static herr_t  H5FD_hdfs_fapl_free(void *_fa);
+static H5FD_t *H5FD_hdfs_open(const char *name, unsigned flags, hid_t fapl_id,
+                              haddr_t maxaddr);
+static herr_t  H5FD_hdfs_close(H5FD_t *_file);
+static int     H5FD_hdfs_cmp(const H5FD_t *_f1, const H5FD_t *_f2);
+static herr_t  H5FD_hdfs_query(const H5FD_t *_f1, unsigned long *flags);
+static haddr_t H5FD_hdfs_get_eoa(const H5FD_t *_file, H5FD_mem_t type);
+static herr_t  H5FD_hdfs_set_eoa(H5FD_t *_file, H5FD_mem_t type, haddr_t addr);
+static haddr_t H5FD_hdfs_get_eof(const H5FD_t *_file, H5FD_mem_t type);
+static herr_t  H5FD_hdfs_get_handle(H5FD_t *_file, hid_t fapl, 
+                                    void** file_handle);
+static herr_t  H5FD_hdfs_read(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, 
+                               haddr_t addr, size_t size, void *buf);
+static herr_t  H5FD_hdfs_write(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, 
+                               haddr_t addr, size_t size, const void *buf);
+static herr_t  H5FD_hdfs_truncate(H5FD_t *_file, hid_t dxpl_id, 
+                                  hbool_t closing);
+static herr_t  H5FD_hdfs_lock(H5FD_t *_file, hbool_t rw);
+static herr_t  H5FD_hdfs_unlock(H5FD_t *_file);
+static herr_t  H5FD_hdfs_validate_config(const H5FD_hdfs_fapl_t * fa);
+
+static const H5FD_class_t H5FD_hdfs_g = {
+    "hdfs",                     /* name                 */
+    MAXADDR,                    /* maxaddr              */
+    H5F_CLOSE_WEAK,             /* fc_degree            */
+    H5FD_hdfs_term,             /* terminate            */
+    NULL,                       /* sb_size              */
+    NULL,                       /* sb_encode            */
+    NULL,                       /* sb_decode            */
+    sizeof(H5FD_hdfs_fapl_t),   /* fapl_size            */
+    H5FD_hdfs_fapl_get,         /* fapl_get             */
+    H5FD_hdfs_fapl_copy,        /* fapl_copy            */
+    H5FD_hdfs_fapl_free,        /* fapl_free            */
+    0,                          /* dxpl_size            */
+    NULL,                       /* dxpl_copy            */
+    NULL,                       /* dxpl_free            */
+    H5FD_hdfs_open,             /* open                 */
+    H5FD_hdfs_close,            /* close                */
+    H5FD_hdfs_cmp,              /* cmp                  */
+    H5FD_hdfs_query,            /* query                */
+    NULL,                       /* get_type_map         */
+    NULL,                       /* alloc                */
+    NULL,                       /* free                 */
+    H5FD_hdfs_get_eoa,          /* get_eoa              */
+    H5FD_hdfs_set_eoa,          /* set_eoa              */
+    H5FD_hdfs_get_eof,          /* get_eof              */
+    H5FD_hdfs_get_handle,       /* get_handle           */
+    H5FD_hdfs_read,             /* read                 */
+    H5FD_hdfs_write,            /* write                */
+    NULL,                       /* flush                */
+    H5FD_hdfs_truncate,         /* truncate             */
+    H5FD_hdfs_lock,             /* lock                 */
+    H5FD_hdfs_unlock,           /* unlock               */
+    H5FD_FLMAP_DICHOTOMY        /* fl_map               */
+};
+
+/* Declare a free list to manage the H5FD_hdfs_t struct */
+H5FL_DEFINE_STATIC(H5FD_hdfs_t);
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD__init_package
+ *
+ * Purpose:     Initializes any interface-specific data or routines.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Changes:     Rename as appropriate for hdfs vfd.
+ *              Jacob Smith 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD__init_package(void)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_STATIC
+
+    if (H5FD_hdfs_init() < 0) {
+        HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, 
+                    "unable to initialize hdfs VFD")
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD__init_package() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_init
+ *
+ * Purpose:     Initialize this driver by registering the driver with the
+ *              library.
+ *
+ * Return:      Success:    The driver ID for the hdfs driver.
+ *              Failure:    Negative
+ *
+ * Programmer:  Robb Matzke
+ *              Thursday, July 29, 1999
+ *
+ * Changes:     Rename as appropriate for hdfs vfd.
+ *              Jacob Smith 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+hid_t
+H5FD_hdfs_init(void)
+{
+    hid_t ret_value = H5I_INVALID_HID; /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_init() called.\n");
+#endif
+
+    if (H5I_VFL != H5I_get_type(H5FD_HDFS_g)) {
+        H5FD_HDFS_g = H5FD_register(
+                &H5FD_hdfs_g,
+                sizeof(H5FD_class_t),
+                FALSE);
+    }
+
+#if HDFS_STATS
+    /* pre-compute statsbin boundaries
+     */
+    for (unsigned bin_i = 0; bin_i < HDFS_STATS_BIN_COUNT; bin_i++) {
+        unsigned long long value = 0;
+        HDFS_STATS_POW(bin_i, &value)
+        hdfs_stats_boundaries[bin_i] = value;
+    }
+#endif
+
+    ret_value = H5FD_HDFS_g;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_hdfs_init() */
+
+
+/*---------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_term
+ *
+ * Purpose:     Shut down the VFD
+ *
+ * Returns:     SUCCEED (Can't fail)
+ *
+ * Programmer:  Quincey Koziol
+ *              Friday, Jan 30, 2004
+ *
+ * Changes:     Rename as appropriate for hdfs vfd.
+ *              Jacob Smith 2018
+ *
+ *---------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_term(void)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_term() called.\n");
+#endif
+
+    /* Reset VFL ID */
+    H5FD_HDFS_g = 0;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5FD_hdfs_term() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pset_fapl_hdfs
+ *
+ * Purpose:     Modify the file access property list to use the H5FD_HDFS
+ *              driver defined in this source file.  All driver specfic 
+ *              properties are passed in as a pointer to a suitably 
+ *              initialized instance of H5FD_hdfs_fapl_t
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  John Mainzer
+ *              9/10/17
+ *
+ * Changes:     Rename as appropriate for hdfs vfd.
+ *              Jacob Smith 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_fapl_hdfs(hid_t             fapl_id, 
+                 H5FD_hdfs_fapl_t *fa)
+{
+    H5P_genplist_t *plist     = NULL; /* Property list pointer */
+    herr_t          ret_value = FAIL;
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", fapl_id, fa);
+
+    HDassert(fa != NULL);
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5Pset_fapl_hdfs() called.\n");
+#endif
+
+    plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS);
+    if (plist == NULL) { 
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, \
+                    "not a file access property list")
+    }
+
+    if (FAIL == H5FD_hdfs_validate_config(fa)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "invalid hdfs config")
+    }
+
+    ret_value = H5P_set_driver(plist, H5FD_HDFS, (void *)fa);
+
+done:
+    FUNC_LEAVE_API(ret_value)
+
+} /* H5Pset_fapl_hdfs() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_validate_config()
+ *
+ * Purpose:     Test to see if the supplied instance of H5FD_hdfs_fapl_t
+ *              contains internally consistant data.  Return SUCCEED if so,
+ *              and FAIL otherwise.
+ *
+ *              Note the difference between internally consistant and 
+ *              correct.  As we will have to try to access the target 
+ *              object to determine whether the supplied data is correct,
+ *              we will settle for internal consistancy at this point
+ *
+ * Return:      SUCCEED if instance of H5FD_hdfs_fapl_t contains internally 
+ *              consistant data, FAIL otherwise.
+ *
+ * Programmer:  Jacob Smith
+ *              9/10/17
+ *
+ * Changes:     None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_validate_config(const H5FD_hdfs_fapl_t * fa)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(fa != NULL);
+
+    if ( fa->version != H5FD__CURR_HDFS_FAPL_T_VERSION ) {
+         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                     "Unknown H5FD_hdfs_fapl_t version");
+    }
+
+    if ( fa->namenode_port > 65535 ) {
+         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                     "Invalid namenode port number");
+    }
+    if ( fa->namenode_port < 0 ) {
+         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                     "Invalid namenode port number");
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_validate_config() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pget_fapl_hdfs
+ *
+ * Purpose:     Returns information about the hdfs file access property
+ *              list though the function arguments.
+ *
+ * Return:      Success:        Non-negative
+ *
+ *              Failure:        Negative
+ *
+ * Programmer:  John Mainzer
+ *              9/10/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_fapl_hdfs(hid_t             fapl_id, 
+                 H5FD_hdfs_fapl_t *fa_out)
+{
+    const H5FD_hdfs_fapl_t *fa        = NULL;
+    H5P_genplist_t         *plist     = NULL;
+    herr_t                  ret_value = SUCCEED;
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", fapl_id, fa_out);
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5Pget_fapl_hdfs() called.\n");
+#endif
+
+    if (fa_out == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "fa_out is NULL")
+    }
+    plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS);
+    if (plist == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL,
+                    "not a file access list")
+    }
+    if (H5FD_HDFS != H5P_peek_driver(plist)) {
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL,
+                    "incorrect VFL driver")
+    }
+
+    fa = (const H5FD_hdfs_fapl_t *)H5P_peek_driver_info(plist);
+    if (fa == NULL) {
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL,
+                    "bad VFL driver info")
+    }
+
+    /* Copy the hdfs fapl data out */
+    HDmemcpy(fa_out, fa, sizeof(H5FD_hdfs_fapl_t));
+
+done:
+    FUNC_LEAVE_API(ret_value)
+
+} /* H5Pget_fapl_hdfs() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_fapl_get
+ *
+ * Purpose:     Gets a file access property list which could be used to
+ *              create an identical file.
+ *
+ * Return:      Success:        Ptr to new file access property list value.
+ *
+ *              Failure:        NULL
+ *
+ * Programmer:  John Mainzer
+ *              9/8/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static void *
+H5FD_hdfs_fapl_get(H5FD_t *_file)
+{
+    H5FD_hdfs_t      *file      = (H5FD_hdfs_t*)_file;
+    H5FD_hdfs_fapl_t *fa        = NULL;
+    void             *ret_value = NULL;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    fa = (H5FD_hdfs_fapl_t *)H5MM_calloc(sizeof(H5FD_hdfs_fapl_t));
+    if (fa == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, 
+                    "memory allocation failed")
+    }
+
+    /* Copy the fields of the structure */
+    HDmemcpy(fa, &(file->fa), sizeof(H5FD_hdfs_fapl_t));
+
+    ret_value = fa;
+
+done:
+    if (ret_value == NULL && fa != NULL) {
+        H5MM_xfree(fa); /* clean up on error */
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_fapl_get() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_fapl_copy
+ *
+ * Purpose:     Copies the hdfs-specific file access properties.
+ *
+ * Return:      Success:        Ptr to a new property list
+ *
+ *              Failure:        NULL
+ *
+ * Programmer:  John Mainzer
+ *              9/8/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static void *
+H5FD_hdfs_fapl_copy(const void *_old_fa)
+{
+    const H5FD_hdfs_fapl_t *old_fa    = (const H5FD_hdfs_fapl_t*)_old_fa;
+    H5FD_hdfs_fapl_t       *new_fa    = NULL;
+    void                   *ret_value = NULL;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    new_fa = (H5FD_hdfs_fapl_t *)H5MM_malloc(sizeof(H5FD_hdfs_fapl_t));
+    if (new_fa == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, 
+                    "memory allocation failed")
+    }
+
+    HDmemcpy(new_fa, old_fa, sizeof(H5FD_hdfs_fapl_t));
+    ret_value = new_fa;
+
+done:
+    if (ret_value == NULL && new_fa != NULL) {
+        H5MM_xfree(new_fa); /* clean up on error */
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_fapl_copy() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_fapl_free
+ *
+ * Purpose:     Frees the hdfs-specific file access properties.
+ *
+ * Return:      SUCCEED (cannot fail)
+ *
+ * Programmer:  John Mainzer
+ *              9/8/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_fapl_free(void *_fa)
+{
+    H5FD_hdfs_fapl_t *fa = (H5FD_hdfs_fapl_t*)_fa;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(fa != NULL); /* sanity check */ 
+
+    H5MM_xfree(fa);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* H5FD_hdfs_fapl_free() */
+
+#if HDFS_STATS
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: hdfs_reset_stats()
+ *
+ * Purpose:
+ *
+ *     Reset the stats collection elements in this virtual file structure.
+ *
+ *     Clears any set data in stats bins; initializes/zeroes values.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - Occurs if the file is invalid somehow
+ *
+ * Programmer: Jacob Smith
+ *             2017-12-08
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+static herr_t
+hdfs_reset_stats(H5FD_hdfs_t *file)
+{
+    unsigned i         = 0;
+    herr_t   ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDprintf("hdfs_reset_stats() called\n");
+#endif
+
+    if (file == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file was null")
+    }
+
+    for (i = 0; i <= HDFS_STATS_BIN_COUNT; i++) {
+        file->raw[i].bytes  = 0;
+        file->raw[i].count  = 0;
+        file->raw[i].min    = (unsigned long long)HDFS_STATS_STARTING_MIN;
+        file->raw[i].max    = 0;
+
+        file->meta[i].bytes = 0;
+        file->meta[i].count = 0;
+        file->meta[i].min   = (unsigned long long)HDFS_STATS_STARTING_MIN;
+        file->meta[i].max   = 0;
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* hdfs_reset_stats */
+#endif /* HDFS_STATS */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_open()
+ *
+ * Purpose:
+ *
+ *     Create and/or opens a file as an HDF5 file.
+ *
+ *     Any flag except H5F_ACC_RDONLY will cause an error.
+ * 
+ * Return:
+ *
+ *     Success: A pointer to a new file data structure. 
+ *              The public fields will be initialized by the caller, which is 
+ *              always H5FD_open().
+ *
+ *     Failure: NULL
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static H5FD_t *
+H5FD_hdfs_open(
+        const char *path, 
+        unsigned    flags, 
+        hid_t       fapl_id, 
+        haddr_t     maxaddr)
+{
+    H5FD_t           *ret_value = NULL;
+#ifdef H5_HAVE_LIBHDFS
+    H5FD_hdfs_t      *file      = NULL;
+    hdfs_t           *handle    = NULL;
+    H5FD_hdfs_fapl_t  fa;
+#endif
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifndef H5_HAVE_LIBHDFS
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, NULL,
+                "Illegal open of unsupported virtual file (hdfs)");
+#else
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_open() called.\n");
+#endif /* HDFS_DEBUG */
+
+    /* Sanity check on file offsets */
+    HDcompile_assert(sizeof(HDoff_t) >= sizeof(size_t));
+
+    /* Check arguments */
+    if (!path || !*path) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "invalid file name")
+    }
+    if (0 == maxaddr || HADDR_UNDEF == maxaddr) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, NULL,
+                    "bogus maxaddr")
+    }
+    if (ADDR_OVERFLOW(maxaddr)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, NULL,
+                    "bogus maxaddr")
+    }
+    if (flags != H5F_ACC_RDONLY) {
+        HGOTO_ERROR(H5E_ARGS, H5E_UNSUPPORTED, NULL,
+                    "only Read-Only access allowed")
+    }
+    if (fapl_id == H5P_DEFAULT || fapl_id == H5P_FILE_ACCESS_DEFAULT) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "fapl cannot be H5P_DEFAULT")
+    }
+    if (FAIL == H5Pget_fapl_hdfs(fapl_id, &fa)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "can't get property list")
+    }
+
+    handle = H5FD_hdfs_handle_open(
+            path,
+            fa.namenode_name,
+            fa.namenode_port,
+            fa.user_name,
+            fa.kerberos_ticket_cache,
+            fa.stream_buffer_size);
+
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_VFL, H5E_CANTOPENFILE, NULL,
+                    "could not open")
+    }
+
+    HDassert(handle->magic == HDFS_HDFST_MAGIC);
+
+    /* create new file struct 
+     */
+    file = H5FL_CALLOC(H5FD_hdfs_t);
+    if (file == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, 
+                    "unable to allocate file struct")
+    }
+    file->hdfs_handle = handle;
+    HDmemcpy(&(file->fa), &fa, sizeof(H5FD_hdfs_fapl_t));
+
+#if HDFS_STATS
+    if (FAIL == hdfs_reset_stats(file)) {
+        HGOTO_ERROR(H5E_INTERNAL, H5E_UNINITIALIZED, NULL, 
+                    "unable to reset file statistics")
+    }
+#endif /* HDFS_STATS */
+
+    ret_value = (H5FD_t*)file;
+#endif /* H5_HAVE_LIBHDFS */
+
+done:
+#ifdef H5_HAVE_LIBHDFS
+    if (ret_value == NULL) {
+        if (handle != NULL) { 
+            if (FAIL == H5FD_hdfs_handle_close(handle)) {
+                HDONE_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, NULL, 
+                            "unable to close HDFS file handle")
+            }
+        }
+        if (file != NULL) {
+            file = H5FL_FREE(H5FD_hdfs_t, file);
+        }
+    } /* if null return value (error) */
+#endif /* H5_HAVE_LIBHDFS */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_open() */
+
+#if HDFS_STATS
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: hdfs_fprint_stats()
+ *
+ * Purpose:
+ * 
+ *     Tabulate and pretty-print statistics for this virtual file.
+ *
+ *     Should be called upon file close.
+ *
+ *     Shows number of reads and bytes read, broken down by
+ *     "raw" (H5FD_MEM_DRAW)
+ *     or "meta" (any other flag)
+ *
+ *     Prints filename and listing of total number of reads and bytes read,
+ *     both as a grand total and separate  meta- and rawdata reads.
+ *
+ *     If any reads were done, prints out two tables:
+ *
+ *     1. overview of raw- and metadata reads
+ *         - min (smallest size read)
+ *         - average of size read
+ *             - k,M,G suffixes by powers of 1024 (2^10)
+ *         - max (largest size read)
+ *     2. tabulation of "bins", sepraring reads into exponentially-larger
+ *        ranges of size.
+ *         - columns for number of reads, total bytes, and average size, with 
+ *           separate sub-colums for raw- and metadata reads.
+ *         - each row represents one bin, identified by the top of its range
+ *     
+ *     Bin ranges can be modified with pound-defines at the top of this file.
+ *
+ *     Bins without any reads in their bounds are not printed.
+ *
+ *     An "overflow" bin is also present, to catch "big" reads.
+ *
+ *     Output for all bins (and range ceiling and average size report) 
+ *     is divied by powers of 1024. By corollary, four digits before the decimal
+ *     is valid.
+ *
+ *     - 41080 bytes is represented by 40.177k, not 41.080k
+ *     - 1004.831M represents approx. 1052642000 bytes
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - occurs if the file passed in is invalid
+ *         - TODO: if stream is invalid? how can we check this?
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+static herr_t
+hdfs_fprint_stats(
+        FILE              *stream,
+        const H5FD_hdfs_t *file)
+{
+    herr_t             ret_value    = SUCCEED;
+    parsed_url_t      *purl         = NULL;
+    unsigned           i            = 0;
+    unsigned long      count_meta   = 0;
+    unsigned long      count_raw    = 0;
+    double             average_meta = 0.0;
+    double             average_raw  = 0.0;
+    unsigned long long min_meta  = (unsigned long long)HDFS_STATS_STARTING_MIN;
+    unsigned long long min_raw   = (unsigned long long)HDFS_STATS_STARTING_MIN;
+    unsigned long long max_meta     = 0;
+    unsigned long long max_raw      = 0;
+    unsigned long long bytes_raw    = 0;
+    unsigned long long bytes_meta   = 0;
+    double             re_dub       = 0.0; /* re-usable double variable */
+    unsigned           suffix_i     = 0;
+    const char         suffixes[]   = { ' ', 'K', 'M', 'G', 'T', 'P' };
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    if (stream == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file stream cannot be null" )
+    }
+    if (file == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file cannot be null")
+    }
+    if (file->hdfs_handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "hdfs handle cannot be null")
+    }
+    if (file->hdfs_handle->magic != HDFS_HDFST_MAGIC) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "hdfs handle has invalid magic")
+    }
+
+    /* TODO: See what libhdfs exposes to us. */
+
+#if 0
+    if (file->s3r_handle->purl == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "parsed url structure cannot be null")
+    }
+    purl = file->s3r_handle->purl;
+
+    /******************
+     * PRINT FILENAME *
+     ******************/
+
+    HDfprintf(stream, "stats for %s://%s", purl->scheme, purl->host);
+    if (purl->port != NULL && purl->port[0] != '\0') {
+        HDfprintf(stream, ":%s", purl->port);
+    }
+    if (purl->query != NULL && purl->query[0] != '\0') {
+        if (purl->path != NULL && purl->path[0] != '\0') {
+            HDfprintf(stream, "/%s", purl->path);
+        } else {
+            HDfprintf(stream, "/");
+        }
+        HDfprintf(stream, "?%s", purl->query);
+    } else if (purl->path != NULL && purl->path[0] != '\0') {
+        HDfprintf(stream, "/%s", purl->path);
+    }
+    HDfprintf(stream, "\n");
+#endif
+
+    /*******************
+     * AGGREGATE STATS *
+     *******************/
+
+    for (i = 0; i <= HDFS_STATS_BIN_COUNT; i++) {
+        const hdfs_statsbin *r = &file->raw[i];
+        const hdfs_statsbin *m = &file->meta[i];
+
+        if (m->min < min_meta)  min_meta = m->min;
+        if (r->min < min_raw)   min_raw  = r->min;
+        if (m->max > max_meta)  max_meta = m->max;
+        if (r->max > max_raw)   max_raw  = r->max;
+
+        count_raw  += r->count;
+        count_meta += m->count;
+        bytes_raw  += r->bytes;
+        bytes_meta += m->bytes;
+    }
+    if (count_raw  > 0) average_raw  = (double)bytes_raw / (double)count_raw;
+    if (count_meta > 0) average_meta = (double)bytes_meta / (double)count_meta;
+
+    /******************
+     * PRINT OVERVIEW *
+     ******************/
+
+    HDfprintf(stream, "TOTAL READS: %llu  (%llu meta, %llu raw)\n",
+              count_raw + count_meta, count_meta, count_raw);
+    HDfprintf(stream, "TOTAL BYTES: %llu  (%llu meta, %llu raw)\n",
+              bytes_raw + bytes_meta, bytes_meta, bytes_raw);
+
+    if (count_raw + count_meta == 0) {
+        goto done;
+    }
+
+    /*************************
+     * PRINT AGGREGATE STATS *
+     *************************/
+
+    HDfprintf(stream, "SIZES     meta      raw\n");
+    HDfprintf(stream, "  min ");
+    if (count_meta == 0) {
+        HDfprintf(stream, "   0.000  ");
+    } else {
+        re_dub = (double)min_meta;
+        for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+            re_dub /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+        HDfprintf(stream, "%8.3lf%c ", re_dub, suffixes[suffix_i]);
+    }
+
+    if (count_raw == 0) {
+        HDfprintf(stream, "   0.000 \n");
+    } else {
+        re_dub = (double)min_raw;
+        for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+            re_dub /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+        HDfprintf(stream, "%8.3lf%c\n", re_dub, suffixes[suffix_i]);
+    }
+
+    HDfprintf(stream, "  avg ");
+    re_dub = (double)average_meta;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+        re_dub /= 1024.0;
+    }
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c ", re_dub, suffixes[suffix_i]);
+
+    re_dub = (double)average_raw;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+        re_dub /= 1024.0;
+    }
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c\n", re_dub, suffixes[suffix_i]);
+
+    HDfprintf(stream, "  max ");
+    re_dub = (double)max_meta;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+        re_dub /= 1024.0;
+    }
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c ", re_dub, suffixes[suffix_i]);
+
+    re_dub = (double)max_raw;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+        re_dub /= 1024.0;
+    }
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c\n", re_dub, suffixes[suffix_i]);
+
+    /******************************
+     * PRINT INDIVIDUAL BIN STATS *
+     ******************************/
+
+    HDfprintf(stream, 
+        "BINS             # of reads      total bytes         average size\n");
+    HDfprintf(stream, 
+        "    up-to      meta     raw     meta      raw       meta      raw\n");
+
+    for (i = 0; i <= HDFS_STATS_BIN_COUNT; i++) {
+        const hdfs_statsbin *m;
+        const hdfs_statsbin *r;
+        unsigned long long   range_end = 0;
+        char                 bm_suffix = ' '; /* bytes-meta */
+        double               bm_val    = 0.0;
+        char                 br_suffix = ' '; /* bytes-raw */
+        double               br_val    = 0.0;
+        char                 am_suffix = ' '; /* average-meta */
+        double               am_val    = 0.0;
+        char                 ar_suffix = ' '; /* average-raw */
+        double               ar_val    = 0.0;
+
+        m = &file->meta[i];
+        r = &file->raw[i];
+        if (r->count == 0 && m->count == 0) {
+            continue;
+        }
+
+        range_end = hdfs_stats_boundaries[i];
+
+        if (i == HDFS_STATS_BIN_COUNT) {
+            range_end = hdfs_stats_boundaries[i-1];
+            HDfprintf(stream, ">");
+        } else {
+            HDfprintf(stream, " ");
+        }
+
+        bm_val = (double)m->bytes;
+        for (suffix_i = 0; bm_val >= 1024.0; suffix_i++) {
+            bm_val /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+        bm_suffix = suffixes[suffix_i];
+
+        br_val = (double)r->bytes;
+        for (suffix_i = 0; br_val >= 1024.0; suffix_i++) {
+            br_val /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+        br_suffix = suffixes[suffix_i];
+
+        if (m->count > 0) {
+            am_val = (double)(m->bytes) / (double)(m->count);
+        }
+        for (suffix_i = 0; am_val >= 1024.0; suffix_i++) {
+            am_val /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+        am_suffix = suffixes[suffix_i];
+
+        if (r->count > 0) {
+            ar_val = (double)(r->bytes) / (double)(r->count);
+        }
+        for (suffix_i = 0; ar_val >= 1024.0; suffix_i++) {
+            ar_val /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+        ar_suffix = suffixes[suffix_i];
+
+        re_dub = (double)range_end;
+        for (suffix_i = 0; re_dub >= 1024.0; suffix_i++) {
+            re_dub /= 1024.0;
+        }
+        HDassert(suffix_i < sizeof(suffixes));
+
+        HDfprintf(
+                stream, 
+                " %8.3f%c %7d %7d %8.3f%c %8.3f%c %8.3f%c %8.3f%c\n",
+                re_dub, suffixes[suffix_i], /* bin ceiling      */
+                m->count,                   /* metadata reads   */
+                r->count,                   /* rawdata reads    */
+                bm_val, bm_suffix,          /* metadata bytes   */
+                br_val, br_suffix,          /* rawdata bytes    */
+                am_val, am_suffix,          /* metadata average */
+                ar_val, ar_suffix);         /* rawdata average  */
+        fflush(stream);
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+    
+} /* hdfs_fprint_stats */
+#endif /* HDFS_STATS */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_close()
+ *
+ * Purpose:
+ *
+ *     Close an HDF5 file.
+ *
+ * Return:
+ * 
+ *     SUCCEED/FAIL
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_close(H5FD_t *_file)
+{
+    herr_t       ret_value = SUCCEED;
+#ifdef H5_HAVE_LIBHDFS
+    H5FD_hdfs_t *file      = (H5FD_hdfs_t *)_file;
+#endif
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifndef H5_HAVE_LIBHDFS
+    HGOTO_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, FAIL,
+                "Illegal close of unsupported Virtual File (hdfs)")
+#else
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_close() called.\n");
+#endif
+
+    /* Sanity checks 
+     */
+    HDassert(file != NULL);
+    HDassert(file->hdfs_handle != NULL);
+    HDassert(file->hdfs_handle->magic == HDFS_HDFST_MAGIC);
+
+    /* Close the underlying request handle 
+     */
+    if (file->hdfs_handle != NULL) { 
+        if (FAIL == H5FD_hdfs_handle_close(file->hdfs_handle)) {
+            HGOTO_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, FAIL, 
+                        "unable to close HDFS file handle")
+        }
+    }
+
+#if HDFS_STATS
+    /* TODO: mechanism to re-target stats printout */
+    if (FAIL == hdfs_fprint_stats(stdout, file)) {
+        HGOTO_ERROR(H5E_INTERNAL, H5E_ERROR, FAIL, 
+                    "problem while writing file statistics")
+    }
+#endif /* HDFS_STATS */
+
+    /* Release the file info 
+     */
+    file = H5FL_FREE(H5FD_hdfs_t, file);
+#endif /* H5_HAVE_LIBHDFS */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_hdfs_close() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_cmp()
+ *
+ * Purpose:
+ *
+ *     Compares two files using this driver by their HDFS-provided file info,
+ *     field-by-field.
+ *
+ * Return:
+ *     + Equivalent:      0
+ *     + Not Equivalent: -1
+ *
+ * Programmer: Gerd Herber
+ *             May 2018
+ *
+ * Changes:
+ *
+ *     + Replace `if (ret_value == 0)` chain with `HGOTO_DONE` jumps.
+ *         Jacob Smith 17 May 2018
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+H5FD_hdfs_cmp(const H5FD_t *_f1,
+              const H5FD_t *_f2)
+{
+    int                ret_value = 0;
+#ifdef H5_HAVE_LIBHDFS
+    const H5FD_hdfs_t *f1        = (const H5FD_hdfs_t *)_f1;
+    const H5FD_hdfs_t *f2        = (const H5FD_hdfs_t *)_f2;
+    hdfsFileInfo      *finfo1    = NULL;
+    hdfsFileInfo      *finfo2    = NULL;
+#endif /* H5_HAVE_LIBHDFS */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#ifdef H5_HAVE_LIBHDFS
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_cmp() called.\n");
+#endif /* HDFS_DEBUG */
+
+    HDassert(f1->hdfs_handle != NULL);
+    HDassert(f2->hdfs_handle != NULL);
+    HDassert(f1->hdfs_handle->magic == HDFS_HDFST_MAGIC);
+    HDassert(f2->hdfs_handle->magic == HDFS_HDFST_MAGIC);
+
+    finfo1 = f1->hdfs_handle->fileinfo;
+    finfo2 = f2->hdfs_handle->fileinfo;
+    HDassert(finfo1 != NULL);
+    HDassert(finfo2 != NULL);
+
+    if (finfo1->mKind        != finfo2->mKind)        HGOTO_DONE(-1);
+    if (finfo1->mName        != finfo2->mName)        HGOTO_DONE(-1);
+    if (finfo1->mLastMod     != finfo2->mLastMod)     HGOTO_DONE(-1);
+    if (finfo1->mSize        != finfo2->mSize)        HGOTO_DONE(-1);
+    if (finfo1->mReplication != finfo2->mReplication) HGOTO_DONE(-1);
+    if (finfo1->mBlockSize   != finfo2->mBlockSize)   HGOTO_DONE(-1);
+    if (strcmp(finfo1->mOwner, finfo2->mOwner))       HGOTO_DONE(-1);
+    if (strcmp(finfo1->mGroup, finfo2->mGroup))       HGOTO_DONE(-1);
+    if (finfo1->mPermissions != finfo2->mPermissions) HGOTO_DONE(-1);
+    if (finfo1->mLastAccess  != finfo2->mLastAccess)  HGOTO_DONE(-1);
+#endif /* H5_HAVE_LIBHDFS */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_cmp() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_hdfs_query
+ *
+ * Purpose:     Set the flags that this VFL driver is capable of supporting.
+ *              (listed in H5FDpublic.h)
+ *
+ *              Note that since the HDFS VFD is read only, most flags 
+ *              are irrelevant.
+ *
+ *              The term "set" is highly misleading...
+ *              stores/copies the supported flags in the out-pointer `flags`.
+ *
+ * Return:      SUCCEED (Can't fail)
+ *
+ * Programmer:  John Mainzer
+ *              9/11/17
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_query(
+        const H5FD_t  H5_ATTR_UNUSED *_file, 
+        unsigned long                *flags) /* out variable */
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_query() called.\n");
+#endif
+
+    if (flags) {
+        *flags = 0;
+        *flags |= H5FD_FEAT_DATA_SIEVE; 
+    }
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* H5FD_hdfs_query() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_get_eoa()
+ *
+ * Purpose:
+ *
+ *     Gets the end-of-address marker for the file. The EOA marker
+ *     is the first address past the last byte allocated in the
+ *     format address space.
+ *
+ * Return:
+ *
+ *     The end-of-address marker.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static haddr_t
+H5FD_hdfs_get_eoa(
+        const H5FD_t                *_file, 
+        H5FD_mem_t   H5_ATTR_UNUSED  type)
+{
+#ifdef H5_HAVE_LIBHDFS
+    const H5FD_hdfs_t *file = (const H5FD_hdfs_t *)_file;
+#endif /* H5_HAVE_LIBHDFS */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_get_eoa() called.\n");
+#endif
+
+#ifdef H5_HAVE_LIBHDFS
+    FUNC_LEAVE_NOAPI(file->eoa)
+#else
+    FUNC_LEAVE_NOAPI(0)
+#endif /* H5_HAVE_LIBHDFS */
+
+} /* end H5FD_hdfs_get_eoa() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_set_eoa()
+ *
+ * Purpose:
+ *
+ *     Set the end-of-address marker for the file.
+ *
+ * Return:
+ *
+ *      SUCCEED  (can't fail)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-03
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_set_eoa(
+        H5FD_t                    *_file, 
+        H5FD_mem_t H5_ATTR_UNUSED  type, 
+        haddr_t                    addr)
+{
+#ifdef H5_HAVE_LIBHDFS
+    H5FD_hdfs_t *file = (H5FD_hdfs_t *)_file;
+#endif /* H5_HAVE_LIBHDFS */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_set_eoa() called.\n");
+#endif
+
+#ifdef H5_HAVE_LIBHDFS
+    file->eoa = addr;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+#else
+    FUNC_LEAVE_NOAPI(FAIL)
+#endif /* H5_HAVE_LIBHDFS */
+
+} /* H5FD_hdfs_set_eoa() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_get_eof()
+ *
+ * Purpose:
+ *
+ *     Returns the end-of-file marker.
+ *
+ * Return:
+ *
+ *     EOF: the first address past the end of the "file", either the 
+ *     filesystem file or the HDF5 file.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ *-------------------------------------------------------------------------
+ */
+static haddr_t
+H5FD_hdfs_get_eof(
+        const H5FD_t                *_file, 
+        H5FD_mem_t   H5_ATTR_UNUSED  type)
+{
+#ifdef H5_HAVE_LIBHDFS
+    const H5FD_hdfs_t *file = (const H5FD_hdfs_t *)_file;
+#endif /* H5_HAVE_LIBHDFS */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_get_eof() called.\n");
+#endif
+
+#ifdef H5_HAVE_LIBHDFS
+    HDassert(file->hdfs_handle != NULL);
+    HDassert(file->hdfs_handle->magic == HDFS_HDFST_MAGIC);
+
+    FUNC_LEAVE_NOAPI((size_t) file->hdfs_handle->fileinfo->mSize)
+#else
+    FUNC_LEAVE_NOAPI((size_t)0)
+#endif /* H5_HAVE_LIBHDFS */
+
+} /* end H5FD_hdfs_get_eof() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_get_handle()
+ *
+ * Purpose:
+ *
+ *     Returns the HDFS handle (hdfs_t) of hdfs file driver.
+ *
+ * Returns:
+ *
+ *     SUCCEED/FAIL
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_get_handle(
+        H5FD_t                 *_file, 
+        hid_t  H5_ATTR_UNUSED   fapl, 
+        void                  **file_handle)
+{
+    herr_t       ret_value = SUCCEED;
+#ifdef H5_HAVE_LIBHDFS
+    H5FD_hdfs_t *file      = (H5FD_hdfs_t *)_file;
+#endif
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_get_handle() called.\n");
+#endif /* HDFS_DEBUG */
+
+#ifdef H5_HAVE_LIBHDFS
+    if (!file_handle) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file handle not valid")
+    }
+
+    *file_handle = file->hdfs_handle;
+#else
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL,
+                "Illegal get-handle of unsupported virtual file (hdfs)");
+#endif /* H5_HAVE_LIBHDFS */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_hdfs_get_handle() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_read()
+ *
+ * Purpose: 
+ *
+ *     Reads SIZE bytes of data from FILE beginning at address ADDR
+ *     into buffer BUF according to data transfer properties in DXPL_ID.
+ *
+ * Return:
+ *
+ *     Success: `SUCCEED`
+ *         - Result is stored in caller-supplied buffer BUF.
+ *     Failure: `FAIL`
+ *         - Unable to complete read.
+ *         - Contents of buffer `buf` are undefined.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-??
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_read(
+        H5FD_t                    *_file, 
+        H5FD_mem_t H5_ATTR_UNUSED  type, 
+        hid_t      H5_ATTR_UNUSED  dxpl_id,
+        haddr_t                    addr, /* start offset   */
+        size_t                     size, /* length of read */
+        void                      *buf)  /* out            */
+{
+    herr_t       ret_value = SUCCEED;
+#if H5_HAVE_LIBHDFS
+    H5FD_hdfs_t *file      = (H5FD_hdfs_t *)_file;
+    size_t       filesize  = 0;
+#endif /* H5_HAVE_LIBHDFS */
+#if HDFS_STATS
+    /* working variables for storing stats */
+    hdfs_statsbin *bin   = NULL;
+    unsigned       bin_i = 0;
+#endif /* HDFS_STATS */
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_read() called.\n");
+#endif /* HDFS_DEBUG */
+
+#ifndef H5_HAVE_LIBHDFS
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL,
+                "Illegal get-handle of unsupported virtual file (hdfs)");
+#else
+    HDassert(file != NULL);
+    HDassert(file->hdfs_handle != NULL);
+    HDassert(file->hdfs_handle->magic == HDFS_HDFST_MAGIC);
+    HDassert(buf != NULL);
+
+    filesize = (size_t) file->hdfs_handle->fileinfo->mSize;
+
+    if ((addr > filesize) || ((addr + size) > filesize)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL,
+                    "range exceeds file address")
+    }
+
+    if (FAIL == hdfsPread(
+            file->hdfs_handle->filesystem,
+            file->hdfs_handle->file,
+            (tOffset)addr,
+            buf,
+            (tSize)size))
+    {
+        HGOTO_ERROR(H5E_VFL, H5E_READERROR, FAIL,
+                    "unable to execute read")
+    }
+
+#if HDFS_STATS
+
+    /* Find which "bin" this read fits in. Can be "overflow" bin.
+     */
+    for (bin_i = 0; bin_i < HDFS_STATS_BIN_COUNT; bin_i++) {
+        if ((unsigned long long)size < hdfs_stats_boundaries[bin_i]) {
+            break;
+        }
+    }
+    bin = (type == H5FD_MEM_DRAW)
+        ? &file->raw[bin_i]
+        : &file->meta[bin_i];
+
+    /* Store collected stats in appropriate bin 
+     */
+    if (bin->count == 0) {
+        bin->min = size;
+        bin->max = size;
+    } else {
+        if (size < bin->min) bin->min = size;
+        if (size > bin->max) bin->max = size;
+    }
+    bin->count++;
+    bin->bytes += (unsigned long long)size;
+
+#endif /* HDFS_STATS */
+#endif /* H5_HAVE_LIBHDFS */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_hdfs_read() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_write()
+ *
+ * Purpose: 
+ *
+ *     Write bytes to file.
+ *     UNSUPPORTED IN READ-ONLY HDFS VFD.
+ *
+ * Return: 
+ *
+ *     FAIL (Not possible with Read-Only S3 file.)
+ *
+ * Programmer: Jacob Smith
+ *             2017-10-23
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_write(
+        H5FD_t     H5_ATTR_UNUSED *_file, 
+        H5FD_mem_t H5_ATTR_UNUSED  type, 
+        hid_t      H5_ATTR_UNUSED  dxpl_id,
+        haddr_t    H5_ATTR_UNUSED  addr, 
+        size_t     H5_ATTR_UNUSED  size, 
+        const void H5_ATTR_UNUSED *buf)
+{
+    herr_t ret_value = FAIL;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_write() called.\n");
+#endif
+
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL,
+                "cannot write to read-only file.")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_hdfs_write() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_truncate()
+ *
+ * Purpose:
+ *
+ *     Makes sure that the true file size is the same (or larger)
+ *     than the end-of-address.
+ *
+ *     NOT POSSIBLE ON READ-ONLY S3 FILES.
+ *
+ * Return:
+ *
+ *     FAIL (Not possible on Read-Only S3 files.)
+ *
+ * Programmer: Jacob Smith
+ *             2017-10-23
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_truncate(
+        H5FD_t  H5_ATTR_UNUSED *_file, 
+        hid_t   H5_ATTR_UNUSED  dxpl_id, 
+        hbool_t H5_ATTR_UNUSED  closing)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if HDFS_DEBUG
+    HDfprintf(stdout, "H5FD_hdfs_truncate() called.\n");
+#endif
+
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL,
+                "cannot truncate read-only file.")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_hdfs_truncate() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_lock()
+ *
+ * Purpose:
+ *
+ *     Place an advisory lock on a file.
+ *     No effect on Read-Only S3 file.
+ *
+ *     Suggestion: remove lock/unlock from class
+ *               > would result in error at H5FD_[un]lock() (H5FD.c)
+ *
+ * Return:
+ *
+ *     SUCCEED (No-op always succeeds)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-03
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_lock(
+        H5FD_t  H5_ATTR_UNUSED *_file, 
+        hbool_t H5_ATTR_UNUSED  rw)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* end H5FD_hdfs_lock() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_hdfs_unlock()
+ *
+ * Purpose:
+ *
+ *     Remove the existing lock on the file.
+ *     No effect on Read-Only S3 file.
+ *
+ * Return:
+ *
+ *     SUCCEED (No-op always succeeds)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-03
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_hdfs_unlock(H5FD_t H5_ATTR_UNUSED *_file)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* end H5FD_hdfs_unlock() */
+
diff --git a/src/H5FDhdfs.h b/src/H5FDhdfs.h
new file mode 100644
index 0000000..3d4128d
--- /dev/null
+++ b/src/H5FDhdfs.h
@@ -0,0 +1,122 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Read-Only HDFS Virtual File Driver (VFD)                                  *
+ * Copyright (c) 2018, The HDF Group.                                        *
+ *                                                                           *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * NOTICE:                                                                   *
+ * All information contained herein is, and remains, the property of The HDF *
+ * Group. The intellectual and technical concepts contained herein are       *
+ * proprietary to The HDF Group. Dissemination of this information or        *
+ * reproduction of this material is strictly forbidden unless prior written  *
+ * permission is obtained from The HDF Group.                                *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Programmer:  Jacob Smith
+ *              2018-04-23
+ *
+ * Purpose:	The public header file for the hdfs driver.
+ */
+
+#ifndef H5FDhdfs_H
+#define H5FDhdfs_H
+
+#define H5FD_HDFS (H5FD_hdfs_init())
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/****************************************************************************
+ *
+ * Structure: H5FD_hdfs_fapl_t
+ *
+ * Purpose:
+ *
+ *     H5FD_hdfs_fapl_t is a public structure that is used to pass
+ *     configuration information to the appropriate HDFS VFD via the FAPL.
+ *     A pointer to an instance of this structure is a parameter to
+ *     H5Pset_fapl_hdfs() and H5Pget_fapl_hdfs().
+ *
+ *
+ *
+ * `version` (int32_t)
+ *
+ *     Version number of the `H5FD_hdfs_fapl_t` structure.  Any instance passed 
+ *     to the above calls must have a recognized version number, or an error
+ *     will be flagged.
+ *
+ *     This field should be set to `H5FD__CURR_HDFS_FAPL_T_VERSION`.
+ *
+ * `namenode_name` (const char[])
+ *
+ *     Name of "Name Node" to access as the HDFS server.
+ *
+ *     Must not be longer than `H5FD__HDFS_NODE_NAME_SPACE`.
+ *
+ *     TBD: Can be NULL.
+ *
+ * `namenode_port` (int32_t) TBD
+ *
+ *     Port number to use to connect with Name Node.
+ *
+ *     TBD: If 0, uses a default port.
+ *
+ * `kerberos_ticket_cache` (const char[])
+ *
+ *     Path to the location of the Kerberos authentication cache.
+ *
+ *     Must not be longer than `H5FD__HDFS_KERB_CACHE_PATH_SPACE`.
+ *
+ *     TBD: Can be NULL.
+ *
+ * `user_name` (const char[])
+ *
+ *     Username to use when accessing file.
+ *
+ *     Must not be longer than `H5FD__HDFS_USER_NAME_SPACE`.
+ *
+ *     TBD: Can be NULL.
+ *
+ * `stream_buffer_size` (int32_t)
+ *
+ *     Size (in bytes) of the file read stream buffer.
+ *
+ *     TBD: If -1, relies on a default value.
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *             2018-04-23
+ *
+ * Changes: None
+ *
+ ****************************************************************************/
+
+#define H5FD__CURR_HDFS_FAPL_T_VERSION 1
+
+#define H5FD__HDFS_NODE_NAME_SPACE 128
+#define H5FD__HDFS_USER_NAME_SPACE 128
+#define H5FD__HDFS_KERB_CACHE_PATH_SPACE 128
+
+typedef struct H5FD_hdfs_fapl_t {
+    int32_t version;
+    char    namenode_name[H5FD__HDFS_NODE_NAME_SPACE + 1];
+    int32_t namenode_port;
+    char    user_name[H5FD__HDFS_USER_NAME_SPACE + 1];
+    char    kerberos_ticket_cache[H5FD__HDFS_KERB_CACHE_PATH_SPACE + 1];
+    int32_t stream_buffer_size;
+} H5FD_hdfs_fapl_t;
+
+H5_DLL hid_t H5FD_hdfs_init(void);
+H5_DLL herr_t H5Pget_fapl_hdfs(hid_t fapl_id, H5FD_hdfs_fapl_t *fa_out);
+H5_DLL herr_t H5Pset_fapl_hdfs(hid_t fapl_id, H5FD_hdfs_fapl_t *fa);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ifndef H5FDhdfs_H */
+
+
diff --git a/src/H5FDros3.c b/src/H5FDros3.c
new file mode 100644
index 0000000..86642aa
--- /dev/null
+++ b/src/H5FDros3.c
@@ -0,0 +1,1847 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Read-Only S3 Virtual File Driver (VFD)                                   
+ *
+ * Programmer: Jacob Smith <jake.smith@hdfgroup.org>
+ *             2017-10-13
+ *
+ * Purpose: 
+ *
+ *     Provide read-only access to files hosted on Amazon's S3 service.
+ *     Relies on "s3comms" utility layer to implement the AWS REST API.
+ */
+
+/* This source code file is part of the H5FD driver module */
+#include "H5FDdrvr_module.h"
+
+#include "H5private.h"      /* Generic Functions        */
+#include "H5Eprivate.h"     /* Error handling           */
+#include "H5FDprivate.h"    /* File drivers             */
+#include "H5FDros3.h"       /* ros3 file driver         */
+#include "H5FLprivate.h"    /* Free Lists               */
+#include "H5Iprivate.h"     /* IDs                      */
+#include "H5MMprivate.h"    /* Memory management        */
+#include "H5FDs3comms.h"    /* S3 Communications        */
+
+/* toggle function call prints: 1 turns on
+ */
+#define ROS3_DEBUG 0
+
+/* toggle stats collection and reporting
+ */
+#define ROS3_STATS 0
+
+/* The driver identification number, initialized at runtime
+ */
+static hid_t H5FD_ROS3_g = 0;
+
+#if ROS3_STATS
+
+/* arbitrarily large value, such that any reasonable size read will be "less"
+ * than this value and set a true minimum
+ * not 0 because that may be a valid recorded minimum in degenerate cases
+ */
+#define ROS3_STATS_STARTING_MIN 0xfffffffful
+
+/* Configuration definitions for stats collection and breakdown
+ *
+ * 2^10 = 1024
+ *     Reads up to 1024 bytes (1 kB) fall in bin 0
+ * 2^(10+(1*16)) = 2^26 = 64MB
+ *     Reads of 64MB or greater fall in "overflow" bin[BIN_COUNT]
+ */
+#define ROS3_STATS_BASE         2
+#define ROS3_STATS_INTERVAL     1
+#define ROS3_STATS_START_POWER 10
+#define ROS3_STATS_BIN_COUNT   16 /* MUST BE GREATER THAN 0 */
+
+
+/*
+ * Calculate `BASE ^ (START_POWER + (INTERVAL * bin_i))`
+ * Stores result at `(unsigned long long *) out_ptr`.
+ * Used in computing boundaries between stats bins.
+ */
+#define ROS3_STATS_POW(bin_i, out_ptr) {                       \
+    unsigned long long donotshadowresult = 1;                  \
+    unsigned           donotshadowindex  = 0;                  \
+    for (donotshadowindex = 0;                                 \
+         donotshadowindex < (((bin_i) * ROS3_STATS_INTERVAL) + \
+                              ROS3_STATS_START_POWER);         \
+         donotshadowindex++)                                   \
+    {                                                          \
+        donotshadowresult *= ROS3_STATS_BASE;                  \
+    }                                                          \
+    *(out_ptr) = donotshadowresult;                            \
+}
+
+/* array to hold pre-computed boundaries for stats bins
+ */
+static unsigned long long ros3_stats_boundaries[ROS3_STATS_BIN_COUNT];
+
+/***************************************************************************
+ *
+ * Structure: ros3_statsbin
+ *
+ * Purpose:
+ *
+ *     Structure for storing per-file ros3 VFD usage statistics.
+ *
+ *
+ *
+ * `count` (unsigned long long)
+ *
+ *     Number of reads with size in this bin's range.
+ *
+ * `bytes` (unsigned long long)
+ *
+ *     Total number of bytes read through this bin.
+ *
+ * `min` (unsigned long long)
+ *
+ *     Smallest read size in this bin.
+ *
+ * `max` (unsigned long long)
+ *
+ *     Largest read size in this bin.
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes: None
+ *
+ ***************************************************************************/
+typedef struct {
+    unsigned long long count;
+    unsigned long long bytes;
+    unsigned long long min;
+    unsigned long long max;
+} ros3_statsbin;
+
+#endif /* ROS3_STATS */
+
+/***************************************************************************
+ *
+ * Structure: H5FD_ros3_t
+ *
+ * Purpose:
+ *
+ *     H5FD_ros3_t is a structure used to store all information needed to 
+ *     maintain R/O access to a single HDF5 file that has been stored as a
+ *     S3 object.  This structure is created when such a file is "opened" and 
+ *     discarded when it is "closed".
+ *
+ *     Presents an S3 object as a file to the HDF5 library.
+ *
+ *
+ *
+ * `pub` (H5FD_t)
+ *
+ *     Instance of H5FD_t which contains all fields common to all VFDs.
+ *     It must be the first item in this structure, since at higher levels,
+ *     this structure will be treated as an instance of H5FD_t.
+ *
+ * `fa` (H5FD_ros3_fapl_t)
+ *
+ *     Instance of `H5FD_ros3_fapl_t` containing the S3 configuration data 
+ *     needed to "open" the HDF5 file.
+ *
+ * `eoa` (haddr_t)
+ *
+ *     End of addressed space in file. After open, it should always
+ *     equal the file size.
+ *
+ * `s3r_handle` (s3r_t *)
+ *     
+ *     Instance of S3 Request handle associated with the target resource.
+ *     Responsible for communicating with remote host and presenting file 
+ *     contents as indistinguishable from a file on the local filesystem.
+ *
+ * *** present only if ROS3_SATS is flagged to enable stats collection ***
+ *
+ * `meta` (ros3_statsbin[])
+ * `raw` (ros3_statsbin[])
+ *
+ *     Only present if ros3 stats collection is enabled.
+ *
+ *     Arrays of `ros3_statsbin` structures to record raw- and metadata reads.
+ *
+ *     Records count and size of reads performed by the VFD, and is used to
+ *     print formatted usage statistics to stdout upon VFD shutdown.
+ *
+ *     Reads of each raw- and metadata type are recorded in an individual bin
+ *     determined by the size of the read.  The last bin of each type is
+ *     reserved for "big" reads, with no defined upper bound.
+ *
+ * *** end ROS3_STATS ***
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes: None.
+ *
+ ***************************************************************************/
+typedef struct H5FD_ros3_t {
+    H5FD_t            pub;
+    H5FD_ros3_fapl_t  fa;
+    haddr_t           eoa;
+    s3r_t            *s3r_handle;
+#if ROS3_STATS
+    ros3_statsbin    meta[ROS3_STATS_BIN_COUNT + 1];
+    ros3_statsbin    raw[ROS3_STATS_BIN_COUNT + 1];
+#endif
+} H5FD_ros3_t;
+
+/*
+ * These macros check for overflow of various quantities.  These macros
+ * assume that HDoff_t is signed and haddr_t and size_t are unsigned.
+ *
+ * ADDR_OVERFLOW:   Checks whether a file address of type `haddr_t'
+ *                  is too large to be represented by the second argument
+ *                  of the file seek function.
+ *
+ */
+#define MAXADDR (((haddr_t)1<<(8*sizeof(HDoff_t)-1))-1)
+#define ADDR_OVERFLOW(A)    (HADDR_UNDEF==(A) || ((A) & ~(haddr_t)MAXADDR))
+
+/* Prototypes */
+static herr_t  H5FD_ros3_term(void);
+static void   *H5FD_ros3_fapl_get(H5FD_t *_file);
+static void   *H5FD_ros3_fapl_copy(const void *_old_fa);
+static herr_t  H5FD_ros3_fapl_free(void *_fa);
+static H5FD_t *H5FD_ros3_open(const char *name, unsigned flags, hid_t fapl_id,
+                              haddr_t maxaddr);
+static herr_t  H5FD_ros3_close(H5FD_t *_file);
+static int     H5FD_ros3_cmp(const H5FD_t *_f1, const H5FD_t *_f2);
+static herr_t  H5FD_ros3_query(const H5FD_t *_f1, unsigned long *flags);
+static haddr_t H5FD_ros3_get_eoa(const H5FD_t *_file, H5FD_mem_t type);
+static herr_t  H5FD_ros3_set_eoa(H5FD_t *_file, H5FD_mem_t type, haddr_t addr);
+static haddr_t H5FD_ros3_get_eof(const H5FD_t *_file, H5FD_mem_t type);
+static herr_t  H5FD_ros3_get_handle(H5FD_t *_file, hid_t fapl, 
+                                    void** file_handle);
+static herr_t  H5FD_ros3_read(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, 
+                               haddr_t addr, size_t size, void *buf);
+static herr_t  H5FD_ros3_write(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, 
+                               haddr_t addr, size_t size, const void *buf);
+static herr_t  H5FD_ros3_truncate(H5FD_t *_file, hid_t dxpl_id, 
+                                  hbool_t closing);
+static herr_t  H5FD_ros3_lock(H5FD_t *_file, hbool_t rw);
+static herr_t  H5FD_ros3_unlock(H5FD_t *_file);
+static herr_t  H5FD_ros3_validate_config(const H5FD_ros3_fapl_t * fa);
+
+static const H5FD_class_t H5FD_ros3_g = {
+    "ros3",                     /* name                 */
+    MAXADDR,                    /* maxaddr              */
+    H5F_CLOSE_WEAK,             /* fc_degree            */
+    H5FD_ros3_term,             /* terminate            */
+    NULL,                       /* sb_size              */
+    NULL,                       /* sb_encode            */
+    NULL,                       /* sb_decode            */
+    sizeof(H5FD_ros3_fapl_t),   /* fapl_size            */
+    H5FD_ros3_fapl_get,         /* fapl_get             */
+    H5FD_ros3_fapl_copy,        /* fapl_copy            */
+    H5FD_ros3_fapl_free,        /* fapl_free            */
+    0,                          /* dxpl_size            */
+    NULL,                       /* dxpl_copy            */
+    NULL,                       /* dxpl_free            */
+    H5FD_ros3_open,             /* open                 */
+    H5FD_ros3_close,            /* close                */
+    H5FD_ros3_cmp,              /* cmp                  */
+    H5FD_ros3_query,            /* query                */
+    NULL,                       /* get_type_map         */
+    NULL,                       /* alloc                */
+    NULL,                       /* free                 */
+    H5FD_ros3_get_eoa,          /* get_eoa              */
+    H5FD_ros3_set_eoa,          /* set_eoa              */
+    H5FD_ros3_get_eof,          /* get_eof              */
+    H5FD_ros3_get_handle,       /* get_handle           */
+    H5FD_ros3_read,             /* read                 */
+    H5FD_ros3_write,            /* write                */
+    NULL,                       /* flush                */
+    H5FD_ros3_truncate,         /* truncate             */
+    H5FD_ros3_lock,             /* lock                 */
+    H5FD_ros3_unlock,           /* unlock               */
+    H5FD_FLMAP_DICHOTOMY        /* fl_map               */
+};
+
+/* Declare a free list to manage the H5FD_ros3_t struct */
+H5FL_DEFINE_STATIC(H5FD_ros3_t);
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD__init_package
+ *
+ * Purpose:     Initializes any interface-specific data or routines.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Changes:     Rename as appropriate for ros3 vfd.
+ *              Jacob Smith 2017
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD__init_package(void)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_STATIC
+
+    if (H5FD_ros3_init() < 0) {
+        HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, 
+                    "unable to initialize ros3 VFD")
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD__init_package() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_ros3_init
+ *
+ * Purpose:     Initialize this driver by registering the driver with the
+ *              library.
+ *
+ * Return:      Success:    The driver ID for the ros3 driver.
+ *              Failure:    Negative
+ *
+ * Programmer:  Robb Matzke
+ *              Thursday, July 29, 1999
+ *
+ * Changes:     Rename as appropriate for ros3 vfd.
+ *              Jacob Smith 2017
+ *
+ *-------------------------------------------------------------------------
+ */
+hid_t
+H5FD_ros3_init(void)
+{
+    hid_t ret_value = H5I_INVALID_HID; /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_init() called.\n");
+#endif
+
+    if (H5I_VFL != H5I_get_type(H5FD_ROS3_g))
+        H5FD_ROS3_g = H5FD_register(&H5FD_ros3_g, sizeof(H5FD_class_t), FALSE);
+
+#if ROS3_STATS
+    /* pre-compute statsbin boundaries
+     */
+    for (unsigned bin_i = 0; bin_i < ROS3_STATS_BIN_COUNT; bin_i++) {
+        unsigned long long value = 0;
+        ROS3_STATS_POW(bin_i, &value)
+        ros3_stats_boundaries[bin_i] = value;
+    }
+#endif
+
+    /* Set return value */
+    ret_value = H5FD_ROS3_g;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_ros3_init() */
+
+
+/*---------------------------------------------------------------------------
+ * Function:    H5FD_ros3_term
+ *
+ * Purpose:     Shut down the VFD
+ *
+ * Returns:     SUCCEED (Can't fail)
+ *
+ * Programmer:  Quincey Koziol
+ *              Friday, Jan 30, 2004
+ *
+ * Changes:     Rename as appropriate for ros3 vfd.
+ *              Jacob Smith 2017
+ *
+ *---------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_term(void)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_term() called.\n");
+#endif
+
+    /* Reset VFL ID */
+    H5FD_ROS3_g = 0;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5FD_ros3_term() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pset_fapl_ros3
+ *
+ * Purpose:     Modify the file access property list to use the H5FD_ROS3
+ *              driver defined in this source file.  All driver specfic 
+ *              properties are passed in as a pointer to a suitably 
+ *              initialized instance of H5FD_ros3_fapl_t
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  John Mainzer
+ *              9/10/17
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_fapl_ros3(hid_t             fapl_id, 
+                 H5FD_ros3_fapl_t *fa)
+{
+    H5P_genplist_t *plist     = NULL; /* Property list pointer */
+    herr_t          ret_value = FAIL;
+
+
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", fapl_id, fa);
+
+    HDassert(fa != NULL);
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5Pset_fapl_ros3() called.\n");
+#endif
+
+    plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS);
+    if (plist == NULL) { 
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, \
+                    "not a file access property list")
+    }
+
+    if (FAIL == H5FD_ros3_validate_config(fa))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid ros3 config")
+
+    ret_value = H5P_set_driver(plist, H5FD_ROS3, (void *)fa);
+
+done:
+
+    FUNC_LEAVE_API(ret_value)
+
+} /* H5Pset_fapl_ros3() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_ros3_validate_config()
+ *
+ * Purpose:     Test to see if the supplied instance of H5FD_ros3_fapl_t
+ *              contains internally consistant data.  Return SUCCEED if so,
+ *              and FAIL otherwise.
+ *
+ *              Note the difference between internally consistant and 
+ *              correct.  As we will have to try to access the target 
+ *              object to determine whether the supplied data is correct,
+ *              we will settle for internal consistancy at this point
+ *
+ * Return:      SUCCEED if instance of H5FD_ros3_fapl_t contains internally 
+ *              consistant data, FAIL otherwise.
+ *
+ * Programmer:  Jacob Smith
+ *              9/10/17
+ *
+ * Changes:     Add checks for authenticate flag requring populated
+ *              `aws_region` and `secret_id` strings.
+ *                  -- Jacob Smith 2017-11-01
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_validate_config(const H5FD_ros3_fapl_t * fa)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(fa != NULL);
+
+    if ( fa->version != H5FD__CURR_ROS3_FAPL_T_VERSION ) {
+         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                     "Unknown H5FD_ros3_fapl_t version");
+    }
+
+    /* if set to authenticate, region and id cannot be empty strings
+     */
+    if (fa->authenticate == TRUE) {
+        if ((fa->aws_region[0] == '\0') ||
+            (fa->secret_id[0]  == '\0'))
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "Inconsistent authentication information");
+        }
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_ros3_validate_config() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pget_fapl_ros3
+ *
+ * Purpose:     Returns information about the ros3 file access property
+ *              list though the function arguments.
+ *
+ * Return:      Success:        Non-negative
+ *
+ *              Failure:        Negative
+ *
+ * Programmer:  John Mainzer
+ *              9/10/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_fapl_ros3(hid_t             fapl_id, 
+                 H5FD_ros3_fapl_t *fa_out)
+{
+    const H5FD_ros3_fapl_t *fa;
+    H5P_genplist_t         *plist     = NULL;    /* Property list pointer */
+    herr_t                  ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", fapl_id, fa_out);
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5Pget_fapl_ros3() called.\n");
+#endif
+
+    if (fa_out == NULL)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "fa_out is NULL")
+
+    plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS);
+    if (plist == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file access list")
+    }
+
+    if (H5FD_ROS3 != H5P_peek_driver(plist)) {
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "incorrect VFL driver")
+    }
+
+    fa = (const H5FD_ros3_fapl_t *)H5P_peek_driver_info(plist);
+    if (fa == NULL) {
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "bad VFL driver info")
+    }
+
+    /* Copy the ros3 fapl data out */
+    HDmemcpy(fa_out, fa, sizeof(H5FD_ros3_fapl_t));
+
+done:
+    FUNC_LEAVE_API(ret_value)
+
+} /* H5Pget_fapl_ros3() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_ros3_fapl_get
+ *
+ * Purpose:     Gets a file access property list which could be used to
+ *              create an identical file.
+ *
+ * Return:      Success:        Ptr to new file access property list value.
+ *
+ *              Failure:        NULL
+ *
+ * Programmer:  John Mainzer
+ *              9/8/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static void *
+H5FD_ros3_fapl_get(H5FD_t *_file)
+{
+    H5FD_ros3_t      *file      = (H5FD_ros3_t*)_file;
+    H5FD_ros3_fapl_t *fa        = NULL;
+    void             *ret_value = NULL;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    fa = (H5FD_ros3_fapl_t *)H5MM_calloc(sizeof(H5FD_ros3_fapl_t));
+    if (fa == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, 
+                    "memory allocation failed")
+    }
+
+    /* Copy the fields of the structure */
+    HDmemcpy(fa, &(file->fa), sizeof(H5FD_ros3_fapl_t));
+
+    /* Set return value */
+    ret_value = fa;
+
+done:
+    if (ret_value == NULL) {
+        if (fa != NULL)
+            H5MM_xfree(fa); 
+    }
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_ros3_fapl_get() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_ros3_fapl_copy
+ *
+ * Purpose:     Copies the ros3-specific file access properties.
+ *
+ * Return:      Success:        Ptr to a new property list
+ *
+ *              Failure:        NULL
+ *
+ * Programmer:  John Mainzer
+ *              9/8/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static void *
+H5FD_ros3_fapl_copy(const void *_old_fa)
+{
+    const H5FD_ros3_fapl_t *old_fa    = (const H5FD_ros3_fapl_t*)_old_fa;
+    H5FD_ros3_fapl_t       *new_fa    = NULL;
+    void                   *ret_value = NULL;     /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    new_fa = (H5FD_ros3_fapl_t *)H5MM_malloc(sizeof(H5FD_ros3_fapl_t));
+    if (new_fa == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, 
+                    "memory allocation failed");
+    }
+
+    HDmemcpy(new_fa, old_fa, sizeof(H5FD_ros3_fapl_t));
+    ret_value = new_fa;
+
+done:
+    if (ret_value == NULL) {
+        if (new_fa != NULL)
+            H5MM_xfree(new_fa);
+    }
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_ros3_fapl_copy() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_ros3_fapl_free
+ *
+ * Purpose:     Frees the ros3-specific file access properties.
+ *
+ * Return:      SUCCEED (cannot fail)
+ *
+ * Programmer:  John Mainzer
+ *              9/8/17
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_fapl_free(void *_fa)
+{
+    H5FD_ros3_fapl_t *fa = (H5FD_ros3_fapl_t*)_fa;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(fa != NULL); /* sanity check */ 
+
+    H5MM_xfree(fa);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* H5FD_ros3_fapl_free() */
+
+#if ROS3_STATS
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: ros3_reset_stats()
+ *
+ * Purpose:
+ *
+ *     Reset the stats collection elements in this virtual file structure.
+ *
+ *     Clears any set data in stats bins; initializes/zeroes values.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - Occurs if the file is invalid somehow
+ *
+ * Programmer: Jacob Smith
+ *             2017-12-08
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+static herr_t
+ros3_reset_stats(H5FD_ros3_t *file)
+{
+    unsigned i         = 0;
+    herr_t   ret_value = SUCCEED;
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if ROS3_DEBUG
+    HDprintf("ros3_reset_stats() called\n");
+#endif
+
+    if (file == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file was null");
+    }
+
+    for (i = 0; i <= ROS3_STATS_BIN_COUNT; i++) {
+        file->raw[i].bytes  = 0;
+        file->raw[i].count  = 0;
+        file->raw[i].min    = (unsigned long long)ROS3_STATS_STARTING_MIN;
+        file->raw[i].max    = 0;
+
+        file->meta[i].bytes = 0;
+        file->meta[i].count = 0;
+        file->meta[i].min   = (unsigned long long)ROS3_STATS_STARTING_MIN;
+        file->meta[i].max   = 0;
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* ros3_reset_stats */
+#endif /* ROS3_STATS */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_open()
+ *
+ * Purpose:
+ *
+ *     Create and/or opens a file as an HDF5 file.
+ *
+ *     Any flag except H5F_ACC_RDONLY will cause an error.
+ * 
+ *     Name (as received from `H5FD_open()`) must conform to web url:
+ *         NAME   :: HTTP "://" DOMAIN [PORT] ["/" [URI] [QUERY] ]
+ *         HTTP   :: "http" [ "s" ] 
+ *         DOMAIN :: e.g., "mybucket.host.org"
+ *         PORT   :: ":" <number> (e.g., ":9000" )
+ *         URI    :: <string> (e.g., "path/to/resource.hd5" )
+ *         QUERY  :: "?" <string> (e.g., "arg1=param1&arg2=param2")
+ *
+ * Return:
+ *
+ *     Success: A pointer to a new file data structure. 
+ *              The public fields will be initialized by the caller, which is 
+ *              always H5FD_open().
+ *
+ *     Failure: NULL
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static H5FD_t *
+H5FD_ros3_open(const char *url, 
+               unsigned    flags, 
+               hid_t       fapl_id, 
+               haddr_t     maxaddr)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    H5FD_ros3_t      *file      = NULL;
+    struct tm        *now       = NULL;
+    char              iso8601now[ISO8601_SIZE];
+    unsigned char     signing_key[SHA256_DIGEST_LENGTH];
+    s3r_t            *handle    = NULL;
+    H5FD_ros3_fapl_t  fa;
+#endif
+    H5FD_t           *ret_value = NULL;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+#ifdef H5_HAVE_ROS3_VFD
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_open() called.\n");
+#endif
+
+
+    /* Sanity check on file offsets */
+    HDcompile_assert(sizeof(HDoff_t) >= sizeof(size_t));
+
+    /* Check arguments */
+    if (!url || !*url)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL, "invalid file name")
+    if (0 == maxaddr || HADDR_UNDEF == maxaddr)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, NULL, "bogus maxaddr")
+    if (ADDR_OVERFLOW(maxaddr))
+        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, NULL, "bogus maxaddr")
+    if (flags != H5F_ACC_RDONLY)
+        HGOTO_ERROR(H5E_ARGS, H5E_UNSUPPORTED, NULL,
+                    "only Read-Only access allowed")
+
+    if (FAIL == H5Pget_fapl_ros3(fapl_id, &fa)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL, "can't get property list")
+    }
+
+    if (CURLE_OK != curl_global_init(CURL_GLOBAL_DEFAULT)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "unable to initialize curl global (placeholder flags)")
+    }
+
+    /* open file; procedure depends on whether or not the fapl instructs to
+     * authenticate requests or not.
+     */
+    if (fa.authenticate == TRUE) {
+        /* compute signing key (part of AWS/S3 REST API)
+         * can be re-used by user/key for 7 days after creation.
+         * find way to re-use/share
+         */
+        now = gmnow();
+        HDassert( now != NULL );
+        if (ISO8601NOW(iso8601now, now) != (ISO8601_SIZE - 1)) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "problem while writing iso8601 timestamp")
+        }
+        if (FAIL == H5FD_s3comms_signing_key(signing_key,
+                                             (const char *)fa.secret_key,
+                                             (const char *)fa.aws_region,
+                                             (const char *)iso8601now) ) 
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "problem while computing signing key")
+        }
+
+        handle = H5FD_s3comms_s3r_open(
+                 url,
+                 (const char *)fa.aws_region,
+                 (const char *)fa.secret_id,
+                 (const unsigned char *)signing_key);
+    } else {
+        handle = H5FD_s3comms_s3r_open(url, NULL, NULL, NULL);
+    } /* if/else should authenticate */
+
+    if (handle == NULL) {
+        /* If we want to check CURL's say on the matter in a controlled
+         * fashion, this is the place to do it, but would need to make a 
+         * few minor changes to s3comms `s3r_t` and `s3r_read()`.
+         */ 
+        HGOTO_ERROR(H5E_VFL, H5E_CANTOPENFILE, NULL, "could not open");
+    }
+
+    /* create new file struct 
+     */
+    file = H5FL_CALLOC(H5FD_ros3_t);
+    if (file == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, 
+                    "unable to allocate file struct")
+    }
+
+    file->s3r_handle = handle;
+    HDmemcpy(&(file->fa), &fa, sizeof(H5FD_ros3_fapl_t));
+
+#if ROS3_STATS
+    if (FAIL == ros3_reset_stats(file)) {
+        HGOTO_ERROR(H5E_INTERNAL, H5E_UNINITIALIZED, NULL, 
+                    "unable to reset file statistics")
+    }
+#endif /* ROS3_STATS */
+
+    ret_value = (H5FD_t*)file;
+
+done:
+    if (ret_value == NULL) {
+        if (handle != NULL) { 
+            if (FAIL == H5FD_s3comms_s3r_close(handle)) {
+                HDONE_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, NULL, 
+                            "unable to close s3 file handle")
+            }
+        }
+        if (file != NULL) {
+            file = H5FL_FREE(H5FD_ros3_t, file);
+        }
+        curl_global_cleanup(); /* early cleanup because open failed */
+    } /* if null return value (error) */
+#endif /* H5_HAVE_ROS3_VFD */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_ros3_open() */
+
+#if ROS3_STATS
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: ros3_fprint_stats()
+ *
+ * Purpose:
+ * 
+ *     Tabulate and pretty-print statistics for this virtual file.
+ *
+ *     Should be called upon file close.
+ *
+ *     Shows number of reads and bytes read, broken down by
+ *     "raw" (H5FD_MEM_DRAW)
+ *     or "meta" (any other flag)
+ *
+ *     Prints filename and listing of total number of reads and bytes read,
+ *     both as a grand total and separate  meta- and rawdata reads.
+ *
+ *     If any reads were done, prints out two tables:
+ *
+ *     1. overview of raw- and metadata reads
+ *         - min (smallest size read)
+ *         - average of size read
+ *             - k,M,G suffixes by powers of 1024 (2^10)
+ *         - max (largest size read)
+ *     2. tabulation of "bins", sepraring reads into exponentially-larger
+ *        ranges of size.
+ *         - columns for number of reads, total bytes, and average size, with 
+ *           separate sub-colums for raw- and metadata reads.
+ *         - each row represents one bin, identified by the top of its range
+ *     
+ *     Bin ranges can be modified with pound-defines at the top of this file.
+ *
+ *     Bins without any reads in their bounds are not printed.
+ *
+ *     An "overflow" bin is also present, to catch "big" reads.
+ *
+ *     Output for all bins (and range ceiling and average size report) 
+ *     is divied by powers of 1024. By corollary, four digits before the decimal
+ *     is valid.
+ *
+ *     - 41080 bytes is represented by 40.177k, not 41.080k
+ *     - 1004.831M represents approx. 1052642000 bytes
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - occurs if the file passed in is invalid
+ *         - TODO: if stream is invalid? how can we check this?
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+static herr_t
+ros3_fprint_stats(FILE              *stream,
+                  const H5FD_ros3_t *file)
+{
+    herr_t             ret_value    = SUCCEED;
+    parsed_url_t      *purl         = NULL;
+    unsigned           i            = 0;
+    unsigned long      count_meta   = 0;
+    unsigned long      count_raw    = 0;
+    double             average_meta = 0.0;
+    double             average_raw  = 0.0;
+    unsigned long long min_meta   = (unsigned long long)ROS3_STATS_STARTING_MIN;
+    unsigned long long min_raw    = (unsigned long long)ROS3_STATS_STARTING_MIN;
+    unsigned long long max_meta     = 0;
+    unsigned long long max_raw      = 0;
+    unsigned long long bytes_raw    = 0;
+    unsigned long long bytes_meta   = 0;
+    double             re_dub       = 0.0; /* re-usable double variable */
+    unsigned           suffix_i     = 0;
+    const char         suffixes[]   = { ' ', 'K', 'M', 'G', 'T', 'P' };
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    if (stream == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file stream cannot be null" );
+    }
+    if (file == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "file cannot be null");
+    }
+    if (file->s3r_handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "s3 request handle cannot be null");
+    }
+    if (file->s3r_handle->purl == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "parsed url structure cannot be null");
+    }
+    purl = file->s3r_handle->purl;
+
+    /******************
+     * PRINT FILENAME *
+     ******************/
+
+    HDfprintf(stream, "stats for %s://%s", purl->scheme, purl->host);
+    if (purl->port != NULL && purl->port[0] != '\0')
+        HDfprintf(stream, ":%s", purl->port);
+    if (purl->query != NULL && purl->query[0] != '\0') {
+        if (purl->path != NULL && purl->path[0] != '\0')
+            HDfprintf(stream, "/%s", purl->path);
+        else
+            HDfprintf(stream, "/");
+        HDfprintf(stream, "?%s", purl->query);
+    } else if (purl->path != NULL && purl->path[0] != '\0') {
+        HDfprintf(stream, "/%s", purl->path);
+    }
+    HDfprintf(stream, "\n");
+
+    /*******************
+     * AGGREGATE STATS *
+     *******************/
+
+    for (i = 0; i <= ROS3_STATS_BIN_COUNT; i++) {
+        const ros3_statsbin *r = &file->raw[i];
+        const ros3_statsbin *m = &file->meta[i];
+
+        if (m->min < min_meta)  min_meta = m->min;
+        if (r->min < min_raw)   min_raw  = r->min;
+        if (m->max > max_meta)  max_meta = m->max;
+        if (r->max > max_raw)   max_raw  = r->max;
+
+        count_raw  += r->count;
+        count_meta += m->count;
+        bytes_raw  += r->bytes;
+        bytes_meta += m->bytes;
+    }
+    if (count_raw > 0)
+        average_raw = (double)bytes_raw / (double)count_raw;
+    if (count_meta > 0)
+        average_meta = (double)bytes_meta / (double)count_meta;
+
+    /******************
+     * PRINT OVERVIEW *
+     ******************/
+
+    HDfprintf(stream, "TOTAL READS: %llu  (%llu meta, %llu raw)\n",
+              count_raw + count_meta, count_meta, count_raw);
+    HDfprintf(stream, "TOTAL BYTES: %llu  (%llu meta, %llu raw)\n",
+              bytes_raw + bytes_meta, bytes_meta, bytes_raw);
+
+    if (count_raw + count_meta == 0) 
+        goto done;
+
+    /*************************
+     * PRINT AGGREGATE STATS *
+     *************************/
+
+    HDfprintf(stream, "SIZES     meta      raw\n");
+    HDfprintf(stream, "  min ");
+    if (count_meta == 0) {
+        HDfprintf(stream, "   0.000  ");
+    } else {
+        re_dub = (double)min_meta;
+        for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+            re_dub /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+        HDfprintf(stream, "%8.3lf%c ", re_dub, suffixes[suffix_i]);
+    }
+
+    if (count_raw == 0) {
+        HDfprintf(stream, "   0.000 \n");
+    } else {
+        re_dub = (double)min_raw;
+        for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+            re_dub /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+        HDfprintf(stream, "%8.3lf%c\n", re_dub, suffixes[suffix_i]);
+    }
+
+    HDfprintf(stream, "  avg ");
+    re_dub = (double)average_meta;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+        re_dub /= 1024.0;
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c ", re_dub, suffixes[suffix_i]);
+
+    re_dub = (double)average_raw;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+        re_dub /= 1024.0;
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c\n", re_dub, suffixes[suffix_i]);
+
+    HDfprintf(stream, "  max ");
+    re_dub = (double)max_meta;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+        re_dub /= 1024.0;
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c ", re_dub, suffixes[suffix_i]);
+
+    re_dub = (double)max_raw;
+    for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+        re_dub /= 1024.0;
+    HDassert(suffix_i < sizeof(suffixes));
+    HDfprintf(stream, "%8.3lf%c\n", re_dub, suffixes[suffix_i]);
+
+    /******************************
+     * PRINT INDIVIDUAL BIN STATS *
+     ******************************/
+
+    HDfprintf(stream, 
+        "BINS             # of reads      total bytes         average size\n");
+    HDfprintf(stream, 
+        "    up-to      meta     raw     meta      raw       meta      raw\n");
+
+    for (i = 0; i <= ROS3_STATS_BIN_COUNT; i++) {
+        const ros3_statsbin *m;
+        const ros3_statsbin *r;
+        unsigned long long   range_end = 0;
+        char                 bm_suffix = ' '; /* bytes-meta */
+        double               bm_val    = 0.0;
+        char                 br_suffix = ' '; /* bytes-raw */
+        double               br_val    = 0.0;
+        char                 am_suffix = ' '; /* average-meta */
+        double               am_val    = 0.0;
+        char                 ar_suffix = ' '; /* average-raw */
+        double               ar_val    = 0.0;
+
+        m = &file->meta[i];
+        r = &file->raw[i];
+        if (r->count == 0 && m->count == 0) 
+            continue;
+
+        range_end = ros3_stats_boundaries[i];
+
+        if (i == ROS3_STATS_BIN_COUNT) {
+            range_end = ros3_stats_boundaries[i-1];
+            HDfprintf(stream, ">");
+        } else {
+            HDfprintf(stream, " ");
+        }
+
+        bm_val = (double)m->bytes;
+        for (suffix_i = 0; bm_val >= 1024.0; suffix_i++)
+            bm_val /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+        bm_suffix = suffixes[suffix_i];
+
+        br_val = (double)r->bytes;
+        for (suffix_i = 0; br_val >= 1024.0; suffix_i++)
+            br_val /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+        br_suffix = suffixes[suffix_i];
+
+        if (m->count > 0)
+            am_val = (double)(m->bytes) / (double)(m->count);
+        for (suffix_i = 0; am_val >= 1024.0; suffix_i++)
+            am_val /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+        am_suffix = suffixes[suffix_i];
+
+        if (r->count > 0)
+            ar_val = (double)(r->bytes) / (double)(r->count);
+        for (suffix_i = 0; ar_val >= 1024.0; suffix_i++)
+            ar_val /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+        ar_suffix = suffixes[suffix_i];
+
+        re_dub = (double)range_end;
+        for (suffix_i = 0; re_dub >= 1024.0; suffix_i++)
+            re_dub /= 1024.0;
+        HDassert(suffix_i < sizeof(suffixes));
+
+        HDfprintf(stream, 
+                  " %8.3f%c %7d %7d %8.3f%c %8.3f%c %8.3f%c %8.3f%c\n",
+                  re_dub, suffixes[suffix_i], /* bin ceiling      */
+                  m->count,                   /* metadata reads   */
+                  r->count,                   /* rawdata reads    */
+                  bm_val, bm_suffix,          /* metadata bytes   */
+                  br_val, br_suffix,          /* rawdata bytes    */
+                  am_val, am_suffix,          /* metadata average */
+                  ar_val, ar_suffix);         /* rawdata average  */
+
+        fflush(stream);
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+    
+} /* ros3_fprint_stats */
+#endif /* ROS3_STATS */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_close()
+ *
+ * Purpose:
+ *
+ *     Close an HDF5 file.
+ *
+ * Return:
+ * 
+ *     SUCCEED/FAIL
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_close(H5FD_t *_file)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    H5FD_ros3_t *file      = (H5FD_ros3_t *)_file;
+    herr_t       ret_value = SUCCEED;
+#else
+    herr_t       ret_value = FAIL;
+#endif
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+#ifdef H5_HAVE_ROS3_VFD
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_close() called.\n");
+#endif
+
+    /* Sanity checks 
+     */
+    HDassert(file != NULL);
+    HDassert(file->s3r_handle != NULL);
+
+    /* Close the underlying request handle 
+     */
+    if (FAIL == H5FD_s3comms_s3r_close(file->s3r_handle)) {
+        HGOTO_ERROR(H5E_VFL, H5E_CANTCLOSEFILE, FAIL, 
+                    "unable to close S3 request handle")
+    }
+
+#if ROS3_STATS
+    /* TODO: mechanism to re-target stats printout */
+    if (FAIL == ros3_fprint_stats(stdout, file)) {
+        HGOTO_ERROR(H5E_INTERNAL, H5E_ERROR, FAIL, 
+                    "problem while writing file statistics")
+    }
+#endif /* ROS3_STATS */
+
+    /* Release the file info 
+     */
+    file = H5FL_FREE(H5FD_ros3_t, file);
+
+done:
+    curl_global_cleanup(); /* cleanup to answer init on open */
+#endif /* H5_HAVE_ROS3_VFD */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_ros3_close() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_cmp()
+ *
+ * Purpose:
+ *
+ *     Compares two files belonging to this driver using an arbitrary 
+ *     (but consistent) ordering:
+ *
+ *     + url scheme
+ *     + url host
+ *     + url port
+ *     + url path
+ *     + url query
+ *     + fapl aws_region
+ *     + fapl secret_id
+ *     + fapl secret_key
+ *
+ *     tl;dr -> check URL, check crentials
+ *
+ * Return:
+ *      
+ *     - Equivalent:      0
+ *     - Not Equivalent: -1
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-06
+ *
+ * Changes:
+ *
+ *     + Change from strcmp-like return values (-1, 0, 1) to instead return
+ *       binary equivalence (0) or inequality (-1).
+ *     + Replace "if still equal then check this" waterfall with GOTO jumps.
+ *     Jacob Smith 2018-05-17
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+H5FD_ros3_cmp(const H5FD_t *_f1,
+              const H5FD_t *_f2)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    const H5FD_ros3_t  *f1        = (const H5FD_ros3_t *)_f1;
+    const H5FD_ros3_t  *f2        = (const H5FD_ros3_t *)_f2;
+    const parsed_url_t *purl1     = NULL;
+    const parsed_url_t *purl2     = NULL;
+#endif
+    int                 ret_value = 0;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+#ifdef H5_HAVE_ROS3_VFD
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_cmp() called.\n");
+#endif
+
+    HDassert(f1->s3r_handle != NULL);
+    HDassert(f2->s3r_handle != NULL);
+
+    purl1 = (const parsed_url_t *)f1->s3r_handle->purl;
+    purl2 = (const parsed_url_t *)f2->s3r_handle->purl;
+    HDassert(purl1 != NULL);
+    HDassert(purl2 != NULL);
+    HDassert(purl1->scheme != NULL);
+    HDassert(purl2->scheme != NULL);
+    HDassert(purl1->host != NULL);
+    HDassert(purl2->host != NULL);
+
+    /* URL: SCHEME */
+    if (HDstrcmp(purl1->scheme, purl2->scheme)) HGOTO_DONE(-1);
+
+    /* URL: HOST */
+    if (HDstrcmp(purl1->host, purl2->host)) HGOTO_DONE(-1);
+
+    /* URL: PORT */
+    if (purl1->port && purl2->port) {
+        if (HDstrcmp(purl1->port, purl2->port)) HGOTO_DONE(-1);
+    } else if (purl1->port) {
+        HGOTO_DONE(-1);
+    } else if (purl2->port) {
+        HGOTO_DONE(-1);
+    }
+
+    /* URL: PATH */
+    if (purl1->path && purl2->path) {
+        if (HDstrcmp(purl1->path, purl2->path)) HGOTO_DONE(-1);
+    } else if (purl1->path && !purl2->path) {
+        HGOTO_DONE(-1);
+    } else if (purl2->path && !purl1->path) {
+        HGOTO_DONE(-1);
+    }
+
+    /* URL: QUERY */
+    if (purl1->query && purl2->query) {
+        if (HDstrcmp(purl1->query, purl2->query)) HGOTO_DONE(-1);
+    } else if (purl1->query && !purl2->query) {
+        HGOTO_DONE(-1);
+    } else if (purl2->query && !purl1->query) {
+        HGOTO_DONE(-1);
+    }
+
+    /* FAPL: AWS_REGION */
+    if (f1->fa.aws_region[0] != '\0' && f1->fa.aws_region[0] != '\0') {
+        if (HDstrcmp(f1->fa.aws_region, f2->fa.aws_region)) HGOTO_DONE(-1);
+    } else if (f1->fa.aws_region[0] != '\0') {
+        HGOTO_DONE(-1);
+    } else if (f2->fa.aws_region[0] != '\0') {
+        HGOTO_DONE(-1);
+    }
+
+    /* FAPL: SECRET_ID */
+    if (f1->fa.secret_id[0] != '\0' && f1->fa.secret_id[0] != '\0') {
+        if (HDstrcmp(f1->fa.secret_id, f2->fa.secret_id)) HGOTO_DONE(-1);
+    } else if (f1->fa.secret_id[0] != '\0') {
+        HGOTO_DONE(-1);
+    } else if (f2->fa.secret_id[0] != '\0') {
+        HGOTO_DONE(-1);
+    }
+
+    /* FAPL: SECRET_KEY */
+    if (f1->fa.secret_key[0] != '\0' && f1->fa.secret_key[0] != '\0') {
+        if (HDstrcmp(f1->fa.secret_key, f2->fa.secret_key)) HGOTO_DONE(-1);
+    } else if (f1->fa.secret_key[0] != '\0') {
+        HGOTO_DONE(-1);
+    } else if (f2->fa.secret_key[0] != '\0') {
+        HGOTO_DONE(-1);
+    }
+#endif /* H5_HAVE_ROS3_VFD */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_ros3_cmp() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5FD_ros3_query
+ *
+ * Purpose:     Set the flags that this VFL driver is capable of supporting.
+ *              (listed in H5FDpublic.h)
+ *
+ *              Note that since the ROS3 VFD is read only, most flags 
+ *              are irrelevant.
+ *
+ *              The term "set" is highly misleading...
+ *              stores/copies the supported flags in the out-pointer `flags`.
+ *
+ * Return:      SUCCEED (Can't fail)
+ *
+ * Programmer:  John Mainzer
+ *              9/11/17
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_query(const H5FD_t H5_ATTR_UNUSED *_file, 
+                unsigned long *flags /* out */)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_query() called.\n");
+#endif
+
+    /* Set the VFL feature flags that this driver supports */
+    if (flags) {
+        *flags = 0;
+        /* OK to perform data sieving for faster raw data reads & writes */
+        *flags |= H5FD_FEAT_DATA_SIEVE; 
+    } /* end if */
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* H5FD_ros3_query() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_get_eoa()
+ *
+ * Purpose:
+ *
+ *     Gets the end-of-address marker for the file. The EOA marker
+ *     is the first address past the last byte allocated in the
+ *     format address space.
+ *
+ * Return:
+ *
+ *     The end-of-address marker.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static haddr_t
+H5FD_ros3_get_eoa(const H5FD_t                *_file, 
+                  H5FD_mem_t   H5_ATTR_UNUSED  type)
+{
+    const H5FD_ros3_t *file = (const H5FD_ros3_t *)_file;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_get_eoa() called.\n");
+#endif
+
+    FUNC_LEAVE_NOAPI(file->eoa)
+
+} /* end H5FD_ros3_get_eoa() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_set_eoa()
+ *
+ * Purpose:
+ *
+ *     Set the end-of-address marker for the file.
+ *
+ * Return:
+ *
+ *      SUCCEED  (can't fail)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-03
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_set_eoa(H5FD_t                    *_file, 
+                  H5FD_mem_t H5_ATTR_UNUSED  type, 
+                  haddr_t                    addr)
+{
+    H5FD_ros3_t *file = (H5FD_ros3_t *)_file;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_set_eoa() called.\n");
+#endif
+
+    file->eoa = addr;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* H5FD_ros3_set_eoa() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_get_eof()
+ *
+ * Purpose:
+ *
+ *     Returns the end-of-file marker.
+ *
+ * Return:
+ *
+ *     EOF: the first address past the end of the "file", either the 
+ *     filesystem file or the HDF5 file.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ *-------------------------------------------------------------------------
+ */
+static haddr_t
+H5FD_ros3_get_eof(const H5FD_t                *_file, 
+                  H5FD_mem_t   H5_ATTR_UNUSED  type)
+{
+    const H5FD_ros3_t *file = (const H5FD_ros3_t *)_file;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_get_eof() called.\n");
+#endif
+
+    FUNC_LEAVE_NOAPI(H5FD_s3comms_s3r_get_filesize(file->s3r_handle))
+
+} /* end H5FD_ros3_get_eof() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_get_handle()
+ *
+ * Purpose:
+ *
+ *     Returns the S3 Request handle (s3r_t) of ros3 file driver.
+ *
+ * Returns:
+ *
+ *     SUCCEED/FAIL
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-02
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_get_handle(H5FD_t                *_file, 
+                     hid_t H5_ATTR_UNUSED   fapl, 
+                     void                 **file_handle)
+{
+    H5FD_ros3_t *file      = (H5FD_ros3_t *)_file;
+    herr_t       ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_get_handle() called.\n");
+#endif
+
+    if(!file_handle)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file handle not valid")
+
+    *file_handle = file->s3r_handle;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_ros3_get_handle() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_read()
+ *
+ * Purpose: 
+ *
+ *     Reads SIZE bytes of data from FILE beginning at address ADDR
+ *     into buffer BUF according to data transfer properties in DXPL_ID.
+ *
+ * Return:
+ *
+ *     Success: `SUCCEED`
+ *         - Result is stored in caller-supplied buffer BUF.
+ *     Failure: `FAIL`
+ *         - Unable to complete read.
+ *         - Contents of buffer `buf` are undefined.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-??
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_read(H5FD_t                    *_file, 
+               H5FD_mem_t H5_ATTR_UNUSED  type, 
+               hid_t      H5_ATTR_UNUSED  dxpl_id,
+               haddr_t                    addr, /* start offset   */
+               size_t                     size, /* length of read */
+               void                      *buf)  /* out            */
+{
+    H5FD_ros3_t *file      = (H5FD_ros3_t *)_file;
+    size_t       filesize  = 0;
+    herr_t       ret_value = SUCCEED;                  /* Return value */
+#if ROS3_STATS
+    /* working variables for storing stats */
+    ros3_statsbin *bin   = NULL;
+    unsigned       bin_i = 0;
+#endif /* ROS3_STATS */
+    
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_read() called.\n");
+#endif
+
+    HDassert(file != NULL);
+    HDassert(file->s3r_handle != NULL);
+    HDassert(buf != NULL);
+
+    filesize = H5FD_s3comms_s3r_get_filesize(file->s3r_handle);
+
+    if ((addr > filesize) || ((addr + size) > filesize)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "range exceeds file address")
+    }
+
+    if (FAIL == H5FD_s3comms_s3r_read(file->s3r_handle, addr, size, buf) ) {
+        HGOTO_ERROR(H5E_VFL, H5E_READERROR, FAIL, "unable to execute read")
+    }
+
+#if ROS3_STATS
+
+    /* Find which "bin" this read fits in. Can be "overflow" bin.
+     */
+    for (bin_i = 0; bin_i < ROS3_STATS_BIN_COUNT; bin_i++) {
+        if ((unsigned long long)size < ros3_stats_boundaries[bin_i])
+            break;
+    }
+    bin = (type == H5FD_MEM_DRAW)
+        ? &file->raw[bin_i]
+        : &file->meta[bin_i];
+
+    /* Store collected stats in appropriate bin 
+     */
+    if (bin->count == 0) {
+        bin->min = size;
+        bin->max = size;
+    } else {
+        if (size < bin->min) 
+            bin->min = size;
+        if (size > bin->max)
+            bin->max = size;
+    }
+    bin->count++;
+    bin->bytes += (unsigned long long)size;
+
+#endif /* ROS3_STATS */
+
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_ros3_read() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_write()
+ *
+ * Purpose: 
+ *
+ *     Write bytes to file.
+ *     UNSUPPORTED IN READ-ONLY ROS3 VFD.
+ *
+ * Return: 
+ *
+ *     FAIL (Not possible with Read-Only S3 file.)
+ *
+ * Programmer: Jacob Smith
+ *             2017-10-23
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_write(H5FD_t     H5_ATTR_UNUSED *_file, 
+                H5FD_mem_t H5_ATTR_UNUSED  type, 
+                hid_t      H5_ATTR_UNUSED  dxpl_id,
+                haddr_t    H5_ATTR_UNUSED  addr, 
+                size_t     H5_ATTR_UNUSED  size, 
+                const void H5_ATTR_UNUSED *buf)
+{
+    herr_t ret_value = FAIL;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_write() called.\n");
+#endif
+
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL,
+                "cannot write to read-only file.")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_ros3_write() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_truncate()
+ *
+ * Purpose:
+ *
+ *     Makes sure that the true file size is the same (or larger)
+ *     than the end-of-address.
+ *
+ *     NOT POSSIBLE ON READ-ONLY S3 FILES.
+ *
+ * Return:
+ *
+ *     FAIL (Not possible on Read-Only S3 files.)
+ *
+ * Programmer: Jacob Smith
+ *             2017-10-23
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_truncate(H5FD_t  H5_ATTR_UNUSED *_file, 
+                   hid_t   H5_ATTR_UNUSED  dxpl_id, 
+                   hbool_t H5_ATTR_UNUSED  closing)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if ROS3_DEBUG
+    HDfprintf(stdout, "H5FD_ros3_truncate() called.\n");
+#endif
+
+    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL,
+                "cannot truncate read-only file.")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5FD_ros3_truncate() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_lock()
+ *
+ * Purpose:
+ *
+ *     Place an advisory lock on a file.
+ *     No effect on Read-Only S3 file.
+ *
+ *     Suggestion: remove lock/unlock from class
+ *               > would result in error at H5FD_[un]lock() (H5FD.c)
+ *
+ * Return:
+ *
+ *     SUCCEED (No-op always succeeds)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-03
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_lock(H5FD_t  H5_ATTR_UNUSED *_file, 
+               hbool_t H5_ATTR_UNUSED  rw)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* end H5FD_ros3_lock() */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function: H5FD_ros3_unlock()
+ *
+ * Purpose:
+ *
+ *     Remove the existing lock on the file.
+ *     No effect on Read-Only S3 file.
+ *
+ * Return:
+ *
+ *     SUCCEED (No-op always succeeds)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-03
+ *
+ * Changes: None.
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5FD_ros3_unlock(H5FD_t H5_ATTR_UNUSED *_file)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+    FUNC_LEAVE_NOAPI(SUCCEED)
+
+} /* end H5FD_ros3_unlock() */
+
+
diff --git a/src/H5FDros3.h b/src/H5FDros3.h
new file mode 100644
index 0000000..7dfc95b
--- /dev/null
+++ b/src/H5FDros3.h
@@ -0,0 +1,105 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Read-Only S3 Virtual File Driver (VFD)                                   
+ *
+ * Programmer:  John Mainzer
+ *              2017-10-10
+ *
+ * Purpose:	The public header file for the ros3 driver.
+ */
+#ifndef H5FDros3_H
+#define H5FDros3_H
+
+#define H5FD_ROS3 (H5FD_ros3_init())
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/****************************************************************************
+ *
+ * Structure: H5FD_ros3_fapl_t
+ *
+ * Purpose:
+ *
+ *     H5FD_ros3_fapl_t is a public structure that is used to pass S3 
+ *     authentication data to the appropriate S3 VFD via the FAPL.  A pointer 
+ *     to an instance of this structure is a parameter to H5Pset_fapl_ros3() 
+ *     and H5Pget_fapl_ros3().
+ *
+ *
+ *
+ * `version` (int32_t)
+ *
+ *     Version number of the H5FD_ros3_fapl_t structure.  Any instance passed 
+ *     to the above calls must have a recognized version number, or an error
+ *     will be flagged.
+ *
+ *     This field should be set to H5FD__CURR_ROS3_FAPL_T_VERSION.
+ *
+ * `authenticate` (hbool_t)
+ *
+ *     Flag TRUE or FALSE whether or not requests are to be authenticated
+ *     with the AWS4 algorithm. 
+ *     If TRUE, `aws_region`, `secret_id`, and `secret_key` must be populated. 
+ *     If FALSE, those three components are unused.
+ *
+ * `aws_region` (char[])
+ *
+ *     String: name of the AWS "region" of the host, e.g. "us-east-1".
+ *
+ * `secret_id` (char[])
+ *
+ *     String: "Access ID" for the resource.
+ *
+ * `secret_key` (char[])
+ *
+ *     String: "Secret Access Key" associated with the ID and resource.
+ *
+ *
+ *
+ * Programmer: John Mainzer
+ *
+ * Changes:
+ *
+ *     - Add documentation of fields (except `version`)
+ *     --- Jacob Smith 2017-12-04
+ *
+ ****************************************************************************/
+
+#define H5FD__CURR_ROS3_FAPL_T_VERSION     1
+
+#define H5FD__ROS3_MAX_REGION_LEN         32
+#define H5FD__ROS3_MAX_SECRET_ID_LEN     128
+#define H5FD__ROS3_MAX_SECRET_KEY_LEN    128
+
+typedef struct H5FD_ros3_fapl_t {
+    int32_t version;
+    hbool_t authenticate;
+    char    aws_region[H5FD__ROS3_MAX_REGION_LEN + 1];
+    char    secret_id[H5FD__ROS3_MAX_SECRET_ID_LEN + 1];
+    char    secret_key[H5FD__ROS3_MAX_SECRET_KEY_LEN + 1];
+} H5FD_ros3_fapl_t;
+
+H5_DLL hid_t H5FD_ros3_init(void);
+H5_DLL herr_t H5Pget_fapl_ros3(hid_t fapl_id, H5FD_ros3_fapl_t * fa_out);
+H5_DLL herr_t H5Pset_fapl_ros3(hid_t fapl_id, H5FD_ros3_fapl_t * fa);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ifndef H5FDros3_H */
+
+
diff --git a/src/H5FDs3comms.c b/src/H5FDs3comms.c
new file mode 100644
index 0000000..8c0515d
--- /dev/null
+++ b/src/H5FDs3comms.c
@@ -0,0 +1,3775 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*****************************************************************************
+ * Read-Only S3 Virtual File Driver (VFD)                                   
+ *
+ * Source for S3 Communications module
+ *
+ * ***NOT A FILE DRIVER***
+ *
+ * Provide functions and structures required for interfacing with Amazon
+ * Simple Storage Service (S3).
+ *
+ * Provide S3 object access as if it were a local file.
+ *
+ * Connect to remote host, send and receive HTTP requests and responses
+ * as part of the AWS REST API, authenticating requests as appropriate.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-30
+ *
+ *****************************************************************************/
+
+/****************/
+/* Module Setup */
+/****************/
+
+/***********/
+/* Headers */
+/***********/
+
+#include "H5private.h"   /* generic functions */
+#include "H5Eprivate.h"  /* error handling    */
+#include "H5MMprivate.h" /* memory management */
+#include "H5FDs3comms.h" /* S3 Communications */
+
+/****************/
+/* Local Macros */
+/****************/
+
+/* toggle debugging (enable with 1)
+ */
+#define S3COMMS_DEBUG 0
+
+/* manipulate verbosity of CURL output
+ * operates separately from S3COMMS_DEBUG
+ *
+ * 0 -> no explicit curl output
+ * 1 -> on error, print failure info to stderr
+ * 2 -> in addition to above, print information for all performs; sets all
+ *      curl handles with CURLOPT_VERBOSE
+ */
+#define S3COMMS_CURL_VERBOSITY 0
+
+/* size to allocate for "bytes=<first_byte>[-<last_byte>]" HTTP Range value
+ */
+#define S3COMMS_MAX_RANGE_STRING_SIZE 128
+
+/******************/
+/* Local Typedefs */
+/******************/
+
+/********************/
+/* Local Structures */
+/********************/
+
+/* struct s3r_datastruct
+ * Structure passed to curl write callback
+ * pointer to data region and record of bytes written (offset)
+ */
+struct s3r_datastruct {
+    unsigned long  magic;
+    char          *data;
+    size_t         size;
+};
+#define S3COMMS_CALLBACK_DATASTRUCT_MAGIC 0x28c2b2ul
+
+/********************/
+/* Local Prototypes */
+/********************/
+
+size_t curlwritecallback(char   *ptr,
+                         size_t  size,
+                         size_t  nmemb,
+                         void   *userdata);
+
+herr_t H5FD_s3comms_s3r_getsize(s3r_t *handle);
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+/*******************/
+/* Local Variables */
+/*******************/
+
+/*************/
+/* Functions */
+/*************/
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: curlwritecallback()
+ *
+ * Purpose:
+ *
+ *     Function called by CURL to write received data.
+ *
+ *     Writes bytes to `userdata`.
+ *
+ *     Internally manages number of bytes processed.
+ *
+ * Return:
+ *
+ *     - Number of bytes processed.
+ *         - Should equal number of bytes passed to callback.
+ *         - Failure will result in curl error: CURLE_WRITE_ERROR.
+ *
+ * Programmer: Jacob Smith
+ *             2017-08-17
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+size_t
+curlwritecallback(char   *ptr,
+                  size_t  size,
+                  size_t  nmemb,
+                  void   *userdata)
+{
+    struct s3r_datastruct *sds     = (struct s3r_datastruct *)userdata;
+    size_t                 product = (size * nmemb);
+    size_t                 written = 0;
+
+    if (sds->magic != S3COMMS_CALLBACK_DATASTRUCT_MAGIC)
+        return written;
+
+    if (size > 0) {
+        HDmemcpy(&(sds->data[sds->size]), ptr, product);
+        sds->size += product;
+        written = product;
+    }
+
+    return written;
+
+} /* curlwritecallback */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_hrb_node_set()
+ *
+ * Purpose:
+ *
+ *     Create, insert, modify, and remove elements in a field node list.
+ *
+ *     `name` cannot be null; will return FAIL and list will be unaltered.
+ *
+ *     Entries are accessed via the lowercase representation of their name:
+ *     "Host", "host", and "hOSt" would all access the same node,
+ *     but name's case is relevant in HTTP request output.
+ *
+ *     List pointer `L` must always point to either of :
+ *     - header node with lowest alphabetical order (by lowername)
+ *     - NULL, if list is empty
+ *
+ *    Types of operations:
+ *
+ *    - CREATE
+ *        - If `L` is NULL and `name` and `value` are not NULL,
+ *          a new node is created at `L`, starting a list.
+ *    - MODIFY
+ *        - If a node is found with a matching lowercase name and `value`
+ *          is not NULL, the existing name, value, and cat values are released
+ *          and replaced with the new data.
+ *        - No modifications are made to the list pointers.
+ *    - REMOVE
+ *        - If `value` is NULL, will attempt to remove node with matching
+ *          lowercase name.
+ *        - If no match found, returns FAIL and list is not modified.
+ *        - When removing a node, all its resources is released.
+ *        - If removing the last node in the list, list pointer is set to NULL.
+ *    - INSERT
+ *        - If no nodes exists with matching lowercase name and `value`
+ *          is not NULL, a new node is created, inserted into list
+ *          alphabetically by lowercase name.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - List was successfully modified
+ *     - FAILURE: `FAIL`
+ *         - Unable to perform operation
+ *             - Forbidden (attempting to remove absent node, e.g.)
+ *             - Internal error
+ *
+ * Programmer: Jacob Smith
+ *             2017-09-22
+ *
+ * Changes:
+ *
+ *     - Change return value to herr_t
+ *     - Change list pointer to pointer-to-pointer-to-node
+ *     - Change to use singly-linked list (from twin doubly-linked lists)
+ *       with modification to hrb_node_t
+ *     --- Jake Smith 2017-01-17
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_hrb_node_set(hrb_node_t **L,
+                          const char  *name,
+                          const char  *value)
+{
+    size_t      i          = 0;
+    char       *valuecpy   = NULL;
+    char       *namecpy    = NULL;
+    size_t      namelen    = 0;
+    char       *lowername  = NULL;
+    char       *nvcat      = NULL;
+    hrb_node_t *node_ptr   = NULL;
+    hrb_node_t *new_node   = NULL;
+    hbool_t     is_looking = TRUE;
+    herr_t      ret_value  = SUCCEED;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_hrb_node_set.\n");
+    HDprintf("NAME: %s\n", name);
+    HDprintf("VALUE: %s\n", value);
+    HDprintf("LIST:\n->");
+    for (node_ptr = (*L); node_ptr != NULL; node_ptr = node_ptr->next)
+        HDfprintf(stdout, "{%s}\n->", node_ptr->cat);
+    HDprintf("(null)\n");
+    fflush(stdout);
+    node_ptr = NULL;
+#endif
+
+    if (name == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "unable to operate on null name.\n");
+    }
+    namelen = HDstrlen(name);
+
+    /***********************
+     * PREPARE ALL STRINGS *
+     **********************/
+
+    /* copy and lowercase name
+     */
+    lowername = (char *)H5MM_malloc(sizeof(char) * (namelen + 1));
+    if (lowername == NULL) {
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                    "cannot make space for lowercase name copy.\n");
+    }
+    for (i = 0; i < namelen; i++) {
+        lowername[i] = (char)tolower((int)name[i]);
+    }
+    lowername[namelen] = 0;
+
+    /* If value supplied, copy name, value, and concatenated "name: value".
+     * If NULL, we will be removing a node or doing nothing, so no need for
+     * copies
+     */
+    if (value != NULL) {
+        size_t valuelen   = HDstrlen(value);
+        size_t catlen     = namelen + valuelen + 2; /* HDstrlen(": ") -> +2 */
+        int    sprint_ret = 0;
+
+        namecpy = (char *)H5MM_malloc(sizeof(char) * (namelen + 1));
+        if (namecpy == NULL) {
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                        "cannot make space for name copy.\n");
+        }
+        HDmemcpy(namecpy, name, namelen + 1);
+
+        valuecpy = (char *)H5MM_malloc(sizeof(char) * (valuelen + 1));
+        if (valuecpy == NULL) {
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                        "cannot make space for value copy.\n");
+        }
+        HDmemcpy(valuecpy, value, valuelen + 1);
+
+        nvcat = (char *)H5MM_malloc(sizeof(char) * (catlen + 1));
+        if (nvcat == NULL) {
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                        "cannot make space for concatenated string.\n");
+        }
+        sprint_ret = HDsnprintf(nvcat, (catlen + 1), "%s: %s", name, value);
+        if (sprint_ret <= 0)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "error while concatenating `%s: %s", name, value);
+        HDassert( catlen == (size_t)sprint_ret );
+
+        /* create new_node, should we need it
+         */
+        new_node = (hrb_node_t *)H5MM_malloc(sizeof(hrb_node_t));
+        if (new_node == NULL) {
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                        "cannot make space for new set.\n");
+        }
+
+        new_node->magic     = S3COMMS_HRB_NODE_MAGIC;
+        new_node->name      = NULL;
+        new_node->value     = NULL;
+        new_node->cat       = NULL;
+        new_node->lowername = NULL;
+        new_node->next      = NULL;
+    }
+
+    /***************
+     * ACT ON LIST *
+     ***************/
+
+    if (*L == NULL)  {
+        if (value == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "trying to remove node from empty list");
+        } else {
+#if S3COMMS_DEBUG
+HDprintf("CREATE NEW\n"); fflush(stdout);
+#endif
+            /*******************
+             * CREATE NEW LIST *
+             *******************/
+
+            new_node->cat       = nvcat;
+            new_node->name      = namecpy;
+            new_node->lowername = lowername;
+            new_node->value     = valuecpy;
+
+            *L = new_node;
+            goto done; /* bypass further seeking */
+        }
+    }
+
+    /* sanity-check pointer passed in
+     */
+    HDassert( (*L) != NULL );
+    HDassert( (*L)->magic == S3COMMS_HRB_NODE_MAGIC );
+    node_ptr = (*L);
+
+    /* Check whether to modify/remove first node in list
+     */
+    if (strcmp(lowername, node_ptr->lowername) == 0) {
+
+        is_looking = FALSE;
+
+        if (value == NULL) {
+#if S3COMMS_DEBUG
+HDprintf("REMOVE HEAD\n"); fflush(stdout);
+#endif
+            /***************
+             * REMOVE HEAD *
+             ***************/
+
+            *L = node_ptr->next;
+
+#if S3COMMS_DEBUG
+HDprintf("FREEING CAT (node)\n"); fflush(stdout);
+#endif
+            H5MM_xfree(node_ptr->cat);
+#if S3COMMS_DEBUG
+HDprintf("FREEING LOWERNAME (node)\n"); fflush(stdout);
+#endif
+            H5MM_xfree(node_ptr->lowername);
+#if S3COMMS_DEBUG
+HDprintf("FREEING NAME (node)\n"); fflush(stdout);
+#endif
+            H5MM_xfree(node_ptr->name);
+#if S3COMMS_DEBUG
+HDprintf("FREEING VALUE (node)\n"); fflush(stdout);
+#endif
+            H5MM_xfree(node_ptr->value);
+#if S3COMMS_DEBUG
+HDprintf("MAGIC OK? %s\n",
+        (node_ptr->magic == S3COMMS_HRB_NODE_MAGIC) ? "YES" : "NO");
+fflush(stdout);
+#endif
+            HDassert( node_ptr->magic == S3COMMS_HRB_NODE_MAGIC );
+            node_ptr->magic += 1ul;
+#if S3COMMS_DEBUG
+HDprintf("FREEING POINTER\n"); fflush(stdout);
+#endif
+            H5MM_xfree(node_ptr);
+
+#if S3COMMS_DEBUG
+HDprintf("FREEING WORKING LOWERNAME\n"); fflush(stdout);
+#endif
+            H5MM_xfree(lowername); lowername = NULL;
+        } else {
+#if S3COMMS_DEBUG
+HDprintf("MODIFY HEAD\n"); fflush(stdout);
+#endif
+            /***************
+             * MODIFY HEAD *
+             ***************/
+
+            H5MM_xfree(node_ptr->cat);
+            H5MM_xfree(node_ptr->name);
+            H5MM_xfree(node_ptr->value);
+
+            node_ptr->name = namecpy;
+            node_ptr->value = valuecpy;
+            node_ptr->cat = nvcat;
+
+            H5MM_xfree(lowername);
+            lowername = NULL;
+            new_node->magic += 1ul;
+            H5MM_xfree(new_node);
+            new_node  = NULL;
+        }
+    } else if (strcmp(lowername, node_ptr->lowername) < 0) {
+
+        is_looking = FALSE;
+
+        if (value == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "trying to remove a node 'before' head");
+        } else {
+#if S3COMMS_DEBUG
+HDprintf("PREPEND NEW HEAD\n"); fflush(stdout);
+#endif
+            /*******************
+             * INSERT NEW HEAD *
+             *******************/
+
+            new_node->name      = namecpy;
+            new_node->value     = valuecpy;
+            new_node->lowername = lowername;
+            new_node->cat       = nvcat;
+            new_node->next      = node_ptr;
+            *L = new_node;
+        }
+    }
+
+    /***************
+     * SEARCH LIST *
+     ***************/
+
+    while (is_looking) {
+        if (node_ptr->next == NULL) {
+
+            is_looking = FALSE;
+
+            if (value == NULL) {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "trying to remove absent node");
+            } else {
+#if S3COMMS_DEBUG
+HDprintf("APPEND A NODE\n"); fflush(stdout);
+#endif
+                /*******************
+                 * APPEND NEW NODE *
+                 *******************/
+
+                HDassert( strcmp(lowername, node_ptr->lowername) > 0 );
+                new_node->name      = namecpy;
+                new_node->value     = valuecpy;
+                new_node->lowername = lowername;
+                new_node->cat       = nvcat;
+                node_ptr->next      = new_node;
+            }
+        } else if (strcmp(lowername, node_ptr->next->lowername) < 0) {
+
+            is_looking = FALSE;
+
+            if (value == NULL) {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "trying to remove absent node");
+            } else {
+#if S3COMMS_DEBUG
+HDprintf("INSERT A NODE\n"); fflush(stdout);
+#endif
+                /*******************
+                 * INSERT NEW NODE *
+                 *******************/
+
+                HDassert( strcmp(lowername, node_ptr->lowername) > 0 );
+                new_node->name      = namecpy;
+                new_node->value     = valuecpy;
+                new_node->lowername = lowername;
+                new_node->cat       = nvcat;
+                new_node->next      = node_ptr->next;
+                node_ptr->next      = new_node;
+            }
+        } else if (strcmp(lowername, node_ptr->next->lowername) == 0) {
+
+            is_looking = FALSE;
+
+            if (value == NULL) {
+                /*****************
+                 * REMOVE A NODE *
+                 *****************/
+
+                hrb_node_t *tmp = node_ptr->next;
+                node_ptr->next = tmp->next;
+
+#if S3COMMS_DEBUG
+HDprintf("REMOVE A NODE\n"); fflush(stdout);
+#endif
+                H5MM_xfree(tmp->cat);
+                H5MM_xfree(tmp->lowername);
+                H5MM_xfree(tmp->name);
+                H5MM_xfree(tmp->value);
+
+                HDassert( tmp->magic == S3COMMS_HRB_NODE_MAGIC );
+                tmp->magic += 1ul;
+                H5MM_xfree(tmp);
+
+                H5MM_xfree(lowername);
+                lowername = NULL;
+            } else {
+#if S3COMMS_DEBUG
+HDprintf("MODIFY A NODE\n"); fflush(stdout);
+#endif
+                /*****************
+                 * MODIFY A NODE *
+                 *****************/
+
+                node_ptr = node_ptr->next;
+                H5MM_xfree(node_ptr->name);
+                H5MM_xfree(node_ptr->value);
+                H5MM_xfree(node_ptr->cat);
+
+                HDassert( new_node->magic == S3COMMS_HRB_NODE_MAGIC );
+                new_node->magic += 1ul;
+                H5MM_xfree(new_node);
+                H5MM_xfree(lowername);
+                new_node  = NULL;
+                lowername = NULL;
+
+                node_ptr->name  = namecpy;
+                node_ptr->value = valuecpy;
+                node_ptr->cat   = nvcat;
+            }
+        } else {
+            /****************
+             * KEEP LOOKING *
+             ****************/
+
+             node_ptr = node_ptr->next;
+        }
+    }
+
+done:
+    if (ret_value == FAIL) {
+        /* clean up
+         */
+        if (nvcat     != NULL) H5MM_xfree(nvcat);
+        if (namecpy   != NULL) H5MM_xfree(namecpy);
+        if (lowername != NULL) H5MM_xfree(lowername);
+        if (valuecpy  != NULL) H5MM_xfree(valuecpy);
+        if (new_node  != NULL) {
+            HDassert( new_node->magic == S3COMMS_HRB_NODE_MAGIC );
+            new_node->magic += 1ul;
+            H5MM_xfree(new_node);
+        }
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_hrb_node_set */
+
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_hrb_destroy()
+ *
+ * Purpose:
+ *
+ *    Destroy and free resources _directly_ associated with an HTTP Buffer.
+ *
+ *    Takes a pointer to pointer to the buffer structure.
+ *    This allows for the pointer itself to be NULLed from within the call.
+ *
+ *    If buffer or buffer pointer is NULL, there is no effect.
+ *
+ *    Headers list at `first_header` is not touched.
+ *
+ *    - Programmer should re-use or destroy `first_header` pointer
+ *      (hrb_node_t *) as suits their purposes.
+ *    - Recommend fetching prior to destroy()
+ *      e.g., `reuse_node = hrb_to_die->first_header; destroy(hrb_to_die);`
+ *      or maintaining an external reference.
+ *    - Destroy node/list separately as appropriate
+ *    - Failure to account for this will result in a memory leak.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - successfully released buffer resources
+ *         - if `buf` is NULL or `*buf` is NULL, no effect
+ *     - FAILURE: `FAIL`
+ *         - `buf->magic != S3COMMS_HRB_MAGIC`
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-21
+ *
+ * Changes:
+ *
+ *     - Conditional free() of `hrb_node_t` pointer properties based on
+ *       `which_free` property.
+ *     --- Jacob Smith 2017-08-08
+ *
+ *     - Integrate with HDF5.
+ *     - Returns herr_t instead of nothing.
+ *     --- Jacob Smith 2017-09-21
+ *
+ *     - Change argument to from *buf to **buf, to null pointer within call
+ *     --- Jacob Smith 2017-20-05
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_hrb_destroy(hrb_t **_buf)
+{
+    hrb_t  *buf       = NULL;
+    herr_t  ret_value = SUCCEED;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_hrb_destroy.\n");
+#endif
+
+    if (_buf != NULL && *_buf != NULL) {
+        buf = *_buf;
+        if (buf->magic != S3COMMS_HRB_MAGIC) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "pointer's magic does not match.\n");
+        }
+
+        H5MM_xfree(buf->verb);
+        H5MM_xfree(buf->version);
+        H5MM_xfree(buf->resource);
+        buf->magic += 1ul;
+        H5MM_xfree(buf);
+        *_buf = NULL;
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_hrb_destroy */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_hrb_init_request()
+ *
+ * Purpose:
+ *
+ *     Create a new HTTP Request Buffer
+ *
+ *     All non-null arguments should be null-terminated strings.
+ *
+ *     If `verb` is NULL, defaults to "GET".
+ *     If `http_version` is NULL, defaults to "HTTP/1.1".
+ *
+ *     `resource` cannot be NULL; should be string beginning with slash
+ *     character ('/').
+ *
+ *     All strings are copied into the structure, making them safe from
+ *     modification in source strings.
+ *
+ * Return:
+ *
+ *     - SUCCESS: pointer to new `hrb_t`
+ *     - FAILURE: `NULL`
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-21
+ *
+ * Changes:
+ *
+ *     - Update struct membership for newer 'generic' `hrb_t` format.
+ *     --- Jacob Smith, 2017-07-24
+ *
+ *     - Rename from `hrb_new()` to `hrb_request()`
+ *     --- Jacob Smith, 2017-07-25
+ *
+ *     - Integrate with HDF5.
+ *     - Rename from 'hrb_request()` to `H5FD_s3comms_hrb_init_request()`.
+ *     - Remove `host` from input parameters.
+ *         - Host, as with all other fields, must now be added through the
+ *           add-field functions.
+ *     - Add `version` (HTTP version string, e.g. "HTTP/1.1") to parameters.
+ *     --- Jacob Smith 2017-09-20
+ *
+ *     - Update to use linked-list `hrb_node_t` headers in structure.
+ *     --- Jacob Smith 2017-10-05
+ *
+ *----------------------------------------------------------------------------
+ */
+hrb_t *
+H5FD_s3comms_hrb_init_request(const char *_verb,
+                              const char *_resource,
+                              const char *_http_version)
+{
+    hrb_t  *request   = NULL;
+    char   *res       = NULL;
+    size_t  reslen    = 0;
+    hrb_t  *ret_value = NULL;
+    char   *verb      = NULL;
+    size_t  verblen   = 0;
+    char   *vrsn      = NULL;
+    size_t  vrsnlen   = 0;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_hrb_init_request.\n");
+#endif
+
+    if (_resource == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "resource string cannot be null.\n");
+    }
+
+    /* populate valid NULLs with defaults
+     */
+    if (_verb == NULL)
+        _verb = "GET";
+
+    if (_http_version == NULL)
+        _http_version = "HTTP/1.1";
+
+    /* malloc space for and prepare structure
+     */
+    request = (hrb_t *)H5MM_malloc(sizeof(hrb_t));
+    if (request == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, NULL,
+                    "no space for request structure");
+    }
+    request->magic        = S3COMMS_HRB_MAGIC;
+    request->body         = NULL;
+    request->body_len     = 0;
+    request->first_header = NULL;
+
+
+
+    /* malloc and copy strings for the structure
+     */
+    if (_resource[0] == '/') {
+        reslen = HDstrlen(_resource) + 1;
+        res = (char *)H5MM_malloc(sizeof(char) * reslen);
+        if (res == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, NULL,
+                        "no space for resource string");
+        }
+        HDstrncpy(res, _resource, reslen);
+    } else {
+        int sprint_ret = 0;
+        reslen = HDstrlen(_resource) + 2;
+        res = (char *)H5MM_malloc(sizeof(char) * reslen);
+        if (res == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, NULL,
+                        "no space for resource string");
+        }
+        sprint_ret = HDsnprintf(res, reslen, "/%s", _resource);
+        if (sprint_ret <= 0)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "errro while appending resource string %s", _resource);
+        HDassert( (reslen - 1) == (size_t)sprint_ret );
+    } /* start resource string with '/' */
+
+    verblen = HDstrlen(_verb) + 1;
+    verb = (char *)H5MM_malloc(sizeof(char) * verblen);
+    if (verb == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "no space for verb string");
+    }
+    HDstrncpy(verb, _verb, verblen);
+
+    vrsnlen = HDstrlen(_http_version) + 1;
+    vrsn = (char *)H5MM_malloc(sizeof(char) * vrsnlen);
+    if (vrsn == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "no space for http-version string");
+    }
+    HDstrncpy(vrsn, _http_version, vrsnlen);
+
+
+
+    /* place new copies into structure
+     */
+    request->resource = res;
+    request->verb     = verb;
+    request->version  = vrsn;
+
+    ret_value = request;
+
+done:
+
+    /* if there is an error, clean up after ourselves
+     */
+    if (ret_value == NULL) {
+        if (request != NULL)  H5MM_xfree(request);
+        if (vrsn    != NULL)  H5MM_xfree(vrsn);
+        if (verb    != NULL)  H5MM_xfree(verb);
+        if (res     != NULL)  H5MM_xfree(res);
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_hrb_init_request */
+
+
+
+/****************************************************************************
+ * S3R FUNCTIONS
+ ****************************************************************************/
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_s3r_close()
+ *
+ * Purpose:
+ *
+ *     Close communications through given S3 Request Handle (`s3r_t`)
+ *     and clean up associated resources.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - fails if handle is null or has invalid magic number
+ *
+ *
+ * Programmer: Jacob Smith
+ *             2017-08-31
+ *
+ * Changes:
+ *
+ *    - Remove all messiness related to the now-gone "setopt" utility
+ *      as it no longer exists in the handle.
+ *    - Return type to `void`.
+ *    --- Jacob Smith 2017-09-01
+ *
+ *    - Incorporate into HDF environment.
+ *    - Rename from `s3r_close()` to `H5FD_s3comms_s3r_close()`.
+ *    --- Jacob Smith 2017-10-06
+ *
+ *    - Change separate host, resource, port info to `parsed_url_t` struct ptr.
+ *    --- Jacob Smith 2017-11-01
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_s3r_close(s3r_t *handle)
+{
+    herr_t ret_value = SUCCEED;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_s3r_close.\n");
+#endif
+
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle cannot be null.\n");
+    }
+    if (handle->magic != S3COMMS_S3R_MAGIC) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has invalid magic.\n");
+    }
+
+    curl_easy_cleanup(handle->curlhandle);
+
+    H5MM_xfree(handle->secret_id);
+    H5MM_xfree(handle->region);
+    H5MM_xfree(handle->signing_key);
+
+    HDassert( handle->httpverb != NULL );
+    H5MM_xfree(handle->httpverb);
+
+    if (FAIL == H5FD_s3comms_free_purl(handle->purl)) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "unable to release parsed url structure")
+    }
+
+    H5MM_xfree(handle);
+
+#endif /* H5_HAVE_ROS3_VFD */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_s3r_close */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_s3r_get_filesize()
+ *
+ * Purpose:
+ *
+ *     Retrieve the filesize of an open request handle.
+ *
+ *     Wrapper "getter" to hide implementation details.
+ *
+ *
+ * Return:
+ *
+ *     - SUCCESS: size of file, in bytes, if handle is valid.
+ *     - FAILURE: 0, if handle is NULL or undefined.
+ *
+ * Programmer: Jacob Smith 2017-01-14
+ *
+ * Changes: None
+ *
+ *----------------------------------------------------------------------------
+ */
+size_t
+H5FD_s3comms_s3r_get_filesize(s3r_t *handle) {
+
+    size_t ret_value = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#ifdef H5_HAVE_ROS3_VFD
+    if (handle != NULL)
+        ret_value = handle->filesize;
+#endif /* H5_HAVE_ROS3_VFD */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_s3r_get_filesize */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_s3r_getsize()
+ *
+ * Purpose:
+ *
+ *    Get the number of bytes of handle's target resource.
+ *
+ *    Sets handle and curlhandle with to enact an HTTP HEAD request on file,
+ *    and parses received headers to extract "Content-Length" from response
+ *    headers, storing file size at `handle->filesize`.
+ *
+ *    Critical step in opening (initiating) an `s3r_t` handle.
+ *
+ *    Wraps `s3r_read()`.
+ *    Sets curlhandle to write headers to a temporary buffer (using extant
+ *    write callback) and provides no buffer for body.
+ *
+ *    Upon exit, unsets HTTP HEAD settings from curl handle, returning to
+ *    initial state. In event of error, curl handle state is undefined and is
+ *    not to be trusted.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *
+ * Programmer: Jacob Smith
+ *             2017-08-23
+ *
+ * Changes:
+ *
+ *     - Update to revised `s3r_t` format and life cycle.
+ *     --- Jacob Smith 2017-09-01
+ *
+ *     - Conditional change to static header buffer and structure.
+ *     --- Jacob Smith 2017-09-05
+ *
+ *     - Incorporate into HDF environment.
+ *     - Rename from `s3r_getsize()` to `H5FD_s3comms_s3r_getsize()`.
+ *     --- Jacob Smith 2017-10-06
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_s3r_getsize(s3r_t *handle)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    uintmax_t             content_length = 0;
+    CURL                  *curlh          = NULL;
+    char                  *end            = NULL;
+    char                  *headerresponse = NULL;
+    herr_t                 ret_value      = SUCCEED;
+    struct s3r_datastruct  sds            = {
+            S3COMMS_CALLBACK_DATASTRUCT_MAGIC,
+            NULL,
+            0 };
+    char                  *start          = NULL;
+#else
+    herr_t                 ret_value      = FAIL;
+#endif /* H5_HAVE_ROS3_VFD */
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_s3r_getsize.\n");
+#endif
+
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle cannot be null.\n");
+    }
+    if (handle->magic != S3COMMS_S3R_MAGIC) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has invalid magic.\n");
+    }
+    if (handle->curlhandle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has bad (null) curlhandle.\n")
+    }
+
+    /********************
+     * PREPARE FOR HEAD *
+     ********************/
+
+    curlh = handle->curlhandle;
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_NOBODY,
+                         1L) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "error while setting CURL option (CURLOPT_NOBODY). "
+                    "(placeholder flags)");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_HEADERDATA,
+                         &sds) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "error while setting CURL option (CURLOPT_HEADERDATA). "
+                    "(placeholder flags)");
+    }
+
+    HDassert( handle->httpverb == NULL );
+    handle->httpverb = (char *)H5MM_malloc(sizeof(char) * 16);
+    if (handle->httpverb == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                    "unable to allocate space for S3 request HTTP verb");
+    }
+    HDmemcpy(handle->httpverb, "HEAD", 5);
+
+    headerresponse = (char *)H5MM_malloc(sizeof(char) * CURL_MAX_HTTP_HEADER);
+    if (headerresponse == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                    "unable to allocate space for curl header response");
+    }
+    sds.data = headerresponse;
+
+    /*******************
+     * PERFORM REQUEST *
+     *******************/
+
+    /* these parameters fetch the entire file,
+     * but, with a NULL destination and NOBODY and HEADERDATA supplied above,
+     * only http metadata will be sent by server and recorded by s3comms
+     */
+    if (FAIL ==
+        H5FD_s3comms_s3r_read(handle, 0, 0, NULL) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "problem in reading during getsize.\n");
+    }
+
+    if (sds.size > CURL_MAX_HTTP_HEADER) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "HTTP metadata buffer overrun\n");
+    } else if (sds.size == 0) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "No HTTP metadata\n");
+#if S3COMMS_DEBUG
+    } else {
+        HDfprintf(stderr, "GETSIZE: OK\n");
+#endif
+    }
+
+
+    /******************
+     * PARSE RESPONSE *
+     ******************/
+
+    start = strstr(headerresponse,
+                   "\r\nContent-Length: ");
+    if (start == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "could not find \"Content-Length\" in response.\n");
+    }
+
+    /* move "start" to beginning of value in line; find end of line
+     */
+    start = start + HDstrlen("\r\nContent-Length: ");
+    end = strstr(start, "\r\n");
+    if (end == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "could not find end of content length line");
+    }
+
+    /* place null terminator at end of numbers
+     */
+    *end = '\0';
+
+    content_length = strtoumax((const char *)start,
+                             NULL,
+                             0);
+
+    if (UINTMAX_MAX > SIZE_MAX && content_length > SIZE_MAX) {
+        HGOTO_ERROR(H5E_ARGS, H5E_OVERFLOW, FAIL, "content_length overflows size_t\n");
+    }
+
+    if (content_length == 0 ||    
+        errno          == ERANGE) /* errno set by strtoumax*/
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+            "could not convert found \"Content-Length\" response (\"%s\")",
+            start); /* range is null-terminated, remember */
+    }
+
+    handle->filesize = (size_t)content_length;
+
+    /**********************
+     * UNDO HEAD SETTINGS *
+     **********************/
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_NOBODY,
+                         NULL) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "error while setting CURL option (CURLOPT_NOBODY). "
+                    "(placeholder flags)");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_HEADERDATA,
+                         NULL) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "error while setting CURL option (CURLOPT_HEADERDATA). "
+                    "(placeholder flags)");
+    }
+
+done:
+    H5MM_xfree(headerresponse);
+    sds.magic += 1; /* set to bad magic */
+
+#endif /* H5_HAVE_ROS3_VFD */
+
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_s3r_getsize */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_s3r_open()
+ *
+ * Purpose:
+ *
+ *     Logically 'open' a file hosted on S3.
+ *
+ *     - create new Request Handle
+ *     - copy supplied url
+ *     - copy authentication info if supplied
+ *     - create CURL handle
+ *     - fetch size of file
+ *         - connect with server and execute HEAD request
+ *     - return request handle ready for reads
+ *
+ *     To use 'default' port to connect, `port` should be 0.
+ *
+ *     To prevent AWS4 authentication, pass null pointer to `region`, `id`,
+ *     and `signing_key`.
+ *
+ *     Uses `H5FD_s3comms_parse_url()` to validate and parse url input.
+ *
+ * Return:
+ *
+ *     - SUCCESS: Pointer to new request handle.
+ *     - FAILURE: NULL
+ *         - occurs if:
+ *             - authentication strings are inconsistent
+ *             - must _all_ be null, or have at least `region` and `id`
+ *             - url is NULL (no filename)
+ *             - unable to parse url (malformed?)
+ *             - error while performing `getsize()`
+ *
+ * Programmer: Jacob Smith
+ *             2017-09-01
+ *
+ * Changes:
+ *
+ *     - Incorporate into HDF environment.
+ *     - Rename from `s3r_open()` to `H5FD_s3comms_s3r_open()`.
+ *     --- Jacob Smith 2017-10-06
+ *
+ *     - Remove port number from signature.
+ *     - Name (`url`) must be complete url with http scheme and optional port
+ *       number in string.
+ *         - e.g., "http://bucket.aws.com:9000/myfile.dat?query=param"
+ *     - Internal storage of host, resource, and port information moved into
+ *       `parsed_url_t` struct pointer.
+ *     --- Jacob Smith 2017-11-01
+ *
+ *----------------------------------------------------------------------------
+ */
+s3r_t *
+H5FD_s3comms_s3r_open(const char          *url,
+                      const char          *region,
+                      const char          *id,
+                      const unsigned char *signing_key)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    size_t        tmplen    = 0;
+    CURL         *curlh     = NULL;
+    s3r_t        *handle    = NULL;
+    parsed_url_t *purl      = NULL;
+#endif
+    s3r_t        *ret_value = NULL;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_s3r_open.\n");
+#endif
+
+
+
+    if (url == NULL || url[0] == '\0') {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "url cannot be null.\n");
+    }
+
+    if (FAIL == H5FD_s3comms_parse_url(url, &purl)) {
+        /* probably a malformed url, but could be internal error */
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTCREATE, NULL,
+                    "unable to create parsed url structure");
+    }
+    HDassert( purl != NULL ); /* if above passes, this must be true */
+    HDassert( purl->magic == S3COMMS_PARSED_URL_MAGIC );
+
+    handle = (s3r_t *)H5MM_malloc(sizeof(s3r_t));
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, NULL,
+                    "could not malloc space for handle.\n");
+    }
+
+    handle->magic        = S3COMMS_S3R_MAGIC;
+    handle->purl         = purl;
+    handle->filesize     = 0;
+    handle->region       = NULL;
+    handle->secret_id    = NULL;
+    handle->signing_key  = NULL;
+    handle->httpverb     = NULL;
+
+    /*************************************
+     * RECORD AUTHENTICATION INFORMATION *
+     *************************************/
+
+    if ((region      != NULL && *region      != '\0') ||
+        (id          != NULL && *id          != '\0') ||
+        (signing_key != NULL && *signing_key != '\0'))
+    {
+        /* if one exists, all three must exist
+         */
+        if (region == NULL || region[0] == '\0') {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "region cannot be null.\n");
+        }
+        if (id == NULL || id[0] == '\0') {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "secret id cannot be null.\n");
+        }
+        if (signing_key == NULL || signing_key[0] == '\0') {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "signing key cannot be null.\n");
+        }
+
+        /* copy strings
+         */
+        tmplen = HDstrlen(region) + 1;
+        handle->region = (char *)H5MM_malloc(sizeof(char) * tmplen);
+        if (handle->region == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "could not malloc space for handle region copy.\n");
+        }
+        HDmemcpy(handle->region, region, tmplen);
+
+        tmplen = HDstrlen(id) + 1;
+        handle->secret_id = (char *)H5MM_malloc(sizeof(char) * tmplen);
+        if (handle->secret_id == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "could not malloc space for handle ID copy.\n");
+        }
+        HDmemcpy(handle->secret_id, id, tmplen);
+
+        tmplen = SHA256_DIGEST_LENGTH;
+        handle->signing_key =
+                (unsigned char *)H5MM_malloc(sizeof(unsigned char) * tmplen);
+        if (handle->signing_key == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "could not malloc space for handle key copy.\n");
+        }
+        HDmemcpy(handle->signing_key, signing_key, tmplen);
+    } /* if authentication information provided */
+
+    /************************
+     * INITIATE CURL HANDLE *
+     ************************/
+
+    curlh = curl_easy_init();
+
+    if (curlh == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "problem creating curl easy handle!\n");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_HTTPGET,
+                         1L) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "error while setting CURL option (CURLOPT_HTTPGET). "
+                    "(placeholder flags)");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_HTTP_VERSION,
+                         CURL_HTTP_VERSION_1_1) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "error while setting CURL option (CURLOPT_HTTP_VERSION). "
+                    "(placeholder flags)");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_FAILONERROR,
+                         1L) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "error while setting CURL option (CURLOPT_FAILONERROR). "
+                    "(placeholder flags)");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_WRITEFUNCTION,
+                         curlwritecallback) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "error while setting CURL option (CURLOPT_WRITEFUNCTION). "
+                    "(placeholder flags)");
+    }
+
+    if ( CURLE_OK !=
+        curl_easy_setopt(curlh,
+                         CURLOPT_URL,
+                         url) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                    "error while setting CURL option (CURLOPT_URL). "
+                    "(placeholder flags)");
+    }
+
+#if S3COMMS_CURL_VERBOSITY > 1
+    /* CURL will print (to stdout) information for each operation
+     */
+    curl_easy_setopt(curlh, CURLOPT_VERBOSE, 1L);
+#endif
+
+    handle->curlhandle = curlh;
+
+    /*******************
+     * OPEN CONNECTION *
+     * * * * * * * * * *
+     *  GET FILE SIZE  *
+     *******************/
+
+    if (FAIL ==
+        H5FD_s3comms_s3r_getsize(handle) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                     "problem in H5FD_s3comms_s3r_getsize.\n");
+    }
+
+    /*********************
+     * FINAL PREPARATION *
+     *********************/
+
+    HDassert( handle->httpverb != NULL );
+    HDmemcpy(handle->httpverb, "GET", 4);
+
+    ret_value = handle;
+#endif /* H5_HAVE_ROS3_VFD */
+
+done:
+    if (ret_value == NULL) {
+#ifdef H5_HAVE_ROS3_VFD
+        if (curlh != NULL) {
+            curl_easy_cleanup(curlh);
+        }
+        if (FAIL == H5FD_s3comms_free_purl(purl)) {
+            HDONE_ERROR(H5E_ARGS, H5E_BADVALUE, NULL,
+                        "unable to free parsed url structure")
+        }
+        if (handle != NULL) {
+            H5MM_xfree(handle->region);
+            H5MM_xfree(handle->secret_id);
+            H5MM_xfree(handle->signing_key);
+            if (handle->httpverb != NULL) {
+                H5MM_xfree(handle->httpverb);
+            }
+            H5MM_xfree(handle);
+        }
+#endif /* H5_HAVE_ROS3_VFD */
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_s3r_open */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_s3r_read()
+ *
+ * Purpose:
+ *
+ *     Read file pointed to by request handle, writing specified
+ *     `offset` .. `offset + len` bytes to buffer `dest`.
+ *
+ *     If `len` is 0, reads entirety of file starting at `offset`.
+ *     If `offset` and `len` are both 0, reads entire file.
+ *
+ *     If `offset` or `offset+len` is greater than the file size, read is
+ *     aborted and returns `FAIL`.
+ *
+ *     Uses configured "curl easy handle" to perform request.
+ *
+ *     In event of error, buffer should remain unaltered.
+ *
+ *     If handle is set to authorize a request, creates a new (temporary)
+ *     HTTP Request object (hrb_t) for generating requisite headers,
+ *     which is then translated to a `curl slist` and set in the curl handle
+ *     for the request.
+ *
+ *     `dest` _may_ be NULL, but no body data will be recorded.
+ *
+ *     - In general practice, NULL should never be passed in as `dest`.
+ *     - NULL `dest` passed in by internal function `s3r_getsize()`, in
+ *       conjunction with CURLOPT_NOBODY to preempt transmission of file data
+ *       from server.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *
+ * Programmer: Jacob Smith
+ *             2017-08-22
+ *
+ * Changes:
+ *
+ *     - Revise structure to prevent unnecessary hrb_t element creation.
+ *     - Rename tmprstr -> rangebytesstr to reflect purpose.
+ *     - Insert needed `free()`s, particularly for `sds`.
+ *     --- Jacob Smith 2017-08-23
+ *
+ *     - Revise heavily to accept buffer, range as parameters.
+ *     - Utilize modified s3r_t format.
+ *     --- Jacob Smith 2017-08-31
+ *
+ *     - Incorporate into HDF library.
+ *     - Rename from `s3r_read()` to `H5FD_s3comms_s3r_read()`.
+ *     - Return `herr_t` succeed/fail instead of S3code.
+ *     - Update to use revised `hrb_t` and `hrb_node_t` structures.
+ *     --- Jacob Smith 2017-10-06
+ *
+ *     - Update to use `parsed_url_t *purl` in handle.
+ *     --- Jacob Smith 2017-11-01
+ *
+ *     - Better define behavior upon read past EOF
+ *     --- Jacob Smith 2017-01-19
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_s3r_read(s3r_t   *handle,
+                      haddr_t  offset,
+                      size_t   len,
+                      void    *dest)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    CURL                  *curlh         = NULL;
+    CURLcode               p_status      = CURLE_OK;
+    struct curl_slist     *curlheaders   = NULL;
+    hrb_node_t            *headers       = NULL;
+    hrb_node_t            *node          = NULL;
+    struct tm             *now           = NULL;
+    char                  *rangebytesstr = NULL;
+    hrb_t                 *request       = NULL;
+    int                    ret           = 0; /* working variable to check  */
+                                              /* return value of HDsnprintf  */
+    struct s3r_datastruct *sds           = NULL;
+    herr_t                 ret_value     = SUCCEED;
+#else
+    herr_t                 ret_value     = FAIL;
+#endif /* H5_HAVE_ROS3_VFD */
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_s3r_read.\n");
+#endif
+
+    /**************************************
+     * ABSOLUTELY NECESSARY SANITY-CHECKS *
+     **************************************/
+
+    if (handle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle cannot be null.\n");
+    }
+    if (handle->magic != S3COMMS_S3R_MAGIC) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has invalid magic.\n");
+    }
+    if (handle->curlhandle == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has bad (null) curlhandle.\n")
+    }
+    if (handle->purl == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "handle has bad (null) url.\n")
+    }
+    HDassert( handle->purl->magic == S3COMMS_PARSED_URL_MAGIC );
+    if (offset > handle->filesize || (len + offset) > handle->filesize) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "unable to read past EoF")
+    }
+
+    curlh = handle->curlhandle;
+
+    /*********************
+     * PREPARE WRITEDATA *
+     *********************/
+
+    if (dest != NULL) {
+        sds = (struct s3r_datastruct *)H5MM_malloc(
+                sizeof(struct s3r_datastruct));
+        if (sds == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                        "could not malloc destination datastructure.\n");
+        }
+
+        sds->magic = S3COMMS_CALLBACK_DATASTRUCT_MAGIC;
+        sds->data = (char *)dest;
+        sds->size = 0;
+        if (CURLE_OK !=
+            curl_easy_setopt(curlh,
+                             CURLOPT_WRITEDATA,
+                             sds) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, FAIL,
+                        "error while setting CURL option (CURLOPT_WRITEDATA). "
+                        "(placeholder flags)");
+        }
+    }
+
+    /*********************
+     * FORMAT HTTP RANGE *
+     *********************/
+
+    if (len > 0) {
+        rangebytesstr = (char *)H5MM_malloc(sizeof(char) * \
+                                            S3COMMS_MAX_RANGE_STRING_SIZE );
+        if (rangebytesstr == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                        "could not malloc range format string.\n");
+        }
+        ret = HDsnprintf(rangebytesstr,
+                       (S3COMMS_MAX_RANGE_STRING_SIZE),
+                       "bytes="H5_PRINTF_HADDR_FMT"-"H5_PRINTF_HADDR_FMT,
+                       offset,
+                       offset + len - 1);
+        if (ret == 0 || ret >= S3COMMS_MAX_RANGE_STRING_SIZE)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to format HTTP Range value");
+    } else if (offset > 0) {
+        rangebytesstr = (char *)H5MM_malloc(sizeof(char) * \
+                                            S3COMMS_MAX_RANGE_STRING_SIZE);
+        if (rangebytesstr == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                        "could not malloc range format string.\n");
+        }
+        ret = HDsnprintf(rangebytesstr,
+                       (S3COMMS_MAX_RANGE_STRING_SIZE),
+                      "bytes="H5_PRINTF_HADDR_FMT"-",
+                      offset);
+        if (ret == 0 || ret >= S3COMMS_MAX_RANGE_STRING_SIZE)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to format HTTP Range value");
+    }
+
+    /*******************
+     * COMPILE REQUEST *
+     *******************/
+
+    if (handle->signing_key == NULL) {
+        /* Do not authenticate.
+         */
+        if (rangebytesstr != NULL) {
+            /* Pass in range directly
+             */
+            char *bytesrange_ptr = NULL; /* pointer past "bytes=" portion */
+
+            bytesrange_ptr = strchr(rangebytesstr, '=');
+            HDassert( bytesrange_ptr != NULL );
+            bytesrange_ptr++; /* move to first char past '=' */
+            HDassert( *bytesrange_ptr != '\0' );
+
+            if (CURLE_OK !=
+                curl_easy_setopt(curlh,
+                                 CURLOPT_RANGE,
+                                 bytesrange_ptr) )
+            {
+                HGOTO_ERROR(H5E_VFL, H5E_UNINITIALIZED, FAIL,
+                        "error while setting CURL option (CURLOPT_RANGE). ");
+            }
+        }
+    } else {
+        /* authenticate request
+         */
+        char authorization[512];
+            /*   512 := approximate max length...
+             *    67 <len("AWS4-HMAC-SHA256 Credential=///s3/aws4_request,"
+             *           "SignedHeaders=,Signature=")>
+             * +   8 <yyyyMMDD>
+             * +  64 <hex(sha256())>
+             * + 128 <max? len(secret_id)>
+             * +  20 <max? len(region)>
+             * + 128 <max? len(signed_headers)>
+             */
+        char buffer1[512]; /* -> Canonical Request -> Signature */
+        char buffer2[256]; /* -> String To Sign -> Credential */
+        char iso8601now[ISO8601_SIZE];
+        char signed_headers[48];
+            /* should be large enough for nominal listing:
+             * "host;range;x-amz-content-sha256;x-amz-date"
+             * + '\0', with "range;" possibly absent
+             */
+
+        /* zero start of strings */
+        authorization[0]  = 0;
+        buffer1[0]        = 0;
+        buffer2[0]        = 0;
+        iso8601now[0]     = 0;
+        signed_headers[0] = 0;
+
+        /**** VERIFY INFORMATION EXISTS ****/
+
+        if (handle->region == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "handle must have non-null region.\n");
+        }
+        if (handle->secret_id == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "handle must have non-null secret_id.\n");
+        }
+        if (handle->signing_key == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "handle must have non-null signing_key.\n");
+        }
+        if (handle->httpverb == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "handle must have non-null httpverb.\n");
+        }
+        if (handle->purl->host == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "handle must have non-null host.\n");
+        }
+        if (handle->purl->path == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "handle must have non-null resource.\n");
+        }
+
+        /**** CREATE HTTP REQUEST STRUCTURE (hrb_t) ****/
+
+        request = H5FD_s3comms_hrb_init_request(
+                      (const char *)handle->httpverb,
+                      (const char *)handle->purl->path,
+                      "HTTP/1.1");
+        if (request == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "could not allocate hrb_t request.\n");
+        }
+        HDassert( request->magic == S3COMMS_HRB_MAGIC );
+
+        now = gmnow();
+        if (ISO8601NOW(iso8601now, now) != (ISO8601_SIZE - 1)) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "could not format ISO8601 time.\n");
+        }
+
+        if (FAIL ==
+            H5FD_s3comms_hrb_node_set(
+                    &headers,
+                    "x-amz-date",
+                    (const char *)iso8601now) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to set x-amz-date header")
+        }
+        if (headers == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem building headers list. "
+                        "(placeholder flags)\n");
+        }
+        HDassert( headers->magic == S3COMMS_HRB_NODE_MAGIC );
+
+        if (FAIL ==
+            H5FD_s3comms_hrb_node_set(
+                    &headers,
+                    "x-amz-content-sha256",
+                    (const char *)EMPTY_SHA256) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to set x-amz-content-sha256 header")
+        }
+        if (headers == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem building headers list. "
+                        "(placeholder flags)\n");
+        }
+        HDassert( headers->magic == S3COMMS_HRB_NODE_MAGIC );
+
+        if (rangebytesstr != NULL) {
+            if (FAIL ==
+                H5FD_s3comms_hrb_node_set(
+                        &headers,
+                        "Range",
+                        (const char *)rangebytesstr) )
+            {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "unable to set range header")
+            }
+            if (headers == NULL) {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "problem building headers list. "
+                            "(placeholder flags)\n");
+            }
+            HDassert( headers->magic == S3COMMS_HRB_NODE_MAGIC );
+        }
+
+    if (FAIL ==
+        H5FD_s3comms_hrb_node_set(
+            &headers,
+            "Host",
+            (const char *)handle->purl->host) )
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+            "unable to set host header")
+    }
+    if (headers == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+            "problem building headers list. "
+            "(placeholder flags)\n");
+    }
+    HDassert( headers->magic == S3COMMS_HRB_NODE_MAGIC );
+
+        request->first_header = headers;
+
+        /**** COMPUTE AUTHORIZATION ****/
+
+        if (FAIL ==      /* buffer1 -> canonical request */
+            H5FD_s3comms_aws_canonical_request(buffer1,
+                    signed_headers,
+                    request) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "(placeholder flags)\n");
+        }
+        if ( FAIL ==     /* buffer2->string-to-sign */
+             H5FD_s3comms_tostringtosign(buffer2,
+                                         buffer1,
+                                         iso8601now,
+                                         handle->region) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "(placeholder flags)\n");
+        }
+        if (FAIL ==     /* buffer1 -> signature */
+            H5FD_s3comms_HMAC_SHA256(handle->signing_key,
+                                     SHA256_DIGEST_LENGTH,
+                                     buffer2,
+                                     HDstrlen(buffer2),
+                                     buffer1) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "(placeholder flags)\n");
+        }
+
+        iso8601now[8] = 0; /* trim to yyyyMMDD */
+        ret = S3COMMS_FORMAT_CREDENTIAL(buffer2,
+                                        handle->secret_id,
+                                        iso8601now,
+                                        handle->region,
+                                        "s3");
+        if (ret == 0 || ret >= S3COMMS_MAX_CREDENTIAL_SIZE)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to format aws4 credential string");
+
+        ret = HDsnprintf(authorization,
+                512,
+                "AWS4-HMAC-SHA256 Credential=%s,SignedHeaders=%s,Signature=%s",
+                buffer2,
+                signed_headers,
+                buffer1);
+        if (ret == 0 || ret >= 512)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to format aws4 authorization string");
+
+        /* append authorization header to http request buffer
+         */
+        if (FAIL ==
+            H5FD_s3comms_hrb_node_set(
+                    &headers,
+                    "Authorization",
+                    (const char *)authorization) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to set Authorization header")
+        }
+        if (headers == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem building headers list. "
+                        "(placeholder flags)\n");
+        }
+
+        /* update hrb's "first header" pointer
+         */
+        request->first_header = headers;
+
+        /**** SET CURLHANDLE HTTP HEADERS FROM GENERATED DATA ****/
+
+        node = request->first_header;
+        while (node != NULL) {
+            HDassert( node->magic == S3COMMS_HRB_NODE_MAGIC );
+            curlheaders = curl_slist_append(curlheaders,
+                                            (const char *)node->cat);
+            if (curlheaders == NULL) {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "could not append header to curl slist. "
+                            "(placeholder flags)\n");
+            }
+            node = node->next;
+        }
+
+        /* sanity-check
+         */
+        if (curlheaders == NULL) {
+            /* above loop was probably never run */
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "curlheaders was never populated.\n");
+        }
+
+        /* finally, set http headers in curl handle
+         */
+        if (CURLE_OK !=
+            curl_easy_setopt(curlh,
+                             CURLOPT_HTTPHEADER,
+                             curlheaders) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "error while setting CURL option "
+                        "(CURLOPT_HTTPHEADER). (placeholder flags)");
+        }
+
+    } /* if should authenticate (info provided) */
+
+    /*******************
+     * PERFORM REQUEST *
+     *******************/
+
+#if S3COMMS_CURL_VERBOSITY > 0
+    /* In event of error, print detailed information to stderr
+     * This is not the default behavior.
+     */
+    {
+        long int httpcode = 0;
+        char     curlerrbuf[CURL_ERROR_SIZE];
+        curlerrbuf[0] = '\0';
+
+        if (CURLE_OK !=
+            curl_easy_setopt(curlh, CURLOPT_ERRORBUFFER, curlerrbuf) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem setting error buffer")
+        }
+
+        p_status = curl_easy_perform(curlh);
+
+        if (p_status != CURLE_OK) {
+            if (CURLE_OK !=
+                curl_easy_getinfo(curlh, CURLINFO_RESPONSE_CODE, &httpcode) )
+            {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "problem getting response code")
+            }
+            HDfprintf(stderr, "CURL ERROR CODE: %d\nHTTP CODE: %d\n",
+                     p_status, httpcode);
+            HDfprintf(stderr, "%s\n", curl_easy_strerror(p_status));
+            HGOTO_ERROR(H5E_VFL, H5E_CANTOPENFILE, FAIL,
+                    "problem while performing request.\n");
+        }
+        if (CURLE_OK !=
+            curl_easy_setopt(curlh, CURLOPT_ERRORBUFFER, NULL) )
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem unsetting error buffer")
+        }
+    } /* verbose error reporting */
+#else
+    p_status = curl_easy_perform(curlh);
+
+    if (p_status != CURLE_OK) {
+        HGOTO_ERROR(H5E_VFL, H5E_CANTOPENFILE, FAIL,
+                    "curl cannot perform request\n")
+    }
+#endif
+
+#if S3COMMS_DEBUG
+    if (dest != NULL) {
+        HDfprintf(stderr, "len: %d\n", (int)len);
+        HDfprintf(stderr, "CHECKING FOR BUFFER OVERFLOW\n");
+        if (sds == NULL) {
+            HDfprintf(stderr, "sds is NULL!\n");
+        } else {
+            HDfprintf(stderr, "sds: 0x%lx\n", (long long)sds);
+            HDfprintf(stderr, "sds->size: %d\n", (int)sds->size);
+            if (len > sds->size) {
+                HDfprintf(stderr, "buffer overwrite\n");
+            }
+        }
+    } else {
+        HDfprintf(stderr, "performed on entire file\n");
+    }
+#endif
+
+done:
+    /* clean any malloc'd resources
+     */
+    if (curlheaders != NULL) {
+        curl_slist_free_all(curlheaders);
+        curlheaders = NULL;
+    }
+    if (rangebytesstr != NULL) {
+        H5MM_xfree(rangebytesstr);
+        rangebytesstr = NULL;
+    }
+    if (sds != NULL) {
+        H5MM_xfree(sds);
+        sds = NULL;
+    }
+    if (request != NULL) {
+        while (headers != NULL)
+            if (FAIL ==
+                H5FD_s3comms_hrb_node_set(&headers, headers->name, NULL))
+            {
+                HDONE_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "cannot release header node")
+            }
+        HDassert( NULL == headers );
+        if (FAIL == H5FD_s3comms_hrb_destroy(&request)) {
+                HDONE_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "cannot release header request structure")
+        }
+        HDassert( NULL == request );
+    }
+
+    if (curlh != NULL) {
+        /* clear any Range */
+        if (CURLE_OK != curl_easy_setopt(curlh, CURLOPT_RANGE, NULL) )
+                HDONE_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "cannot unset CURLOPT_RANGE")
+
+        /* clear headers */
+        if (CURLE_OK != curl_easy_setopt(curlh, CURLOPT_HTTPHEADER, NULL) )
+                HDONE_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "cannot unset CURLOPT_HTTPHEADER")
+    }
+
+#endif /* H5_HAVE_ROS3_VFD */
+
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_s3r_read */
+
+
+
+/****************************************************************************
+ * MISCELLANEOUS FUNCTIONS
+ ****************************************************************************/
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: gmnow()
+ *
+ * Purpose:
+ *
+ *    Get the output of `time.h`'s `gmtime()` call while minimizing setup
+ *    clutter where important.
+ *
+ * Return:
+ *
+ *    Pointer to resulting `struct tm`,as created by gmtime(time_t * T).
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-12
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+struct tm *
+gmnow(void)
+{
+    time_t     now;
+    time_t    *now_ptr = &now;
+    struct tm *ret_value = NULL;
+
+    /* Doctor assert, checks against error in time() */
+    if ( (time_t)(-1) != time(now_ptr) )
+        ret_value = gmtime(now_ptr);
+
+    HDassert( ret_value != NULL );
+
+    return ret_value;
+
+} /* gmnow */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_aws_canonical_request()
+ *
+ * Purpose:
+ *
+ *     Compose AWS "Canonical Request" (and signed headers string)
+ *     as defined in the REST API documentation.
+ *
+ *     Both destination strings are null-terminated.
+ *
+ *     Destination string arguments must be provided with adequate space.
+ *
+ *     Canonical Request format:
+ *
+ *      <HTTP VERB>"\n"
+ *      <resource path>"\n"
+ *      <query string>"\n"
+ *      <header1>"\n" (`lowercase(name)`":"`trim(value)`)
+ *      <header2>"\n"
+ *      ... (headers sorted by name)
+ *      <header_n>"\n"
+ *      "\n"
+ *      <signed headers>"\n" (`lowercase(header 1 name)`";"`header 2 name`;...)
+ *      <hex-string of sha256sum of body> ("e3b0c4429...", e.g.)
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - writes canonical request to respective `...dest` strings
+ *     - FAILURE: `FAIL`
+ *         - one or more input argument was NULL
+ *         - internal error
+ *
+ * Programmer: Jacob Smith
+ *             2017-10-04
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_aws_canonical_request(char  *canonical_request_dest,
+                                   char  *signed_headers_dest,
+                                   hrb_t *http_request)
+{
+    hrb_node_t *node         = NULL;
+    const char *query_params = ""; /* unused at present */
+    herr_t      ret_value    = SUCCEED;
+    int         ret          = 0; /* return value of HDsnprintf */
+    size_t      len          = 0; /* working string length variable */
+    char        tmpstr[256];
+
+    /* "query params" refers to the optional element in the URL, e.g.
+     *     http://bucket.aws.com/myfile.txt?max-keys=2&prefix=J
+     *                                      ^-----------------^
+     *
+     * Not handled/implemented as of 2017-10-xx.
+     * Element introduced as empty placeholder and reminder.
+     * Further research to be done if this is ever relevant for the
+     * VFD use-cases.
+     */
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_aws_canonical_request.\n");
+#endif
+
+    if (http_request == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "hrb object cannot be null.\n");
+    }
+    HDassert( http_request->magic == S3COMMS_HRB_MAGIC );
+
+    if (canonical_request_dest == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "canonical request destination cannot be null.\n");
+    }
+
+    if (signed_headers_dest == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "signed headers destination cannot be null.\n");
+    }
+
+    /* HTTP verb, resource path, and query string lines
+     */
+    len = (HDstrlen(http_request->verb) +
+          HDstrlen(http_request->resource) +
+          HDstrlen(query_params) +
+          3 );
+    ret = HDsnprintf(canonical_request_dest,
+                   len + 1,
+                   "%s\n%s\n%s\n",
+                   http_request->verb,
+                   http_request->resource,
+                   query_params);
+    if (ret == 0 || (size_t)ret > len)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "unable to compose canonical request first line");
+
+    /* write in canonical headers, building signed headers concurrently
+     */
+    node = http_request->first_header; /* assumed at first sorted */
+    while (node != NULL) {
+        size_t join_len  = 0; /* string len of joined header-value */
+
+        HDassert( node->magic == S3COMMS_HRB_NODE_MAGIC );
+
+        len = HDstrlen(node->lowername);
+        join_len = HDstrlen(node->value) + len + 2; /* +2 <- ":\n" */
+        ret = HDsnprintf(tmpstr,
+                       join_len + 1, /* +1 for null terminator */
+                       "%s:%s\n",
+                       node->lowername,
+                       node->value);
+        if (ret == 0 || (size_t)ret > join_len)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to concatenate HTTP header %s:%s",
+                         node->lowername,
+                         node->value);
+        strcat(canonical_request_dest, tmpstr);
+
+        len += 1; /* semicolon */
+        ret = HDsnprintf(tmpstr,
+                       len + 1,
+                       "%s;",
+                       node->lowername);
+        if (ret == 0 || (size_t)ret > len)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to append signed header %s",
+                        node->lowername);
+        strcat(signed_headers_dest, tmpstr);
+
+        node = node->next;
+    }
+
+    /* remove tailing ';' from signed headers sequence
+     */
+    signed_headers_dest[HDstrlen(signed_headers_dest) - 1] = '\0';
+
+    /* append signed headers and payload hash
+     * NOTE: at present, no HTTP body is handled, per the nature of
+     *       requests/range-gets
+     */
+    strcat(canonical_request_dest, "\n");
+    strcat(canonical_request_dest, signed_headers_dest);
+    strcat(canonical_request_dest, "\n");
+    strcat(canonical_request_dest, EMPTY_SHA256);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_aws_canonical_request */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_bytes_to_hex()
+ *
+ * Purpose:
+ *
+ *     Produce human-readable hex string [0-9A-F] from sequence of bytes.
+ *
+ *     For each byte (char), writes two-character hexadecimal representation.
+ *
+ *     No null-terminator appended.
+ *
+ *     Assumes `dest` is allocated to enough size (msg_len * 2).
+ *
+ *     Fails if either `dest` or `msg` are null.
+ *
+ *     `msg_len` message length of 0 has no effect.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - hex string written to `dest` (not null-terminated)
+ *     - FAILURE: `FAIL`
+ *         - `dest == NULL`
+ *         - `msg == NULL`
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-12
+ *
+ * Changes:
+ *
+ *     - Integrate into HDF.
+ *     - Rename from hex() to H5FD_s3comms_bytes_to_hex.
+ *     - Change return type from `void` to `herr_t`.
+ *     --- Jacob Smtih 2017-09-14
+ *
+ *     - Add bool parameter `lowercase` to configure upper/lowercase output
+ *       of a-f hex characters.
+ *     --- Jacob Smith 2017-09-19
+ *
+ *     - Change bool type to `hbool_t`
+ *     --- Jacob Smtih 2017-10-11
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_bytes_to_hex(char                *dest,
+                          const unsigned char *msg,
+                          size_t               msg_len,
+                          hbool_t              lowercase)
+{
+    size_t i         = 0;
+    herr_t ret_value = SUCCEED;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_bytes_to_hex.\n");
+#endif
+
+    if (dest == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "hex destination cannot be null.\n")
+    }
+    if (msg == NULL) {
+       HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                   "bytes sequence cannot be null.\n")
+    }
+
+    for (i = 0; i < msg_len; i++) {
+        int chars_written =
+                HDsnprintf(&(dest[i * 2]),
+                         3, /* 'X', 'X', '\n' */
+                         (lowercase == TRUE) ? "%02x"
+                                             : "%02X",
+                         msg[i]);
+        if (chars_written != 2)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem while writing hex chars for %c",
+                        msg[i]);
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_bytes_to_hex */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_free_purl()
+ *
+ * Purpose:
+ *
+ *     Release resources from a parsed_url_t pointer.
+ *
+ *     If pointer is null, nothing happens.
+ *
+ * Return:
+ *
+ *     `SUCCEED` (never fails)
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-01
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_free_purl(parsed_url_t *purl)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+#if S3COMMS_DEBUG
+    HDprintf("called H5FD_s3comms_free_purl.\n");
+#endif
+
+    if (purl != NULL) {
+        HDassert( purl->magic == S3COMMS_PARSED_URL_MAGIC );
+        if (purl->scheme != NULL) H5MM_xfree(purl->scheme);
+        if (purl->host   != NULL) H5MM_xfree(purl->host);
+        if (purl->port   != NULL) H5MM_xfree(purl->port);
+        if (purl->path   != NULL) H5MM_xfree(purl->path);
+        if (purl->query  != NULL) H5MM_xfree(purl->query);
+        purl->magic += 1ul;
+        H5MM_xfree(purl);
+    }
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* H5FD_s3comms_free_purl */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_HMAC_SHA256()
+ *
+ * Purpose:
+ *
+ *     Generate Hash-based Message Authentication Checksum using the SHA-256
+ *     hashing algorithm.
+ *
+ *     Given a key, message, and respective lengths (to accommodate null
+ *     characters in either), generate _hex string_ of authentication checksum
+ *     and write to `dest`.
+ *
+ *     `dest` must be at least `SHA256_DIGEST_LENGTH * 2` characters in size.
+ *     Not enforceable by this function.
+ *     `dest` will _not_ be null-terminated by this function.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - hex string written to `dest` (not null-terminated)
+ *     - FAILURE: `FAIL`
+ *         - `dest == NULL`
+ *         - error while generating hex string output
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-??
+ *
+ * Changes:
+ *
+ *     - Integrate with HDF5.
+ *     - Rename from `HMAC_SHA256` to `H5FD_s3comms_HMAC_SHA256`.
+ *     - Rename output parameter from `md` to `dest`.
+ *     - Return `herr_t` type instead of `void`.
+ *     - Call `H5FD_s3comms_bytes_to_hex` to generate hex cleartext for output.
+ *     --- Jacob Smith 2017-09-19
+ *
+ *     - Use static char array instead of malloc'ing `md`
+ *     --- Jacob Smith 2017-10-10
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_HMAC_SHA256(const unsigned char *key,
+                         size_t               key_len,
+                         const char          *msg,
+                         size_t               msg_len,
+                         char                *dest)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    unsigned char md[SHA256_DIGEST_LENGTH];
+    unsigned int  md_len    = SHA256_DIGEST_LENGTH;
+    herr_t        ret_value = SUCCEED;
+#else
+    herr_t        ret_value = FAIL;
+#endif /* H5_HAVE_ROS3_VFD */
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_HMAC_SHA256.\n");
+#endif
+
+    if (dest == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "destination cannot be null.");
+    }
+
+    HMAC(EVP_sha256(),
+         key,
+         (int)key_len,
+         (const unsigned char *)msg,
+         msg_len,
+         md,
+         &md_len);
+
+    if (FAIL ==
+        H5FD_s3comms_bytes_to_hex(dest,
+                                  (const unsigned char *)md,
+                                  (size_t)md_len,
+                                  true))
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "could not convert to hex string.");
+    }
+
+#endif /* H5_HAVE_ROS3_VFD */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_HMAC_SHA256 */
+
+
+/*-----------------------------------------------------------------------------
+ *
+ * Function: H5FD__s3comms_load_aws_creds_from_file()
+ *
+ * Purpose:
+ *
+ *     Extract AWS configuration information from a target file.
+ *
+ *     Given a file and a profile name, e.g. "ros3_vfd_test", attempt to locate
+ *     that region in the file. If not found, returns in error and output
+ *     pointers are not modified.
+ *
+ *     If the profile label is found, attempts to locate and parse configuration
+ *     data, stopping at the first line where:
+ *     + reached end of file
+ *     + line does not start with a recognized setting name
+ *
+ *     Following AWS documentation, looks for any of:
+ *     + aws_access_key_id
+ *     + aws_secret_access_key
+ *     + region
+ *
+ *     To be valid, the setting must begin the line with one of the keywords,
+ *     followed immediately by an equals sign '=', and have some data before
+ *     newline at end of line.
+ *     + `spam=eggs` would be INVALID because name is unrecognized
+ *     + `region = us-east-2` would be INVALID because of spaces
+ *     + `region=` would be INVALID because no data.
+ *
+ *     Upon successful parsing of a setting line, will store the result in the
+ *     corresponding output pointer. If the output pointer is NULL, will skip
+ *     any matching setting line while parsing -- useful to prevent overwrite
+ *     when reading from multiple files.
+ *
+ * Return:
+ *
+ *     + SUCCESS: `SUCCEED`
+ *         + no error. settings may or may not have been loaded.
+ *     + FAILURE: `FAIL`
+ *         + internal error occurred.
+ *         + -1 :: unable to format profile label
+ *         + -2 :: profile name/label not found in file
+ *         + -3 :: some other error
+ *
+ * Programmer: Jacob Smith
+ *             2018-02-27
+ *
+ * Changes: None
+ *
+ *-----------------------------------------------------------------------------
+ */
+static herr_t
+H5FD__s3comms_load_aws_creds_from_file(
+        FILE       *file,
+        const char *profile_name,
+        char       *key_id,
+        char       *access_key,
+        char       *aws_region)
+{
+    char        profile_line[32];
+    char        buffer[128];
+    const char *setting_names[] = {
+        "region",
+        "aws_access_key_id",
+        "aws_secret_access_key",
+    };
+    char * const setting_pointers[] = {
+        aws_region,
+        key_id,
+        access_key,
+    };
+    unsigned  setting_count = 3;
+    herr_t    ret_value     = SUCCEED;
+    unsigned  buffer_i      = 0;
+    unsigned  setting_i     = 0;
+    int       found_setting = 0;
+    char     *line_buffer   = &(buffer[0]);
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called load_aws_creds_from_file.\n");
+#endif
+
+    /* format target line for start of profile */
+    if (32 < HDsnprintf(profile_line, 32, "[%s]", profile_name))
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTCOPY, FAIL,
+                    "unable to format profile label")
+
+    /* look for start of profile */
+    do {
+        /* clear buffer */
+        for (buffer_i=0; buffer_i < 128; buffer_i++) buffer[buffer_i] = 0;
+
+        line_buffer = fgets(line_buffer, 128, file);
+        if (line_buffer == NULL) /* reached end of file */
+            goto done;
+    } while (strncmp(line_buffer, profile_line, HDstrlen(profile_line)));
+
+    /* extract credentials from lines */
+    do {
+        size_t      setting_name_len = 0;
+        const char *setting_name     = NULL;
+        char        line_prefix[128];
+
+        /* clear buffer */
+        for (buffer_i=0; buffer_i < 128; buffer_i++) buffer[buffer_i] = 0;
+
+        /* collect a line from file */
+        line_buffer = fgets(line_buffer, 128, file);
+        if (line_buffer == NULL)
+            goto done; /* end of file */
+
+        /* loop over names to see if line looks like assignment */
+        for (setting_i = 0; setting_i < setting_count; setting_i++) {
+            setting_name = setting_names[setting_i];
+            setting_name_len = HDstrlen(setting_name);
+            if (128 < HDsnprintf(
+                    line_prefix,
+                    setting_name_len+2,
+                    "%s=",
+                    setting_name))
+                HGOTO_ERROR(H5E_ARGS, H5E_CANTCOPY, FAIL,
+                            "unable to format line prefix")
+
+            /* found a matching name? */
+            if (!HDstrncmp(line_buffer, line_prefix, setting_name_len + 1)) {
+                found_setting = 1;
+
+                /* skip NULL destination buffer */
+                if (setting_pointers[setting_i] == NULL)
+                   break;
+
+                /* advance to end of name in string */
+                do {
+                    line_buffer++;
+                } while (*line_buffer != 0 && *line_buffer != '=');
+
+                if (*line_buffer == 0 || *(line_buffer+1) == 0)
+                    HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                                "incomplete assignment in file")
+                line_buffer++; /* was pointing at '='; advance */
+
+                /* copy line buffer into out pointer */
+                HDstrncpy(setting_pointers[setting_i], (const char *)line_buffer,
+                        HDstrlen(line_buffer));
+
+                /* "trim" tailing whitespace by replacing with null terminator*/
+                buffer_i = 0;
+                while (!isspace(setting_pointers[setting_i][buffer_i]))
+                    buffer_i++;
+                setting_pointers[setting_i][buffer_i] = '\0';
+
+                break; /* have read setting; don't compare with others */
+            }
+        }
+    } while (found_setting);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD__s3comms_load_aws_creds_from_file */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_load_aws_profile()
+ *
+ * Purpose :
+ *
+ *     Read aws profile elements from standard location on system and store
+ *     settings in memory.
+ *
+ *     Looks for both `~/.aws/config` and `~/.aws/credentials`, the standard
+ *     files for AWS tools. If a file exists (can be opened), looks for the
+ *     given profile name and reads the settings into the relevant buffer.
+ *
+ *     Any setting duplicated in both files will be set to that from
+ *     `credentials`.
+ *
+ *     Settings are stored in the supplied buffers as null-terminated strings.
+ *
+ * Return:
+ *
+ *     + SUCCESS: `SUCCEED` (0)
+ *         + no error occurred and all settings were populated
+ *     + FAILURE: `FAIL` (-1)
+ *         + internal error occurred
+ *         + unable to locate profile
+ *         + region, key id, and secret key were not all found and set
+ *
+ * Programmer: Jacob Smith
+ *             2018-02-27
+ *
+ * Changes: None
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_load_aws_profile(const char *profile_name,
+                              char       *key_id_out,
+                              char       *secret_access_key_out,
+                              char       *aws_region_out)
+{
+    herr_t ret_value = SUCCEED;
+    FILE *credfile = NULL;
+    char awspath[117];
+    char filepath[128];
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_load_aws_profile.\n");
+#endif
+
+    /* TODO: Windows and other path gotchas */
+    if (117 < HDsnprintf(awspath, 117, "%s/.aws/", getenv("HOME")))
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTCOPY, FAIL,
+                    "unable to format home-aws path")
+    if (128 < HDsnprintf(filepath, 128, "%s%s", awspath, "credentials"))
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTCOPY, FAIL,
+                    "unable to format credentials path")
+
+    credfile = fopen(filepath, "r");
+    if (credfile != NULL) {
+        if (FAIL == H5FD__s3comms_load_aws_creds_from_file(
+                credfile,
+                profile_name,
+                key_id_out,
+                secret_access_key_out,
+                aws_region_out))
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to load from aws credentials")
+        if (EOF == fclose(credfile))
+            HGOTO_ERROR(H5E_FILE, H5E_CANTCLOSEFILE, FAIL,
+                        "unable to close credentials file")
+        credfile = NULL;
+    }
+
+    if (128 < HDsnprintf(filepath, 128, "%s%s", awspath, "config"))
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTCOPY, FAIL,
+                    "unable to format config path")
+    credfile = fopen(filepath, "r");
+    if (credfile != NULL) {
+        if (FAIL == H5FD__s3comms_load_aws_creds_from_file(
+                credfile,
+                profile_name,
+                (*key_id_out == 0) ? key_id_out : NULL,
+                (*secret_access_key_out == 0) ? secret_access_key_out : NULL,
+                (*aws_region_out == 0) ? aws_region_out : NULL))
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "unable to load from aws config")
+        if (EOF == fclose(credfile))
+            HGOTO_ERROR(H5E_FILE, H5E_CANTCLOSEFILE, FAIL,
+                        "unable to close config file")
+        credfile = NULL;
+    }
+
+    /* fail if not all three settings were loaded */
+    if (*key_id_out == 0 ||
+        *secret_access_key_out == 0 ||
+        *aws_region_out == 0)
+    {
+        ret_value = FAIL;
+    }
+
+done:
+    if (credfile != NULL) {
+        if (EOF == fclose(credfile))
+            HDONE_ERROR(H5E_ARGS, H5E_ARGS, FAIL,
+                        "problem error-closing aws configuration file")
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_load_aws_profile */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_nlowercase()
+ *
+ * Purpose:
+ *
+ *     From string starting at `s`, write `len` characters to `dest`,
+ *     converting all to lowercase.
+ *
+ *     Behavior is undefined if `s` is NULL or `len` overruns the allocated
+ *     space of either `s` or `dest`.
+ *
+ *     Provided as convenience.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - upon completion, `dest` is populated
+ *     - FAILURE: `FAIL`
+ *         - `dest == NULL`
+ *
+ * Programmer: Jacob Smith
+ *             2017-09-18
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_nlowercase(char       *dest,
+                        const char *s,
+                        size_t      len)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_nlowercase.\n");
+#endif
+
+    if (dest == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "destination cannot be null.\n");
+    }
+
+    if (len > 0) {
+        HDmemcpy(dest, s, len);
+        do {
+            len--;
+            dest[len] = (char)tolower( (int)dest[len] );
+        } while (len > 0);
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_nlowercase */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_parse_url()
+ *
+ * Purpose:
+ *
+ *     Parse URL-like string and stuff URL components into
+ *     `parsed_url` structure, if possible.
+ *
+ *     Expects null-terminated string of format:
+ *     SCHEME "://" HOST [":" PORT ] ["/" [ PATH ] ] ["?" QUERY]
+ *     where SCHEME :: "[a-zA-Z/.-]+"
+ *           PORT   :: "[0-9]"
+ *
+ *     Stores resulting structure in argument pointer `purl`, if successful,
+ *     creating and populating new `parsed_url_t` structure pointer.
+ *     Empty or absent elements are NULL in new purl structure.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - `purl` pointer is populated
+ *     - FAILURE: `FAIL`
+ *         - unable to parse
+ *             - `purl` is unaltered (probably NULL)
+ *
+ * Programmer: Jacob Smith
+ *             2017-10-30
+ *
+ * Changes: None.
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_parse_url(const char    *str,
+                       parsed_url_t **_purl)
+{
+    parsed_url_t *purl         = NULL; /* pointer to new structure */
+    const char   *tmpstr       = NULL; /* working pointer in string */
+    const char   *curstr       = str;  /* "start" pointer in string */
+    long int      len          = 0;    /* substring length */
+    long int      urllen       = 0;    /* length of passed-in url string */
+    unsigned int  i            = 0;
+    herr_t        ret_value    = FAIL;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT;
+
+#if S3COMMS_DEBUG
+    HDprintf("called H5FD_s3comms_parse_url.\n");
+#endif
+
+    if (str == NULL || *str == '\0') {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "invalid url string");
+    }
+
+    urllen = (long int)HDstrlen(str);
+
+    purl = (parsed_url_t *)H5MM_malloc(sizeof(parsed_url_t));
+    if (purl == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                    "can't allocate space for parsed_url_t");
+    }
+    purl->magic  = S3COMMS_PARSED_URL_MAGIC;
+    purl->scheme = NULL;
+    purl->host   = NULL;
+    purl->port   = NULL;
+    purl->path   = NULL;
+    purl->query  = NULL;
+
+    /***************
+     * READ SCHEME *
+     ***************/
+
+    tmpstr = HDstrchr(curstr, ':');
+    if (tmpstr == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "invalid SCHEME construction: probably not URL");
+    }
+    len = tmpstr - curstr;
+    HDassert( (0 <= len) && (len < urllen) );
+
+    /* check for restrictions
+     */
+    for (i = 0; i < len; i++) {
+        /* scheme = [a-zA-Z+-.]+ (terminated by ":") */
+        if (!isalpha(curstr[i]) &&
+             '+' != curstr[i] &&
+             '-' != curstr[i] &&
+             '.' != curstr[i])
+        {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "invalid SCHEME construction");
+        }
+    }
+    /* copy lowercased scheme to structure
+     */
+    purl->scheme = (char *)H5MM_malloc(sizeof(char) * (size_t)(len + 1));
+    if (purl->scheme == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                    "can't allocate space for SCHEME");
+    }
+    (void)HDstrncpy(purl->scheme, curstr, (size_t)len);
+    purl->scheme[len] = '\0';
+    for ( i = 0; i < len; i++ ) {
+        purl->scheme[i] = (char)tolower(purl->scheme[i]);
+    }
+
+    /* Skip "://" */
+    tmpstr += 3;
+    curstr = tmpstr;
+
+    /*************
+     * READ HOST *
+     *************/
+
+    if (*curstr == '[') {
+        /* IPv6 */
+        while (']' != *tmpstr) {
+            if (tmpstr == 0) { /* end of string reached! */
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "reached end of URL: incomplete IPv6 HOST");
+            }
+            tmpstr++;
+        }
+        tmpstr++;
+    } else {
+        while (0 != *tmpstr) {
+            if (':' == *tmpstr ||
+                '/' == *tmpstr ||
+                '?' == *tmpstr)
+            {
+                break;
+            }
+            tmpstr++;
+        }
+    } /* if IPv4 or IPv6 */
+    len = tmpstr - curstr;
+    if (len == 0) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "HOST substring cannot be empty");
+    } else if (len > urllen) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "problem with length of HOST substring");
+    }
+
+    /* copy host
+     */
+    purl->host = (char *)H5MM_malloc(sizeof(char) * (size_t)(len + 1));
+    if (purl->host == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                    "can't allocate space for HOST");
+    }
+    (void)HDstrncpy(purl->host, curstr, (size_t)len);
+    purl->host[len] = 0;
+
+    /*************
+     * READ PORT *
+     *************/
+
+    if (':' == *tmpstr) {
+        tmpstr += 1; /* advance past ':' */
+        curstr = tmpstr;
+        while ((0 != *tmpstr) && ('/' != *tmpstr) && ('?' != *tmpstr)) {
+            tmpstr++;
+        }
+        len = tmpstr - curstr;
+        if (len == 0) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "PORT element cannot be empty");
+        } else if (len > urllen) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem with length of PORT substring");
+        }
+        for (i = 0; i < len; i ++) {
+            if (!isdigit(curstr[i])) {
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "PORT is not a decimal string");
+            }
+        }
+
+        /* copy port
+         */
+        purl->port = (char *)H5MM_malloc(sizeof(char) * (size_t)(len + 1));
+        if (purl->port == NULL) { /* cannot malloc */
+                HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                            "can't allocate space for PORT");
+        }
+        (void)HDstrncpy(purl->port, curstr, (size_t)len);
+        purl->port[len] = 0;
+    } /* if PORT element */
+
+    /*************
+     * READ PATH *
+     *************/
+
+    if ('/' == *tmpstr) {
+        /* advance past '/' */
+        tmpstr += 1;
+        curstr = tmpstr;
+
+        /* seek end of PATH
+         */
+        while ((0 != *tmpstr) && ('?' != *tmpstr)) {
+            tmpstr++;
+        }
+        len = tmpstr - curstr;
+        if (len > urllen) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem with length of PATH substring");
+        }
+        if (len > 0) {
+            purl->path = (char *)H5MM_malloc(sizeof(char) * (size_t)(len + 1));
+            if (purl->path == NULL) {
+                    HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                                "can't allocate space for PATH");
+            } /* cannot malloc path pointer */
+            (void)HDstrncpy(purl->path, curstr, (size_t)len);
+            purl->path[len] = 0;
+        }
+    } /* if PATH element */
+
+    /**************
+     * READ QUERY *
+     **************/
+
+    if ('?' == *tmpstr) {
+        tmpstr += 1;
+        curstr = tmpstr;
+        while (0 != *tmpstr) {
+            tmpstr++;
+        }
+        len = tmpstr - curstr;
+        if (len == 0) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "QUERY cannot be empty");
+        } else if (len > urllen) {
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "problem with length of QUERY substring");
+        }
+        purl->query = (char *)H5MM_malloc(sizeof(char) * (size_t)(len + 1));
+        if (purl->query == NULL) {
+            HGOTO_ERROR(H5E_ARGS, H5E_CANTALLOC, FAIL,
+                        "can't allocate space for QUERY");
+        } /* cannot malloc path pointer */
+        (void)HDstrncpy(purl->query, curstr, (size_t)len);
+        purl->query[len] = 0;
+    } /* if QUERY exists */
+
+
+
+    *_purl = purl;
+    ret_value =  SUCCEED;
+
+done:
+    if (ret_value == FAIL) {
+        H5FD_s3comms_free_purl(purl);
+    }
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_parse_url */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_percent_encode_char()
+ *
+ * Purpose:
+ *
+ *     "Percent-encode" utf-8 character `c`, e.g.,
+ *         '$' -> "%24"
+ *         '¢' -> "%C2%A2"
+ *
+ *     `c` cannot be null.
+ *
+ *     Does not (currently) accept multi-byte characters...
+ *     limit to (?) u+00ff, well below upper bound for two-byte utf-8 encoding
+ *        (u+0080..u+07ff).
+ *
+ *     Writes output to `repr`.
+ *     `repr` cannot be null.
+ *     Assumes adequate space i `repr`...
+ *         >>> char[4] or [7] for most characters,
+ *         >>> [13] as theoretical maximum.
+ *
+ *     Representation `repr` is null-terminated.
+ *
+ *     Stores length of representation (without null terminator) at pointer
+ *     `repr_len`.
+ *
+ * Return : SUCCEED/FAIL
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - percent-encoded representation  written to `repr`
+ *         - 'repr' is null-terminated
+ *     - FAILURE: `FAIL`
+ *         - `c` or `repr` was NULL
+ *
+ * Programmer: Jacob Smith
+ *
+ * Changes:
+ *
+ *     - Integrate into HDF.
+ *     - Rename from `hexutf8` to `H5FD_s3comms_percent_encode_char`.
+ *     --- Jacob Smith 2017-09-15
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_percent_encode_char(char                *repr,
+                                 const unsigned char  c,
+                                 size_t              *repr_len)
+{
+    unsigned int        acc           = 0;
+    unsigned int        i             = 0;
+    unsigned int        k             = 0;
+    unsigned int        stack[4]      = {0, 0, 0, 0};
+    unsigned int        stack_size    = 0;
+    int                 chars_written = 0;
+    herr_t              ret_value     = SUCCEED;
+#if S3COMMS_DEBUG
+    unsigned char       s[2]          = {c, 0};
+    unsigned char       hex[3]        = {0, 0, 0};
+#endif
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_percent_encode_char.\n");
+#endif
+
+    if (repr == NULL) {
+       HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no destination `repr`.\n")
+    }
+
+#if S3COMMS_DEBUG
+    H5FD_s3comms_bytes_to_hex((char *)hex, s, 1, FALSE);
+    HDfprintf(stdout, "    CHAR: \'%s\'\n", s);
+    HDfprintf(stdout, "    CHAR-HEX: \"%s\"\n", hex);
+#endif
+
+    if (c <= (unsigned char)0x7f) {
+        /* character represented in a single "byte"
+         * and single percent-code
+         */
+#if S3COMMS_DEBUG
+        HDfprintf(stdout, "    SINGLE-BYTE\n");
+#endif
+        *repr_len = 3;
+        chars_written = HDsnprintf(repr, 4, "%%%02X", c);
+        if (chars_written != 3)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "cannot write char %c",
+                        c);
+    } else {
+        /* multi-byte, multi-percent representation
+         */
+#if S3COMMS_DEBUG
+        HDfprintf(stdout, "    MULTI-BYTE\n");
+#endif
+        stack_size = 0;
+        k = (unsigned int)c;
+        *repr_len = 0;
+        do {
+            /* push number onto stack in six-bit slices
+             */
+            acc = k;
+            acc >>= 6; /* cull least */
+            acc <<= 6; /* six bits   */
+            stack[stack_size++] = k - acc; /* max six-bit number */
+            k = acc >> 6;
+        } while (k > 0);
+
+        /* now have "stack" of two to four six-bit numbers
+         * to be put into UTF-8 byte fields
+         */
+
+#if S3COMMS_DEBUG
+        HDfprintf(stdout, "    STACK:\n    {\n");
+        for (i = 0; i < stack_size; i++) {
+            H5FD_s3comms_bytes_to_hex((char *)hex,
+                                      (unsigned char *)(&stack[i]),
+                                      1,
+                                      FALSE);
+            hex[2] = 0;
+            HDfprintf(stdout, "      %s,\n", hex);
+        }
+        HDfprintf(stdout, "    }\n");
+#endif
+
+        /****************
+         * leading byte *
+         ****************/
+
+        /* prepend 11[1[1]]0 to first byte */
+        /* 110xxxxx, 1110xxxx, or 11110xxx */
+        acc = 0xC0; /* 2^7 + 2^6 -> 11000000 */
+        acc += (stack_size > 2) ? 0x20 : 0;
+        acc += (stack_size > 3) ? 0x10 : 0;
+        stack_size -= 1;
+        chars_written = HDsnprintf(repr, 4, "%%%02X", acc + stack[stack_size]);
+        if (chars_written != 3)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                        "cannot write char %c",
+                        c);
+        *repr_len += 3;
+
+        /************************
+         * continuation byte(s) *
+         ************************/
+
+        /* 10xxxxxx */
+        for (i = 0; i < stack_size; i++) {
+            chars_written = HDsnprintf(&repr[i*3 + 3],
+                                     4,
+                                     "%%%02X",
+                                     128 + stack[stack_size - 1 - i]);
+            if (chars_written != 3)
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "cannot write char %c",
+                            c);
+            *repr_len += 3;
+        }
+    }
+    *(repr + *repr_len) = '\0';
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_percent_encode_char */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_signing_key()
+ *
+ * Purpose:
+ *
+ *     Create AWS4 "Signing Key" from secret key, AWS region, and timestamp.
+ *
+ *     Sequentially runs HMAC_SHA256 on strings in specified order,
+ *     generating re-usable checksum (according to documentation, valid for
+ *     7 days from time given).
+ *
+ *     `secret` is `access key id` for targeted service/bucket/resource.
+ *
+ *     `iso8601now` must conform to format, yyyyMMDD'T'hhmmss'Z'
+ *     e.g. "19690720T201740Z".
+ *
+ *     `region` should be one of AWS service region names, e.g. "us-east-1".
+ *
+ *     Hard-coded "service" algorithm requirement to "s3".
+ *
+ *     Inputs must be null-terminated strings.
+ *
+ *     Writes to `md` the raw byte data, length of `SHA256_DIGEST_LENGTH`.
+ *     Programmer must ensure that `md` is appropriately allocated.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - raw byte data of signing key written to `md`
+ *     - FAILURE: `FAIL`
+ *         - if any input arguments was NULL
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-13
+ *
+ * Changes:
+ *
+ *     - Integrate into HDF5.
+ *     - Return herr_t type.
+ *     --- Jacob Smith 2017-09-18
+ *
+ *     - NULL check and fail of input parameters.
+ *     --- Jacob Smith 2017-10-10
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_signing_key(unsigned char *md,
+                         const char    *secret,
+                         const char    *region,
+                         const char    *iso8601now)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    char          *AWS4_secret     = NULL;
+    size_t         AWS4_secret_len = 0;
+    unsigned char  datekey[SHA256_DIGEST_LENGTH];
+    unsigned char  dateregionkey[SHA256_DIGEST_LENGTH];
+    unsigned char  dateregionservicekey[SHA256_DIGEST_LENGTH];
+    int            ret             = 0; /* return value of HDsnprintf */
+    herr_t         ret_value       = SUCCEED;
+#else
+    herr_t         ret_value       = SUCCEED;
+#endif /* H5_HAVE_ROS3_VFD */
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_signing_key.\n");
+#endif
+
+    if (md == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "Destination `md` cannot be NULL.\n")
+    }
+    if (secret == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "`secret` cannot be NULL.\n")
+    }
+    if (region == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "`region` cannot be NULL.\n")
+    }
+    if (iso8601now == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "`iso8601now` cannot be NULL.\n")
+    }
+
+    AWS4_secret_len = 4 + HDstrlen(secret) + 1;
+    AWS4_secret = (char*)H5MM_malloc(sizeof(char *) * AWS4_secret_len);
+    if (AWS4_secret == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "Could not allocate space.\n")
+    }
+
+    /* prepend "AWS4" to start of the secret key
+     */
+    ret = HDsnprintf(AWS4_secret, AWS4_secret_len,"%s%s", "AWS4", secret);
+    if ((size_t)ret != (AWS4_secret_len - 1))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "problem writing AWS4+secret `%s`",
+                    secret);
+
+    /* hash_func, key, len(key), msg, len(msg), digest_dest, digest_len_dest
+     * we know digest length, so ignore via NULL
+     */
+    HMAC(EVP_sha256(),
+         (const unsigned char *)AWS4_secret,
+         (int)HDstrlen(AWS4_secret),
+         (const unsigned char*)iso8601now,
+         8, /* 8 --> length of 8 --> "yyyyMMDD"  */
+         datekey,
+         NULL);
+    HMAC(EVP_sha256(),
+         (const unsigned char *)datekey,
+         SHA256_DIGEST_LENGTH,
+         (const unsigned char *)region,
+         HDstrlen(region),
+         dateregionkey,
+         NULL);
+    HMAC(EVP_sha256(),
+         (const unsigned char *)dateregionkey,
+         SHA256_DIGEST_LENGTH,
+         (const unsigned char *)"s3",
+         2,
+         dateregionservicekey,
+         NULL);
+    HMAC(EVP_sha256(),
+         (const unsigned char *)dateregionservicekey,
+         SHA256_DIGEST_LENGTH,
+         (const unsigned char *)"aws4_request",
+         12,
+         md,
+         NULL);
+
+done:
+    H5MM_xfree(AWS4_secret);
+
+#endif /* H5_HAVE_ROS3_VFD */
+
+    FUNC_LEAVE_NOAPI(ret_value);
+
+} /* H5FD_s3comms_signing_key */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_tostringtosign()
+ *
+ * Purpose:
+ *
+ *     Get AWS "String to Sign" from Canonical Request, timestamp,
+ *     and AWS "region".
+ *
+ *     Common between single request and "chunked upload",
+ *     conforms to:
+ *         "AWS4-HMAC-SHA256\n" +
+ *         <ISO8601 date format> + "\n" +  // yyyyMMDD'T'hhmmss'Z'
+ *         <yyyyMMDD> + "/" + <AWS Region> + "/s3/aws4-request\n" +
+ *         hex(SHA256(<CANONICAL-REQUEST>))
+ *
+ *     Inputs `creq` (canonical request string), `now` (ISO8601 format),
+ *     and `region` (s3 region designator string) must all be
+ *     null-terminated strings.
+ *
+ *     Result is written to `dest` with null-terminator.
+ *     It is left to programmer to ensure `dest` has adequate space.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *         - "string to sign" written to `dest` and null-terminated
+ *     - FAILURE: `FAIL`
+ *         - if any of the inputs are NULL
+ *         - if an error is encountered while computing checksum
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-??
+ *
+ * Changes:
+ *
+ *     - Integrate with HDF5.
+ *     - Rename from `tostringtosign` to `H5FD_s3comms_tostringtosign`.
+ *     - Return `herr_t` instead of characters written.
+ *     - Use HDF-friendly bytes-to-hex function (`H5FD_s3comms_bytes_to_hex`)
+ *       instead of general-purpose, deprecated `hex()`.
+ *     - Adjust casts to openssl's `SHA256`.
+ *     - Input strings are now `const`.
+ *     --- Jacob Smith 2017-09-19
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_tostringtosign(char       *dest,
+                            const char *req,
+                            const char *now,
+                            const char *region)
+{
+#ifdef H5_HAVE_ROS3_VFD
+    unsigned char checksum[SHA256_DIGEST_LENGTH * 2 + 1];
+    size_t        d         = 0;
+    char          day[9];
+    char          hexsum[SHA256_DIGEST_LENGTH * 2 + 1];
+    size_t        i         = 0;
+    int           ret       = 0; /* HDsnprintf return value */
+    herr_t        ret_value = SUCCEED;
+    char          tmp[128];
+#else
+    herr_t        ret_value = FAIL;
+#endif /* H5_HAVE_ROS3_VFD */
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#ifdef H5_HAVE_ROS3_VFD
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_tostringtosign.\n");
+#endif
+
+    if (dest == NULL)  {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "destination buffer cannot be null.\n")
+    }
+    if (req == NULL)  {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "canonical request cannot be null.\n")
+    }
+    if (now == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "Timestring cannot be NULL.\n")
+    }
+    if (region == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "Region cannot be NULL.\n")
+    }
+
+
+
+    for (i = 0; i < 128; i++) {
+        tmp[i] = '\0';
+    }
+    for (i = 0; i < SHA256_DIGEST_LENGTH * 2 + 1; i++) {
+        checksum[i] = '\0';
+        hexsum[i] = '\0';
+    }
+    HDstrncpy(day, now, 8);
+    day[8] = '\0';
+    ret = HDsnprintf(tmp, 127, "%s/%s/s3/aws4_request", day, region);
+    if (ret <= 0 || ret >= 127)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "problem adding day and region to string")
+
+
+
+    HDmemcpy((dest + d), "AWS4-HMAC-SHA256\n", 17);
+    d = 17;
+
+    HDmemcpy((dest+d), now, HDstrlen(now));
+    d += HDstrlen(now);
+    dest[d++] = '\n';
+
+    HDmemcpy((dest + d), tmp, HDstrlen(tmp));
+    d += HDstrlen(tmp);
+    dest[d++] = '\n';
+
+    SHA256((const unsigned char *)req,
+           HDstrlen(req),
+           checksum);
+
+    if (FAIL ==
+        H5FD_s3comms_bytes_to_hex(hexsum,
+                                  (const unsigned char *)checksum,
+                                  SHA256_DIGEST_LENGTH,
+                                  true))
+    {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "could not create hex string");
+    }
+
+    for (i = 0; i < SHA256_DIGEST_LENGTH * 2; i++) {
+        dest[d++] = hexsum[i];
+    }
+
+    dest[d] = '\0';
+
+#endif /* H5_HAVE_ROS3_VFD */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5ros3_tostringtosign */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_trim()
+ *
+ * Purpose:
+ *
+ *     Remove all whitespace characters from start and end of a string `s`
+ *     of length `s_len`, writing trimmed string copy to `dest`.
+ *     Stores number of characters remaining at `n_written`.
+ *
+ *     Destination for trimmed copy `dest` cannot be null.
+ *     `dest` must have adequate space allocated for trimmed copy.
+ *         If inadequate space, behavior is undefined, possibly resulting
+ *         in segfault or overwrite of other data.
+ *
+ *     If `s` is NULL or all whitespace, `dest` is untouched and `n_written`
+ *     is set to 0.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - `dest == NULL`
+ *
+ * Programmer: Jacob Smith
+ *             2017-09-18
+ *
+ * Changes:
+ *
+ *     - Rename from `trim()` to `H5FD_s3comms_trim()`.
+ *     - Incorporate into HDF5.
+ *     - Returns `herr_t` type.
+ *     --- Jacob Smith 2017-??-??
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_trim(char   *dest,
+                  char   *s,
+                  size_t  s_len,
+                  size_t *n_written)
+{
+    herr_t               ret_value = SUCCEED;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "called H5FD_s3comms_trim.\n");
+#endif
+
+    if (dest == NULL) {
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "destination cannot be null.")
+    }
+    if (s == NULL) {
+        s_len = 0;
+    }
+
+
+
+    if (s_len > 0) {
+        /* Find first non-whitespace character from start;
+         * reduce total length per character.
+         */
+        while ((s_len > 0) &&
+               isspace((unsigned char)s[0]) && s_len > 0)
+        {
+             s++;
+             s_len--;
+        }
+
+        /* Find first non-whitespace character from tail;
+         * reduce length per-character.
+         * If length is 0 already, there is no non-whitespace character.
+         */
+        if (s_len > 0) {
+            do {
+                s_len--;
+            } while( isspace((unsigned char)s[s_len]) );
+            s_len++;
+
+            /* write output into dest
+             */
+            HDmemcpy(dest, s, s_len);
+        }
+    }
+
+    *n_written = s_len;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_trim */
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Function: H5FD_s3comms_uriencode()
+ *
+ * Purpose:
+ *
+ *     URIencode (percent-encode) every byte except "[a-zA-Z0-9]-._~".
+ *
+ *     For each character in source string `_s` from `s[0]` to `s[s_len-1]`,
+ *     writes to `dest` either the raw character or its percent-encoded
+ *     equivalent.
+ *
+ *     See `H5FD_s3comms_bytes_to_hex` for information on percent-encoding.
+ *
+ *     Space (' ') character encoded as "%20" (not "+")
+ *
+ *     Forward-slash ('/') encoded as "%2F" only when `encode_slash == true`.
+ *
+ *     Records number of characters written at `n_written`.
+ *
+ *     Assumes that `dest` has been allocated with enough space.
+ *
+ *     Neither `dest` nor `s` can be NULL.
+ *
+ *     `s_len == 0` will have no effect.
+ *
+ * Return:
+ *
+ *     - SUCCESS: `SUCCEED`
+ *     - FAILURE: `FAIL`
+ *         - source strings `s` or destination `dest` are NULL
+ *         - error while attempting to percent-encode a character
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-??
+ *
+ * Changes:
+ *
+ *     - Integrate to HDF environment.
+ *     - Rename from `uriencode` to `H5FD_s3comms_uriencode`.
+ *     - Change return from characters written to herr_t;
+ *       move to i/o parameter `n_written`.
+ *     - No longer append null-terminator to string;
+ *       programmer may append or not as appropriate upon return.
+ *     --- Jacob Smith 2017-09-15
+ *
+ *----------------------------------------------------------------------------
+ */
+herr_t
+H5FD_s3comms_uriencode(char       *dest,
+                       const char *s,
+                       size_t      s_len,
+                       hbool_t     encode_slash,
+                       size_t     *n_written)
+{
+    char   c         = 0;
+    size_t dest_off  = 0;
+    char   hex_buffer[13];
+    size_t hex_off   = 0;
+    size_t hex_len   = 0;
+    herr_t ret_value = SUCCEED;
+    size_t s_off     = 0;
+
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+#if S3COMMS_DEBUG
+    HDfprintf(stdout, "H5FD_s3comms_uriencode called.\n");
+#endif
+
+    if (s == NULL)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "source string cannot be NULL");
+    if (dest == NULL)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "destination cannot be NULL");
+
+    /* Write characters to destination, converting to percent-encoded
+     * "hex-utf-8" strings if necessary.
+     * e.g., '$' -> "%24"
+     */
+    for (s_off = 0; s_off < s_len; s_off++) {
+        c = s[s_off];
+        if (isalnum(c) ||
+            c == '.'   ||
+            c == '-'   ||
+            c == '_'   ||
+            c == '~'   ||
+            (c == '/' && encode_slash == FALSE))
+        {
+            dest[dest_off++] = c;
+        } else {
+            hex_off = 0;
+            if (FAIL ==
+                H5FD_s3comms_percent_encode_char(hex_buffer,
+                                                 (const unsigned char)c,
+                                                 &hex_len))
+            {
+                hex_buffer[0] = c;
+                hex_buffer[1] = 0;
+                HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                            "unable to percent-encode character \'%s\' "
+                            "at %d in \"%s\"", hex_buffer, (int)s_off, s);
+            }
+
+            for (hex_off = 0; hex_off < hex_len; hex_off++) {
+                dest[dest_off++] = hex_buffer[hex_off];
+            }
+        }
+    }
+
+    if (dest_off < s_len)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL,
+                    "buffer overflow");
+
+    *n_written = dest_off;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* H5FD_s3comms_uriencode */
+
+
diff --git a/src/H5FDs3comms.h b/src/H5FDs3comms.h
new file mode 100644
index 0000000..93a5a81
--- /dev/null
+++ b/src/H5FDs3comms.h
@@ -0,0 +1,633 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*****************************************************************************
+ * Read-Only S3 Virtual File Driver (VFD)                                   
+ *
+ * This is the header for the S3 Communications module
+ *
+ * ***NOT A FILE DRIVER***
+ *
+ * Purpose:
+ *
+ *     - Provide structures and functions related to communicating with
+ *       Amazon S3 (Simple Storage Service).
+ *     - Abstract away the REST API (HTTP,
+ *       networked communications) behind a series of uniform function calls.
+ *     - Handle AWS4 authentication, if appropriate.
+ *     - Fail predictably in event of errors.
+ *     - Eventually, support more S3 operations, such as creating, writing to,
+ *       and removing Objects remotely.
+ *
+ *     translates:
+ *     `read(some_file, bytes_offset, bytes_length, &dest_buffer);`
+ *     to:
+ *     ```
+ *     GET myfile HTTP/1.1
+ *     Host: somewhere.me
+ *     Range: bytes=4096-5115
+ *     ```
+ *     and places received bytes from HTTP response...
+ *     ```
+ *     HTTP/1.1 206 Partial-Content
+ *     Content-Range: 4096-5115/63239
+ *
+ *     <bytes>
+ *     ```
+ *     ...in destination buffer.
+ *
+ * TODO: put documentation in a consistent place and point to it from here.
+ *
+ * Programmer: Jacob Smith
+ *             2017-11-30
+ *
+ *****************************************************************************/
+
+#include <ctype.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#ifdef H5_HAVE_ROS3_VFD
+#include <curl/curl.h>
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#include <openssl/sha.h>
+#endif /* ifdef H5_HAVE_ROS3_VFD */
+
+/*****************
+ * PUBLIC MACROS *
+ *****************/
+
+/* hexadecimal string of pre-computed sha256 checksum of the empty string
+ * hex(sha256sum(""))
+ */
+#define EMPTY_SHA256 \
+"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+
+/* string length (plus null terminator)
+ * example ISO8601-format string: "20170713T145903Z" (YYYYmmdd'T'HHMMSS'_')
+ */
+#define ISO8601_SIZE 17
+
+/* string length (plus null terminator)
+ * example RFC7231-format string: "Fri, 30 Jun 2017 20:41:55 GMT"
+ */
+#define RFC7231_SIZE 30
+
+/*---------------------------------------------------------------------------
+ *
+ * Macro: ISO8601NOW()
+ *
+ * Purpose:
+ *
+ *     write "YYYYmmdd'T'HHMMSS'Z'" (less single-quotes) to dest
+ *     e.g., "20170630T204155Z"
+ *
+ *     wrapper for strftime()
+ *
+ *     It is left to the programmer to check return value of
+ *     ISO8601NOW (should equal ISO8601_SIZE - 1).
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-??
+ *
+ *---------------------------------------------------------------------------
+ */
+#define ISO8601NOW(dest, now_gm) \
+strftime((dest), ISO8601_SIZE, "%Y%m%dT%H%M%SZ", (now_gm))
+
+/*---------------------------------------------------------------------------
+ *
+ * Macro: RFC7231NOW()
+ *
+ * Purpose:
+ *
+ *     write "Day, dd Mmm YYYY HH:MM:SS GMT" to dest
+ *     e.g., "Fri, 30 Jun 2017 20:41:55 GMT"
+ *
+ *     wrapper for strftime()
+ *
+ *     It is left to the programmer to check return value of
+ *     RFC7231NOW (should equal RFC7231_SIZE - 1).
+ *
+ * Programmer: Jacob Smith
+ *             2017-07-??
+ *
+ *---------------------------------------------------------------------------
+ */
+#define RFC7231NOW(dest, now_gm) \
+strftime((dest), RFC7231_SIZE, "%a, %d %b %Y %H:%M:%S GMT", (now_gm))
+
+
+/* Reasonable maximum length of a credential string.
+ * Provided for error-checking S3COMMS_FORMAT_CREDENTIAL (below).
+ *  17 <- "////aws4_request\0"
+ *   2 < "s3" (service)
+ *   8 <- "YYYYmmdd" (date)
+ * 128 <- (access_id)
+ * 155 :: sum
+ */
+#define S3COMMS_MAX_CREDENTIAL_SIZE 155
+
+
+/*---------------------------------------------------------------------------
+ *
+ * Macro: H5FD_S3COMMS_FORMAT_CREDENTIAL()
+ *
+ * Purpose:
+ *
+ *     Format "S3 Credential" string from inputs, for AWS4.
+ *
+ *     Wrapper for HDsnprintf().
+ *
+ *     _HAS NO ERROR-CHECKING FACILITIES_
+ *     It is left to programmer to ensure that return value confers success.
+ *     e.g.,
+ *     ```
+ *     assert( S3COMMS_MAX_CREDENTIAL_SIZE >=
+ *             S3COMMS_FORMAT_CREDENTIAL(...) );
+ *     ```
+ *
+ *     "<access-id>/<date>/<aws-region>/<aws-service>/aws4_request"
+ *     assuming that `dest` has adequate space.
+ *
+ *     ALL inputs must be null-terminated strings.
+ *
+ *     `access` should be the user's access key ID.
+ *     `date` must be of format "YYYYmmdd".
+ *     `region` should be relevant AWS region, i.e. "us-east-1".
+ *     `service` should be "s3".
+ *
+ * Programmer: Jacob Smith
+ *             2017-09-19
+ *
+ * Changes: None.
+ *
+ *---------------------------------------------------------------------------
+ */
+#define S3COMMS_FORMAT_CREDENTIAL(dest, access, iso8601_date, region, service) \
+HDsnprintf((dest), S3COMMS_MAX_CREDENTIAL_SIZE,                                  \
+         "%s/%s/%s/%s/aws4_request",                                           \
+         (access), (iso8601_date), (region), (service))
+
+/*********************
+ * PUBLIC STRUCTURES *
+ *********************/
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Structure: hrb_node_t
+ *
+ * HTTP Header Field Node
+ *
+ *
+ *
+ * Maintain a ordered (linked) list of HTTP Header fields.
+ *
+ * Provides efficient access and manipulation of a logical sequence of
+ * HTTP header fields, of particular use when composing an
+ * "S3 Canonical Request" for authentication.
+ *
+ * - The creation of a Canoncial Request involves:
+ *     - convert field names to lower case
+ *     - sort by this lower-case name
+ *     - convert ": " name-value separator in HTTP string to ":"
+ *     - get sorted lowercase names without field or separator
+ *
+ * As HTTP headers allow headers in any order (excepting the case of multiple
+ * headers with the same name), the list ordering can be optimized for Canonical
+ * Request creation, suggesting alphabtical order. For more expedient insertion
+ * and removal of elements in the list, linked list seems preferable to a
+ * dynamically-expanding array. The usually-smaller number of entries (5 or
+ * fewer) makes performance overhead of traversing the list trivial.
+ *
+ * The above requirements of creating at Canonical Request suggests a reasonable
+ * trade-off of speed for space with the option to compute elements as needed
+ * or to have the various elements prepared and stored in the structure
+ * (e.g. name, value, lowername, concatenated name:value)
+ * The structure currently is implemented to pre-compute.
+ *
+ * At all times, the "first" node of the list should be the least,
+ * alphabetically. For all nodes, the `next` node should be either NULL or
+ * of greater alphabetical value.
+ *
+ * Each node contains its own header field information, plus a pointer to the
+ * next node.
+ *
+ * It is not allowed to have multiple nodes with the same _lowercase_ `name`s
+ * in the same list
+ * (i.e., name is case-insensitive for access and modification.)
+ *
+ * All data (`name`, `value`, `lowername`, and `cat`) are null-terminated
+ * strings allocated specifically for their node.
+ *
+ *
+ *
+ * `magic` (unsigned long)
+ *
+ *     "unique" idenfier number for the structure type
+ *
+ * `name` (char *)
+ *
+ *     Case-meaningful name of the HTTP field.
+ *     Given case is how it is supplied to networking code.
+ *     e.g., "Range"
+ *
+ * `lowername` (char *)
+ *
+ *     Lowercase copy of name.
+ *     e.g., "range"
+ *
+ * `value` (char *)
+ *
+ *     Case-meaningful value of HTTP field.
+ *     e.g., "bytes=0-9"
+ *
+ * `cat` (char *)
+ *
+ *     Concatenated, null-terminated string of HTTP header line,
+ *     as the field would appear in an HTTP request.
+ *     e.g., "Range: bytes=0-9"
+ *
+ * `next` (hrb_node_t *)
+ *
+ *     Pointers to next node in the list, or NULL sentinel as end of list.
+ *     Next node must have a greater `lowername` as determined by strcmp().
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *             2017-09-22
+ *
+ * Changes:
+ *
+ *     - Change from twin doubly-linked lists to singly-linked list.
+ *     --- Jake Smith 2017-01-17
+ *
+ *----------------------------------------------------------------------------
+ */
+typedef struct hrb_node_t {
+    unsigned long      magic;
+    char              *name;
+    char              *value;
+    char              *cat;
+    char              *lowername;
+    struct hrb_node_t *next;
+} hrb_node_t;
+#define S3COMMS_HRB_NODE_MAGIC 0x7F5757UL
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Structure: hrb_t
+ *
+ * HTTP Request Buffer structure
+ *
+ *
+ *
+ * Logically represent an HTTP request
+ *
+ *     GET /myplace/myfile.h5 HTTP/1.1
+ *     Host: over.rainbow.oz
+ *     Date: Fri, 01 Dec 2017 12:35:04 CST
+ *
+ *     <body>
+ *
+ * ...with fast, efficient access to and modification of primary and field
+ * elements.
+ *
+ * Structure for building HTTP requests while hiding much of the string
+ * processing required "under the hood."
+ *
+ * Information about the request target -- the first line -- and the body text,
+ * if any, are managed directly with this structure. All header fields, e.g.,
+ * "Host" and "Date" above, are created with a linked list of `hrb_node_t` and
+ * included in the request by a pointer to the head of the list.
+ *
+ *
+ *
+ * `magic` (unsigned long)
+ *
+ *     "Magic" number confirming that this is an hrb_t structure and
+ *     what operations are valid for it.
+ *
+ *     Must be S3COMMS_HRB_MAGIC to be valid.
+ *
+ * `body` (char *) :
+ *
+ *     Pointer to start of HTTP body.
+ *
+ *     Can be NULL, in which case it is treated as the empty string, "".
+ *
+ * `body_len` (size_t) :
+ *
+ *     Number of bytes (characters) in `body`. 0 if empty or NULL `body`.
+ *
+ * `first_header` (hrb_node_t *) :
+ *
+ *     Pointer to first SORTED header node, if any.
+ *     It is left to the programmer to ensure that this node and associated
+ *     list is destroyed when done.
+ *
+ * `resource` (char *) :
+ *
+ *     Pointer to resource URL string, e.g., "/folder/page.xhtml".
+ *
+ * `verb` (char *) :
+ *
+ *     Pointer to HTTP verb string, e.g., "GET".
+ *
+ * `version` (char *) :
+ *
+ *     Pointer to HTTP version string, e.g., "HTTP/1.1".
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ *----------------------------------------------------------------------------
+ */
+typedef struct {
+    unsigned long  magic;
+    char          *body;
+    size_t         body_len;
+    hrb_node_t    *first_header;
+    char          *resource;
+    char          *verb;
+    char          *version;
+} hrb_t;
+#define S3COMMS_HRB_MAGIC 0x6DCC84UL
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Structure: parsed_url_t
+ *
+ *
+ * Represent a URL with easily-accessed pointers to logical elements within.
+ * These elements (components) are stored as null-terminated strings (or just
+ * NULLs). These components should be allocated for the structure, making the
+ * data as safe as possible from modification. If a component is NULL, it is
+ * either implicit in or absent from the URL.
+ *
+ * "http://mybucket.s3.amazonaws.com:8080/somefile.h5?param=value&arg=value"
+ *  ^--^   ^-----------------------^ ^--^ ^---------^ ^-------------------^
+ * Scheme             Host           Port  Resource        Query/-ies
+ *
+ *
+ *
+ * `magic` (unsigned long)
+ *
+ *     Structure identification and validation identifier.
+ *     Identifies as `parsed_url_t` type.
+ *
+ * `scheme` (char *)
+ *
+ *     String representing which protocol is to be expected.
+ *     _Must_ be present.
+ *     "http", "https", "ftp", e.g.
+ *
+ * `host` (char *)
+ *
+ *     String of host, either domain name, IPv4, or IPv6 format.
+ *     _Must_ be present.
+ *     "over.rainbow.oz", "192.168.0.1", "[0000:0000:0000:0001]"
+ *
+ * `port` (char *)
+ *
+ *     String representation of specified port. Must resolve to a valid unsigned
+ *     integer.
+ *     "9000", "80"
+ *
+ * `path` (char *)
+ *
+ *     Path to resource on host. If not specified, assumes root "/".
+ *     "lollipop_guild.wav", "characters/witches/white.dat"
+ *
+ * `query` (char *)
+ *
+ *     Single string of all query parameters in url (if any).
+ *     "arg1=value1&arg2=value2"
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ *----------------------------------------------------------------------------
+ */
+typedef struct {
+    unsigned long  magic;
+    char          *scheme; /* required */
+    char          *host;   /* required */
+    char          *port;
+    char          *path;
+    char          *query;
+} parsed_url_t;
+#define S3COMMS_PARSED_URL_MAGIC 0x21D0DFUL
+
+
+/*----------------------------------------------------------------------------
+ *
+ * Structure: s3r_t
+ *
+ *
+ *
+ * S3 request structure "handle".
+ *
+ * Holds persistent information for Amazon S3 requests.
+ *
+ * Instantiated through `H5FD_s3comms_s3r_open()`, copies data into self.
+ *
+ * Intended to be re-used for operations on a remote object.
+ *
+ * Cleaned up through `H5FD_s3comms_s3r_close()`.
+ *
+ * _DO NOT_ share handle between threads: curl easy handle `curlhandle` has
+ * undefined behavior if called to perform in multiple threads.
+ *
+ *
+ *
+ * `magic` (unsigned long)
+ *
+ *     "magic" number identifying this structure as unique type.
+ *     MUST equal `S3R_MAGIC` to be valid.
+ *
+ * `curlhandle` (CURL)
+ *
+ *     Pointer to the curl_easy handle generated for the request.
+ *
+ * `httpverb` (char *)
+ *
+ *     Pointer to NULL-terminated string. HTTP verb,
+ *     e.g. "GET", "HEAD", "PUT", etc.
+ *
+ *     Default is NULL, resulting in a "GET" request.
+ *
+ * `purl` (parsed_url_t *)
+ *
+ *     Pointer to structure holding the elements of URL for file open.
+ *
+ *     e.g., "http://bucket.aws.com:8080/myfile.dat?q1=v1&q2=v2"
+ *     parsed into...
+ *     {   scheme: "http"
+ *         host:   "bucket.aws.com"
+ *         port:   "8080"
+ *         path:   "myfile.dat"
+ *         query:  "q1=v1&q2=v2"
+ *     }
+ *
+ *     Cannot be NULL.
+ *
+ * `region` (char *)
+ *
+ *     Pointer to NULL-terminated string, specifying S3 "region",
+ *     e.g., "us-east-1".
+ *
+ *     Required to authenticate.
+ *
+ * `secret_id` (char *)
+ *
+ *     Pointer to NULL-terminated string for "secret" access id to S3 resource.
+ *
+ *     Requred to authenticate.
+ *
+ * `signing_key` (unsigned char *)
+ *
+ *     Pointer to `SHA256_DIGEST_LENGTH`-long string for "re-usable" signing
+ *     key, generated via
+ *     `HMAC-SHA256(HMAC-SHA256(HMAC-SHA256(HMAC-SHA256("AWS4<secret_key>",
+ *         "<yyyyMMDD"), "<aws-region>"), "<aws-service>"), "aws4_request")`
+ *     which may be re-used for several (up to seven (7)) days from creation?
+ *     Computed once upon file open.
+ *
+ *     Requred to authenticate.
+ *
+ *
+ *
+ * Programmer: Jacob Smith
+ *
+ *----------------------------------------------------------------------------
+ */
+typedef struct {
+    unsigned long  magic;
+#ifdef H5_HAVE_ROS3_VFD
+    CURL          *curlhandle;
+    size_t         filesize;
+    char          *httpverb;
+    parsed_url_t  *purl;
+    char          *region;
+    char          *secret_id;
+    unsigned char *signing_key;
+#endif /* ifdef H5_HAVE_ROS3_VFD */
+} s3r_t;
+#define S3COMMS_S3R_MAGIC 0x44d8d79
+
+/*******************************************
+ * DECLARATION OF HTTP FIELD LIST ROUTINES *
+ *******************************************/
+
+herr_t H5FD_s3comms_hrb_node_set(hrb_node_t **L,
+                                 const char  *name,
+                                 const char  *value);
+
+/***********************************************
+ * DECLARATION OF HTTP REQUEST BUFFER ROUTINES *
+ ***********************************************/
+
+herr_t H5FD_s3comms_hrb_destroy(hrb_t **buf);
+
+hrb_t * H5FD_s3comms_hrb_init_request(const char *verb,
+                                      const char *resource,
+                                      const char *host);
+
+/*************************************
+ * DECLARATION OF S3REQUEST ROUTINES *
+ *************************************/
+
+H5_DLL herr_t H5FD_s3comms_s3r_close(s3r_t *handle);
+
+H5_DLL size_t H5FD_s3comms_s3r_get_filesize(s3r_t *handle);
+
+H5_DLL s3r_t * H5FD_s3comms_s3r_open(const char          url[],
+                                     const char          region[],
+                                     const char          id[],
+                                     const unsigned char signing_key[]);
+
+H5_DLL herr_t H5FD_s3comms_s3r_read(s3r_t   *handle,
+                                    haddr_t  offset,
+                                    size_t   len,
+                                    void    *dest);
+
+/*********************************
+ * DECLARATION OF OTHER ROUTINES *
+ *********************************/
+
+H5_DLL struct tm * gmnow(void);
+
+herr_t H5FD_s3comms_aws_canonical_request(char  *canonical_request_dest,
+                                          char  *signed_headers_dest,
+                                          hrb_t *http_request);
+
+H5_DLL herr_t H5FD_s3comms_bytes_to_hex(char                *dest,
+                                 const unsigned char *msg,
+                                 size_t               msg_len,
+                                 hbool_t              lowercase);
+
+herr_t H5FD_s3comms_free_purl(parsed_url_t *purl);
+
+herr_t H5FD_s3comms_HMAC_SHA256(const unsigned char *key,
+                                size_t               key_len,
+                                const char          *msg,
+                                size_t               msg_len,
+                                char                *dest);
+
+herr_t H5FD_s3comms_load_aws_profile(const char *name,
+                                     char       *key_id_out,
+                                     char       *secret_access_key_out,
+                                     char       *aws_region_out);
+
+herr_t H5FD_s3comms_nlowercase(char       *dest,
+                               const char *s,
+                               size_t      len);
+
+herr_t H5FD_s3comms_parse_url(const char    *str,
+                              parsed_url_t **purl);
+
+herr_t H5FD_s3comms_percent_encode_char(char                *repr,
+                                        const unsigned char  c,
+                                        size_t              *repr_len);
+
+H5_DLL herr_t H5FD_s3comms_signing_key(unsigned char *md,
+                                       const char    *secret,
+                                       const char    *region,
+                                       const char    *iso8601now);
+
+herr_t H5FD_s3comms_tostringtosign(char       *dest,
+                                   const char *req_str,
+                                   const char *now,
+                                   const char *region);
+
+H5_DLL herr_t H5FD_s3comms_trim(char   *dest,
+                         char   *s,
+                         size_t  s_len,
+                         size_t *n_written);
+
+H5_DLL herr_t H5FD_s3comms_uriencode(char       *dest,
+                              const char *s,
+                              size_t      s_len,
+                              hbool_t     encode_slash,
+                              size_t     *n_written);
+
+
diff --git a/src/Makefile.am b/src/Makefile.am
index 0eaae1a..f737d5d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -63,8 +63,8 @@ libhdf5_la_SOURCES= H5.c H5checksum.c H5dbg.c H5system.c H5timer.c H5trace.c \
         H5FA.c H5FAcache.c H5FAdbg.c H5FAdblock.c H5FAdblkpage.c H5FAhdr.c \
         H5FAint.c H5FAstat.c H5FAtest.c \
         H5FD.c H5FDcore.c  \
-        H5FDfamily.c H5FDint.c H5FDlog.c \
-        H5FDmulti.c H5FDsec2.c H5FDspace.c H5FDstdio.c H5FDtest.c \
+        H5FDfamily.c H5FDhdfs.c H5FDint.c H5FDlog.c H5FDs3comms.c \
+        H5FDmulti.c H5FDros3.c H5FDsec2.c H5FDspace.c H5FDstdio.c H5FDtest.c \
         H5FL.c H5FO.c H5FS.c H5FScache.c H5FSdbg.c H5FSint.c H5FSsection.c \
         H5FSstat.c H5FStest.c \
         H5G.c H5Gbtree2.c H5Gcache.c \
@@ -138,8 +138,8 @@ include_HEADERS = hdf5.h H5api_adpt.h H5overflow.h H5pubconf.h H5public.h H5vers
         H5Cpublic.h H5Dpublic.h \
         H5Epubgen.h H5Epublic.h H5ESpublic.h H5Fpublic.h \
         H5FDpublic.h H5FDcore.h H5FDdirect.h \
-        H5FDfamily.h H5FDlog.h H5FDmpi.h H5FDmpio.h \
-        H5FDmulti.h H5FDsec2.h  H5FDstdio.h H5FDwindows.h \
+        H5FDfamily.h H5FDhdfs.h H5FDlog.h H5FDmpi.h H5FDmpio.h \
+        H5FDmulti.h H5FDros3.h H5FDsec2.h H5FDstdio.h H5FDwindows.h \
         H5Gpublic.h  H5Ipublic.h H5Lpublic.h \
         H5MMpublic.h H5Opublic.h H5Ppublic.h \
         H5PLextern.h H5PLpublic.h \
diff --git a/src/hdf5.h b/src/hdf5.h
index c12037f..2201e9e 100644
--- a/src/hdf5.h
+++ b/src/hdf5.h
@@ -40,16 +40,18 @@
 #include "H5Zpublic.h"          /* Data filters                             */
 
 /* Predefined file drivers */
-#include "H5FDcore.h"           /* Files stored entirely in memory              */
-#include "H5FDdirect.h"         /* Linux direct I/O                             */
-#include "H5FDfamily.h"         /* File families                                */
+#include "H5FDcore.h"           /* Files stored entirely in memory          */
+#include "H5FDdirect.h"         /* Linux direct I/O                         */
+#include "H5FDfamily.h"         /* File families                            */
+#include "H5FDhdfs.h"           /* Hadoop HDFS                              */
 #include "H5FDlog.h"            /* sec2 driver with I/O logging (for debugging) */
-#include "H5FDmpi.h"            /* MPI-based file drivers                       */
-#include "H5FDmulti.h"          /* Usage-partitioned file family                */
-#include "H5FDsec2.h"           /* POSIX unbuffered file I/O                    */
-#include "H5FDstdio.h"          /* Standard C buffered I/O                      */
+#include "H5FDmpi.h"            /* MPI-based file drivers                   */
+#include "H5FDmulti.h"          /* Usage-partitioned file family            */
+#include "H5FDros3.h"           /* R/O S3 "file" I/O                        */
+#include "H5FDsec2.h"           /* POSIX unbuffered file I/O                */
+#include "H5FDstdio.h"          /* Standard C buffered I/O                  */
 #ifdef H5_HAVE_WINDOWS
-#include "H5FDwindows.h"        /* Win32 I/O                                    */
+#include "H5FDwindows.h"        /* Win32 I/O                                */
 #endif
 
 /* Virtual object layer (VOL) connectors */
diff --git a/src/libhdf5.settings.in b/src/libhdf5.settings.in
index f856ebc..baa99ea 100644
--- a/src/libhdf5.settings.in
+++ b/src/libhdf5.settings.in
@@ -79,6 +79,8 @@ Parallel Filtered Dataset Writes: @PARALLEL_FILTERED_WRITES@
           I/O filters (external): @EXTERNAL_FILTERS@
                              MPE: @MPE@
                       Direct VFD: @DIRECT_VFD@
+              (Read-Only) S3 VFD: @ROS3_VFD@
+            (Read-Only) HDFS VFD: @HAVE_LIBHDFS@
                          dmalloc: @HAVE_DMALLOC@
   Packages w/ extra debug output: @INTERNAL_DEBUG_OUTPUT@
                      API tracing: @TRACE_API@