Major rework of H5PL package code before bringing VOL changes

over.

Brings coding standards in line with the rest of the library,
enforces better software engineering principles, and makes
everything more maintainable.

16 files changed, 2131 insertions, 975 deletions

diff --git a/MANIFEST b/MANIFEST
index 27f38be..739db4a 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -799,8 +799,11 @@
 ./src/H5PBpkg.h
 ./src/H5PBprivate.h
 ./src/H5PL.c
+./src/H5PLint.c
 ./src/H5PLmodule.h
+./src/H5PLpath.c
 ./src/H5PLpkg.h
+./src/H5PLplugin_cache.c
 ./src/H5PLprivate.h
 ./src/H5PLpublic.h
 ./src/H5PLextern.h
diff --git a/bin/trace b/bin/trace
index 3f532ab..cf41238 100755
--- a/bin/trace
+++ b/bin/trace
@@ -76,7 +76,7 @@ $Source = "";
                "off_t"                      => "o",
                "H5O_type_t"                 => "Ot",
                "H5P_class_t"                => "p",
-               "hobj_ref_t"		    => "r",
+               "hobj_ref_t"                 => "r",
                "H5R_type_t"                 => "Rt",
                "char"                       => "s",
                "unsigned char"              => "s",
@@ -124,7 +124,7 @@ $Source = "";
                "H5G_iterate_t"              => "x",
                "H5G_info_t"                 => "x",
                "H5I_free_t"                 => "x",
-               "H5I_search_func_t"         => "x",
+               "H5I_search_func_t"          => "x",
                "H5L_class_t"                => "x",
                "H5L_elink_traverse_t"       => "x",
                "H5L_iterate_t"              => "x",
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 178c954..96ea589 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -516,6 +516,9 @@ IDE_GENERATED_PROPERTIES ("H5PB" "${H5PB_HDRS}" "${H5PB_SOURCES}" )
 
 set (H5PL_SOURCES
     ${HDF5_SRC_DIR}/H5PL.c
+    ${HDF5_SRC_DIR}/H5PLint.c
+    ${HDF5_SRC_DIR}/H5PLpath.c
+    ${HDF5_SRC_DIR}/H5PLplugin_cache.c
 )
 
 set (H5PL_HDRS
diff --git a/src/H5PL.c b/src/H5PL.c
index 65d6c91..fc42554 100644
--- a/src/H5PL.c
+++ b/src/H5PL.c
@@ -22,135 +22,28 @@
 /***********/
 #include "H5private.h"      /* Generic Functions            */
 #include "H5Eprivate.h"     /* Error handling               */
-#include "H5MMprivate.h"    /* Memory management            */
 #include "H5PLpkg.h"        /* Plugin                       */
-#include "H5Zprivate.h"     /* Filter pipeline              */
 
 
 /****************/
 /* Local Macros */
 /****************/
-#ifdef H5_HAVE_WIN32_API
-#define H5PL_EXPAND_ENV_VAR {                                                            \
-        long bufCharCount;                                                               \
-        char *tempbuf;                                                                   \
-        if(NULL == (tempbuf = (char *)H5MM_malloc(H5PL_EXPAND_BUFFER_SIZE)))             \
-            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for expanded path")                          \
-        if((bufCharCount = ExpandEnvironmentStringsA(dl_path, tempbuf, H5PL_EXPAND_BUFFER_SIZE)) > H5PL_EXPAND_BUFFER_SIZE) { \
-            tempbuf = (char *)H5MM_xfree(tempbuf);                                       \
-            HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "expanded path is too long")      \
-        }                                                                                \
-        if(bufCharCount == 0) {                                                          \
-            tempbuf = (char *)H5MM_xfree(tempbuf);                                       \
-            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "failed to expand path")          \
-        }                                                                                \
-        dl_path = (char *)H5MM_xfree(dl_path);                                           \
-        dl_path = tempbuf;                                                               \
- }
-#else
-#define H5PL_EXPAND_ENV_VAR
-#endif /* H5_HAVE_WIN32_API */
-
-/****************************/
-/* Macros for supporting
- * both Windows and Unix */
-/****************************/
-/* Windows support
- *
- * SPECIAL WINDOWS NOTE
- *
- * Some of the Win32 API functions expand to fooA or fooW depending on
- * whether UNICODE or _UNICODE are defined. You MUST explicitly use
- * the A version of the functions to force char * behavior until we
- * work out a scheme for proper Windows Unicode support.
- *
- * If you do not do this, people will be unable to incorporate our
- * source code into their own CMake builds if they define UNICODE.
- */
-#ifdef H5_HAVE_WIN32_API
-
-#define H5PL_PATH_SEPARATOR     ";"
-
-/* Handle for dynamic library */
-#define H5PL_HANDLE HINSTANCE
-
-/* Get a handle to a plugin library.  Windows: TEXT macro handles Unicode strings */
-#define H5PL_OPEN_DLIB(S) LoadLibraryExA(S, NULL, LOAD_WITH_ALTERED_SEARCH_PATH)
-
-/* Get the address of a symbol in dynamic library */
-#define H5PL_GET_LIB_FUNC(H,N) GetProcAddress(H,N)
-
-/* Close dynamic library */
-#define H5PL_CLOSE_LIB(H) FreeLibrary(H)
-
-/* Clear error - nothing to do */
-#define H5PL_CLR_ERROR
-
-/* maximum size for expanding env vars */
-#define H5PL_EXPAND_BUFFER_SIZE 32767
-
-typedef const void *(__cdecl *H5PL_get_plugin_info_t)(void);
-
-/* Unix support */
-#else /* H5_HAVE_WIN32_API */
-
-#define H5PL_PATH_SEPARATOR     ":"
-
-/* Handle for dynamic library */
-#define H5PL_HANDLE void *
-
-/* Get a handle to a plugin library.  Windows: TEXT macro handles Unicode strings */
-#define H5PL_OPEN_DLIB(S) dlopen(S, RTLD_LAZY)
-
-/* Get the address of a symbol in dynamic library */
-#define H5PL_GET_LIB_FUNC(H,N) dlsym(H,N)
-
-/* Close dynamic library */
-#define H5PL_CLOSE_LIB(H) dlclose(H)
-
-/* Clear error */
-#define H5PL_CLR_ERROR HERROR(H5E_PLUGIN, H5E_CANTGET, "can't dlopen:%s", dlerror())
-
-typedef const void *(*H5PL_get_plugin_info_t)(void);
-#endif /* H5_HAVE_WIN32_API */
-
-/* Whether to preload pathnames for plugin libraries */
-#define H5PL_DEFAULT_PATH       H5_DEFAULT_PLUGINDIR
-
-/* Special symbol to indicate no plugin loading */
-#define H5PL_NO_PLUGIN          "::"
 
 
 /******************/
 /* Local Typedefs */
 /******************/
 
-/* Type for the list of info for opened plugin libraries */
-typedef struct H5PL_table_t {
-    H5PL_type_t pl_type;            /* plugin type          */
-    int         pl_id;              /* ID for the plugin    */
-    H5PL_HANDLE handle;             /* plugin handle        */
-} H5PL_table_t;
-
 
 /********************/
 /* Local Prototypes */
 /********************/
 
-static herr_t H5PL__init_path_table(void);
-static htri_t H5PL__find(H5PL_type_t plugin_type, int type_id, char *dir, const void **info);
-static htri_t H5PL__open(H5PL_type_t pl_type, char *libname, int plugin_id, const void **pl_info);
-static htri_t H5PL__search_table(H5PL_type_t plugin_type, int type_id, const void **info);
-static herr_t H5PL__close(H5PL_HANDLE handle);
-
 
 /*********************/
 /* Package Variables */
 /*********************/
 
-/* Package initialization variable */
-hbool_t H5_PKG_INIT_VAR = FALSE;
-
 
 /*****************************/
 /* Library Private Variables */
@@ -161,145 +54,43 @@ hbool_t H5_PKG_INIT_VAR = FALSE;
 /* Local Variables */
 /*******************/
 
-/* Table for opened plugin libraries */
-static size_t           H5PL_table_alloc_g = 0;
-static size_t           H5PL_table_used_g = 0;
-static H5PL_table_t     *H5PL_table_g = NULL;
-
-/* Table of location paths for plugin libraries */
-static char             *H5PL_path_table_g[H5PL_MAX_PATH_NUM];
-static size_t           H5PL_num_paths_g = 0;
-static hbool_t          H5PL_path_found_g = FALSE;
-
-/* Enable all plugin libraries */
-static unsigned int     H5PL_plugin_g = H5PL_ALL_PLUGIN;
-
-
-
-/*--------------------------------------------------------------------------
-NAME
-   H5PL__init_package -- Initialize interface-specific information
-USAGE
-    herr_t H5PL__init_package()
-RETURNS
-    Non-negative on success/Negative on failure
-DESCRIPTION
-    Initializes any interface-specific data or routines.
-
---------------------------------------------------------------------------*/
-herr_t
-H5PL__init_package(void)
-{
-    char        *preload_path;
-
-    FUNC_ENTER_PACKAGE_NOERR
-
-    /* Retrieve pathnames from HDF5_PLUGIN_PRELOAD if the user sets it
-     * to tell the library to load plugin libraries without search.
-     */
-    if(NULL != (preload_path = HDgetenv("HDF5_PLUGIN_PRELOAD")))
-        /* Special symbol "::" means no plugin during data reading. */
-        if(!HDstrcmp(preload_path, H5PL_NO_PLUGIN))
-            H5PL_plugin_g = 0;
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5PL__init_package() */
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5PL_term_package
- *
- * Purpose:     Terminate the H5PL interface: release all memory, reset all
- *              global variables to initial values. This only happens if all
- *              types have been destroyed from other interfaces.
+ * Function:    H5PLset_loading_state
  *
- * Return:      Success:    Positive if any action was taken that might
- *                          affect some other interface; zero otherwise.
- *              Failure:    Negative.
- *
- * Programmer:  Raymond Lu
- *              20 February 2013
- *
- *-------------------------------------------------------------------------
- */
-int
-H5PL_term_package(void)
-{
-    int  n = 0;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOERR
-
-    if(H5_PKG_INIT_VAR) {
-        size_t u;       /* Local index variable */
-
-        /* Close opened dynamic libraries */
-        if(H5PL_table_g) {
-            for(u = 0; u < H5PL_table_used_g; u++)
-                H5PL__close((H5PL_table_g[u]).handle);
-
-            /* Free the table of dynamic libraries */
-            H5PL_table_g = (H5PL_table_t *)H5MM_xfree(H5PL_table_g);
-            H5PL_table_used_g = H5PL_table_alloc_g = 0;
-
-            n++;
-        } /* end if */
-
-        /* Free the table of search paths */
-        if(H5PL_num_paths_g > 0) {
-            for(u = 0; u < H5PL_num_paths_g; u++)
-                if(H5PL_path_table_g[u])
-                    H5PL_path_table_g[u] = (char *)H5MM_xfree(H5PL_path_table_g[u]);
-            H5PL_num_paths_g = 0;
-            H5PL_path_found_g = FALSE;
-
-            n++;
-        } /* end if */
-
-        /* Mark the interface as uninitialized */
-        if(0 == n)
-            H5_PKG_INIT_VAR = FALSE;
-    } /* end if */
-
-    FUNC_LEAVE_NOAPI(n)
-} /* end H5PL_term_package() */
-
-
-/*-------------------------------------------------------------------------
- * Function: H5PLset_loading_state
+ * Purpose:     Control the loading of dynamic plugin types.
  *
- * Purpose: Control the loading of dynamic plugin types.
+ *              The plugin_control_mask parameter is a bitfield that controls
+ *              whether certain classes of plugins (e.g.: filters,
+ *              VOL drivers) will be loaded by the library.
  *
- * This function will not allow plugin types if the pathname from the HDF5_PLUGIN_PRELOAD
- * environment variable is set to the special "::" string.
+ *              plugin bit = 0, will prevent the use of that dynamic plugin type.
+ *              plugin bit = 1, will allow the use of that dynamic plugin type.
  *
- * plugin bit = 0, will prevent the use of that dynamic plugin type.
- * plugin bit = 1, will allow the use of that dynamic plugin type.
+ *              A list of pre-defined masks can be found in H5PLpublic.h.
+ *              Set the mask to 0 to disable all plugins.
  *
- * H5PL_TYPE_FILTER changes just dynamic filters
- * A H5PL_ALL_PLUGIN will enable all dynamic plugin types
- * A zero value will disable all dynamic plugin types
+ *              This function will not allow plugin types if the pathname
+ *              from the HDF5_PLUGIN_PRELOAD environment variable is set to
+ *              the special "::" string.
  *
- * Return: Non-negative or success
+ * Return:      Success:    Non-negative
+ *              Failture:   Negative
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLset_loading_state(unsigned int plugin_type)
+H5PLset_loading_state(unsigned int plugin_control_mask)
 {
-    char *preload_path;
-    herr_t ret_value = SUCCEED; /* Return value */
+    herr_t  ret_value = SUCCEED;        /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE1("e", "Iu", plugin_type);
-
-    /* change the bit value of the requested plugin type(s) */
-    H5PL_plugin_g = plugin_type;
+    H5TRACE1("e", "Iu", plugin_control_mask);
 
-    /* check if special ENV variable is set and disable all plugin types */
-    if(NULL != (preload_path = HDgetenv("HDF5_PLUGIN_PRELOAD")))
-        /* Special symbol "::" means no plugin during data reading. */
-        if(!HDstrcmp(preload_path, H5PL_NO_PLUGIN))
-            H5PL_plugin_g = 0;
+    /* Set the plugin control mask */
+    if(H5PL__set_plugin_control_mask(plugin_control_mask) < 0)
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTSET, FAIL, "error setting plugin control mask")
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -307,27 +98,35 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function: H5PLget_loading_state
+ * Function:    H5PLget_loading_state
  *
- * Purpose: Query state of the loading of dynamic plugin types.
+ * Purpose:     Get the bitmask that controls whether certain classes
+ *              of plugins (e.g.: filters, VOL drivers) will be loaded
+ *              by the library.
  *
- * This function will return the state of the global flag.
+ *              Zero if all plugin types are disabled
+ *              Negative if all plugin types are enabled
+ *              Positive if one or more of the plugin types are enabled
  *
- * Return: Zero if all plugin types are disabled, negative if all
- * plugin types are enabled, positive if one or more of the plugin types are enabled.
+ * Return:      Success:    Non-negative
+ *              Failture:   Negative
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLget_loading_state(unsigned int *plugin_type)
+H5PLget_loading_state(unsigned int *plugin_control_mask)
 {
-    herr_t ret_value = SUCCEED; /* Return value */
+    herr_t ret_value = SUCCEED;     /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE1("e", "*Iu", plugin_type);
+    H5TRACE1("e", "*Iu", plugin_control_mask);
+
+    if (NULL == plugin_control_mask)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_control_mask parameter cannot be NULL")
 
-    if(plugin_type)
-        *plugin_type = H5PL_plugin_g;
+    /* Set the plugin control mask */
+    if(H5PL__get_plugin_control_mask(plugin_control_mask) < 0)
+        HGOTO_ERROR(H5E_ARGS, H5E_CANTGET, FAIL, "error getting plugin control mask")
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -335,674 +134,282 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5PL_load
- *
- * Purpose:     Given the plugin type and identifier, this function searches
- *              and/or loads a dynamic plugin library first among the already
- *              opened libraries then in the designated location paths.
- *
- * Return:      Non-NULL on success/NULL on failure
- *
- * Programmer:  Raymond Lu
- *              13 February 2013
- *
- *-------------------------------------------------------------------------
- */
-const void *
-H5PL_load(H5PL_type_t type, int id)
-{
-    htri_t      found;               /* Whether the plugin was found */
-    const void  *plugin_info = NULL;
-    const void  *ret_value = NULL;
-
-    FUNC_ENTER_NOAPI(NULL)
-
-    switch(type) {
-        case H5PL_TYPE_FILTER:
-            if((H5PL_plugin_g & H5PL_FILTER_PLUGIN) == 0)
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTLOAD, NULL, "required dynamically loaded plugin filter '%d' is not available", id)
-            break;
-
-        case H5PL_TYPE_ERROR:
-        case H5PL_TYPE_NONE:
-        default:
-            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTLOAD, NULL, "required dynamically loaded plugin '%d' is not valid", id)
-    } /* end switch */
-
-    /* Initialize the location paths for dynamic libraries, if they aren't
-     * already set up.
-     */
-    if(FALSE == H5PL_path_found_g)
-        if(H5PL__init_path_table() < 0)
-            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINIT, NULL, "can't initialize search path table")
-
-    /* Search in the table of already loaded plugin libraries */
-    if((found = H5PL__search_table(type, id, &plugin_info)) < 0)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, NULL, "search in table failed")
-
-    /* If not found, iterate through the path table to find the right dynamic library */
-    if(!found) {
-        size_t       i;                   /* Local index variable */
-
-        for(i = 0; i < H5PL_num_paths_g; i++) {
-            if((found = H5PL__find(type, id, H5PL_path_table_g[i], &plugin_info)) < 0)
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, NULL, "search in paths failed")
-
-            /* Break out if found */
-            if(found) {
-                HDassert(plugin_info);
-                break;
-            } /* end if */
-        } /* end for */
-    } /* end if */
-
-    /* Check if we found the plugin */
-    if(found)
-        ret_value = plugin_info;
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL_load() */
-
-
-/*-------------------------------------------------------------------------
- * Function: H5PLappend
+ * Function:    H5PLappend
  *
- * Purpose: Insert a plugin path at the end of the list.
+ * Purpose:     Insert a plugin search path at the end of the list.
  *
- * Return: Non-negative or success.
+ * Return:      Success:    Non-negative
+ *              Failture:   Negative
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLappend(const char *plugin_path)
+H5PLappend(const char *search_path)
 {
     herr_t ret_value = SUCCEED; /* Return value */
-    char        *dl_path = NULL;
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE1("e", "*s", plugin_path);
-    if(H5PL_num_paths_g == H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "too many directories in path for table")
-    if(NULL == plugin_path)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "no path provided")
-    if(NULL == (dl_path = H5MM_strdup(plugin_path)))
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
+    H5TRACE1("e", "*s", search_path);
 
-    H5PL_EXPAND_ENV_VAR
+    /* Check args */
+    if (NULL == search_path)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot be NULL")
+    if (0 == HDstrlen(search_path))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot have length zero")
 
-    H5PL_path_table_g[H5PL_num_paths_g] = dl_path;
-    H5PL_num_paths_g++;
+    /* Append the search path to the path table */
+    if (H5PL__append_path(search_path) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTAPPEND, FAIL, "unable to append search path")
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLappend() */
 
-
+
 /*-------------------------------------------------------------------------
- * Function: H5PLprepend
+ * Function:    H5PLprepend
  *
- * Purpose: Insert a plugin path at the beginning of the list.
+ * Purpose:     Insert a plugin search path at the beginning of the list.
  *
- * Return: Non-negative or success.
+ * Return:      Success:    Non-negative
+ *              Failture:   Negative
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLprepend(const char *plugin_path)
+H5PLprepend(const char *search_path)
 {
     herr_t ret_value = SUCCEED; /* Return value */
-    char        *dl_path = NULL;
-    unsigned int plindex;
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE1("e", "*s", plugin_path);
-    if(H5PL_num_paths_g == H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "too many directories in path for table")
-    if(NULL == plugin_path)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "no path provided")
-    if(NULL == (dl_path = H5MM_strdup(plugin_path)))
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
+    H5TRACE1("e", "*s", search_path);
 
-    H5PL_EXPAND_ENV_VAR
+    /* Check args */
+    if (NULL == search_path)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot be NULL")
+    if (0 == HDstrlen(search_path))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot have length zero")
 
-    for (plindex = (unsigned int)H5PL_num_paths_g; plindex > 0; plindex--)
-        H5PL_path_table_g[plindex] = H5PL_path_table_g[plindex - 1];
-    H5PL_path_table_g[0] = dl_path;
-    H5PL_num_paths_g++;
+    /* Prepend the search path to the path table */
+    if (H5PL__prepend_path(search_path) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to prepend search path")
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLprepend() */
 
-
+
 /*-------------------------------------------------------------------------
- * Function: H5PLreplace
+ * Function:    H5PLreplace
  *
- * Purpose: Replace the path at the specified index.
+ * Purpose:     Replace the path at the specified index. The path at the
+ *              index must exist.
  *
- * Return: Non-negative or success.
+ * Return:      Non-negative or success.
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLreplace(const char *plugin_path, unsigned int index)
+H5PLreplace(const char *search_path, unsigned int index)
 {
-    herr_t ret_value = SUCCEED; /* Return value */
-    char        *dl_path = NULL;
+    unsigned    num_paths;              /* Current number of stored paths */
+    herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE2("e", "*sIu", plugin_path, index);
-    if(NULL == plugin_path)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "no path provided")
-    if(index >= H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "index path out of bounds for table")
-    if(NULL == (dl_path = H5MM_strdup(plugin_path)))
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
+    H5TRACE2("e", "*sIu", search_path, index);
 
-    H5PL_EXPAND_ENV_VAR
+    /* Check args */
+    if (NULL == search_path)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot be NULL")
+    if (0 == HDstrlen(search_path))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot have length zero")
 
-    if(H5PL_path_table_g[index])
-        H5PL_path_table_g[index] = (char *)H5MM_xfree(H5PL_path_table_g[index]);
-    H5PL_path_table_g[index] = dl_path;
+    /* Check index */
+    num_paths = H5PL__get_num_paths();
+    if (0 == num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "path table is empty")
+    else if (index >= num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "index path out of bounds for table - can't be more than %u", (num_paths - 1))
+
+    /* Insert the search path into the path table */
+    if (H5PL__replace_path(search_path, index) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to replace search path")
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLreplace() */
 
-
+
 /*-------------------------------------------------------------------------
- * Function: H5PLinsert
+ * Function:    H5PLinsert
  *
- * Purpose: Insert a plugin path at the specified index, moving other paths after the index.
+ * Purpose:     Insert a plugin search path at the specified index, moving
+ *              other paths after the index.
  *
- * Return: Non-negative or success.
+ * Return:      Success:    Non-negative
+ *              Failture:   Negative
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLinsert(const char *plugin_path, unsigned int index)
+H5PLinsert(const char *search_path, unsigned int index)
 {
-    herr_t ret_value = SUCCEED; /* Return value */
-    char        *dl_path = NULL;
-    unsigned int plindex;
+    unsigned    num_paths;              /* Current number of stored paths */
+    herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE2("e", "*sIu", plugin_path, index);
-    if(H5PL_num_paths_g == H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "too many directories in path for table")
-    if(NULL == plugin_path)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "no path provided")
-    if(index >= H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "index path out of bounds for table")
-    if(NULL == (dl_path = H5MM_strdup(plugin_path)))
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
-
-    H5PL_EXPAND_ENV_VAR
-
-    for(plindex = (unsigned int)H5PL_num_paths_g; plindex > index; plindex--)
-        H5PL_path_table_g[plindex] = H5PL_path_table_g[plindex - 1];
-    H5PL_path_table_g[index] = dl_path;
-    H5PL_num_paths_g++;
+    H5TRACE2("e", "*sIu", search_path, index);
+
+    /* Check args */
+    if (NULL == search_path)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot be NULL")
+    if (0 == HDstrlen(search_path))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "plugin_path parameter cannot have length zero")
+
+    /* Check index */
+    num_paths = H5PL__get_num_paths();
+    if ((0 != num_paths) && (index >= num_paths))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "index path out of bounds for table - can't be more than %u", (num_paths - 1))
+
+    /* Insert the search path into the path table */
+    if (H5PL__insert_path(search_path, index) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to insert search path")
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLinsert() */
 
-
+
 /*-------------------------------------------------------------------------
- * Function: H5PLremove
+ * Function:    H5PLremove
+ *
+ * Purpose:     Remove the plugin path at the specifed index and compact
+ *              the list.
  *
- * Purpose: Remove the plugin path at the specifed index and compacting the list.
+ * Return:      Success:    Non-negative
+ *              Failture:   Negative
  *
- * Return: Non-negative or success.
+ * Return:      Non-negative or success.
  *
  *-------------------------------------------------------------------------
  */
 herr_t
 H5PLremove(unsigned int index)
 {
-    herr_t ret_value = SUCCEED; /* Return value */
-    unsigned int plindex;
+    unsigned    num_paths;              /* Current number of stored paths */
+    herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE1("e", "Iu", index);
-    if(H5PL_num_paths_g == 0)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "no directories in table")
-    if(index >= H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "index path out of bounds for table")
-    if(NULL == H5PL_path_table_g[index])
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "no directory path at index")
-    H5PL_path_table_g[index] = (char *)H5MM_xfree(H5PL_path_table_g[index]);
-
-    H5PL_num_paths_g--;
-    for(plindex = index; plindex < (unsigned int)H5PL_num_paths_g; plindex++)
-        H5PL_path_table_g[plindex] = H5PL_path_table_g[plindex + 1];
-    H5PL_path_table_g[H5PL_num_paths_g] = NULL;
+
+    /* Check index */
+    num_paths = H5PL__get_num_paths();
+    if (0 == num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "path table is empty")
+    else if (index >= num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "index path out of bounds for table - can't be more than %u", (num_paths - 1))
+
+    /* Delete the search path from the path table */
+    if (H5PL__remove_path(index) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTDELETE, FAIL, "unable to remove search path")
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLremove() */
 
-
+
 /*-------------------------------------------------------------------------
- * Function: H5PLget
+ * Function:    H5PLget
+ *
+ * Purpose:     Query the plugin path at a specified index.
+ *
+ *  If 'path_buf' is non-NULL then up to 'buf_size' bytes will be written into
+ *  that buffer and the length of the path name will be returned.
  *
- * Purpose: Query the plugin path at the specified index.
+ *  If 'path_buf' is NULL, this function will simply return the number of
+ *  characters required to store the path name, ignoring 'path_buf' and
+ *  'buf_size'
  *
- * Return: Success: The length of path.
+ *  If an error occurs then the buffer pointed to by 'path_buf'
+ *  (NULL or non-NULL) will be unchanged and the function will return a
+ *  negative value.
  *
- *  If `pathname' is non-NULL then write up to `size' bytes into that
- *  buffer and always return the length of the pathname.
- *  Otherwise `size' is ignored and the function does not store the pathname,
- *  just returning the number of characters required to store the pathname.
- *  If an error occurs then the buffer pointed to by `pathname' (NULL or non-NULL)
- *  is unchanged and the function returns a negative value.
- *  If a zero is returned for the name's length, then there is no pathname
- *  associated with the index.
+ *  If a zero is returned for the name's length, then there is no path name
+ *  associated with the index and the 'path_buf' buffer will be unchanged.
+ *
+ * Return:  Success:    The length of path
+ *          Failure:    A negative value
  *
  *-------------------------------------------------------------------------
  */
 ssize_t
-H5PLget(unsigned int index, char *pathname/*out*/, size_t size)
+H5PLget(unsigned int index, char *path_buf, size_t buf_size)
 {
-    ssize_t      ret_value = 0;    /* Return value */
-    size_t       len = 0;          /* Length of pathname */
-    char        *dl_path = NULL;
+    unsigned    num_paths;              /* Current number of stored paths */
+    const char *path = NULL;            /* path from table */
+    size_t      path_len = 0;           /* Length of path */
+    ssize_t     ret_value = 0;          /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE3("Zs", "Iuxz", index, pathname, size);
-    if(H5PL_num_paths_g == 0)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "no directories in table")
-    if(index >= H5PL_MAX_PATH_NUM)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "index path out of bounds for table")
-    if(NULL == (dl_path = H5PL_path_table_g[index]))
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "no directory path at index")
-    len = HDstrlen(dl_path);
-    if(pathname) {
-        HDstrncpy(pathname, dl_path, MIN((size_t)(len + 1), size));
-        if((size_t)len >= size)
-            pathname[size - 1] = '\0';
+    H5TRACE3("Zs", "Iu*sz", index, path_buf, buf_size);
+
+    /* Check index */
+    num_paths = H5PL__get_num_paths();
+    if (0 == num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "path table is empty")
+    else if (index >= num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, FAIL, "index path out of bounds for table - can't be more than %u", (num_paths - 1))
+
+    /* Check if the search table is empty */
+    if (H5PL__get_num_paths() == 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, (-1), "plugin search path table is empty")
+
+    /* Get the path at the specified index and its length */
+    if (NULL == (path = H5PL__get_path(index)))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_BADVALUE, (-1), "no path stored at that index")
+    path_len = HDstrlen(path);
+
+    /* If the path buffer is not NULL, copy the path to the buffer */
+    if (path_buf) {
+        HDstrncpy(path_buf, path, MIN((size_t)(path_len + 1), buf_size));
+        if ((size_t)path_len >= buf_size)
+            path_buf[buf_size - 1] = '\0';
     } /* end if */
 
     /* Set return value */
-    ret_value = (ssize_t)len;
+    ret_value = (ssize_t)path_len;
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLget() */
 
-
+
 /*-------------------------------------------------------------------------
- * Function: H5PLsize
+ * Function:    H5PLsize
  *
- * Purpose: Query the size of the current list of plugin paths.
+ * Purpose:     Get the number of stored plugin paths.
+ *              XXX: This is a terrible name. Can it be changed?
  *
- * Return: Plugin path size
+ * Return:      SUCCEED/FAIL
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PLsize(unsigned int *listsize)
+H5PLsize(unsigned int *num_paths)
 {
     herr_t ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE1("e", "*Iu", listsize);
+    H5TRACE1("e", "*Iu", num_paths);
 
-    *listsize = (unsigned int)H5PL_num_paths_g;
+    /* Check arguments */
+    if (!num_paths)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "num_paths parameter cannot be NULL")
+
+    /* Get the number of stored plugin paths */
+    *num_paths = H5PL__get_num_paths();
 
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5PLsize() */
 
-
-/*-------------------------------------------------------------------------
- * Function:    H5PL__init_path_table
- *
- * Purpose:     Initialize the path table.
- *
- * Return:      Non-negative on success/Negative on failure
- *
- * Programmer:  Quincey Koziol
- *              18 March 2013
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5PL__init_path_table(void)
-{
-    char        *dl_path = NULL;
-    char        *origin_dl_path;
-    char        *dir;
-    herr_t      ret_value = SUCCEED;    /* Return value */
-
-    FUNC_ENTER_STATIC
-
-    /* Retrieve paths from HDF5_PLUGIN_PATH if the user sets it
-     * or from the default paths if it isn't set.
-     */
-    origin_dl_path = HDgetenv("HDF5_PLUGIN_PATH");
-    if(NULL == origin_dl_path)
-        dl_path = H5MM_strdup(H5PL_DEFAULT_PATH);
-    else
-        dl_path = H5MM_strdup(origin_dl_path);
-    if(NULL == dl_path)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
-
-    H5PL_EXPAND_ENV_VAR
-
-    /* Put paths in the path table.  They are separated by ":" */
-    dir = HDstrtok(dl_path, H5PL_PATH_SEPARATOR);
-    while(dir) {
-        /* Check for too many directories in path */
-        if(H5PL_num_paths_g == H5PL_MAX_PATH_NUM)
-            HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "too many directories in path for table")
-        if(NULL == (H5PL_path_table_g[H5PL_num_paths_g] = H5MM_strdup(dir)))
-            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
-        H5PL_num_paths_g++;
-        dir = HDstrtok(NULL, H5PL_PATH_SEPARATOR);
-    } /* end while */
-
-    H5PL_path_found_g = TRUE;
-
-done:
-    if(dl_path)
-        dl_path = (char *)H5MM_xfree(dl_path);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL__init_path_table() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5PL__find
- *
- * Purpose:     Given a path, this function opens the directory and envokes
- *              another function to go through all files to find the right
- *              plugin library. Two function definitions are for Unix and
- *              Windows.
- *
- * Return:      TRUE on success,
- *              FALSE on not found,
- *              negative on failure
- *
- * Programmer:  Raymond Lu
- *              13 February 2013
- *
- *-------------------------------------------------------------------------
- */
-#ifndef H5_HAVE_WIN32_API
-static htri_t
-H5PL__find(H5PL_type_t plugin_type, int type_id, char *dir, const void **info)
-{
-    char           *pathname = NULL;
-    DIR            *dirp = NULL;
-    struct dirent  *dp;
-    htri_t         ret_value = FALSE;
-
-    FUNC_ENTER_STATIC
-
-    /* Open the directory */
-    if(!(dirp = HDopendir(dir)))
-        HGOTO_ERROR(H5E_PLUGIN, H5E_OPENERROR, FAIL, "can't open directory: %s", dir)
-
-    /* Iterates through all entries in the directory to find the right plugin library */
-    while(NULL != (dp = HDreaddir(dirp))) {
-        /* The library we are looking for should be called libxxx.so... on Unix
-         * or libxxx.xxx.dylib on Mac.
-         */
-#ifndef __CYGWIN__
-        if(!HDstrncmp(dp->d_name, "lib", (size_t)3) &&
-                (HDstrstr(dp->d_name, ".so") || HDstrstr(dp->d_name, ".dylib"))) {
-#else
-        if(!HDstrncmp(dp->d_name, "cyg", (size_t)3) &&
-                HDstrstr(dp->d_name, ".dll") ) {
-
-#endif
-            h5_stat_t   my_stat;
-            size_t      pathname_len;
-            htri_t      found_in_dir;
-
-            /* Allocate & initialize the path name */
-            pathname_len = HDstrlen(dir) + HDstrlen(dp->d_name) + 2;
-            if(NULL == (pathname = (char *)H5MM_malloc(pathname_len)))
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
-            HDsnprintf(pathname, pathname_len, "%s/%s", dir, dp->d_name);
-
-            /* Get info for directory entry */
-            if(HDstat(pathname, &my_stat) == -1)
-                HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't stat file: %s", HDstrerror(errno))
-
-            /* If it is a directory, skip it */
-            if(S_ISDIR(my_stat.st_mode))
-                continue;
-
-            /* Attempt to open the dynamic library as a filter library */
-            if((found_in_dir = H5PL__open(plugin_type, pathname, type_id, info)) < 0)
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
-            if(found_in_dir)
-                HGOTO_DONE(TRUE)    /* Indicate success */
-            pathname = (char *)H5MM_xfree(pathname);
-        } /* end if */
-    } /* end while */
-
-done:
-    if(dirp)
-        if(HDclosedir(dirp) < 0)
-            HDONE_ERROR(H5E_FILE, H5E_CLOSEERROR, FAIL, "can't close directory: %s", HDstrerror(errno))
-    pathname = (char *)H5MM_xfree(pathname);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL__find() */
-#else /* H5_HAVE_WIN32_API */
-static htri_t
-H5PL__find(H5PL_type_t plugin_type, int type_id, char *dir, const void **info)
-{
-    WIN32_FIND_DATAA    fdFile;
-    HANDLE              hFind;
-    char                *pathname = NULL;
-    char                service[2048];
-    htri_t              ret_value = FALSE;
-
-    FUNC_ENTER_STATIC
-
-    /* Specify a file mask. *.* = We want everything! */
-    sprintf(service, "%s\\*.dll", dir);
-    if((hFind = FindFirstFileA(service, &fdFile)) == INVALID_HANDLE_VALUE)
-        HGOTO_ERROR(H5E_PLUGIN, H5E_OPENERROR, FAIL, "can't open directory")
-
-    do {
-        /* Find first file will always return "."
-         * and ".." as the first two directories.
-         */
-        if(HDstrcmp(fdFile.cFileName, ".") != 0 && HDstrcmp(fdFile.cFileName, "..") != 0) {
-            size_t      pathname_len;
-            htri_t      found_in_dir;
-
-            /* Allocate & initialize the path name */
-            pathname_len = HDstrlen(dir) + HDstrlen(fdFile.cFileName) + 2;
-            if(NULL == (pathname = (char *)H5MM_malloc(pathname_len)))
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
-            HDsnprintf(pathname, pathname_len, "%s\\%s", dir, fdFile.cFileName);
-
-            /* Is the entity a File or Folder? */
-            if(fdFile.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
-                continue;
-
-            if((found_in_dir = H5PL__open(plugin_type, pathname, type_id, info)) < 0)
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
-            if(found_in_dir)
-                HGOTO_DONE(TRUE)    /* Indicate success */
-            pathname = (char *)H5MM_xfree(pathname);
-        } /* end if */
-    } while(FindNextFileA(hFind, &fdFile)); /* Find the next file. */
-
-done:
-    if(hFind)
-        FindClose(hFind);
-    if(pathname)
-        pathname = (char *)H5MM_xfree(pathname);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL__find() */
-#endif /* H5_HAVE_WIN32_API */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5PL__open
- *
- * Purpose:     Iterates through all files to find the right plugin library.
- *              It loads the dynamic plugin library and keeps it on the list
- *              of loaded libraries.
- *
- * Return:      TRUE on success,
- *              FALSE on not found,
- *              negative on failure
- *
- * Programmer:  Raymond Lu
- *              13 February 2013
- *
- *-------------------------------------------------------------------------
- */
-static htri_t
-H5PL__open(H5PL_type_t pl_type, char *libname, int pl_id, const void **pl_info)
-{
-    H5PL_HANDLE    handle = NULL;
-    htri_t         ret_value = FALSE;
-
-    FUNC_ENTER_STATIC
-
-    /* There are different reasons why a library can't be open, e.g. wrong architecture.
-     * simply continue if we can't open it.
-     */
-    if(NULL == (handle = H5PL_OPEN_DLIB(libname))) {
-        H5PL_CLR_ERROR; /* clear error */
-    } /* end if */
-    else {
-        H5PL_get_plugin_info_t get_plugin_info = NULL;
-
-        /* Return a handle for the function H5PLget_plugin_info in the dynamic library.
-         * The plugin library is suppose to define this function.
-         */
-        if(NULL == (get_plugin_info = (H5PL_get_plugin_info_t)H5PL_GET_LIB_FUNC(handle, "H5PLget_plugin_info"))) {
-            if(H5PL__close(handle) < 0)
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CLOSEERROR, FAIL, "can't close dynamic library")
-        } /* end if */
-        else {
-            const H5Z_class2_t *plugin_info;
-
-            /* Invoke H5PLget_plugin_info to verify this is the right library we are looking for.
-             * Move on if it isn't.
-             */
-            if(NULL == (plugin_info = (const H5Z_class2_t *)(*get_plugin_info)())) {
-                if(H5PL__close(handle) < 0)
-                    HGOTO_ERROR(H5E_PLUGIN, H5E_CLOSEERROR, FAIL, "can't close dynamic library")
-                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get plugin info")
-            } /* end if */
-
-            /* Successfully found plugin library, check if it's the right one */
-            if(plugin_info->id == pl_id) {
-                /* Expand the table if it is too small */
-                if(H5PL_table_used_g >= H5PL_table_alloc_g) {
-                    size_t n = MAX(H5Z_MAX_NFILTERS, 2 * H5PL_table_alloc_g);
-                    H5PL_table_t *table = (H5PL_table_t *)H5MM_realloc(H5PL_table_g, n * sizeof(H5PL_table_t));
-
-                    if(!table)
-                        HGOTO_ERROR(H5E_RESOURCE, H5E_CANTALLOC, FAIL, "unable to extend dynamic library table")
-
-                    H5PL_table_g = table;
-                    H5PL_table_alloc_g = n;
-                } /* end if */
-
-                (H5PL_table_g[H5PL_table_used_g]).handle = handle;
-                (H5PL_table_g[H5PL_table_used_g]).pl_type = pl_type;
-                (H5PL_table_g[H5PL_table_used_g]).pl_id = plugin_info->id;
-                H5PL_table_used_g++;
-
-                /* Set the plugin info to return */
-                *pl_info = (const void *)plugin_info;
-
-                /* Indicate success */
-                ret_value = TRUE;
-            } /* end if */
-            else
-                if(H5PL__close(handle) < 0)
-                    HGOTO_ERROR(H5E_PLUGIN, H5E_CLOSEERROR, FAIL, "can't close dynamic library")
-        } /* end if */
-    } /* end else */
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL__open() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5PL__search_table
- *
- * Purpose:     Search in the list of already opened dynamic libraries
- *              to see if the one we are looking for is already opened.
- *
- * Return:      TRUE on success,
- *              FALSE on not found,
- *              Negative on failure
- *
- * Programmer:  Raymond Lu
- *              13 February 2013
- *
- *-------------------------------------------------------------------------
- */
-static htri_t
-H5PL__search_table(H5PL_type_t plugin_type, int type_id, const void **info)
-{
-    htri_t         ret_value = FALSE;
-
-    FUNC_ENTER_STATIC
-
-    /* Search in the table of already opened dynamic libraries */
-    if(H5PL_table_used_g > 0) {
-        size_t         i;
-
-        for(i = 0; i < H5PL_table_used_g; i++) {
-            if((plugin_type == (H5PL_table_g[i]).pl_type) && (type_id == (H5PL_table_g[i]).pl_id)) {
-                H5PL_get_plugin_info_t get_plugin_info;
-                const H5Z_class2_t   *plugin_info;
-
-                if(NULL == (get_plugin_info = (H5PL_get_plugin_info_t)H5PL_GET_LIB_FUNC((H5PL_table_g[i]).handle, "H5PLget_plugin_info")))
-                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTGET, FAIL, "can't get function for H5PLget_plugin_info")
-
-                if(NULL == (plugin_info = (const H5Z_class2_t *)(*get_plugin_info)()))
-                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTGET, FAIL, "can't get plugin info")
-
-                *info = plugin_info;
-                HGOTO_DONE(TRUE)
-            } /* end if */
-        } /* end for */
-    } /* end if */
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5PL__search_table() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5PL__close
- *
- * Purpose:     Closes the handle for dynamic library
- *
- * Return:      Non-negative on success/Negative on failure
- *
- * Programmer:  Raymond Lu
- *              13 February 2013
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5PL__close(H5PL_HANDLE handle)
-{
-    FUNC_ENTER_STATIC_NOERR
-
-    H5PL_CLOSE_LIB(handle);
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5PL__close() */
-
diff --git a/src/H5PLextern.h b/src/H5PLextern.h
index 7547ad7..cd5464d 100644
--- a/src/H5PLextern.h
+++ b/src/H5PLextern.h
@@ -11,9 +11,9 @@
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 /*
- * Programmer:  Raymond Lu <songyulu@hdfgroup.org>
- *              13 February 2013
+ * Purpose:     Header file for writing external HDF5 plugins.
  */
+
 #ifndef _H5PLextern_H
 #define _H5PLextern_H
 
diff --git a/src/H5PLint.c b/src/H5PLint.c
new file mode 100644
index 0000000..bd6bf7d
--- /dev/null
+++ b/src/H5PLint.c
@@ -0,0 +1,381 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * 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.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Purpose: Internal routines for managing plugins.
+ *
+ */
+
+
+/****************/
+/* Module Setup */
+/****************/
+
+#include "H5PLmodule.h"          /* This source code file is part of the H5PL module */
+
+
+/***********/
+/* Headers */
+/***********/
+#include "H5private.h"      /* Generic Functions            */
+#include "H5Eprivate.h"     /* Error handling               */
+#include "H5MMprivate.h"    /* Memory management            */
+#include "H5PLpkg.h"        /* Plugin                       */
+#include "H5Zprivate.h"     /* Filter pipeline              */
+
+
+/****************/
+/* Local Macros */
+/****************/
+
+
+/******************/
+/* Local Typedefs */
+/******************/
+
+
+/********************/
+/* Local Prototypes */
+/********************/
+
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+/* Package initialization variable */
+hbool_t H5_PKG_INIT_VAR = FALSE;
+
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+
+/*******************/
+/* Local Variables */
+/*******************/
+
+/* Bitmask that controls whether classes of plugins
+ * (e.g.: filters, VOL drivers) can be loaded.
+ */
+static unsigned int     H5PL_plugin_control_mask_g = H5PL_ALL_PLUGIN;
+
+/* This flag will be set to FALSE if the HDF5_PLUGIN_PRELOAD
+ * environment variable was set to H5PL_NO_PLUGIN at
+ * package initialization.
+ */
+static hbool_t          H5PL_allow_plugins_g = TRUE;
+
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__get_plugin_control_mask
+ *
+ * Purpose:     Gets the internal plugin control mask value.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__get_plugin_control_mask(unsigned int *mask /*out*/)
+{
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE_NOERR
+
+    /* Check args - Just assert on package functions */
+    HDassert(mask);
+
+    /* Return the mask */
+    *mask = H5PL_plugin_control_mask_g;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5PL__get_plugin_control_mask() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__set_plugin_control_mask
+ *
+ * Purpose:     Sets the internal plugin control mask value.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__set_plugin_control_mask(unsigned int mask)
+{
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE_NOERR
+
+    /* Only allow setting this if plugins have not been disabled.
+     * XXX: Note that we don't consider this an error, but instead
+     *      silently ignore it. We may want to consider this behavior
+     *      more carefully.
+     */
+    if (H5PL_allow_plugins_g)
+        H5PL_plugin_control_mask_g = mask;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5PL__set_plugin_control_mask() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__init_package
+ *
+ * Purpose:     Initialize any package-specific data and call any init
+ *              routines for the package.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__init_package(void)
+{
+    char        *env_var = NULL;
+    herr_t      ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check the environment variable to determine if the user wants
+     * to ignore plugins. The special symbol H5PL_NO_PLUGIN (defined in
+     * H5PLpublic.h) means we don't want to load plugins.
+     */
+    if (NULL != (env_var = HDgetenv("HDF5_PLUGIN_PRELOAD")))
+        if (!HDstrcmp(env_var, H5PL_NO_PLUGIN)) {
+            H5PL_plugin_control_mask_g = 0;
+            H5PL_allow_plugins_g = FALSE;
+        }
+
+    /* Create the table of previously-loaded plugins */
+    if (H5PL__create_plugin_cache() < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINIT, FAIL, "can't create plugin cache")
+
+    /* Create the table of search paths for dynamic libraries */
+    if (H5PL__create_path_table() < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINIT, FAIL, "can't create plugin search path table")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__init_package() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL_term_package
+ *
+ * Purpose:     Terminate the H5PL interface: release all memory, reset all
+ *              global variables to initial values. This only happens if all
+ *              types have been destroyed from other interfaces.
+ *
+ * Return:      Success:    Positive if any action was taken that might
+ *                          affect some other interface; zero otherwise
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+int
+H5PL_term_package(void)
+{
+    hbool_t already_closed = FALSE;
+    int     ret_value = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    if (H5_PKG_INIT_VAR) {
+
+        /* Close the plugin cache.
+         * We need to bump the return value if we did any real work here.
+         */
+        if (H5PL__close_plugin_cache(&already_closed) < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTFREE, (-1), "problem closing plugin cache")
+        if (!already_closed)
+            ret_value++;
+
+        /* Close the search path table and free the paths */
+        if (H5PL__close_path_table() < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTFREE, (-1), "problem closing search path table")
+
+        /* Mark the interface as uninitialized */
+        if (0 == ret_value)
+            H5_PKG_INIT_VAR = FALSE;
+    } /* end if */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL_term_package() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL_load
+ *
+ * Purpose:     Given the plugin type and identifier, this function searches
+ *              for and, if found, loads a dynamic plugin library.
+ *
+ *              The function searches first in the cached plugins and then
+ *              in the paths listed in the path table.
+ *
+ * Return:      Success:    A pointer to the plugin info
+ *              Failure:    NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+const void *
+H5PL_load(H5PL_type_t type, int id)
+{
+    H5PL_search_params_t    search_params;
+    hbool_t                 found = FALSE;          /* Whether the plugin was found */
+    const void             *plugin_info = NULL;
+    const void             *ret_value = NULL;
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Check if plugins can be loaded for this plugin type */
+    switch (type) {
+        case H5PL_TYPE_FILTER:
+            if ((H5PL_plugin_control_mask_g & H5PL_FILTER_PLUGIN) == 0)
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTLOAD, NULL, "required dynamically loaded plugin filter '%d' is not available", id)
+            break;
+
+        case H5PL_TYPE_ERROR:
+        case H5PL_TYPE_NONE:
+        default:
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTLOAD, NULL, "required dynamically loaded plugin '%d' is not valid", id)
+    }
+
+    /* Set up the search parameters */
+    search_params.type = type;
+    search_params.id = id;
+
+    /* Search in the table of already loaded plugin libraries */
+    if(H5PL__find_plugin_in_cache(&search_params, &found, &plugin_info) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, NULL, "search in plugin cache  failed")
+
+    /* If not found, try iterating through the path table to find an appropriate plugin */
+    if (!found)
+        if (H5PL__find_plugin_in_path_table(&search_params, &found, &plugin_info) < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, NULL, "search in path table failed")
+
+    /* Set the return value we found the plugin */
+    if (found)
+        ret_value = plugin_info;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL_load() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__open
+ *
+ * Purpose:     Opens a plugin.
+ *
+ *              The success parameter will be set to TRUE and the plugin_info
+ *              parameter will be filled in on success. Otherwise, they
+ *              will be FALSE and NULL, respectively.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__open(const char *path, H5PL_type_t type, int id, hbool_t *success, const void **plugin_info)
+{
+    H5PL_HANDLE             handle = NULL;
+    H5PL_get_plugin_info_t  get_plugin_info = NULL;
+    htri_t                  ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(success);
+    HDassert(plugin_info);
+
+    /* Initialize out parameters */
+    *success = FALSE;
+    *plugin_info = NULL;
+
+    /* There are different reasons why a library can't be open, e.g. wrong architecture.
+     * If we can't open the library, just return.
+     */
+    if (NULL == (handle = H5PL_OPEN_DLIB(path))) {
+        H5PL_CLR_ERROR; /* clear error */
+        HGOTO_DONE(SUCCEED);
+    }
+
+
+    /* Return a handle for the function H5PLget_plugin_info in the dynamic library.
+     * The plugin library is suppose to define this function.
+     *
+     * NOTE: We turn off -Wpedantic in gcc to quiet a warning about converting
+     *       object pointers to function pointers, which is undefined in ANSI C.
+     *       This is basically unavoidable due to the nature of dlsym() and *is*
+     *       defined in POSIX, so it's fine.
+     */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpedantic"
+    if (NULL != (get_plugin_info = (H5PL_get_plugin_info_t)H5PL_GET_LIB_FUNC(handle, "H5PLget_plugin_info"))) {
+#pragma GCC diagnostic pop
+
+        const H5Z_class2_t *info;
+
+        /* Get the plugin info */
+        if (NULL == (info = (const H5Z_class2_t *)(*get_plugin_info)()))
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get plugin info")
+
+        /* Check if the filter IDs match */
+        if (info->id == id) {
+
+            /* Store the plugin in the cache */
+            if (H5PL__add_plugin(type, id, handle))
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to add new plugin to plugin cache")
+
+            /* Set output parameters */
+            *success = TRUE;
+            *plugin_info = (const void *)info;
+        }
+    }
+
+done:
+    if (!success && handle)
+        if (H5PL__close(handle) < 0)
+            HDONE_ERROR(H5E_PLUGIN, H5E_CLOSEERROR, FAIL, "can't close dynamic library")
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__open() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__close
+ *
+ * Purpose:     Closes the handle for dynamic library
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__close(H5PL_HANDLE handle)
+{
+    FUNC_ENTER_PACKAGE_NOERR
+
+    H5PL_CLOSE_LIB(handle);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5PL__close() */
+
diff --git a/src/H5PLmodule.h b/src/H5PLmodule.h
index b441aed..945441e 100644
--- a/src/H5PLmodule.h
+++ b/src/H5PLmodule.h
@@ -11,13 +11,11 @@
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 /*
- * Programmer:	Quincey Koziol <koziol@hdfgroup.org>
- *		Saturday, September 12, 2015
- *
- * Purpose:	This file contains declarations which define macros for the
- *		H5PL package.  Including this header means that the source file
- *		is part of the H5PL package.
+ * Purpose: This file contains declarations which define macros for the
+ *          H5PL package.  Including this header means that the source file
+ *          is part of the H5PL package.
  */
+
 #ifndef _H5PLmodule_H
 #define _H5PLmodule_H
 
diff --git a/src/H5PLpath.c b/src/H5PLpath.c
new file mode 100644
index 0000000..435802a
--- /dev/null
+++ b/src/H5PLpath.c
@@ -0,0 +1,776 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * 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.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Purpose: Code to implement a path table which stores plugin search paths.
+ *
+ *          The path table is implemented as a dynamic, global array which
+ *          will grow as new paths are inserted. The capacity of the path
+ *          table never shrinks (though given the low number of paths
+ *          expected and the low likelihood of paths being removed, this
+ *          seems unlikely to be a problem). Inserts and removals rework
+ *          the array so that there are no 'holes' in the in-use part
+ *          of the array.
+ *
+ *          Note that it's basically up to the user to manage the indexes
+ *          when a complicated series of insert, overwrite, and, remove
+ *          operations take place.
+ */
+
+/****************/
+/* Module Setup */
+/****************/
+
+#include "H5PLmodule.h"          /* This source code file is part of the H5PL module */
+
+
+/***********/
+/* Headers */
+/***********/
+#include "H5private.h"      /* Generic Functions            */
+#include "H5Eprivate.h"     /* Error handling               */
+#include "H5MMprivate.h"    /* Memory management            */
+#include "H5PLpkg.h"        /* Plugin                       */
+
+
+/****************/
+/* Local Macros */
+/****************/
+
+/* Initial capacity of the path table */
+#define H5PL_INITIAL_PATH_CAPACITY      16
+
+/* The amount to add to the capacity when the table is full */
+#define H5PL_PATH_CAPACITY_ADD          16
+
+
+/******************/
+/* Local Typedefs */
+/******************/
+
+
+/********************/
+/* Local Prototypes */
+/********************/
+
+static herr_t H5PL__insert_at(const char *path, unsigned int index);
+static herr_t H5PL__make_space_at(unsigned int index);
+static herr_t H5PL__replace_at(const char *path, unsigned int index);
+static herr_t H5PL__expand_path_table(void);
+static herr_t H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *found, const char *dir, const void **plugin_info);
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+
+/*******************/
+/* Local Variables */
+/*******************/
+
+/* Stored plugin paths to search */
+static char       **H5PL_paths_g = NULL;
+
+/* The number of stored paths */
+static unsigned     H5PL_num_paths_g = 0;
+
+/* The capacity of the path table */
+static unsigned     H5PL_path_capacity_g = H5PL_INITIAL_PATH_CAPACITY;
+
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__insert_at()
+ *
+ * Purpose:     Insert a path at a particular index in the path table.
+ *              Does not clobber! Will move existing paths up to make
+ *              room. Use H5PL__replace_at(index) if you want to clobber.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5PL__insert_at(const char *path, unsigned int index)
+{
+    char    *path_copy = NULL;      /* copy of path string (for storing) */
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(HDstrlen(path));
+
+    /* Expand the table if it is full */
+    if (H5PL_num_paths_g == H5PL_path_capacity_g)
+        if (H5PL__expand_path_table() < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't expand path table")
+
+    /* Copy the path for storage so the caller can dispose of theirs */
+    if (NULL == (path_copy = H5MM_strdup(path)))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't make internal copy of path")
+
+#ifdef H5_HAVE_WIN32_API
+    /* Clean up Microsoft Windows environment variables in the path string */
+    if(H5_expand_windows_env_vars(&path_copy))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTCONVERT, FAIL, "can't expand environment variable string")
+#endif /* H5_HAVE_WIN32_API */
+
+    /* If the table entry is in use, make some space */
+    if (H5PL_paths_g[index])
+        if (H5PL__make_space_at(index) < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "unable to make space in the table for the new entry")
+
+    /* Insert the copy of the search path into the table at the specified index */
+    H5PL_paths_g[index] = path_copy;
+    H5PL_num_paths_g++;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__insert_at() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__make_space_at()
+ *
+ * Purpose:     Free up a slot in the path table, moving existing path
+ *              entries as necessary.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5PL__make_space_at(unsigned int index)
+{
+    unsigned    u;                      /* iterator */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Check args - Just assert on package functions */
+    HDassert(index < H5PL_path_capacity_g);
+
+    /* Copy the paths back to make a space  */
+    for (u = H5PL_num_paths_g; u > index; u--)
+        H5PL_paths_g[u] = H5PL_paths_g[u-1];
+
+    H5PL_paths_g[index] = NULL;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__make_space_at() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__replace_at()
+ *
+ * Purpose:     Replace a path at a particular index in the path table.
+ *              The path in the table must exist and will be freed by this
+ *              function.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5PL__replace_at(const char *path, unsigned int index)
+{
+    char    *path_copy = NULL;      /* copy of path string (for storing) */
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(HDstrlen(path));
+
+    /* Check that the table entry is in use */
+    if (!H5PL_paths_g[index])
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTFREE, FAIL, "path entry at index %u in the table is NULL", index)
+
+    /* Copy the path for storage so the caller can dispose of theirs */
+    if (NULL == (path_copy = H5MM_strdup(path)))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't make internal copy of path")
+
+#ifdef H5_HAVE_WIN32_API
+        /* Clean up Microsoft Windows environment variables in the path string */
+        if (H5_expand_windows_env_vars(&path_copy))
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTCONVERT, FAIL, "can't expand environment variable string")
+#endif /* H5_HAVE_WIN32_API */
+
+    /* Free the existing path entry */
+    H5PL_paths_g[index] = (char *)H5MM_xfree(H5PL_paths_g[index]);
+
+    /* Copy the search path into the table at the specified index */
+    H5PL_paths_g[index] = path_copy;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__replace_at() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__create_path_table
+ *
+ * Purpose:     Create the collection of paths that will be searched
+ *              when loading plugins.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__create_path_table(void)
+{
+    char        *env_var= NULL;         /* Path string from environment variable */
+    char        *paths = NULL;          /* Delimited paths string. Either from the
+                                         * environment variable or the default.
+                                         */
+    char        *next_path = NULL;      /* A path tokenized from the paths string */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Allocate memory for the path table */
+    H5PL_num_paths_g = 0;
+    H5PL_path_capacity_g = H5PL_INITIAL_PATH_CAPACITY;
+    if (NULL == (H5PL_paths_g = (char **)H5MM_calloc((size_t)H5PL_path_capacity_g * sizeof(char *))))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path table")
+
+    /* Retrieve paths from HDF5_PLUGIN_PATH if the user sets it
+     * or from the default paths if it isn't set.
+     */
+    env_var = HDgetenv("HDF5_PLUGIN_PATH");
+    if (NULL == env_var)
+        paths = H5MM_strdup(H5PL_DEFAULT_PATH);
+    else
+        paths = H5MM_strdup(env_var);
+
+    if (NULL == paths)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path copy")
+
+    /* Separate the paths and store them */
+    /* XXX: strtok() is not thread-safe */
+    next_path = HDstrtok(paths, H5PL_PATH_SEPARATOR);
+    while (next_path) {
+
+        /* Insert the path into the table */
+        if (H5PL__append_path(next_path) < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't insert path: %s", next_path)
+
+        /* Get the next path from the environment string */
+        next_path = HDstrtok(NULL, H5PL_PATH_SEPARATOR);
+    } /* end while */
+
+done:
+    if (paths)
+        paths = (char *)H5MM_xfree(paths);
+
+    /* Try to clean up on errors */
+    if (FAIL == ret_value) {
+        if (H5PL_paths_g)
+            H5PL_paths_g = (char **)H5MM_xfree(H5PL_paths_g);
+        H5PL_path_capacity_g = 0;
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__create_path_table() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__close_path_table
+ *
+ * Purpose:     Close the collection of paths that will be searched
+ *              when loading plugins.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__close_path_table(void)
+{
+    unsigned    u;                      /* iterator */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE_NOERR
+
+    /* Free paths */
+    for (u = 0; u < H5PL_num_paths_g; u++)
+        if (H5PL_paths_g[u])
+            H5PL_paths_g[u] = (char *)H5MM_xfree(H5PL_paths_g[u]);
+
+    /* Free path table */
+    H5PL_paths_g = (char **)H5MM_xfree(H5PL_paths_g);
+
+    /* Reset values */
+    H5PL_num_paths_g = 0;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+
+} /* end H5PL__close_path_table() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__get_num_paths
+ *
+ * Purpose:     Gets the number of plugin paths that have been stored.
+ *
+ * Return:      Success:    The number of paths
+ *              Failture:   Can't fail
+ *-------------------------------------------------------------------------
+ */
+unsigned
+H5PL__get_num_paths(void)
+{
+    FUNC_ENTER_PACKAGE_NOERR
+
+    FUNC_LEAVE_NOAPI(H5PL_num_paths_g)
+
+} /* end H5PL__get_num_paths() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__expand_path_table
+ *
+ * Purpose:     Expand the path table when it's full.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5PL__expand_path_table(void)
+{
+    herr_t      ret_value = SUCCEED;
+
+    FUNC_ENTER_STATIC
+
+    /* Update the capacity */
+    H5PL_path_capacity_g += H5PL_PATH_CAPACITY_ADD;
+
+    /* Resize the array */
+    if(NULL == (H5PL_paths_g = (char **)H5MM_realloc(H5PL_paths_g, (size_t)H5PL_path_capacity_g * sizeof(char *))))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "allocating additional memory for path table failed")
+
+    /* Initialize the new memory */
+    HDmemset(H5PL_paths_g + H5PL_num_paths_g, 0, (size_t)H5PL_PATH_CAPACITY_ADD * sizeof(char *));
+
+done:
+    /* Set the path capacity back if there were problems */
+    if (FAIL == ret_value)
+        H5PL_path_capacity_g -= H5PL_PATH_CAPACITY_ADD;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__expand_path_table() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__append_path
+ *
+ * Purpose:     Insert a path at the end of the table.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__append_path(const char *path)
+{
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(HDstrlen(path));
+
+    /* Insert the path at the end of the table */
+    if (H5PL__insert_at(path, H5PL_num_paths_g) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to append search path")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__append_path() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__prepend_path
+ *
+ * Purpose:     Insert a path at the beginning of the table.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__prepend_path(const char *path)
+{
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(HDstrlen(path));
+
+    /* Insert the path at the beginning of the table */
+    if (H5PL__insert_at(path, 0) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to prepend search path")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__prepend_path() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__replace_path
+ *
+ * Purpose:     Replace a path at particular index in the table.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__replace_path(const char *path, unsigned int index)
+{
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(HDstrlen(path));
+    HDassert(index < H5PL_path_capacity_g);
+
+    /* Insert the path at the requested index */
+    if (H5PL__replace_at(path, index) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to replace search path")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__replace_path() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__insert_path
+ *
+ * Purpose:     Insert a path at particular index in the table, moving
+ *              any existing paths back to make space.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__insert_path(const char *path, unsigned int index)
+{
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(path);
+    HDassert(HDstrlen(path));
+    HDassert(index < H5PL_path_capacity_g);
+
+    /* Insert the path at the requested index */
+    if (H5PL__insert_at(path, index) < 0)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTINSERT, FAIL, "unable to insert search path")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__insert_path() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__remove_path
+ *
+ * Purpose:     Remove a path at particular index in the table, freeing
+ *              the path string and moving the paths down to close the gap.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__remove_path(unsigned int index)
+{
+    unsigned    u;                      /* iterator */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(index < H5PL_path_capacity_g);
+
+    /* Check if the path at that index is set */
+    if (!H5PL_paths_g[index])
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTDELETE, FAIL, "search path at index %u is NULL", index)
+
+    /* Delete the path */
+    H5PL_num_paths_g--;
+    H5PL_paths_g[index] = (char *)H5MM_xfree(H5PL_paths_g[index]);
+
+    /* Shift the paths down to close the gap */
+    for (u = index; u < H5PL_num_paths_g; u++)
+        H5PL_paths_g[u] = H5PL_paths_g[u+1];
+
+    /* Set the (former) last path to NULL */
+    H5PL_paths_g[H5PL_num_paths_g] = NULL;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__remove_path() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__get_path
+ *
+ * Purpose:     Get a pointer to a path at particular index in the table.
+ *
+ * Return:      Success:    A pointer to a path string stored in the table
+ *              Failure:    NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+const char *
+H5PL__get_path(unsigned int index)
+{
+    char    *ret_value = NULL;    /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /* Get the path at the requested index */
+    if (index >= H5PL_num_paths_g)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADRANGE, NULL, "path index %u is out of range in table", index)
+
+    return H5PL_paths_g[index];
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__replace_path() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__find_plugin_in_path_table
+ *
+ * Purpose:     Attempts to find a matching plugin in the file system
+ *              using the paths stored in the path table.
+ *.
+ *              The 'found' parameter will be set appropriately.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__find_plugin_in_path_table(const H5PL_search_params_t *search_params, hbool_t *found, const void **plugin_info)
+{
+    unsigned int    u;                          /* iterator */
+    herr_t          ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(search_params);
+    HDassert(found);
+    HDassert(plugin_info);
+
+    /* Initialize output parameters */
+    *found = FALSE;
+    *plugin_info = NULL;
+
+    /* Loop over the paths in the table, checking for an appropriate plugin */
+    for (u = 0; u < H5PL_num_paths_g; u++) {
+
+        /* Search for the plugin in this path */
+        if (H5PL__find_plugin_in_path(search_params, found, H5PL_paths_g[u], plugin_info) < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in path %s encountered an error", H5PL_paths_g[u])
+
+        /* Break out if found */
+        if (*found) {
+            if (!plugin_info)
+                HGOTO_ERROR(H5E_PLUGIN, H5E_BADVALUE, FAIL, "plugin info should not be NULL")
+            break;
+        }
+    }
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__find_plugin_in_path_table() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__find_plugin_in_path
+ *
+ * Purpose:     Given a path, this function opens the directory and envokes
+ *              another function to go through all files to find the right
+ *              plugin library. Two function definitions are for Unix and
+ *              Windows.
+ *
+ *              The found parameter will be set to TRUE and the info
+ *              parameter will be filled in on success.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef H5_HAVE_WIN32_API
+static herr_t
+H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *found, const char *dir, const void **plugin_info)
+{
+    char           *path = NULL;
+    DIR            *dirp = NULL;            /* Directory stream */
+    struct dirent  *dp = NULL;              /* Directory entry */
+    herr_t         ret_value = SUCCEED;
+
+    FUNC_ENTER_STATIC
+
+    /* Check args - Just assert on package functions */
+    HDassert(search_params);
+    HDassert(found);
+    HDassert(dir);
+    HDassert(plugin_info);
+
+    /* Initialize the found parameter */
+    *found = FALSE;
+
+    /* Open the directory */
+    if (!(dirp = HDopendir(dir)))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_OPENERROR, FAIL, "can't open directory: %s", dir)
+
+    /* Iterate through all entries in the directory */
+    while (NULL != (dp = HDreaddir(dirp))) {
+
+        /* The library we are looking for should be called libxxx.so... on Unix
+         * or libxxx.xxx.dylib on Mac.
+         */
+#ifndef __CYGWIN__
+        if (!HDstrncmp(dp->d_name, "lib", (size_t)3) &&
+                (HDstrstr(dp->d_name, ".so") || HDstrstr(dp->d_name, ".dylib"))) {
+#else
+        if (!HDstrncmp(dp->d_name, "cyg", (size_t)3) &&
+                HDstrstr(dp->d_name, ".dll") ) {
+#endif
+
+            h5_stat_t   my_stat;
+            size_t      len;
+
+            /* Allocate & initialize the path name */
+            len = HDstrlen(dir) + HDstrlen(H5PL_PATH_SEPARATOR) + HDstrlen(dp->d_name) + 1 /*\0*/;
+
+            if (NULL == (path = (char *)H5MM_calloc(len)))
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
+
+            HDsnprintf(path, len, "%s/%s", dir, dp->d_name);
+
+            /* Get info for directory entry */
+            if (HDstat(path, &my_stat) == -1)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't stat file %s -- error was: %s", path, HDstrerror(errno))
+
+            /* If it is a directory, skip it */
+            if (S_ISDIR(my_stat.st_mode))
+                continue;
+
+            /* attempt to open the dynamic library as a filter library */
+            if (H5PL__open(path, search_params->type, search_params->id, found, plugin_info) < 0)
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
+            if (*found)
+                HGOTO_DONE(SUCCEED)
+
+            path = (char *)H5MM_xfree(path);
+        } /* end if */
+    } /* end while */
+
+done:
+    if (dirp)
+        if (HDclosedir(dirp) < 0)
+            HDONE_ERROR(H5E_FILE, H5E_CLOSEERROR, FAIL, "can't close directory: %s", HDstrerror(errno))
+
+    path = (char *)H5MM_xfree(path);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__find_plugin_in_path() */
+#else /* H5_HAVE_WIN32_API */
+static herr_t
+H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *found, const char *dir, const void **plugin_info)
+{
+    WIN32_FIND_DATAA    fdFile;
+    HANDLE              hFind = INVALID_HANDLE_VALUE;
+    char                *path = NULL;
+    char                service[2048];
+    herr_t              ret_value = SUCCEED;
+
+    FUNC_ENTER_STATIC
+
+    /* Check args - Just assert on package functions */
+    HDassert(search_params);
+    HDassert(found);
+    HDassert(dir);
+    HDassert(plugin_info);
+
+    /* Initialize the found parameter */
+    *found = FALSE;
+
+    /* Specify a file mask. *.* = We want everything! */
+    HDsprintf(service, "%s\\*.dll", dir);
+    if ((hFind = FindFirstFileA(service, &fdFile)) == INVALID_HANDLE_VALUE)
+        HGOTO_ERROR(H5E_PLUGIN, H5E_OPENERROR, FAIL, "can't open directory")
+
+    /* Loop over all the files */
+    do {
+        /* Ignore '.' and '..' */
+        if (HDstrcmp(fdFile.cFileName, ".") != 0 && HDstrcmp(fdFile.cFileName, "..") != 0) {
+
+            /* XXX: Probably just continue here and move the code below over one tab */
+
+            size_t      len;
+
+            /* Allocate & initialize the path name */
+            len = HDstrlen(dir) + HDstrlen(H5PL_PATH_SEPARATOR) + HDstrlen(fdFile.cFileName) + 1;
+
+            if (NULL == (path = (char *)H5MM_calloc(len)))
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for path")
+
+            HDsnprintf(path, len, "%s\\%s", dir, fdFile.cFileName);
+
+            /* Ignore directories */
+            if (fdFile.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
+                continue;
+
+            /* attempt to open the dynamic library as a filter library */
+            if (H5PL__open(path, search_params->type, search_params->id, found, plugin_info) < 0)
+                HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
+            if (*found)
+                HGOTO_DONE(SUCCEED)
+
+            path = (char *)H5MM_xfree(path);
+        }
+    } while (FindNextFileA(hFind, &fdFile));
+
+done:
+    if (hFind != INVALID_HANDLE_VALUE)
+        FindClose(hFind);
+    if (path)
+        path = (char *)H5MM_xfree(path);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__find_plugin_in_path() */
+#endif /* H5_HAVE_WIN32_API */
+
diff --git a/src/H5PLpkg.h b/src/H5PLpkg.h
index e356893..0d1c271 100644
--- a/src/H5PLpkg.h
+++ b/src/H5PLpkg.h
@@ -11,6 +11,12 @@
  * help@hdfgroup.org.                                                        *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
+/*
+ * Purpose: This file contains declarations which are visible only within
+ *          the H5PL package.  Source files outside the H5PL package should
+ *          include H5PLprivate.h instead.
+ */
+
 #if !(defined H5PL_FRIEND || defined H5PL_MODULE)
 #error "Do not include this file outside the H5PL package!"
 #endif
@@ -27,13 +33,92 @@
 /* Package Private Macros */
 /**************************/
 
-#define H5PL_MAX_PATH_NUM       16
+/* Whether to pre-load pathnames for plugin libraries */
+#define H5PL_DEFAULT_PATH       H5_DEFAULT_PLUGINDIR
+
+
+/****************************/
+/* Macros for supporting    */
+/* both Windows and POSIX   */
+/****************************/
+
+/*******************/
+/* Windows support */
+/*******************/
+/*
+ * SPECIAL WINDOWS NOTE
+ *
+ * Some of the Win32 API functions expand to fooA or fooW depending on
+ * whether UNICODE or _UNICODE are defined. You MUST explicitly use
+ * the A version of the functions to force char * behavior until we
+ * work out a scheme for proper Windows Unicode support.
+ *
+ * If you do not do this, people will be unable to incorporate our
+ * source code into their own CMake builds if they define UNICODE.
+ */
+#ifdef H5_HAVE_WIN32_API
+
+    /* The path separator on this platform */
+#   define H5PL_PATH_SEPARATOR      ";"
+
+    /* Handle for dynamic library */
+#   define H5PL_HANDLE HINSTANCE
+
+    /* Get a handle to a plugin library.  Windows: TEXT macro handles Unicode strings */
+#   define H5PL_OPEN_DLIB(S) LoadLibraryExA(S, NULL, LOAD_WITH_ALTERED_SEARCH_PATH)
+
+    /* Get the address of a symbol in dynamic library */
+#   define H5PL_GET_LIB_FUNC(H,N) GetProcAddress(H,N)
+
+    /* Close dynamic library */
+#   define H5PL_CLOSE_LIB(H) FreeLibrary(H)
+
+    /* Clear error - nothing to do */
+#   define H5PL_CLR_ERROR
+
+    /* maximum size for expanding env vars */
+#   define H5PL_EXPAND_BUFFER_SIZE 32767
+
+    typedef const void *(__cdecl *H5PL_get_plugin_info_t)(void);
+
+#else /* H5_HAVE_WIN32_API */
+
+    /*****************/
+    /* POSIX support */
+    /*****************/
+
+    /* The path separator on this platform */
+#   define H5PL_PATH_SEPARATOR     ":"
+
+    /* Handle for dynamic library */
+#   define H5PL_HANDLE void *
+
+    /* Get a handle to a plugin library.  Windows: TEXT macro handles Unicode strings */
+#   define H5PL_OPEN_DLIB(S) dlopen(S, RTLD_LAZY)
+
+    /* Get the address of a symbol in dynamic library */
+#   define H5PL_GET_LIB_FUNC(H,N) dlsym(H,N)
+
+    /* Close dynamic library */
+#   define H5PL_CLOSE_LIB(H) dlclose(H)
+
+    /* Clear error */
+#   define H5PL_CLR_ERROR HERROR(H5E_PLUGIN, H5E_CANTGET, "can't dlopen:%s", dlerror())
+
+    typedef const void *(*H5PL_get_plugin_info_t)(void);
+#endif /* H5_HAVE_WIN32_API */
 
 
 /****************************/
 /* Package Private Typedefs */
 /****************************/
 
+/* Data used to search for plugins */
+typedef struct H5PL_search_params_t {
+    H5PL_type_t     type;
+    int             id;
+} H5PL_search_params_t;
+
 
 /*****************************/
 /* Package Private Variables */
@@ -44,5 +129,31 @@
 /* Package Private Prototypes */
 /******************************/
 
+/* Accessors to global variables and flags */
+H5_DLL herr_t H5PL__get_plugin_control_mask(unsigned int *mask /*out*/);
+H5_DLL herr_t H5PL__set_plugin_control_mask(unsigned int mask);
+
+/* Plugin search and manipulation */
+H5_DLL herr_t H5PL__open(const char *libname, H5PL_type_t type, int id, hbool_t *success /*out*/, const void **plugin_info /*out*/);
+H5_DLL herr_t H5PL__close(H5PL_HANDLE handle);
+
+/* Plugin cache calls */
+H5_DLL herr_t H5PL__create_plugin_cache(void);
+H5_DLL herr_t H5PL__close_plugin_cache(hbool_t *already_closed /*out*/);
+H5_DLL herr_t H5PL__add_plugin(H5PL_type_t type, int id, H5PL_HANDLE handle);
+H5_DLL herr_t H5PL__find_plugin_in_cache(const H5PL_search_params_t *search_params, hbool_t *found /*out*/, const void **plugin_info /*out*/);
+
+/* Plugin search path calls */
+H5_DLL herr_t H5PL__create_path_table(void);
+H5_DLL herr_t H5PL__close_path_table(void);
+H5_DLL unsigned H5PL__get_num_paths(void);
+H5_DLL herr_t H5PL__append_path(const char *path);
+H5_DLL herr_t H5PL__prepend_path(const char *path);
+H5_DLL herr_t H5PL__replace_path(const char *path, unsigned int index);
+H5_DLL herr_t H5PL__insert_path(const char *path, unsigned int index);
+H5_DLL herr_t H5PL__remove_path(unsigned int index);
+H5_DLL const char *H5PL__get_path(unsigned int index);
+H5_DLL herr_t H5PL__find_plugin_in_path_table(const H5PL_search_params_t *search_params, hbool_t *found /*out*/, const void **plugin_info /*out*/);
+
 #endif /* _H5PLpkg_H */
 
diff --git a/src/H5PLplugin_cache.c b/src/H5PLplugin_cache.c
new file mode 100644
index 0000000..30a0798
--- /dev/null
+++ b/src/H5PLplugin_cache.c
@@ -0,0 +1,308 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * 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.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Purpose: Code to implement a plugin cache which stores information
+ *          about plugins which have already been loaded.
+ *
+ *          The plugin cache is implemented as a dynamic, global array which
+ *          will grow as new plugins are added. The capacity of the cache
+ *          never shrinks since plugins stay in memory once loaded.
+ *
+ *          Note that this functionality has absolutely nothing to do with
+ *          the metadata or chunk caches.
+ */
+
+/****************/
+/* Module Setup */
+/****************/
+
+#include "H5PLmodule.h"          /* This source code file is part of the H5PL module */
+
+
+/***********/
+/* Headers */
+/***********/
+#include "H5private.h"      /* Generic Functions            */
+#include "H5Eprivate.h"     /* Error handling               */
+#include "H5MMprivate.h"    /* Memory management            */
+#include "H5PLpkg.h"        /* Plugin                       */
+#include "H5Zprivate.h"     /* Filter pipeline              */
+
+
+/****************/
+/* Local Macros */
+/****************/
+
+/* Initial capacity of the plugin cache */
+#define H5PL_INITIAL_CACHE_CAPACITY     16
+
+/* The amount to add to the capacity when the cache is full */
+#define H5PL_CACHE_CAPACITY_ADD         16
+
+
+/******************/
+/* Local Typedefs */
+/******************/
+
+/* Type for the list of info for opened plugin libraries */
+typedef struct H5PL_plugin_t {
+    H5PL_type_t     type;           /* Plugin type          */
+    int             id;             /* ID for the plugin    */
+    H5PL_HANDLE     handle;         /* Plugin handle        */
+} H5PL_plugin_t;
+
+
+/********************/
+/* Local Prototypes */
+/********************/
+
+static herr_t H5PL__expand_cache(void);
+
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+
+/*******************/
+/* Local Variables */
+/*******************/
+
+/* Cache for storing opened plugin libraries */
+static H5PL_plugin_t   *H5PL_cache_g = NULL;
+
+/* The number of stored plugins */
+static unsigned int     H5PL_num_plugins_g = 0;
+
+/* The capacity of the plugin cache */
+static unsigned int     H5PL_cache_capacity_g = 0;
+
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__create_plugin_cache
+ *
+ * Purpose:     Create the cache that will store plugins that have already
+ *              been loaded.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__create_plugin_cache(void)
+{
+    herr_t      ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Allocate memory for the plugin cache */
+    H5PL_num_plugins_g = 0;
+
+    H5PL_cache_capacity_g = H5PL_INITIAL_CACHE_CAPACITY;
+
+    if (NULL == (H5PL_cache_g = (H5PL_plugin_t *)H5MM_calloc((size_t)H5PL_cache_capacity_g * sizeof(H5PL_plugin_t))))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for plugin cache")
+
+done:
+    /* Try to clean up on errors */
+    if (FAIL == ret_value) {
+        if (H5PL_cache_g)
+            H5PL_cache_g = (H5PL_plugin_t *)H5MM_xfree(H5PL_cache_g);
+        H5PL_cache_capacity_g = 0;
+    }
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__create_plugin_cache() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__close_plugin_cache
+ *
+ * Purpose:     Close the cache of plugins that have already been loaded,
+ *              closing all the plugins contained inside.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__close_plugin_cache(hbool_t *already_closed /*out*/)
+{
+    unsigned int    u;                      /* iterator */
+    herr_t          ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE_NOERR
+
+    /* Close opened dynamic libraries */
+    if (H5PL_cache_g) {
+
+        /* Close any cached plugins */
+        for (u = 0; u < H5PL_num_plugins_g; u++)
+            H5PL__close((H5PL_cache_g[u]).handle);
+
+        /* Free the cache array */
+        H5PL_cache_g = (H5PL_plugin_t *)H5MM_xfree(H5PL_cache_g);
+        H5PL_num_plugins_g = 0;
+        H5PL_cache_capacity_g = 0;
+
+        /* Note that actually closed the table (needed by package close call) */
+        *already_closed = FALSE;
+    }
+    else
+        *already_closed = TRUE;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__close_plugin_cache() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__expand_cache
+ *
+ * Purpose:     Expand the plugin cache when it's full.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5PL__expand_cache(void)
+{
+    herr_t      ret_value = SUCCEED;
+
+    FUNC_ENTER_STATIC
+
+    /* Update the capacity */
+    H5PL_cache_capacity_g += H5PL_CACHE_CAPACITY_ADD;
+
+    /* Resize the array */
+    if(NULL == (H5PL_cache_g = (H5PL_plugin_t *)H5MM_realloc(H5PL_cache_g, (size_t)H5PL_cache_capacity_g * sizeof(H5PL_plugin_t))))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "allocating additional memory for plugin cache failed")
+
+    /* Initialize the new memory */
+    HDmemset(H5PL_cache_g + H5PL_num_plugins_g, 0, (size_t)H5PL_CACHE_CAPACITY_ADD * sizeof(H5PL_plugin_t));
+
+done:
+    /* Set the cache capacity back if there were problems */
+    if (FAIL == ret_value)
+        H5PL_cache_capacity_g -= H5PL_CACHE_CAPACITY_ADD;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__expand_cache() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__add_plugin
+ *
+ * Purpose:     Add a plugin to the plugin cached.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__add_plugin(H5PL_type_t type, int id, H5PL_HANDLE handle)
+{
+    herr_t      ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Expand the cache if it is too small */
+    if (H5PL_num_plugins_g >= H5PL_cache_capacity_g)
+        if (H5PL__expand_cache() < 0)
+            HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't expand plugin cache")
+
+    /* Store the plugin info and bump the # of plugins */
+    H5PL_cache_g[H5PL_num_plugins_g].type       = type;
+    H5PL_cache_g[H5PL_num_plugins_g].id         = id;
+    H5PL_cache_g[H5PL_num_plugins_g].handle     = handle;
+
+    H5PL_num_plugins_g++;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__add_plugin() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5PL__find_plugin_in_cache
+ *
+ * Purpose:     Attempts to find a matching plugin from the cache.
+ *
+ *              The 'found' parameter will be set appropriately.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5PL__find_plugin_in_cache(const H5PL_search_params_t *search_params, hbool_t *found, const void **plugin_info)
+{
+    unsigned int    u;                          /* iterator */
+    herr_t          ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check args - Just assert on package functions */
+    HDassert(search_params);
+    HDassert(found);
+    HDassert(plugin_info);
+
+    /* Initialize output parameters */
+    *found = FALSE;
+    *plugin_info = NULL;
+
+    /* Loop over all the plugins, looking for one that matches */
+    for (u = 0; u < H5PL_num_plugins_g; u++) {
+
+        /* If the plugin type (filter, etc.) and ID match, query the plugin for its info */
+        if ((search_params->type == (H5PL_cache_g[u]).type) && (search_params->id == (H5PL_cache_g[u]).id)) {
+
+            H5PL_get_plugin_info_t      get_plugin_info_function;
+            const H5Z_class2_t          *filter_info;
+
+            /* Get the "get plugin info" function from the plugin.
+             *
+             * See the other use of H5PL_GET_LIB_FUNC() for an explanation
+             * for why we disable -Wpedantic here.
+             */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpedantic"
+            if (NULL == (get_plugin_info_function = (H5PL_get_plugin_info_t)H5PL_GET_LIB_FUNC((H5PL_cache_g[u]).handle, "H5PLget_plugin_info")))
+                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTGET, FAIL, "can't get function for H5PLget_plugin_info")
+#pragma GCC diagnostic pop
+
+            /* Call the "get plugin info" function */
+            if (NULL == (filter_info = (const H5Z_class2_t *)(*get_plugin_info_function)()))
+                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTGET, FAIL, "can't get plugin info")
+
+            /* Set output parameters */
+            *found = TRUE;
+            *plugin_info = filter_info;
+
+            /* No need to continue processing */
+            break;
+
+        } /* end if */
+
+    } /* end for */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5PL__find_plugin_in_cache() */
+
diff --git a/src/H5PLprivate.h b/src/H5PLprivate.h
index 0ab8f8c..bc12e64 100644
--- a/src/H5PLprivate.h
+++ b/src/H5PLprivate.h
@@ -10,8 +10,8 @@
  * help@hdfgroup.org.                                                        *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
-/* Programmer:  Raymond Lu <songyulu@hdfgroup.org>
- *              13 February 2013
+/*
+ * This file contains private information about the H5PL module
  */
 
 #ifndef _H5PLprivate_H
diff --git a/src/H5PLpublic.h b/src/H5PLpublic.h
index 9ce1fca..3b36ccd 100644
--- a/src/H5PLpublic.h
+++ b/src/H5PLpublic.h
@@ -10,8 +10,8 @@
  * help@hdfgroup.org.                                                        *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
-/* Programmer:  Raymond Lu <songyulu@hdfgroup.org>
- *              13 February 2013
+/*
+ * This file contains public declarations for the H5PL module.
  */
 
 #ifndef _H5PLpublic_H
@@ -24,31 +24,35 @@
 /* Public Typedefs */
 /*******************/
 
+/* Special string to indicate no plugin loading.
+ */
+#define H5PL_NO_PLUGIN          "::"
+
 /* Plugin type used by the plugin library */
 typedef enum H5PL_type_t {
-    H5PL_TYPE_ERROR        = -1,  /*error                    */
-    H5PL_TYPE_FILTER       = 0,   /*filter                   */
-    H5PL_TYPE_NONE         = 1    /*this must be last!       */
+    H5PL_TYPE_ERROR         = -1,   /* Error                    */
+    H5PL_TYPE_FILTER        = 0,    /* Filter                   */
+    H5PL_TYPE_NONE          = 1     /* This must be last!       */
 } H5PL_type_t;
 
 /* Common dynamic plugin type flags used by the set/get_loading_state functions */
-#define H5PL_FILTER_PLUGIN 0x0001
-#define H5PL_ALL_PLUGIN 0xFFFF
+#define H5PL_FILTER_PLUGIN      0x0001
+#define H5PL_ALL_PLUGIN         0xFFFF
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /* plugin state */
-H5_DLL herr_t H5PLset_loading_state(unsigned int plugin_type);
-H5_DLL herr_t H5PLget_loading_state(unsigned int *plugin_type/*out*/);
-H5_DLL herr_t H5PLappend(const char *plugin_path);
-H5_DLL herr_t H5PLprepend(const char *plugin_path);
-H5_DLL herr_t H5PLreplace(const char *plugin_path, unsigned int index);
-H5_DLL herr_t H5PLinsert(const char *plugin_path, unsigned int index);
+H5_DLL herr_t H5PLset_loading_state(unsigned int plugin_control_mask);
+H5_DLL herr_t H5PLget_loading_state(unsigned int *plugin_control_mask /*out*/);
+H5_DLL herr_t H5PLappend(const char *search_path);
+H5_DLL herr_t H5PLprepend(const char *search_path);
+H5_DLL herr_t H5PLreplace(const char *search_path, unsigned int index);
+H5_DLL herr_t H5PLinsert(const char *search_path, unsigned int index);
 H5_DLL herr_t H5PLremove(unsigned int index);
-H5_DLL ssize_t H5PLget(unsigned int index, char *pathname/*out*/, size_t size);
-H5_DLL herr_t H5PLsize(unsigned int *listsize/*out*/);
+H5_DLL ssize_t H5PLget(unsigned int index, char *path_buf /*out*/, size_t buf_size);
+H5_DLL herr_t H5PLsize(unsigned int *num_paths /*out*/);
 
 #ifdef __cplusplus
 }
diff --git a/src/H5system.c b/src/H5system.c
index 7e25540..1e718e7 100644
--- a/src/H5system.c
+++ b/src/H5system.c
@@ -1237,3 +1237,53 @@ H5_get_time(void)
 } /* end H5_get_time() */
 
 
+#ifdef H5_HAVE_WIN32_API
+
+#define H5_WIN32_ENV_VAR_BUFFER_SIZE    32767
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5_expand_windows_env_vars()
+ *
+ * Purpose:     Replaces windows environment variables of the form %foo%
+ *              with user-specific values.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5_expand_windows_env_vars(char **env_var)
+{
+    long    n_chars = 0;
+    char   *temp_buf = NULL;
+    herr_t  ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    /* Allocate buffer for expanded environment variable string */
+    if (NULL == (temp_buf = (char *)H5MM_calloc((size_t)H5_WIN32_ENV_VAR_BUFFER_SIZE)))
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTALLOC, FAIL, "can't allocate memory for expanded path")
+
+    /* Expand the environment variable string */
+    if ((n_chars = ExpandEnvironmentStringsA(*env_var, temp_buf, H5_WIN32_ENV_VAR_BUFFER_SIZE)) > H5_WIN32_ENV_VAR_BUFFER_SIZE) {
+        temp_buf = (char *)H5MM_xfree(temp_buf);
+        HGOTO_ERROR(H5E_PLUGIN, H5E_NOSPACE, FAIL, "expanded path is too long")
+    }
+
+    if (n_chars == 0) {
+        temp_buf = (char *)H5MM_xfree(temp_buf);
+        HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "failed to expand path")
+    }
+
+    *env_var = (char *)H5MM_xfree(*env_var);
+    *env_var = temp_buf;
+
+done:
+    if (FAIL == ret_value && temp_buf)
+        temp_buf = (char *)H5MM_xfree(temp_buf);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5_expand_windows_env_vars() */
+#endif /* H5_HAVE_WIN32_API */
+
diff --git a/src/H5win32defs.h b/src/H5win32defs.h
index 97f7179..4522228 100644
--- a/src/H5win32defs.h
+++ b/src/H5win32defs.h
@@ -119,6 +119,7 @@ extern "C" {
     H5_DLL int c99_snprintf(char* str, size_t size, const char* format, ...);
     H5_DLL int c99_vsnprintf(char* str, size_t size, const char* format, va_list ap);
     H5_DLL int Wnanosleep(const struct timespec *req, struct timespec *rem);
+    H5_DLL herr_t H5_expand_windows_env_vars(char **env_var);
 
     /* Round functions only needed for VS2012 and earlier.
      * They are always built to ensure they don't go stale and
diff --git a/src/Makefile.am b/src/Makefile.am
index 0b664a7..9a64717 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -97,7 +97,7 @@ libhdf5_la_SOURCES= H5.c H5checksum.c H5dbg.c H5system.c H5timer.c H5trace.c \
         H5Pgcpl.c H5Pint.c \
         H5Plapl.c H5Plcpl.c H5Pocpl.c H5Pocpypl.c H5Pstrcpl.c H5Ptest.c \
         H5PB.c \
-        H5PL.c \
+        H5PL.c H5PLint.c H5PLpath.c H5PLplugin_cache.c \
         H5R.c H5Rdeprec.c \
         H5UC.c \
         H5RS.c \
diff --git a/test/plugin.c b/test/plugin.c
index 1254e9a..f536a9e 100644
--- a/test/plugin.c
+++ b/test/plugin.c
@@ -10,9 +10,6 @@
  * help@hdfgroup.org.                                                        *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 /*
- * Programmer:    Raymond Lu
- *        13 February 2013
- *
  * Purpose:    Tests the plugin module (H5PL)
  */
 
@@ -660,13 +657,10 @@ error:
 /*-------------------------------------------------------------------------
  * Function:    test_groups_with_filters
  *
- * Purpose:    Tests opening group with dynamically loaded filters
- *
- * Return:    Success:    0
- *        Failure:    -1
+ * Purpose:     Tests opening group with dynamically loaded filters
  *
- * Programmer:    Raymond Lu
- *              1 April 2013
+ * Return:      Success:    0
+ *              Failure:    -1
  *
  *-------------------------------------------------------------------------
  */
@@ -710,261 +704,380 @@ error:
 
 
 /*-------------------------------------------------------------------------
- * Function:  test_filter_path_apis
+ * Function:  test_path_api_calls
  *
- * Purpose:   Tests accessing the path table for dynamically loaded filters
+ * Purpose:   Tests the H5PL API calls that manipulate the plugin search
+ *            paths.
  *
- * Return:    Success:    0
- *            Failure:    -1
+ * Return:    SUCCEED/FAIL
+ * 
  *-------------------------------------------------------------------------
  */
 static herr_t
-test_filter_path_apis(void)
+test_path_api_calls(void)
 {
-    herr_t       ret_value = -1;
-    unsigned int i;
-    unsigned int ndx;
+    unsigned int n_starting_paths;
+    unsigned int u;                 
+    unsigned int n_paths;
     herr_t       ret;
-    ssize_t      pathlen = -1;
-    char         pathname[256];
-    char         tempname[256];
+    ssize_t      path_len = -1;
+    char         path[256];
+    char         temp_name[256];
+    herr_t       ret_value = -1;
 
     HDputs("Testing access to the filter path table");
 
-    if(H5Zfilter_avail(H5Z_FILTER_DYNLIB1) != TRUE) TEST_ERROR
+    if(H5Zfilter_avail(H5Z_FILTER_DYNLIB1) != TRUE)
+        TEST_ERROR
+
+    /* Set the number of paths to create for this test.
+     *
+     * This should be set high enough to ensure that at least one array
+     * expansion will take place. See H5PLpath.c for details.
+     */
+    n_starting_paths = 42;
+
 
-    H5PLsize(&ndx);
+    /****************/
+    /* H5PLremove() */
+    /****************/
 
+    /* Remove all the current paths */
     TESTING("    remove");
-    /* Remove all existing paths*/
-    for(i=ndx; i > 0; i--)
-        if(H5PLremove(i-1) < 0) {
-            HDfprintf(stderr,"    at %d: %s\n", i, pathname);
+
+    /* Get the current size */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+
+    /* Remove all existing paths */
+    for(u = n_paths; u > 0; u--)
+        if(H5PLremove(u-1) < 0) {
+            HDfprintf(stderr,"    at %u: %s\n", u, path);
             TEST_ERROR
-        } /* end if */
+        }
+
     /* Verify the table is empty */
-    H5PLsize(&ndx);
-    if(ndx > 0) TEST_ERROR
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths > 0)
+        TEST_ERROR
+
     PASSED();
 
-    TESTING("    remove (exceed min)");
-    /* Exceed the min path removal */
+
+    TESTING("    remove (index 0 in empty table)");
+
+    /* Try to remove index zero in an empty list (SHOULD FAIL) */
     H5E_BEGIN_TRY {
         ret = H5PLremove(0);
     } H5E_END_TRY
-    if(ret >= 0) TEST_ERROR
+    if(ret >= 0)
+        TEST_ERROR
+
     PASSED();
 
+
+    /****************/
+    /* H5PLappend() */
+    /****************/
+
     TESTING("    append");
-    /* Create multiple paths to fill table */
-    for(i=0; i < H5PL_MAX_PATH_NUM; i++) {
-        HDsprintf(pathname, "a_path_%d", i);
-        if(H5PLappend(pathname) < 0) {
-            HDfprintf(stderr,"    at %d: %s\n", i, pathname);
+
+    /* Add a bunch of paths to the path table */
+    for(u = 0; u < n_starting_paths; u++) {
+        HDsprintf(path, "a_path_%u", u);
+        if(H5PLappend(path) < 0) {
+            HDfprintf(stderr,"    at %u: %s\n", u, path);
             TEST_ERROR
         }
     }
-    /* Verify the table is full */
-    H5PLsize(&ndx);
-    if(ndx != H5PL_MAX_PATH_NUM) TEST_ERROR
-    PASSED();
 
-    TESTING("    append (exceed)");
-    /* Exceed the max path append */
-    H5E_BEGIN_TRY {
-        HDsprintf(pathname, "a_path_%d", H5PL_MAX_PATH_NUM);
-        ret = H5PLappend(pathname);
-    } H5E_END_TRY
-    if(ret >= 0) TEST_ERROR
     PASSED();
 
-    TESTING("    remove (exceed max)");
-    /* Exceed the max path removal */
+
+    /**********************/
+    /* H5PLremove() again */
+    /**********************/
+
+    TESTING("    remove (index too high)");
+
+    /* Try to remove a path where the index is beyond the table capacity (SHOULD FAIL) */
     H5E_BEGIN_TRY {
-        ret = H5PLremove(H5PL_MAX_PATH_NUM);
+        ret = H5PLremove(n_starting_paths);
     } H5E_END_TRY
-    if(ret >= 0) TEST_ERROR
+
+    if(ret >= 0)
+        TEST_ERROR
+
     PASSED();
 
+
+    /*************/
+    /* H5PLget() */
+    /*************/
+
     TESTING("    get (path name)");
-    if((pathlen = H5PLget(0, NULL, 0)) <= 0) {
+
+    /* Get the path length by passing in NULL */
+    if((path_len = H5PLget(0, NULL, 0)) <= 0) {
         HDfprintf(stderr,"    get path 0 length failed\n");
         TEST_ERROR
     }
-    if(pathlen != 8) TEST_ERROR
+    if(path_len != 8)
+        TEST_ERROR
 
-    if((pathlen = H5PLget(0, pathname, 256)) <= 0) {
-        HDfprintf(stderr,"    get 0 len: %d : %s\n", pathlen, pathname);
+    /* Get the path */
+    if((path_len = H5PLget(0, path, 256)) <= 0) {
+        HDfprintf(stderr,"    get 0 len: %u : %s\n", path_len, path);
         TEST_ERROR
     }
-    if(HDstrcmp(pathname, "a_path_0") != 0) {
-        HDfprintf(stderr,"    get 0: %s\n", pathname);
+    if(HDstrcmp(path, "a_path_0") != 0) {
+        HDfprintf(stderr,"    get 0: %s\n", path);
         TEST_ERROR
     }
+
     PASSED();
 
-    TESTING("    get (bounds)");
-    if((pathlen = H5PLget(1, pathname, 256)) <= 0) TEST_ERROR
-    if(HDstrcmp(pathname, "a_path_1") != 0) {
-        HDfprintf(stderr,"    get 1: %s\n", pathname);
+
+    TESTING("    get (high and low indices)");
+
+    /* Get path at index 1 */
+    if((path_len = H5PLget(1, path, 256)) <= 0)
+        TEST_ERROR
+    if(HDstrcmp(path, "a_path_1") != 0) {
+        HDfprintf(stderr,"    get 1: %s\n", path);
         TEST_ERROR
     }
-    if((pathlen = H5PLget(H5PL_MAX_PATH_NUM - 1, pathname, 256)) <= 0) TEST_ERROR
-    HDsprintf(tempname, "a_path_%d", H5PL_MAX_PATH_NUM - 1);
-    if(HDstrcmp(pathname, tempname) != 0) {
-        HDfprintf(stderr,"    get %d: %s\n", H5PL_MAX_PATH_NUM - 1, pathname);
+
+    /* Get path at the last index */
+    if((path_len = H5PLget(n_starting_paths - 1, path, 256)) <= 0)
+        TEST_ERROR
+    HDsprintf(temp_name, "a_path_%u", n_starting_paths - 1);
+    if(HDstrcmp(path, temp_name) != 0) {
+        HDfprintf(stderr,"    get %u: %s\n", n_starting_paths - 1, path);
         TEST_ERROR
     }
+
     PASSED();
 
-    TESTING("    get (bounds exceed)");
+
+    TESTING("    get (index too high)");
+
+    /* Get path at the last + 1 index (SHOULD FAIL) */
     H5E_BEGIN_TRY {
-        pathlen = H5PLget(H5PL_MAX_PATH_NUM, NULL, 0);
+        path_len = H5PLget(n_starting_paths, NULL, 0);
     } H5E_END_TRY
-    if(pathlen > 0) TEST_ERROR
+    if(path_len > 0)
+        TEST_ERROR
+
     PASSED();
 
-    TESTING("    remove (verify for prepend)");
-    /* Remove one path*/
-    if(H5PLremove(8) < 0) TEST_ERROR
+
+    /*****************/
+    /* H5PLprepend() */
+    /*****************/
+
+    /* We'll remove a path at an arbitrary index and then
+     * prepend a new path.
+     */
+
+    TESTING("    remove (arbitrary index 1)");
+
+    /* Remove one path */
+    if(H5PLremove(8) < 0)
+        TEST_ERROR
 
     /* Verify that the entries were moved */
-    if((pathlen = H5PLget(8, pathname, 256)) <= 0) TEST_ERROR
-    if(HDstrcmp(pathname, "a_path_9") != 0) {
-        HDfprintf(stderr,"    get 8: %s\n", pathname);
+    if((path_len = H5PLget(8, path, 256)) <= 0)
+        TEST_ERROR
+    if(HDstrcmp(path, "a_path_9") != 0) {
+        HDfprintf(stderr,"    get 8: %s\n", path);
         TEST_ERROR
     }
+
+    /* Verify the table shrank */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths != n_starting_paths - 1)
+        TEST_ERROR
+
     PASSED();
 
-    /* Verify the table is not full */
-    H5PLsize(&ndx);
-    if (ndx != H5PL_MAX_PATH_NUM - 1) TEST_ERROR
 
     TESTING("    prepend");
-    /* Prepend one path*/
-    HDsprintf(pathname, "a_path_%d", H5PL_MAX_PATH_NUM + 1);
-    if(H5PLprepend(pathname) < 0) {
-        HDfprintf(stderr,"    prepend %d: %s\n", H5PL_MAX_PATH_NUM + 1, pathname);
+
+    /* Prepend one path */
+    HDsprintf(path, "a_path_%d", n_starting_paths + 1);
+    if(H5PLprepend(path) < 0) {
+        HDfprintf(stderr,"    prepend %u: %s\n", n_starting_paths + 1, path);
         TEST_ERROR
     }
 
-    /* Verify the table is full */
-    H5PLsize(&ndx);
-    if(ndx != H5PL_MAX_PATH_NUM) TEST_ERROR
+    /* Verify the table increased */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths != n_starting_paths)
+        TEST_ERROR
 
     /* Verify that the entries were moved */
-    if(H5PLget(8, pathname, 256) <= 0) TEST_ERROR
-    if(HDstrcmp(pathname, "a_path_7") != 0) {
-        HDfprintf(stderr,"    get 8: %s\n", pathname);
+    if(H5PLget(8, path, 256) <= 0)
+        TEST_ERROR
+    if(HDstrcmp(path, "a_path_7") != 0) {
+        HDfprintf(stderr,"    get 8: %s\n", path);
         TEST_ERROR
     }
-    if(H5PLget(0, pathname, 256) <= 0) TEST_ERROR
-    HDsprintf(tempname, "a_path_%d", H5PL_MAX_PATH_NUM + 1);
-    if(HDstrcmp(pathname, tempname) != 0) {
-        HDfprintf(stderr,"    get 0: %s\n", pathname);
+
+    /* Verify that the path was inserted at index zero */
+    if(H5PLget(0, path, 256) <= 0)
+        TEST_ERROR
+    HDsprintf(temp_name, "a_path_%d", n_starting_paths + 1);
+    if(HDstrcmp(path, temp_name) != 0) {
+        HDfprintf(stderr,"    get 0: %s\n", path);
         TEST_ERROR
     }
-    PASSED();
 
-    TESTING("    prepend (exceed)");
-    /* Exceed the max path prepend */
-    H5E_BEGIN_TRY {
-        HDsprintf(pathname, "a_path_%d", H5PL_MAX_PATH_NUM + 2);
-        ret = H5PLprepend(pathname);
-    } H5E_END_TRY
-    if(ret >= 0) TEST_ERROR
     PASSED();
 
+
+    /*****************/
+    /* H5PLreplace() */
+    /*****************/
+
     TESTING("    replace");
-    /* Replace one path*/
-    HDsprintf(pathname, "a_path_%d", H5PL_MAX_PATH_NUM + 4);
-    if(H5PLreplace(pathname, 1) < 0) {
-        HDfprintf(stderr,"    replace 1: %s\n", pathname);
+
+    /* Replace one path at index 1 */
+    HDsprintf(path, "a_path_%u", n_starting_paths + 4);
+    if(H5PLreplace(path, 1) < 0) {
+        HDfprintf(stderr,"    replace 1: %s\n", path);
         TEST_ERROR
     }
 
-    /* Verify the table is full */
-    H5PLsize(&ndx);
-    if(ndx != H5PL_MAX_PATH_NUM) TEST_ERROR
+    /* Verify the table size remained the same */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths != n_starting_paths)
+        TEST_ERROR
+
+    /* Verify that the entries were not moved by
+     * inspecting the paths at indices +/- 1.
+     */
 
-    /* Verify that the entries were not moved */
-    if(H5PLget(0, pathname, 256) <= 0) TEST_ERROR
-    HDsprintf(tempname, "a_path_%d", H5PL_MAX_PATH_NUM + 1);
-    if(HDstrcmp(pathname, tempname) != 0) {
-        HDfprintf(stderr,"    get 0: %s\n", pathname);
+    /* Check path at index 0 */
+    if(H5PLget(0, path, 256) <= 0)
+        TEST_ERROR
+    HDsprintf(temp_name, "a_path_%u", n_starting_paths + 1);
+    if(HDstrcmp(path, temp_name) != 0) {
+        HDfprintf(stderr,"    get 0: %s\n", path);
         TEST_ERROR
     }
-    if(H5PLget(2, pathname, 256) <= 0) TEST_ERROR
-    if(HDstrcmp(pathname, "a_path_1") != 0) {
-        HDfprintf(stderr,"    get 2: %s\n", pathname);
+
+    /* Check path at index 2 */
+    if(H5PLget(2, path, 256) <= 0)
+        TEST_ERROR
+    if(HDstrcmp(path, "a_path_1") != 0) {
+        HDfprintf(stderr,"    get 2: %s\n", path);
         TEST_ERROR
     }
+
     PASSED();
 
-    TESTING("    remove (verify for insert)");
-    /* Remove one path*/
-    if(H5PLremove(4) < 0) TEST_ERROR
+
+    /****************/
+    /* H5PLinsert() */
+    /****************/
+
+    /* We'll remove a path at an arbitrary index and then
+     * insert a new path.
+     */
+
+    TESTING("    remove (arbitrary index 2)");
+
+    /* Remove one path */
+    if(H5PLremove(4) < 0)
+        TEST_ERROR
 
     /* Verify that the entries were moved */
-    if(H5PLget(4, pathname, 256) <= 0) TEST_ERROR
-    if(HDstrcmp(pathname, "a_path_4") != 0) {
-        HDfprintf(stderr,"    get 4: %s\n", pathname);
+    if(H5PLget(4, path, 256) <= 0)
+        TEST_ERROR
+    if(HDstrcmp(path, "a_path_4") != 0) {
+        HDfprintf(stderr,"    get 4: %s\n", path);
         TEST_ERROR
     }
+
+    /* Verify the table size */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths != n_starting_paths - 1)
+        TEST_ERROR
     PASSED();
 
-    /* Verify the table is not full */
-    H5PLsize(&ndx);
-    if(ndx != 15) TEST_ERROR
 
     TESTING("    insert");
-    /* Insert one path*/
-    HDsprintf(pathname, "a_path_%d", H5PL_MAX_PATH_NUM + 5);
-    if(H5PLinsert(pathname, 3) < 0) {
-        HDfprintf(stderr,"    insert 3: %s\n", pathname);
+
+    /* Insert one path at index 3*/
+    HDsprintf(path, "a_path_%d", n_starting_paths + 5);
+    if(H5PLinsert(path, 3) < 0) {
+        HDfprintf(stderr,"    insert 3: %s\n", path);
         TEST_ERROR
     }
 
     /* Verify that the entries were moved */
-    if(H5PLget(4, pathname, 256) <= 0) TEST_ERROR
-    if(HDstrcmp(pathname, "a_path_2") != 0) {
-        HDfprintf(stderr,"    get 4: %s\n", pathname);
+    if(H5PLget(4, path, 256) <= 0)
+        TEST_ERROR
+    if(HDstrcmp(path, "a_path_2") != 0) {
+        HDfprintf(stderr,"    get 4: %s\n", path);
         TEST_ERROR
     }
+
+    /* Verify the table size increased */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths != n_starting_paths)
+        TEST_ERROR
+
     PASSED();
 
-    /* Verify the table is full */
-    H5PLsize(&ndx);
-    if(ndx != H5PL_MAX_PATH_NUM) TEST_ERROR
 
-    TESTING("    insert (exceed)");
-    /* Exceed the max path insert */
-    H5E_BEGIN_TRY {
-        HDsprintf(pathname, "a_path_%d", H5PL_MAX_PATH_NUM + 6);
-        ret = H5PLinsert(pathname, 12);
-    } H5E_END_TRY
-    if(ret >= 0) TEST_ERROR
+    /****************/
+    /* H5PLremove() */
+    /****************/
+
+    /* Remove all the current paths */
+    TESTING("    remove (all)");
+
+    /* Get the current size */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+
+    /* Remove all existing paths */
+    for(u = n_paths; u > 0; u--)
+        if(H5PLremove(u-1) < 0) {
+            HDfprintf(stderr,"    at %u: %s\n", u, path);
+            TEST_ERROR
+        }
+
+    /* Verify the table is empty */
+    if(H5PLsize(&n_paths) < 0)
+        TEST_ERROR
+    if(n_paths > 0)
+        TEST_ERROR
 
     PASSED();
 
-    ret_value = 0;
+
+    return SUCCEED;
 
 error:
-    return ret_value;
-}
+    return FAIL;
+} /* end test_path_api_calls() */
 
 
 /*-------------------------------------------------------------------------
  * Function:    main
  *
- * Purpose:    Tests the plugin module (H5PL)
- *
- * Return:    Success:    exit(EXIT_SUCCESS)
+ * Purpose:     Tests the plugin module (H5PL)
  *
- *        Failure:    exit(EXIT_FAILURE)
- *
- * Programmer:    Raymond Lu
- *        14 March 2013
+ * Return:      EXIT_SUCCESS/EXIT_FAILURE
  *
  *-------------------------------------------------------------------------
  */
@@ -1063,18 +1176,19 @@ main(void)
     if(H5Fclose(file) < 0) TEST_ERROR
 
     /* Test the APIs for access to the filter plugin path table */
-    nerrors += (test_filter_path_apis() < 0  ? 1 : 0);
+    nerrors += (test_path_api_calls() < 0  ? 1 : 0);
 
-    if(nerrors) TEST_ERROR
+    if(nerrors)
+        TEST_ERROR
 
     HDprintf("All plugin tests passed.\n");
     h5_cleanup(FILENAME, fapl);
 
-    return 0;
+    HDexit(EXIT_SUCCESS);
 
 error:
     nerrors = MAX(1, nerrors);
     HDprintf("***** %d PLUGIN TEST%s FAILED! *****\n", nerrors, 1 == nerrors ? "" : "S");
-    return 1;
-}
+    HDexit(EXIT_FAILURE);
+} /* end main() */