VFD plugins (#602)

* Implement support for loading of Virtual File Drivers as plugins

Fix plugin caching for VOL connector and VFD plugins

Fix plugin iteration to skip paths that can't be opened

* Enable dynamic loading of VFDs with HDF5_DRIVER environment variable

* Temporarily disable error reporting during H5F_open double file open

* Default to using HDstat in h5_get_file_size for unknown VFDs

* Use macros for some environment variables that HDF5 interprets

* Update "null" and "ctl testing" VFDs

4 files changed, 152 insertions, 94 deletions

diff --git a/tools/lib/h5diff.c b/tools/lib/h5diff.c
index 0ad319e..74db58f 100644
--- a/tools/lib/h5diff.c
+++ b/tools/lib/h5diff.c
@@ -648,14 +648,16 @@ h5diff(const char *fname1, const char *fname2, const char *objname1, const char
      *-------------------------------------------------------------------------
      */
     /* open file 1 */
-    if (opts->custom_vol[0]) {
-        if ((fapl1_id = h5tools_get_fapl(H5P_DEFAULT, &(opts->vol_info[0]), NULL)) < 0) {
+    if (opts->custom_vol[0] || opts->custom_vfd[0]) {
+        if ((fapl1_id = h5tools_get_fapl(H5P_DEFAULT, opts->custom_vol[0] ? &(opts->vol_info[0]) : NULL,
+                                         opts->custom_vfd[0] ? &(opts->vfd_info[0]) : NULL)) < 0) {
             parallel_print("h5diff: unable to create fapl for input file\n");
             H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to create input fapl\n");
         }
     }
 
-    if ((file1_id = h5tools_fopen(fname1, H5F_ACC_RDONLY, fapl1_id, FALSE, NULL, (size_t)0)) < 0) {
+    if ((file1_id = h5tools_fopen(fname1, H5F_ACC_RDONLY, fapl1_id, (fapl1_id != H5P_DEFAULT), NULL,
+                                  (size_t)0)) < 0) {
         parallel_print("h5diff: <%s>: unable to open file\n", fname1);
         H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "<%s>: unable to open file\n", fname1);
     }
@@ -663,14 +665,16 @@ h5diff(const char *fname1, const char *fname2, const char *objname1, const char
 
     /* open file 2 */
 
-    if (opts->custom_vol[1]) {
-        if ((fapl2_id = h5tools_get_fapl(H5P_DEFAULT, &(opts->vol_info[1]), NULL)) < 0) {
+    if (opts->custom_vol[1] || opts->custom_vfd[1]) {
+        if ((fapl2_id = h5tools_get_fapl(H5P_DEFAULT, opts->custom_vol[1] ? &(opts->vol_info[1]) : NULL,
+                                         opts->custom_vfd[1] ? &(opts->vfd_info[1]) : NULL)) < 0) {
             parallel_print("h5diff: unable to create fapl for output file\n");
             H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to create output fapl\n");
         }
     }
 
-    if ((file2_id = h5tools_fopen(fname2, H5F_ACC_RDONLY, fapl2_id, FALSE, NULL, (size_t)0)) < 0) {
+    if ((file2_id = h5tools_fopen(fname2, H5F_ACC_RDONLY, fapl2_id, (fapl2_id != H5P_DEFAULT), NULL,
+                                  (size_t)0)) < 0) {
         parallel_print("h5diff: <%s>: unable to open file\n", fname2);
         H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "<%s>: unable to open file\n", fname2);
     }
diff --git a/tools/lib/h5diff.h b/tools/lib/h5diff.h
index 7b41538..8d7ac13 100644
--- a/tools/lib/h5diff.h
+++ b/tools/lib/h5diff.h
@@ -89,7 +89,9 @@ typedef struct {
     char *                    obj_name[2];             /* name for object */
     struct subset_t *         sset[2];                 /* subsetting parameters */
     h5tools_vol_info_t        vol_info[2];             /* VOL information for input file, output file */
+    h5tools_vfd_info_t        vfd_info[2];             /* VFD information for input file, output file */
     hbool_t                   custom_vol[2];           /* Using a custom input, output VOL? */
+    hbool_t                   custom_vfd[2];           /* Using a custom input, output VFD? */
 } diff_opt_t;
 
 /*-------------------------------------------------------------------------
diff --git a/tools/lib/h5tools.c b/tools/lib/h5tools.c
index eee9c53..4de2c5c 100644
--- a/tools/lib/h5tools.c
+++ b/tools/lib/h5tools.c
@@ -459,8 +459,8 @@ h5tools_set_error_file(const char *fname, int is_bin)
 /*-------------------------------------------------------------------------
  * Function: h5tools_set_fapl_vfd
  *
- * Purpose:  Given a VFL driver name, sets the appropriate driver on the
- *           specified FAPL.
+ * Purpose:  Given a VFL driver name or ID, sets the appropriate driver on
+ *           the specified FAPL.
  *
  * Return:   positive - succeeded
  *           negative - failed
@@ -471,107 +471,139 @@ h5tools_set_fapl_vfd(hid_t fapl_id, h5tools_vfd_info_t *vfd_info)
 {
     herr_t ret_value = SUCCEED;
 
-    /* Determine which driver the user wants to open the file with */
-    if (!HDstrcmp(vfd_info->name, drivernames[SEC2_VFD_IDX])) {
-        /* SEC2 Driver */
-        if (H5Pset_fapl_sec2(fapl_id) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_sec2 failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[DIRECT_VFD_IDX])) {
+    switch (vfd_info->type) {
+        case VFD_BY_NAME:
+            /* Determine which driver the user wants to open the file with */
+            if (!HDstrcmp(vfd_info->u.name, drivernames[SEC2_VFD_IDX])) {
+                /* SEC2 Driver */
+                if (H5Pset_fapl_sec2(fapl_id) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_sec2 failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[DIRECT_VFD_IDX])) {
 #ifdef H5_HAVE_DIRECT
-        /* Direct Driver */
-        if (H5Pset_fapl_direct(fapl_id, 1024, 4096, 8 * 4096) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_direct failed");
+                /* Direct Driver */
+                if (H5Pset_fapl_direct(fapl_id, 1024, 4096, 8 * 4096) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_direct failed");
 #else
-        H5TOOLS_GOTO_ERROR(FAIL, "Direct VFD is not enabled");
+                H5TOOLS_GOTO_ERROR(FAIL, "Direct VFD is not enabled");
 #endif
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[LOG_VFD_IDX])) {
-        unsigned long long log_flags = H5FD_LOG_LOC_IO | H5FD_LOG_ALLOC;
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[LOG_VFD_IDX])) {
+                unsigned long long log_flags = H5FD_LOG_LOC_IO | H5FD_LOG_ALLOC;
 
-        /* Log Driver */
-        if (H5Pset_fapl_log(fapl_id, NULL, log_flags, (size_t)0) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_log failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[WINDOWS_VFD_IDX])) {
+                /* Log Driver */
+                if (H5Pset_fapl_log(fapl_id, NULL, log_flags, (size_t)0) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_log failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[WINDOWS_VFD_IDX])) {
 #ifdef H5_HAVE_WINDOWS
-        /* There is no Windows VFD - use SEC2 */
-        if (H5Pset_fapl_sec2(fapl_id) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_sec2 failed");
+                /* There is no Windows VFD - use SEC2 */
+                if (H5Pset_fapl_sec2(fapl_id) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_sec2 failed");
 #else
-        H5TOOLS_GOTO_ERROR(FAIL, "Windows VFD is not enabled");
+                H5TOOLS_GOTO_ERROR(FAIL, "Windows VFD is not enabled");
 #endif
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[STDIO_VFD_IDX])) {
-        /* Stdio Driver */
-        if (H5Pset_fapl_stdio(fapl_id) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_stdio failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[CORE_VFD_IDX])) {
-        /* Core Driver */
-        if (H5Pset_fapl_core(fapl_id, (size_t)H5_MB, TRUE) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_core failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[FAMILY_VFD_IDX])) {
-        /* FAMILY Driver */
-        /* Set member size to be 0 to indicate the current first member size
-         * is the member size.
-         */
-        if (H5Pset_fapl_family(fapl_id, (hsize_t)0, H5P_DEFAULT) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_family failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[SPLIT_VFD_IDX])) {
-        /* SPLIT Driver */
-        if (H5Pset_fapl_split(fapl_id, "-m.h5", H5P_DEFAULT, "-r.h5", H5P_DEFAULT) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_split failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[MULTI_VFD_IDX])) {
-        /* MULTI Driver */
-        if (H5Pset_fapl_multi(fapl_id, NULL, NULL, NULL, NULL, TRUE) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_multi failed");
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[MPIO_VFD_IDX])) {
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[STDIO_VFD_IDX])) {
+                /* Stdio Driver */
+                if (H5Pset_fapl_stdio(fapl_id) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_stdio failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[CORE_VFD_IDX])) {
+                /* Core Driver */
+                if (H5Pset_fapl_core(fapl_id, (size_t)H5_MB, TRUE) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_core failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[FAMILY_VFD_IDX])) {
+                /* FAMILY Driver */
+                /* Set member size to be 0 to indicate the current first member size
+                 * is the member size.
+                 */
+                if (H5Pset_fapl_family(fapl_id, (hsize_t)0, H5P_DEFAULT) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_family failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[SPLIT_VFD_IDX])) {
+                /* SPLIT Driver */
+                if (H5Pset_fapl_split(fapl_id, "-m.h5", H5P_DEFAULT, "-r.h5", H5P_DEFAULT) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_split failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[MULTI_VFD_IDX])) {
+                /* MULTI Driver */
+                if (H5Pset_fapl_multi(fapl_id, NULL, NULL, NULL, NULL, TRUE) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_multi failed");
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[MPIO_VFD_IDX])) {
 #ifdef H5_HAVE_PARALLEL
-        int mpi_initialized, mpi_finalized;
+                int mpi_initialized, mpi_finalized;
 
-        /* MPI-I/O Driver */
+                /* MPI-I/O Driver */
 
-        /* check if MPI is available. */
-        MPI_Initialized(&mpi_initialized);
-        MPI_Finalized(&mpi_finalized);
+                /* check if MPI is available. */
+                MPI_Initialized(&mpi_initialized);
+                MPI_Finalized(&mpi_finalized);
 
-        if (mpi_initialized && !mpi_finalized) {
-            if (H5Pset_fapl_mpio(fapl_id, MPI_COMM_WORLD, MPI_INFO_NULL) < 0)
-                H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_mpio failed");
-        }
+                if (mpi_initialized && !mpi_finalized) {
+                    if (H5Pset_fapl_mpio(fapl_id, MPI_COMM_WORLD, MPI_INFO_NULL) < 0)
+                        H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_mpio failed");
+                }
 #else
-        H5TOOLS_GOTO_ERROR(FAIL, "MPI-I/O VFD is not enabled");
+                H5TOOLS_GOTO_ERROR(FAIL, "MPI-I/O VFD is not enabled");
 #endif /* H5_HAVE_PARALLEL */
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[ROS3_VFD_IDX])) {
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[ROS3_VFD_IDX])) {
 #ifdef H5_HAVE_ROS3_VFD
-        if (!vfd_info->info)
-            H5TOOLS_GOTO_ERROR(FAIL, "Read-only S3 VFD info is invalid");
-        if (H5Pset_fapl_ros3(fapl_id, (H5FD_ros3_fapl_t *)vfd_info->info) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_ros3() failed");
+                if (!vfd_info->info)
+                    H5TOOLS_GOTO_ERROR(FAIL, "Read-only S3 VFD info is invalid");
+                if (H5Pset_fapl_ros3(fapl_id, (H5FD_ros3_fapl_t *)vfd_info->info) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_ros3() failed");
 #else
-        H5TOOLS_GOTO_ERROR(FAIL, "Read-only S3 VFD is not enabled");
+                H5TOOLS_GOTO_ERROR(FAIL, "Read-only S3 VFD is not enabled");
 #endif
-    }
-    else if (!HDstrcmp(vfd_info->name, drivernames[HDFS_VFD_IDX])) {
+            }
+            else if (!HDstrcmp(vfd_info->u.name, drivernames[HDFS_VFD_IDX])) {
 #ifdef H5_HAVE_LIBHDFS
-        if (!vfd_info->info)
-            H5TOOLS_GOTO_ERROR(FAIL, "HDFS VFD info is invalid");
-        if (H5Pset_fapl_hdfs(fapl_id, (H5FD_hdfs_fapl_t *)vfd_info->info) < 0)
-            H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_hdfs() failed");
+                if (!vfd_info->info)
+                    H5TOOLS_GOTO_ERROR(FAIL, "HDFS VFD info is invalid");
+                if (H5Pset_fapl_hdfs(fapl_id, (H5FD_hdfs_fapl_t *)vfd_info->info) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "H5Pset_fapl_hdfs() failed");
 #else
-        H5TOOLS_GOTO_ERROR(FAIL, "The HDFS VFD is not enabled");
+                H5TOOLS_GOTO_ERROR(FAIL, "The HDFS VFD is not enabled");
 #endif
+            }
+            else {
+                /*
+                 * Try to load VFD plugin.
+                 *
+                 * Currently, driver configuration strings are unsupported.
+                 */
+                if (H5Pset_driver_by_name(fapl_id, vfd_info->u.name, (const char *)vfd_info->info) < 0)
+                    H5TOOLS_GOTO_ERROR(FAIL, "can't load VFD plugin by driver name '%s'", vfd_info->u.name);
+            }
+
+            break;
+
+        case VFD_BY_VALUE:
+            /*
+             * Try to load VFD plugin.
+             *
+             * Currently, driver configuration strings are unsupported.
+             */
+            if (H5Pset_driver_by_value(fapl_id, vfd_info->u.value, (const char *)vfd_info->info) < 0)
+                H5TOOLS_GOTO_ERROR(FAIL, "can't load VFD plugin by driver value '%ld'",
+                                   (long int)vfd_info->u.value);
+            break;
+
+        default:
+            H5TOOLS_GOTO_ERROR(FAIL, "invalid VFD retrieval type");
     }
-    else
-        H5TOOLS_GOTO_ERROR(FAIL, "invalid VFD name");
 
 done:
+    if (ret_value < 0) {
+        /* Clear error message unless asked for */
+        if (enable_error_stack <= 1)
+            H5Epop(H5tools_ERR_STACK_g, 1);
+    }
+
     return ret_value;
 }
 
@@ -671,6 +703,10 @@ done:
     if (ret_value < 0) {
         if (connector_id >= 0 && H5Idec_ref(connector_id) < 0)
             H5TOOLS_ERROR(FAIL, "failed to decrement refcount on VOL connector ID");
+
+        /* Clear error message unless asked for */
+        if (enable_error_stack <= 1)
+            H5Epop(H5tools_ERR_STACK_g, 1);
     }
 
     return ret_value;
@@ -719,9 +755,15 @@ h5tools_get_fapl(hid_t prev_fapl_id, h5tools_vol_info_t *vol_info, h5tools_vfd_i
     ret_value = new_fapl_id;
 
 done:
-    if ((new_fapl_id >= 0) && (ret_value < 0)) {
-        H5Pclose(new_fapl_id);
-        new_fapl_id = H5I_INVALID_HID;
+    if (ret_value < 0) {
+        if (new_fapl_id >= 0) {
+            H5Pclose(new_fapl_id);
+            new_fapl_id = H5I_INVALID_HID;
+        }
+
+        /* Clear error message unless asked for */
+        if (enable_error_stack <= 1)
+            H5Epop(H5tools_ERR_STACK_g, 1);
     }
 
     return ret_value;
@@ -937,8 +979,9 @@ h5tools_fopen(const char *fname, unsigned flags, hid_t fapl_id, hbool_t use_spec
                 if (drivernum == LOG_VFD_IDX)
                     continue;
 
-                vfd_info.info = NULL;
-                vfd_info.name = drivernames[drivernum];
+                vfd_info.type   = VFD_BY_NAME;
+                vfd_info.info   = NULL;
+                vfd_info.u.name = drivernames[drivernum];
 
                 /* Get a fapl reflecting the selected VOL connector and VFD */
                 if ((tmp_fapl_id = h5tools_get_fapl(fapl_id, &vol_info, &vfd_info)) < 0)
@@ -989,6 +1032,10 @@ done:
     if (tmp_fapl_id >= 0)
         H5Pclose(tmp_fapl_id);
 
+    /* Clear error message unless asked for */
+    if (ret_value < 0 && enable_error_stack <= 1)
+        H5Epop(H5tools_ERR_STACK_g, 1);
+
     return ret_value;
 }
 
diff --git a/tools/lib/h5tools.h b/tools/lib/h5tools.h
index 9d065f3..dde4026 100644
--- a/tools/lib/h5tools.h
+++ b/tools/lib/h5tools.h
@@ -553,6 +553,7 @@ typedef struct h5tools_context_t {
  */
 
 typedef enum { VOL_BY_NAME, VOL_BY_VALUE } h5tools_vol_info_type_t;
+typedef enum { VFD_BY_NAME, VFD_BY_VALUE } h5tools_vfd_info_type_t;
 
 typedef struct h5tools_vol_info_t {
     h5tools_vol_info_type_t type;
@@ -568,12 +569,16 @@ typedef struct h5tools_vol_info_t {
 } h5tools_vol_info_t;
 
 typedef struct h5tools_vfd_info_t {
+    h5tools_vfd_info_type_t type;
 
     /* Pointer to information to be passed to the driver for its setup */
     const void *info;
 
-    /* Name of the VFD */
-    const char *name;
+    /* Field specifying either the driver's name or value (ID) */
+    union {
+        const char *       name;
+        H5FD_class_value_t value;
+    } u;
 } h5tools_vfd_info_t;
 
 /* This enum should match the entries in the above 'volnames'