HDFFV-9724 Initial changes and test

9 files changed, 879 insertions, 15 deletions

diff --git a/src/H5Dint.c b/src/H5Dint.c
index b6c0341..2123836 100644
--- a/src/H5Dint.c
+++ b/src/H5Dint.c
@@ -63,6 +63,8 @@ static herr_t H5D__update_oh_info(H5F_t *file, hid_t dxpl_id, H5D_t *dset,
         hid_t dapl_id);
 static herr_t H5D_build_extfile_prefix(const H5D_t *dset, hid_t dapl_id,
         char **extfile_prefix);
+static herr_t H5D_build_vds_prefix(const H5D_t *dset, hid_t dapl_id,
+        char **vds_prefix);
 static herr_t H5D__open_oid(H5D_t *dataset, hid_t dapl_id, hid_t dxpl_id);
 static herr_t H5D__init_storage(const H5D_io_info_t *io_info, hbool_t full_overwrite,
         hsize_t old_dim[]);
@@ -1037,6 +1039,81 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* H5D_build_extfile_prefix() */
 
+
+/*--------------------------------------------------------------------------
+ * Function:    H5D_build_vds_prefix
+ *
+ * Purpose:     Determine the vds file prefix to be used and store
+ *              it in vds_prefix. Stores an empty string if no prefix
+ *              should be used.
+ *
+ * Return:      SUCCEED/FAIL
+ *--------------------------------------------------------------------------
+ */
+static herr_t
+H5D_build_vds_prefix(const H5D_t *dset, hid_t dapl_id, char **vds_prefix /*out*/)
+{
+    char            *prefix = NULL;       /* prefix used to look for the file               */
+    char            *vdspath = NULL;      /* absolute path of directory the HDF5 file is in */
+    size_t          vdspath_len;          /* length of vdstpath                              */
+    size_t          prefix_len;           /* length of prefix                               */
+    size_t          vds_prefix_len;       /* length of expanded prefix                      */
+    H5P_genplist_t  *plist = NULL;        /* Property list pointer                          */
+    herr_t          ret_value = SUCCEED;  /* Return value                                   */
+
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(dset);
+    HDassert(dset->oloc.file);
+
+    vdspath = H5F_EXTPATH(dset->oloc.file);
+    HDassert(vdspath);
+
+    /* XXX: Future thread-safety note - getenv is not required
+     *      to be reentrant.
+     */
+    prefix = HDgetenv("HDF5_VDS_PREFIX");
+
+    if(prefix == NULL || *prefix == '\0') {
+        /* Set prefix to value of H5D_ACS_VDS_PREFIX_NAME property */
+        if(NULL == (plist = H5P_object_verify(dapl_id, H5P_DATASET_ACCESS)))
+            HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+        if(H5P_peek(plist, H5D_ACS_VDS_PREFIX_NAME, &prefix) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get vds prefix")
+    } /* end if */
+
+    /* Prefix has to be checked for NULL / empty string again because the
+     * code above might have updated it.
+     */
+    if(prefix == NULL || *prefix == '\0' || HDstrcmp(prefix, ".") == 0) {
+        /* filename is interpreted as relative to the current directory,
+         * does not need to be expanded
+         */
+        if(NULL == (*vds_prefix = (char *)H5MM_strdup("")))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
+    } /* end if */
+    else {
+        if (HDstrncmp(prefix, "${ORIGIN}", HDstrlen("${ORIGIN}")) == 0) {
+            /* Replace ${ORIGIN} at beginning of prefix by directory of HDF5 file */
+            vdspath_len = HDstrlen(vdspath);
+            prefix_len = HDstrlen(prefix);
+            vds_prefix_len = vdspath_len + prefix_len - HDstrlen("${ORIGIN}") + 1;
+
+            if(NULL == (*vds_prefix = (char *)H5MM_malloc(vds_prefix_len)))
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate buffer")
+            HDsnprintf(*vds_prefix, vds_prefix_len, "%s%s", vdspath, prefix + HDstrlen("${ORIGIN}"));
+        } /* end if */
+        else {
+            if(NULL == (*vds_prefix = (char *)H5MM_strdup(prefix)))
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
+        } /* end else */
+    } /* end else */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5D_build_vds_prefix() */
+
 
 /*-------------------------------------------------------------------------
  * Function:    H5D__create
@@ -1220,6 +1297,10 @@ H5D__create(H5F_t *file, hid_t type_id, const H5S_t *space, hid_t dcpl_id,
     if(H5D_build_extfile_prefix(new_dset, dapl_id, &new_dset->shared->extfile_prefix) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, NULL, "unable to initialize external file prefix")
 
+    /* Set the vds file prefix */
+    if(H5D_build_vds_prefix(new_dset, dapl_id, &new_dset->shared->vds_prefix) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, NULL, "unable to initialize vds  prefix")
+
     /* Add the dataset to the list of opened objects in the file */
     if(H5FO_top_incr(new_dset->oloc.file, new_dset->oloc.addr) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINC, NULL, "can't incr object ref. count")
@@ -1265,6 +1346,7 @@ done:
             if(new_dset->shared->dcpl_id != 0 && H5I_dec_ref(new_dset->shared->dcpl_id) < 0)
                 HDONE_ERROR(H5E_DATASET, H5E_CANTDEC, NULL, "unable to decrement ref count on property list")
             new_dset->shared->extfile_prefix = (char *)H5MM_xfree(new_dset->shared->extfile_prefix);
+            new_dset->shared->vds_prefix = (char *)H5MM_xfree(new_dset->shared->vds_prefix);
             new_dset->shared = H5FL_FREE(H5D_shared_t, new_dset->shared);
         } /* end if */
         new_dset->oloc.file = NULL;
@@ -1351,6 +1433,7 @@ H5D_open(const H5G_loc_t *loc, hid_t dapl_id, hid_t dxpl_id)
     H5D_shared_t    *shared_fo = NULL;
     H5D_t           *dataset = NULL;
     char            *extfile_prefix = NULL;  /* Expanded external file prefix */
+    char            *vds_prefix = NULL;      /* Expanded vds prefix */
     H5D_t           *ret_value = NULL;       /* Return value */
 
     FUNC_ENTER_NOAPI(NULL)
@@ -1374,6 +1457,10 @@ H5D_open(const H5G_loc_t *loc, hid_t dapl_id, hid_t dxpl_id)
     if(H5D_build_extfile_prefix(dataset, dapl_id, &extfile_prefix) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, NULL, "unable to initialize external file prefix")
 
+    /* Get the vds prefix */
+    if(H5D_build_vds_prefix(dataset, dapl_id, &vds_prefix) < 0)
+        HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, NULL, "unable to initialize vds prefix")
+
     /* Check if dataset was already open */
     if(NULL == (shared_fo = (H5D_shared_t *)H5FO_opened(dataset->oloc.file, dataset->oloc.addr))) {
         /* Clear any errors from H5FO_opened() */
@@ -1399,6 +1486,11 @@ H5D_open(const H5G_loc_t *loc, hid_t dapl_id, hid_t dxpl_id)
         /* Prevent string from being freed during done: */
         extfile_prefix = NULL;
 
+        /* Set the vds file prefix */
+        dataset->shared->vds_prefix = vds_prefix;
+        /* Prevent string from being freed during done: */
+        vds_prefix = NULL;
+
     } /* end if */
     else {
         /* Point to shared info */
@@ -1430,12 +1522,14 @@ H5D_open(const H5G_loc_t *loc, hid_t dapl_id, hid_t dxpl_id)
 
 done:
     extfile_prefix = (char *)H5MM_xfree(extfile_prefix);
+    vds_prefix = (char *)H5MM_xfree(vds_prefix);
 
     if(ret_value == NULL) {
         /* Free the location--casting away const*/
         if(dataset) {
             if(shared_fo == NULL && dataset->shared) {   /* Need to free shared fo */
                 dataset->shared->extfile_prefix = (char *)H5MM_xfree(dataset->shared->extfile_prefix);
+                dataset->shared->vds_prefix = (char *)H5MM_xfree(dataset->shared->vds_prefix);
                 dataset->shared = H5FL_FREE(H5D_shared_t, dataset->shared);
             }
 
@@ -1818,6 +1912,9 @@ H5D_close(H5D_t *dataset)
         /* Free the external file prefix */
         dataset->shared->extfile_prefix = (char *)H5MM_xfree(dataset->shared->extfile_prefix);
 
+        /* Free the vds file prefix */
+        dataset->shared->vds_prefix = (char *)H5MM_xfree(dataset->shared->vds_prefix);
+
         /* Release layout, fill-value, efl & pipeline messages */
         if(dataset->shared->dcpl_id != H5P_DATASET_CREATE_DEFAULT)
             free_failed |= (H5O_msg_reset(H5O_PLINE_ID, &dataset->shared->dcpl_cache.pline) < 0) ||
@@ -3360,6 +3457,10 @@ H5D_get_access_plist(H5D_t *dset)
     if(H5P_set(new_plist, H5D_ACS_VDS_PRINTF_GAP_NAME, &(dset->shared->layout.storage.u.virt.printf_gap)) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set VDS printf gap")
 
+    /* Set the vds prefix option */
+    if(H5P_set(new_plist, H5D_ACS_VDS_PREFIX_NAME, &(dset->shared->vds_prefix)) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set vds prefix")
+
     /* Set the external file prefix option */
     if(H5P_set(new_plist, H5D_ACS_EFILE_PREFIX_NAME, &(dset->shared->extfile_prefix)) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set external file prefix")
diff --git a/src/H5Dpkg.h b/src/H5Dpkg.h
index 542abd0..45f2d3a 100644
--- a/src/H5Dpkg.h
+++ b/src/H5Dpkg.h
@@ -476,6 +476,7 @@ typedef struct H5D_shared_t {
 
     H5D_append_flush_t   append_flush;   /* Append flush property information */
     char                *extfile_prefix; /* expanded external file prefix */
+    char                *vds_prefix;     /* expanded vds prefix */
 } H5D_shared_t;
 
 struct H5D_t {
@@ -598,7 +599,7 @@ H5_DLL herr_t H5D_set_io_info_dxpls(H5D_io_info_t *io_info, hid_t dxpl_id);
 H5_DLL herr_t H5D__format_convert(H5D_t *dataset, hid_t dxpl_id);
 
 /* Internal I/O routines */
-H5_DLL herr_t H5D__pre_write(H5D_t *dset, hbool_t direct_write, hid_t mem_type_id, 
+H5_DLL herr_t H5D__pre_write(H5D_t *dset, hbool_t direct_write, hid_t mem_type_id,
     const H5S_t *mem_space, const H5S_t *file_space, hid_t dxpl_id, const void *buf);
 H5_DLL herr_t H5D__read(H5D_t *dataset, hid_t mem_type_id,
     const H5S_t *mem_space, const H5S_t *file_space, hid_t dset_xfer_plist,
diff --git a/src/H5Dprivate.h b/src/H5Dprivate.h
index fb994d8..ed13467 100644
--- a/src/H5Dprivate.h
+++ b/src/H5Dprivate.h
@@ -47,12 +47,13 @@
 #define H5D_CRT_EXT_FILE_LIST_NAME "efl"                 /* External file list */
 
 /* ========  Dataset access property names ======== */
-#define H5D_ACS_DATA_CACHE_NUM_SLOTS_NAME   "rdcc_nslots"   /* Size of raw data chunk cache(slots) */
-#define H5D_ACS_DATA_CACHE_BYTE_SIZE_NAME   "rdcc_nbytes"   /* Size of raw data chunk cache(bytes) */
-#define H5D_ACS_PREEMPT_READ_CHUNKS_NAME    "rdcc_w0"       /* Preemption read chunks first */
-#define H5D_ACS_VDS_VIEW_NAME               "vds_view"      /* VDS view option */
+#define H5D_ACS_DATA_CACHE_NUM_SLOTS_NAME   "rdcc_nslots"    /* Size of raw data chunk cache(slots) */
+#define H5D_ACS_DATA_CACHE_BYTE_SIZE_NAME   "rdcc_nbytes"    /* Size of raw data chunk cache(bytes) */
+#define H5D_ACS_PREEMPT_READ_CHUNKS_NAME    "rdcc_w0"        /* Preemption read chunks first */
+#define H5D_ACS_VDS_VIEW_NAME               "vds_view"       /* VDS view option */
 #define H5D_ACS_VDS_PRINTF_GAP_NAME         "vds_printf_gap" /* VDS printf gap size */
-#define H5D_ACS_APPEND_FLUSH_NAME    "append_flush"         /* Append flush actions */
+#define H5D_ACS_VDS_PREFIX_NAME             "vds_prefix"     /* VDS file prefix */
+#define H5D_ACS_APPEND_FLUSH_NAME           "append_flush"   /* Append flush actions */
 #define H5D_ACS_EFILE_PREFIX_NAME           "external file prefix" /* External file prefix */
 
 /* ======== Data transfer properties ======== */
diff --git a/src/H5Dvirtual.c b/src/H5Dvirtual.c
index 3be2353..e0a4a83 100644
--- a/src/H5Dvirtual.c
+++ b/src/H5Dvirtual.c
@@ -731,6 +731,38 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5D__virtual_delete */
 
+
+/*--------------------------------------------------------------------------
+ * Function: H5D__virtual_build_name
+ *
+ * Purpose:  Prepend PREFIX to FILE_NAME and store in FULL_NAME
+ *
+ * Return:   Non-negative on success/Negative on failure
+ *--------------------------------------------------------------------------*/
+static herr_t
+H5D__virtual_build_name(char *prefix, char *file_name, char **full_name/*out*/)
+{
+    size_t      prefix_len;             /* length of prefix */
+    size_t      fname_len;              /* Length of external link file name */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    prefix_len = HDstrlen(prefix);
+    fname_len = HDstrlen(file_name);
+
+    /* Allocate a buffer to hold the filename + prefix + possibly the delimiter + terminating null byte */
+    if(NULL == (*full_name = (char *)H5MM_malloc(prefix_len + fname_len + 2)))
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "unable to allocate filename buffer")
+
+    /* Compose the full file name */
+    HDsnprintf(*full_name, (prefix_len + fname_len + 2), "%s%s%s", prefix,
+        (H5_CHECK_DELIMITER(prefix[prefix_len - 1]) ? "" : H5_DIR_SEPS), file_name);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5D__virtual_build_name() */
+
 
 /*-------------------------------------------------------------------------
  * Function:    H5D__virtual_open_source_dset
@@ -750,9 +782,11 @@ H5D__virtual_open_source_dset(const H5D_t *vdset,
     H5O_storage_virtual_srcdset_t *source_dset, hid_t dxpl_id)
 {
     H5F_t       *src_file = NULL;       /* Source file */
+    char        *vds_prefix = NULL;     /* Source file vds_prefix */
     hbool_t     src_file_open = FALSE;  /* Whether we have opened and need to close src_file */
     H5G_loc_t   src_root_loc;           /* Object location of source file root group */
     herr_t      ret_value = SUCCEED;    /* Return value */
+    char        *full_name = NULL;      /* File name with prefix */
 
     FUNC_ENTER_STATIC
 
@@ -762,14 +796,27 @@ H5D__virtual_open_source_dset(const H5D_t *vdset,
     HDassert(!source_dset->dset);
     HDassert(source_dset->file_name);
     HDassert(source_dset->dset_name);
+    vds_prefix = vdset->shared->vds_prefix;
 
     /* Check if we need to open the source file */
     if(HDstrcmp(source_dset->file_name, ".")) {
-        /* Open the source file */
-        if(NULL == (src_file = H5F_open(source_dset->file_name, H5F_INTENT(vdset->oloc.file) & (H5F_ACC_RDWR | H5F_ACC_SWMR_WRITE | H5F_ACC_SWMR_READ), H5P_FILE_CREATE_DEFAULT, vdset->shared->layout.storage.u.virt.source_fapl, dxpl_id)))
-            H5E_clear_stack(NULL); /* Quick hack until proper support for H5Fopen with missing file is implemented */
-        else
-            src_file_open = TRUE;
+        if(vds_prefix && HDstrlen(vds_prefix) > 0) {
+            if(H5D__virtual_build_name(vds_prefix, source_dset->file_name, &full_name/*out*/) < 0)
+                HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "can't prepend prefix to filename")
+            /* Open the source file */
+            if(NULL == (src_file = H5F_open(full_name, H5F_INTENT(vdset->oloc.file) & (H5F_ACC_RDWR | H5F_ACC_SWMR_WRITE | H5F_ACC_SWMR_READ), H5P_FILE_CREATE_DEFAULT, vdset->shared->layout.storage.u.virt.source_fapl, dxpl_id)))
+                H5E_clear_stack(NULL); /* Quick hack until proper support for H5Fopen with missing file is implemented */
+            else
+                src_file_open = TRUE;
+            full_name = (char *)H5MM_xfree(full_name);
+        }
+        else {
+            /* Open the source file */
+            if(NULL == (src_file = H5F_open(source_dset->file_name, H5F_INTENT(vdset->oloc.file) & (H5F_ACC_RDWR | H5F_ACC_SWMR_WRITE | H5F_ACC_SWMR_READ), H5P_FILE_CREATE_DEFAULT, vdset->shared->layout.storage.u.virt.source_fapl, dxpl_id)))
+                H5E_clear_stack(NULL); /* Quick hack until proper support for H5Fopen with missing file is implemented */
+            else
+                src_file_open = TRUE;
+        }
     } /* end if */
     else
         /* Source file is ".", use the virtual dataset's file */
@@ -1407,7 +1454,7 @@ H5D__virtual_set_extent_unlim(const H5D_t *dset, hid_t dxpl_id)
                                 HGOTO_ERROR(H5E_DATASET, H5E_CANTCLIP, FAIL, "failed to clip unlimited selection")
                         } /* end if */
 
-                        /* Update cached values unlim_extent_source and 
+                        /* Update cached values unlim_extent_source and
                          * clip_size_virtual */
                         storage->list[i].unlim_extent_source = curr_dims[storage->list[i].unlim_dim_source];
                         storage->list[i].clip_size_virtual = clip_size;
@@ -1559,7 +1606,7 @@ H5D__virtual_set_extent_unlim(const H5D_t *dset, hid_t dxpl_id)
             HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "unable to modify size of data space")
 
         /* Mark the space as dirty, for later writing to the file */
-        if(H5F_INTENT(dset->oloc.file) & H5F_ACC_RDWR) 
+        if(H5F_INTENT(dset->oloc.file) & H5F_ACC_RDWR)
             if(H5D__mark(dset, dxpl_id, H5D_MARK_SPACE) < 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "unable to mark dataspace as dirty")
     } /* end if */
@@ -2246,7 +2293,7 @@ H5D__virtual_pre_io(H5D_io_info_t *io_info,
                             HGOTO_ERROR(H5E_DATASET, H5E_CLOSEERROR, FAIL, "can't close projected memory space")
                         storage->list[i].sub_dset[j].projected_mem_space = NULL;
                     } /* end if */
-                    else 
+                    else
                         *tot_nelmts += (hsize_t)select_nelmts;
                 } /* end if */
             } /* end for */
@@ -2506,7 +2553,7 @@ H5D__virtual_read(H5D_io_info_t *io_info, const H5D_type_info_t *type_info,
                             HGOTO_ERROR(H5E_DATASET, H5E_CANTCLIP, FAIL, "unable to clip fill selection")
 
             /* Write fill values to memory buffer */
-            if(H5D__fill(io_info->dset->shared->dcpl_cache.fill.buf, io_info->dset->shared->type, io_info->u.rbuf, 
+            if(H5D__fill(io_info->dset->shared->dcpl_cache.fill.buf, io_info->dset->shared->type, io_info->u.rbuf,
                          type_info->mem_type, fill_space, io_info->md_dxpl_id) < 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, FAIL, "filling buf failed")
 
diff --git a/src/H5Fprivate.h b/src/H5Fprivate.h
index 18d0460..262e63b 100644
--- a/src/H5Fprivate.h
+++ b/src/H5Fprivate.h
@@ -489,6 +489,7 @@ typedef struct H5F_t H5F_t;
 #define H5F_ACS_METADATA_READ_ATTEMPTS_NAME     "metadata_read_attempts" /* # of metadata read attempts */
 #define H5F_ACS_OBJECT_FLUSH_CB_NAME            "object_flush_cb" 	 /* Object flush callback */
 #define H5F_ACS_EFC_SIZE_NAME                   "efc_size"      /* Size of external file cache */
+#define H5F_ACS_VDS_SIZE_NAME                   "vds_size"      /* Size of vds file cache */
 #define H5F_ACS_FILE_IMAGE_INFO_NAME            "file_image_info" /* struct containing initial file image and callback info */
 #define H5F_ACS_CLEAR_STATUS_FLAGS_NAME         "clear_status_flags" /* Whether to clear superblock status_flags (private property only used by h5clear) */
 #define H5F_ACS_USE_MDC_LOGGING_NAME            "use_mdc_logging" /* Whether to use metadata cache logging */
diff --git a/src/H5Pdapl.c b/src/H5Pdapl.c
index 494de3e..da06297 100644
--- a/src/H5Pdapl.c
+++ b/src/H5Pdapl.c
@@ -71,6 +71,17 @@
 #define H5D_ACS_VDS_PRINTF_GAP_DEF              (hsize_t)0
 #define H5D_ACS_VDS_PRINTF_GAP_ENC              H5P__encode_hsize_t
 #define H5D_ACS_VDS_PRINTF_GAP_DEC              H5P__decode_hsize_t
+/* Definitions for VDS file prefix */
+#define H5D_ACS_VDS_PREFIX_SIZE                 sizeof(char *)
+#define H5D_ACS_VDS_PREFIX_DEF                  NULL /*default is no prefix */
+#define H5D_ACS_VDS_PREFIX_SET                  H5P__dapl_vds_file_pref_set
+#define H5D_ACS_VDS_PREFIX_GET                  H5P__dapl_vds_file_pref_get
+#define H5D_ACS_VDS_PREFIX_ENC                  H5P__dapl_vds_file_pref_enc
+#define H5D_ACS_VDS_PREFIX_DEC                  H5P__dapl_vds_file_pref_dec
+#define H5D_ACS_VDS_PREFIX_DEL                  H5P__dapl_vds_file_pref_del
+#define H5D_ACS_VDS_PREFIX_COPY                 H5P__dapl_vds_file_pref_copy
+#define H5D_ACS_VDS_PREFIX_CMP                  H5P__dapl_vds_file_pref_cmp
+#define H5D_ACS_VDS_PREFIX_CLOSE                H5P__dapl_vds_file_pref_close
 /* Definition for append flush */
 #define H5D_ACS_APPEND_FLUSH_SIZE               sizeof(H5D_append_flush_t)
 #define H5D_ACS_APPEND_FLUSH_DEF                {0,{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},NULL,NULL}
@@ -112,6 +123,14 @@ static herr_t H5P__decode_chunk_cache_nbytes(const void **_pp, void *_value);
 /* Property list callbacks */
 static herr_t H5P__dacc_vds_view_enc(const void *value, void **pp, size_t *size);
 static herr_t H5P__dacc_vds_view_dec(const void **pp, void *value);
+static herr_t H5P__dapl_vds_file_pref_set(hid_t prop_id, const char* name, size_t size, void* value);
+static herr_t H5P__dapl_vds_file_pref_get(hid_t prop_id, const char* name, size_t size, void* value);
+static herr_t H5P__dapl_vds_file_pref_enc(const void *value, void **_pp, size_t *size);
+static herr_t H5P__dapl_vds_file_pref_dec(const void **_pp, void *value);
+static herr_t H5P__dapl_vds_file_pref_del(hid_t prop_id, const char* name, size_t size, void* value);
+static herr_t H5P__dapl_vds_file_pref_copy(const char* name, size_t size, void* value);
+static int H5P__dapl_vds_file_pref_cmp(const void *value1, const void *value2, size_t size);
+static herr_t H5P__dapl_vds_file_pref_close(const char* name, size_t size, void* value);
 
 /* Property list callbacks */
 static herr_t H5P__dapl_efile_pref_set(hid_t prop_id, const char* name, size_t size, void* value);
@@ -160,6 +179,7 @@ const H5P_libclass_t H5P_CLS_DACC[1] = {{
 /* Property value defaults */
 static const H5D_append_flush_t H5D_def_append_flush_g = H5D_ACS_APPEND_FLUSH_DEF;   /* Default setting for append flush */
 static const char *H5D_def_efile_prefix_g = H5D_ACS_EFILE_PREFIX_DEF;                /* Default external file prefix string */
+static const char *H5D_def_vds_prefix_g = H5D_ACS_VDS_PREFIX_DEF;                    /* Default vds prefix string */
 
 
 /*-------------------------------------------------------------------------
@@ -210,6 +230,12 @@ H5P__dacc_reg_prop(H5P_genclass_t *pclass)
             NULL, NULL, NULL, NULL) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
 
+    /* Register property for vds prefix */
+    if(H5P_register_real(pclass, H5D_ACS_VDS_PREFIX_NAME, H5D_ACS_VDS_PREFIX_SIZE, &H5D_def_vds_prefix_g,
+            NULL, H5D_ACS_VDS_PREFIX_SET, H5D_ACS_VDS_PREFIX_GET, H5D_ACS_VDS_PREFIX_ENC, H5D_ACS_VDS_PREFIX_DEC,
+            H5D_ACS_VDS_PREFIX_DEL, H5D_ACS_VDS_PREFIX_COPY, H5D_ACS_VDS_PREFIX_CMP, H5D_ACS_VDS_PREFIX_CLOSE) < 0)
+         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
     /* Register info for append flush */
     /* (Note: this property should not have an encode/decode callback -QAK) */
     if(H5P_register_real(pclass, H5D_ACS_APPEND_FLUSH_NAME, H5D_ACS_APPEND_FLUSH_SIZE, &H5D_def_append_flush_g,
@@ -226,6 +252,254 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5P__dacc_reg_prop() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_set
+ *
+ * Purpose:     Copies a vds file prefix property when it's set
+ *              for a property list
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_set(hid_t H5_ATTR_UNUSED prop_id, const char H5_ATTR_UNUSED *name,
+    size_t H5_ATTR_UNUSED size, void *value)
+{
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Sanity check */
+    HDassert(value);
+
+    /* Copy the prefix */
+    *(char **)value = H5MM_xstrdup(*(const char **)value);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__dapl_vds_file_pref_set() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_get
+ *
+ * Purpose:     Copies a vds file prefix property when it's retrieved
+ *              from a property list
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_get(hid_t H5_ATTR_UNUSED prop_id, const char H5_ATTR_UNUSED *name,
+    size_t H5_ATTR_UNUSED size, void *value)
+{
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Sanity check */
+    HDassert(value);
+
+    /* Copy the prefix */
+    *(char **)value = H5MM_xstrdup(*(const char **)value);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__dapl_vds_file_pref_get() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_enc
+ *
+ * Purpose:     Callback routine which is called whenever the vds file flags
+ *              property in the dataset access property list is
+ *              encoded.
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_enc(const void *value, void **_pp, size_t *size)
+{
+    const char *vds_file_pref = *(const char * const *)value;
+    uint8_t **pp = (uint8_t **)_pp;
+    size_t len = 0;
+    uint64_t enc_value;
+    unsigned enc_size;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDcompile_assert(sizeof(size_t) <= sizeof(uint64_t));
+
+    /* calculate prefix length */
+    if(NULL != vds_file_pref)
+        len = HDstrlen(vds_file_pref);
+
+    enc_value = (uint64_t)len;
+    enc_size = H5VM_limit_enc_size(enc_value);
+    HDassert(enc_size < 256);
+
+    if(NULL != *pp) {
+        /* encode the length of the prefix */
+        *(*pp)++ = (uint8_t)enc_size;
+        UINT64ENCODE_VAR(*pp, enc_value, enc_size);
+
+        /* encode the prefix */
+        if(NULL != vds_file_pref) {
+            HDmemcpy(*(char **)pp, vds_file_pref, len);
+            *pp += len;
+        } /* end if */
+    } /* end if */
+
+    *size += (1 + enc_size);
+    if(NULL != vds_file_pref)
+        *size += len;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__dapl_vds_file_pref_enc() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_dec
+ *
+ * Purpose:     Callback routine which is called whenever the vds file prefix
+ *              property in the dataset access property list is
+ *              decoded.
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_dec(const void **_pp, void *_value)
+{
+    char **vds_file_pref = (char **)_value;
+    const uint8_t **pp = (const uint8_t **)_pp;
+    size_t len;
+    uint64_t enc_value;                 /* Decoded property value */
+    unsigned enc_size;                  /* Size of encoded property */
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    HDassert(pp);
+    HDassert(*pp);
+    HDassert(vds_file_pref);
+    HDcompile_assert(sizeof(size_t) <= sizeof(uint64_t));
+
+    /* Decode the size */
+    enc_size = *(*pp)++;
+    HDassert(enc_size < 256);
+
+    /* Decode the value */
+    UINT64DECODE_VAR(*pp, enc_value, enc_size);
+    len = (size_t)enc_value;
+
+    if(0 != len) {
+        /* Make a copy of the user's prefix string */
+        if(NULL == (*vds_file_pref = (char *)H5MM_malloc(len + 1)))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_CANTINIT, FAIL, "memory allocation failed for prefix")
+        HDstrncpy(*vds_file_pref, *(const char **)pp, len);
+        (*vds_file_pref)[len] = '\0';
+
+        *pp += len;
+    } /* end if */
+    else
+        *vds_file_pref = NULL;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5P__dapl_vds_file_pref_dec() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_del
+ *
+ * Purpose:     Frees memory used to store the vds file prefix string
+ *
+ * Return:      SUCCEED (Can't fail)
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_del(hid_t H5_ATTR_UNUSED prop_id, const char H5_ATTR_UNUSED *name,
+    size_t H5_ATTR_UNUSED size, void *value)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(value);
+
+    H5MM_xfree(*(void **)value);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__dapl_vds_file_pref_del() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_copy
+ *
+ * Purpose:     Creates a copy of the vds file prefix string
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_copy(const char H5_ATTR_UNUSED *name, size_t H5_ATTR_UNUSED size, void *value)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(value);
+
+    *(char **)value = H5MM_xstrdup(*(const char **)value);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__dapl_vds_file_pref_copy() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:       H5P__dapl_vds_file_pref_cmp
+ *
+ * Purpose:        Callback routine which is called whenever the vds file prefix
+ *                 property in the dataset creation property list is
+ *                 compared.
+ *
+ * Return:         zero if VALUE1 and VALUE2 are equal, non zero otherwise.
+ *-------------------------------------------------------------------------
+ */
+static int
+H5P__dapl_vds_file_pref_cmp(const void *value1, const void *value2, size_t H5_ATTR_UNUSED size)
+{
+    const char *pref1 = *(const char * const *)value1;
+    const char *pref2 = *(const char * const *)value2;
+    int ret_value = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    if(NULL == pref1 && NULL != pref2)
+        HGOTO_DONE(1);
+    if(NULL != pref1 && NULL == pref2)
+        HGOTO_DONE(-1);
+    if(NULL != pref1 && NULL != pref2)
+        ret_value = HDstrcmp(pref1, pref2);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5P__dapl_vds_file_pref_cmp() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5P__dapl_vds_file_pref_close
+ *
+ * Purpose:     Frees memory used to store the vds file prefix string
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__dapl_vds_file_pref_close(const char H5_ATTR_UNUSED *name, size_t H5_ATTR_UNUSED size, void *value)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    HDassert(value);
+
+    H5MM_xfree(*(void **)value);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__dapl_vds_file_pref_close() */
+
 
 /*-------------------------------------------------------------------------
  * Function:    H5P__dapl_efile_pref_set
@@ -1220,3 +1494,95 @@ done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Pget_efile_prefix() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pset_virtual_prefix
+ *
+ * Purpose:     Set a prefix to be applied to the path of any vds files
+ *              traversed.
+  *
+ *              If the prefix starts with ${ORIGIN}, this will be replaced by
+ *              the absolute path of the directory of the HDF5 file containing
+ *              the dataset.
+ *
+ *              If the prefix is ".", no prefix will be applied.
+ *
+ *              This property can be overwritten by the environment variable
+ *              HDF5_VDS_PREFIX.
+ *
+ * Return:    Non-negative on success/Negative on failure
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_virtual_prefix(hid_t plist_id, const char *prefix)
+{
+    H5P_genplist_t *plist;              /* Property list pointer */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*s", plist_id, prefix);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id, H5P_DATASET_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Set prefix */
+    if(H5P_set(plist, H5D_ACS_VDS_PREFIX_NAME, &prefix) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set prefix info")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pset_virtual_prefix() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pget_virtual_prefix
+ *
+ * Purpose:    Gets the prefix to be applied to any vds file
+ *              traversals made using this property list.
+ *
+ *              If the pointer is not NULL, it points to a user-allocated
+ *              buffer.
+ *
+ * Return:    Non-negative on success/Negative on failure
+ *-------------------------------------------------------------------------
+ */
+ssize_t
+H5Pget_virtual_prefix(hid_t plist_id, char *prefix, size_t size)
+{
+    H5P_genplist_t *plist;              /* Property list pointer */
+    char           *my_prefix;          /* Library's copy of the prefix */
+    size_t          len;                /* Length of prefix string */
+    ssize_t         ret_value;          /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE3("Zs", "i*sz", plist_id, prefix, size);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id, H5P_DATASET_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Get the current prefix */
+    if(H5P_peek(plist, H5D_ACS_VDS_PREFIX_NAME, &my_prefix) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get vds file prefix")
+
+    /* Check for prefix being set */
+    if(my_prefix) {
+        /* Copy to user's buffer, if given */
+        len = HDstrlen(my_prefix);
+        if(prefix) {
+            HDstrncpy(prefix, my_prefix, MIN(len + 1, size));
+            if(len >= size)
+                prefix[size - 1] = '\0';
+        } /* end if */
+    } /* end if */
+    else
+        len = 0;
+
+    /* Set return value */
+    ret_value = (ssize_t)len;
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pget_virtual_prefix() */
+
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index 915aa38..8650a03 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -2462,6 +2462,75 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5Pset_vds_file_cache_size
+ *
+ * Purpose:     Sets the number of files opened through vds links
+ *              from the file associated with this fapl to be held open
+ *              in that file's vds file cache.  When the maximum
+ *              number of files is reached, the least recently used file
+ *              is closed (unless it is opened from somewhere else).
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_vds_file_cache_size(hid_t plist_id, unsigned vds_size)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "iIu", plist_id, vds_size);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id, H5P_FILE_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Set value */
+    if(H5P_set(plist, H5F_ACS_VDS_SIZE_NAME, &vds_size) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set elink file cache size")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pset_vds_file_cache_size() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pget_vds_file_cache_size
+ *
+ * Purpose:     Gets the number of files opened through vds links
+ *              from the file associated with this fapl to be held open
+ *              in that file's vds file cache.  When the maximum
+ *              number of files is reached, the least recently used file
+ *              is closed (unless it is opened from somewhere else).
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_vds_file_cache_size(hid_t plist_id, unsigned *vds_size)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*Iu", plist_id, vds_size);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id, H5P_FILE_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Get value */
+    if(vds_size)
+        if(H5P_get(plist, H5F_ACS_VDS_SIZE_NAME, vds_size) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get elink file cache size")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pget_vds_file_cache_size() */
+
+
+/*-------------------------------------------------------------------------
  * Function: H5Pset_file_image
  *
  * Purpose:     Sets the initial file image. Some file drivers can initialize 
diff --git a/src/H5Ppublic.h b/src/H5Ppublic.h
index 493a322..38be320 100644
--- a/src/H5Ppublic.h
+++ b/src/H5Ppublic.h
@@ -343,6 +343,8 @@ H5_DLL herr_t H5Pget_libver_bounds(hid_t plist_id, H5F_libver_t *low,
     H5F_libver_t *high);
 H5_DLL herr_t H5Pset_elink_file_cache_size(hid_t plist_id, unsigned efc_size);
 H5_DLL herr_t H5Pget_elink_file_cache_size(hid_t plist_id, unsigned *efc_size);
+H5_DLL herr_t H5Pset_vds_file_cache_size(hid_t plist_id, unsigned vds_size);
+H5_DLL herr_t H5Pget_vds_file_cache_size(hid_t plist_id, unsigned *vds_size);
 H5_DLL herr_t H5Pset_file_image(hid_t fapl_id, void *buf_ptr, size_t buf_len);
 H5_DLL herr_t H5Pget_file_image(hid_t fapl_id, void **buf_ptr_ptr, size_t *buf_len_ptr);
 H5_DLL herr_t H5Pset_file_image_callbacks(hid_t fapl_id,
@@ -420,6 +422,8 @@ H5_DLL herr_t H5Pset_virtual_view(hid_t plist_id, H5D_vds_view_t view);
 H5_DLL herr_t H5Pget_virtual_view(hid_t plist_id, H5D_vds_view_t *view);
 H5_DLL herr_t H5Pset_virtual_printf_gap(hid_t plist_id, hsize_t gap_size);
 H5_DLL herr_t H5Pget_virtual_printf_gap(hid_t plist_id, hsize_t *gap_size);
+H5_DLL herr_t H5Pset_virtual_prefix(hid_t dapl_id, const char* prefix);
+H5_DLL ssize_t H5Pget_virtual_prefix(hid_t dapl_id, char* prefix /*out*/, size_t size);
 H5_DLL herr_t H5Pset_append_flush(hid_t plist_id, unsigned ndims,
     const hsize_t boundary[], H5D_append_cb_t func, void *udata);
 H5_DLL herr_t H5Pget_append_flush(hid_t plist_id, unsigned dims,
diff --git a/test/vds.c b/test/vds.c
index c9b7a1b..3485023 100644
--- a/test/vds.c
+++ b/test/vds.c
@@ -36,6 +36,12 @@ const char *FILENAME[] = {
     "vds_src_1",
     "vds%%_src",
     "vds_dapl",
+    "vds_virt_2",
+    "vds_virt_3",
+    "vds_src_2",
+    "vds_src_3",
+    "vds%%_src2",
+    "vds_dapl2",
     NULL
 };
 
@@ -49,6 +55,8 @@ const char *FILENAME[] = {
 
 #define FILENAME_BUF_SIZE       1024
 
+#define TMPDIR          "tmp/"
+
 
 /*-------------------------------------------------------------------------
  * Function:    vds_select_equal
@@ -1140,6 +1148,271 @@ error:
      return 1;
 } /* end test_api() */
 
+/*-------------------------------------------------------------------------
+ * Function:    vds_link_prefix
+ *
+ * Purpose:     Set up vds link prefix via H5Pset_virtual_prefix() to be "tmp"
+ *        Should be able to access the target source files in tmp directory via the prefix set
+ *        by H5Pset_virtual_prefix()
+ *
+ * Return:      Success:        0
+ *              Failure:        -1
+ *-------------------------------------------------------------------------
+ */
+static int
+test_vds_prefix(unsigned config, hid_t fapl)
+{
+    char        srcfilename[FILENAME_BUF_SIZE];
+    char        srcfilename_map[FILENAME_BUF_SIZE];
+    char        vfilename[FILENAME_BUF_SIZE];
+    char        vfilename2[FILENAME_BUF_SIZE];
+    char        srcfilenamepct[FILENAME_BUF_SIZE];
+    char        srcfilenamepct_map[FILENAME_BUF_SIZE];
+    const char *srcfilenamepct_map_orig = "vds%%%%_src";
+    hid_t       srcfile[4] = {-1, -1, -1, -1}; /* Files with source dsets */
+    hid_t       vfile = -1;     /* File with virtual dset */
+    hid_t       vfile2 = -1;    /* File with copied virtual dset */
+    hid_t       dcpl = -1;      /* Dataset creation property list */
+    hid_t       dapl = -1;      /* Dataset access property list */
+    hid_t       srcspace[4] = {-1, -1, -1, -1}; /* Source dataspaces */
+    hid_t       vspace[4] = {-1, -1, -1, -1}; /* Virtual dset dataspaces */
+    hid_t       memspace = -1;  /* Memory dataspace */
+    hid_t       srcdset[4] = {-1, -1, -1, -1}; /* Source datsets */
+    hid_t       vdset = -1;     /* Virtual dataset */
+    hsize_t     dims[4] = {10, 26, 0, 0}; /* Data space current size */
+    hsize_t     start[4];       /* Hyperslab start */
+    hsize_t     stride[4];      /* Hyperslab stride */
+    hsize_t     count[4];       /* Hyperslab count */
+    hsize_t     block[4];       /* Hyperslab block */
+    hssize_t    offset[2] = {0, 0}; /* Selection offset */
+    int         buf[10][26];    /* Write and expected read buffer */
+    int         rbuf[10][26];   /* Read buffer */
+    int         rbuf99[9][9];   /* 9x9 Read buffer */
+    int         evbuf[10][26];  /* Expected VDS "buffer" */
+    int         erbuf[10][26];  /* Expected read buffer */
+    int         fill = -1;      /* Fill value */
+    herr_t      ret;            /* Generic return value */
+    int         i, j;
+    char        buffer[1024];   /* buffer to read vds_prefix       */
+
+    TESTING("basic virtual dataset I/O via H5Pset_vds_prefix()")
+
+    h5_fixname(FILENAME[0], fapl, vfilename, sizeof vfilename);
+    h5_fixname(FILENAME[7], fapl, vfilename2, sizeof vfilename2);
+    h5_fixname(FILENAME[8], fapl, srcfilename, sizeof srcfilename);
+    h5_fixname_printf(FILENAME[8], fapl, srcfilename_map, sizeof srcfilename_map);
+    h5_fixname(FILENAME[10], fapl, srcfilenamepct, sizeof srcfilenamepct);
+    h5_fixname_printf(srcfilenamepct_map_orig, fapl, srcfilenamepct_map, sizeof srcfilenamepct_map);
+
+    /* create tmp directory and get current working directory path */
+    if (HDmkdir(TMPDIR, (mode_t)0755) < 0 && errno != EEXIST)
+        TEST_ERROR
+
+    /* Create DCPL */
+    if((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
+        TEST_ERROR
+
+    /* Set fill value */
+    if(H5Pset_fill_value(dcpl, H5T_NATIVE_INT, &fill) < 0)
+        TEST_ERROR
+
+    /* Initialize VDS prefix items */
+    if((dapl = H5Pcreate(H5P_DATASET_ACCESS)) < 0)
+        TEST_ERROR
+
+    if(H5Pset_virtual_prefix(dapl, TMPDIR) < 0)
+        TEST_ERROR
+    if(H5Pget_virtual_prefix(dapl, buffer, sizeof(buffer)) < 0)
+        TEST_ERROR
+
+    if(HDstrcmp(buffer, TMPDIR) != 0)
+        FAIL_PUTS_ERROR("vds prefix not set correctly");
+
+    /*
+     * Test 1: All - all selection
+     */
+    /* Create source dataspace */
+    if((srcspace[0] = H5Screate_simple(2, dims, NULL)) < 0)
+        TEST_ERROR
+
+    /* Create virtual dataspace */
+    if((vspace[0] = H5Screate_simple(2, dims, NULL)) < 0)
+        TEST_ERROR
+
+    /* Select all (should not be necessary, but just to be sure) */
+    if(H5Sselect_all(srcspace[0]) < 0)
+        TEST_ERROR
+    if(H5Sselect_all(vspace[0]) < 0)
+        TEST_ERROR
+
+    /* Add virtual layout mapping */
+    if(H5Pset_virtual(dcpl, vspace[0], config & TEST_IO_DIFFERENT_FILE ? srcfilename_map : ".", "src_dset", srcspace[0]) < 0)
+        TEST_ERROR
+
+    /* Create virtual file */
+    if((vfile = H5Fcreate(vfilename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl)) < 0)
+        TEST_ERROR
+
+    /* Create source file if requested */
+    if(config & TEST_IO_DIFFERENT_FILE) {
+        HDgetcwd(buffer, 1024);
+        HDchdir(TMPDIR);
+        if((srcfile[0] = H5Fcreate(srcfilename, H5F_ACC_TRUNC, H5P_DEFAULT, fapl)) < 0)
+            TEST_ERROR
+        HDchdir(buffer);
+    } /* end if */
+    else {
+        srcfile[0] = vfile;
+        if(H5Iinc_ref(srcfile[0]) < 0)
+            TEST_ERROR
+    } /* end if */
+
+    /* Create source dataset */
+    if((srcdset[0] = H5Dcreate2(srcfile[0], "src_dset", H5T_NATIVE_INT, srcspace[0], H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        TEST_ERROR
+
+    /* Create virtual dataset */
+    if((vdset = H5Dcreate2(vfile, "v_dset", H5T_NATIVE_INT, vspace[0], H5P_DEFAULT, dcpl, dapl)) < 0)
+        TEST_ERROR
+
+    /* Populate write buffer */
+    for(i = 0; i < (int)(sizeof(buf) / sizeof(buf[0])); i++)
+        for(j = 0; j < (int)(sizeof(buf[0]) / sizeof(buf[0][0])); j++)
+            buf[i][j] = (i * (int)(sizeof(buf[0]) / sizeof(buf[0][0]))) + j;
+
+    /* Write data directly to source dataset */
+    if(H5Dwrite(srcdset[0], H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf[0]) < 0)
+        TEST_ERROR
+
+    /* Close srcdset and srcfile if config option specified */
+    if(config & TEST_IO_CLOSE_SRC) {
+        if(H5Dclose(srcdset[0]) < 0)
+            TEST_ERROR
+        srcdset[0] = -1;
+
+        if(config & TEST_IO_DIFFERENT_FILE) {
+            if(H5Fclose(srcfile[0]) < 0)
+                TEST_ERROR
+            srcfile[0] = -1;
+        } /* end if */
+    } /* end if */
+
+    /* Reopen virtual dataset and file if config option specified */
+    if(config & TEST_IO_REOPEN_VIRT) {
+        if(H5Dclose(vdset) < 0)
+            TEST_ERROR
+        vdset = -1;
+        if(H5Fclose(vfile) < 0)
+            TEST_ERROR
+        vfile = -1;
+        if((vfile = H5Fopen(vfilename, H5F_ACC_RDWR, fapl)) < 0)
+            TEST_ERROR
+        if((vdset = H5Dopen2(vfile, "v_dset", dapl)) < 0)
+            TEST_ERROR
+    } /* end if */
+
+    /* Read data through virtual dataset */
+    HDmemset(rbuf[0], 0, sizeof(rbuf));
+    if(H5Dread(vdset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, rbuf[0]) < 0)
+        TEST_ERROR
+
+    /* Verify read data */
+    for(i = 0; i < (int)(sizeof(buf) / sizeof(buf[0])); i++) {
+        for(j = 0; j < (int)(sizeof(buf[0]) / sizeof(buf[0][0])); j++)
+            if(rbuf[i][j] != buf[i][j]) {
+                TEST_ERROR
+            }
+    }
+
+    /* Adjust write buffer */
+    for(i = 0; i < (int)(sizeof(buf) / sizeof(buf[0])); i++)
+        for(j = 0; j < (int)(sizeof(buf[0]) / sizeof(buf[0][0])); j++)
+            buf[i][j] += (int)(sizeof(buf) / sizeof(buf[0][0]));
+
+    /* Write data through virtual dataset */
+    if(H5Dwrite(vdset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf[0]) < 0)
+        TEST_ERROR
+
+    /* Reopen srcdset and srcfile if config option specified */
+    if(config & TEST_IO_CLOSE_SRC) {
+        if(config & TEST_IO_DIFFERENT_FILE) {
+            HDgetcwd(buffer, 1024);
+            HDchdir(TMPDIR);
+            if((srcfile[0] = H5Fopen(srcfilename, H5F_ACC_RDONLY, fapl)) < 0)
+                TEST_ERROR
+            HDchdir(buffer);
+        }
+        if((srcdset[0] = H5Dopen2(srcfile[0], "src_dset", H5P_DEFAULT)) < 0)
+            TEST_ERROR
+    } /* end if */
+
+    /* Read data directly from source dataset */
+    HDmemset(rbuf[0], 0, sizeof(rbuf));
+    if(H5Dread(srcdset[0], H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, rbuf[0]) < 0)
+        TEST_ERROR
+
+    /* Verify read data */
+    for(i = 0; i < (int)(sizeof(buf) / sizeof(buf[0])); i++)
+        for(j = 0; j < (int)(sizeof(buf[0]) / sizeof(buf[0][0])); j++)
+            if(rbuf[i][j] != buf[i][j])
+                TEST_ERROR
+
+    /* Close */
+    if(H5Dclose(srcdset[0]) < 0)
+        TEST_ERROR
+    srcdset[0] = -1;
+    if(H5Dclose(vdset) < 0)
+        TEST_ERROR
+    vdset = -1;
+    if(H5Fclose(srcfile[0]) < 0)
+        TEST_ERROR
+    srcfile[0] = -1;
+    if(H5Fclose(vfile) < 0)
+        TEST_ERROR
+    vfile = -1;
+    if(H5Sclose(srcspace[0]) < 0)
+        TEST_ERROR
+    srcspace[0] = -1;
+    if(H5Sclose(vspace[0]) < 0)
+        TEST_ERROR
+    vspace[0] = -1;
+
+    PASSED();
+    return 0;
+
+ error:
+    H5E_BEGIN_TRY {
+        for(i = 0; i < (int)(sizeof(srcdset) / sizeof(srcdset[0])); i++) {
+            if(srcdset[i] >= 0)
+                (void)H5Dclose(srcdset[i]);
+        } /* end for */
+        if(vdset >= 0)
+            (void)H5Dclose(vdset);
+        for(i = 0; i < (int)(sizeof(srcfile) / sizeof(srcfile[0])); i++) {
+            if(srcfile[i] >= 0)
+                (void)H5Fclose(srcfile[i]);
+        } /* end for */
+        if(vfile >= 0)
+            (void)H5Fclose(vfile);
+        if(vfile2 >= 0)
+            (void)H5Fclose(vfile2);
+        for(i = 0; i < (int)(sizeof(srcspace) / sizeof(srcspace[0])); i++) {
+            if(srcspace[i] >= 0)
+                (void)H5Sclose(srcspace[i]);
+        } /* end for */
+        for(i = 0; i < (int)(sizeof(vspace) / sizeof(vspace[0])); i++) {
+            if(vspace[i] >= 0)
+                (void)H5Sclose(vspace[i]);
+        } /* end for */
+        if(memspace >= 0)
+            (void)H5Sclose(memspace);
+        if(dcpl >= 0)
+            (void)H5Pclose(dcpl);
+    } H5E_END_TRY;
+
+    return 1;
+} /* end vds_link_prefix() */
+
 
 /*-------------------------------------------------------------------------
  * Function:    test_basic_io
@@ -11299,6 +11572,7 @@ main(void)
     for(bit_config = 0; bit_config < TEST_IO_NTESTS; bit_config++) {
         printf("Config: %s%s%s\n", bit_config & TEST_IO_CLOSE_SRC ? "closed source dataset, " : "", bit_config & TEST_IO_DIFFERENT_FILE ? "different source file" : "same source file", bit_config & TEST_IO_REOPEN_VIRT ? ", reopen virtual file" : "");
         nerrors += test_basic_io(bit_config, fapl);
+        nerrors += test_vds_prefix(bit_config, fapl);
         nerrors += test_unlim(bit_config, fapl);
         nerrors += test_printf(bit_config, fapl);
         nerrors += test_all(bit_config, fapl);