Refactor and standardize named datatype VOL callbacks.

5 files changed, 359 insertions, 176 deletions

diff --git a/src/H5T.c b/src/H5T.c
index 08f689c..a6c3847 100644
--- a/src/H5T.c
+++ b/src/H5T.c
@@ -1612,20 +1612,19 @@ H5T__close_cb(H5T_t *dt)
      * close it through the VOL plugin.
      */
     if(NULL != dt->vol_obj) {
-
         /* Close the plugin-managed datatype data */
-        if(H5VL_datatype_close(dt->vol_obj->data, dt->vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to close datatype");
+        if(H5VL_datatype_close(dt->vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to close datatype")
 
         /* Free the VOL object */
         if(H5VL_free_object(dt->vol_obj) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTDEC, FAIL, "unable to free VOL object");
+            HGOTO_ERROR(H5E_ATTR, H5E_CANTDEC, FAIL, "unable to free VOL object")
         dt->vol_obj = NULL;
-    }
+    } /* end if */
 
     /* Close the datatype */
     if(H5T_close(dt) < 0)
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to close datatype");
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to close datatype")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -1745,7 +1744,7 @@ H5Tcopy(hid_t type_id)
 
     /* Copy datatype */
     if(NULL == (new_dt = H5T_copy(dt, H5T_COPY_TRANSIENT)))
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, H5I_INVALID_HID, "unable to copy");
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, H5I_INVALID_HID, "unable to copy")
 
     /* Atomize result */
     if((ret_value = H5I_register(H5I_DATATYPE, new_dt, TRUE)) < 0)
@@ -2264,30 +2263,30 @@ done:
  *            the return value is an integer type.
  *
  * Return:    Success:    Data type for base data type.
- *
  *            Failure:        NULL
  *
  * Programmer:    Raymond Lu
- *              October 9, 2002
+ *                October 9, 2002
+ *
  *-------------------------------------------------------------------------
  */
 H5T_t *
 H5T_get_super(const H5T_t *dt)
 {
-    H5T_t    *ret_value=NULL;
+    H5T_t *ret_value = NULL;
 
     FUNC_ENTER_NOAPI(NULL)
 
     HDassert(dt);
 
-    if (!dt->shared->parent)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL, "not a derived data type");
-    if (NULL==(ret_value=H5T_copy(dt->shared->parent, H5T_COPY_ALL)))
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to copy parent data type");
+    if(!dt->shared->parent)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, NULL, "not a derived data type")
+    if(NULL == (ret_value = H5T_copy(dt->shared->parent, H5T_COPY_ALL)))
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to copy parent data type")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-}
+} /* end H5T_get_super() */
 
 
 /*-------------------------------------------------------------------------
@@ -3108,7 +3107,7 @@ H5T__create(H5T_class_t type, size_t size)
 
                 /* Copy the default string datatype */
                 if(NULL == (dt = H5T_copy(origin_dt, H5T_COPY_TRANSIENT)))
-                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to copy");
+                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to copy")
 
                 /* Modify the datatype */
                 if(H5T__set_size(dt, size) < 0)
@@ -3230,9 +3229,9 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
 
     /* Allocate space */
     if(NULL == (new_dt = H5FL_MALLOC(H5T_t)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
     if(NULL == (new_dt->shared = H5FL_MALLOC(H5T_shared_t)))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
     /* Copy shared information (entry information is copied last) */
     *(new_dt->shared) = *(old_dt->shared);
@@ -3273,7 +3272,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
 
                     /* Open named datatype again */
                     if(H5O_open(&old_dt->oloc) < 0)
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, NULL, "unable to reopen named data type");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, NULL, "unable to reopen named data type")
 
                     /* Insert opened named datatype into opened object list for the file */
                     if(H5FO_insert(old_dt->sh_loc.file, old_dt->sh_loc.u.loc.oh_addr, new_dt->shared, FALSE)<0)
@@ -3337,7 +3336,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
                         new_dt->shared->u.compnd.memb =
                                 (H5T_cmemb_t *)H5MM_malloc(new_dt->shared->u.compnd.nalloc * sizeof(H5T_cmemb_t));
                         if (NULL == new_dt->shared->u.compnd.memb)
-                            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
+                            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
                         HDmemcpy(new_dt->shared->u.compnd.memb, old_dt->shared->u.compnd.memb,
                                 new_dt->shared->u.compnd.nmembs * sizeof(H5T_cmemb_t));
@@ -3355,7 +3354,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
 
                         /* Range check against compound member's offset */
                         if ((accum_change < 0) && ((ssize_t) new_dt->shared->u.compnd.memb[i].offset < accum_change))
-                            HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, NULL, "invalid field size in datatype");
+                            HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, NULL, "invalid field size in datatype")
 
                         /* Apply the accumulated size change to the offset of the field */
                         new_dt->shared->u.compnd.memb[i].offset += (size_t) accum_change;
@@ -3370,7 +3369,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
 
                             /* check if we couldn't find a match */
                             if(old_match < 0)
-                                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "fields in datatype corrupted");
+                                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "fields in datatype corrupted")
                         } /* end if */
                         else
                             old_match = (int) i;
@@ -3386,7 +3385,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
 
                     /* Range check against datatype size */
                     if ((accum_change < 0) && ((ssize_t) new_dt->shared->size < accum_change))
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, NULL, "invalid field size in datatype");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, NULL, "invalid field size in datatype")
 
                     /* Apply the accumulated size change to the size of the compound struct */
                     new_dt->shared->size += (size_t) accum_change;
@@ -3404,7 +3403,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
                 new_dt->shared->u.enumer.value =
                         (uint8_t *)H5MM_malloc(new_dt->shared->u.enumer.nalloc * new_dt->shared->size);
                 if(NULL == new_dt->shared->u.enumer.value)
-                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
+                    HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
                 HDmemcpy(new_dt->shared->u.enumer.value, old_dt->shared->u.enumer.value,
                         new_dt->shared->u.enumer.nmembs * new_dt->shared->size);
                 for(i = 0; i < new_dt->shared->u.enumer.nmembs; i++) {
@@ -3418,7 +3417,7 @@ H5T_copy(H5T_t *old_dt, H5T_copy_t method)
                 if(method == H5T_COPY_TRANSIENT || method == H5T_COPY_REOPEN) {
                     /* H5T_copy converts any type into a memory type */
                     if(H5T_set_loc(new_dt, NULL, H5T_LOC_MEMORY) < 0)
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "invalid datatype location");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "invalid datatype location")
                 } /* end if */
                 break;
 
@@ -3694,7 +3693,7 @@ H5T_close_real(H5T_t *dt)
     /* Clean up resources, depending on shared state */
     if(dt->shared->state != H5T_STATE_OPEN) {
         if(H5T__free(dt) < 0)
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTFREE, FAIL, "unable to free datatype");
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTFREE, FAIL, "unable to free datatype")
 
         dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
     } /* end if */
@@ -3788,7 +3787,7 @@ H5T_close(H5T_t *dt)
 
     /* Clean up resources */
     if(H5T_close_real(dt) < 0)
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTRELEASE, FAIL, "unable to free datatype");
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTRELEASE, FAIL, "unable to free datatype")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -3837,7 +3836,7 @@ H5T__set_size(H5T_t *dt, size_t size)
 
     if(dt->shared->parent) {
         if(H5T__set_size(dt->shared->parent, size) < 0)
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to set size for parent data type");
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to set size for parent data type")
 
         /* Adjust size of datatype appropriately */
         if(dt->shared->type==H5T_ARRAY)
@@ -3879,7 +3878,7 @@ H5T__set_size(H5T_t *dt, size_t size)
                     size_t      max_size;
 
                     if((num_membs = H5T_get_nmembers(dt)) < 0)
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to get number of members");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to get number of members")
 
                     if(num_membs) {
                         for(i = 0; i < (unsigned)num_membs; i++) {
@@ -3893,7 +3892,7 @@ H5T__set_size(H5T_t *dt, size_t size)
                         max_size = H5T__get_member_size(dt, max_index);
 
                         if(size < (max_offset + max_size))
-                            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "size shrinking will cut off last member ");
+                            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "size shrinking will cut off last member ")
                     } /* end if */
 
                     /* Compound must not have been packed previously */
@@ -3913,7 +3912,7 @@ H5T__set_size(H5T_t *dt, size_t size)
 
                     /* Get a copy of unsigned char type as the base/parent type */
                     if(NULL == (base = (H5T_t *)H5I_object(H5T_NATIVE_UCHAR)))
-                        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid base datatype");
+                        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid base datatype")
                     dt->shared->parent=H5T_copy(base,H5T_COPY_ALL);
 
                     /* change this datatype into a VL string */
@@ -3939,7 +3938,7 @@ H5T__set_size(H5T_t *dt, size_t size)
 
                     /* Set up VL information */
                     if (H5T_set_loc(dt, NULL, H5T_LOC_MEMORY)<0)
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "invalid datatype location");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "invalid datatype location")
                 } /* end if */
                 else {
                     prec = 8 * size;
@@ -3955,7 +3954,7 @@ H5T__set_size(H5T_t *dt, size_t size)
                 if(dt->shared->u.atomic.u.f.sign >= prec+offset ||
                         dt->shared->u.atomic.u.f.epos + dt->shared->u.atomic.u.f.esize > prec+offset ||
                         dt->shared->u.atomic.u.f.mpos + dt->shared->u.atomic.u.f.msize > prec+offset) {
-                    HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "adjust sign, mantissa, and exponent fields first");
+                    HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "adjust sign, mantissa, and exponent fields first")
                 }
                 break;
 
@@ -4095,7 +4094,7 @@ H5T_cmp(const H5T_t *dt1, const H5T_t *dt2, hbool_t superset)
             /* Build an index for each type so the names are sorted */
             if(NULL == (idx1 = (unsigned *)H5MM_malloc(dt1->shared->u.compnd.nmembs * sizeof(unsigned))) ||
                     NULL == (idx2 = (unsigned *)H5MM_malloc(dt2->shared->u.compnd.nmembs * sizeof(unsigned))))
-                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "memory allocation failed");
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "memory allocation failed")
             for(u = 0; u < dt1->shared->u.compnd.nmembs; u++)
                 idx1[u] = idx2[u] = u;
             if(dt1->shared->u.enumer.nmembs > 1) {
@@ -4181,7 +4180,7 @@ H5T_cmp(const H5T_t *dt1, const H5T_t *dt2, hbool_t superset)
             /* Build an index for each type so the names are sorted */
             if(NULL == (idx1 = (unsigned *)H5MM_malloc(dt1->shared->u.enumer.nmembs * sizeof(unsigned))) ||
                     NULL == (idx2 = (unsigned *)H5MM_malloc(dt2->shared->u.enumer.nmembs * sizeof(unsigned))))
-                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "memory allocation failed");
+                HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, 0, "memory allocation failed")
             for(u=0; u<dt1->shared->u.enumer.nmembs; u++)
                 idx1[u] = u;
             if(dt1->shared->u.enumer.nmembs > 1) {
@@ -5190,21 +5189,21 @@ H5T_convert_committed_datatype(H5T_t *dt, H5F_t *f)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, FAIL, "unable to reset path")
 
         /* If the datatype is committed through the VOL, close it */
-        if (NULL != dt->vol_obj) {
+        if(NULL != dt->vol_obj) {
             H5VL_object_t *vol_obj = dt->vol_obj;
 
             /* Close the datatype through the VOL*/
-            if ((ret_value = H5VL_datatype_close(vol_obj->data, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
-                HGOTO_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to close datatype");
+            if(H5VL_datatype_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+                HGOTO_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to close datatype")
 
             /* Free the datatype and set the VOL object pointer to NULL */
-            if (H5VL_free_object(vol_obj) < 0)
-                HGOTO_ERROR(H5E_ATTR, H5E_CANTDEC, FAIL, "unable to free VOL object");
+            if(H5VL_free_object(vol_obj) < 0)
+                HGOTO_ERROR(H5E_ATTR, H5E_CANTDEC, FAIL, "unable to free VOL object")
             dt->vol_obj = NULL;
-        }
+        } /* end if */
 
         dt->shared->state = H5T_STATE_TRANSIENT;
-    }
+    } /* end if */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -5349,7 +5348,7 @@ H5T_set_loc(H5T_t *dt, H5F_t *f, H5T_loc_t loc)
 
                     /* Mark the VL, compound or array type */
                     if((changed=H5T_set_loc(dt->shared->parent,f,loc))<0)
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location")
                     if(changed>0)
                         ret_value=changed;
 
@@ -5373,7 +5372,7 @@ H5T_set_loc(H5T_t *dt, H5F_t *f, H5T_loc_t loc)
 
                         /* Range check against compound member's offset */
                         if ((accum_change < 0) && ((ssize_t) dt->shared->u.compnd.memb[i].offset < accum_change))
-                            HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, FAIL, "invalid field size in datatype");
+                            HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, FAIL, "invalid field size in datatype")
 
                         /* Apply the accumulated size change to the offset of the field */
                         dt->shared->u.compnd.memb[i].offset += (size_t) accum_change;
@@ -5389,7 +5388,7 @@ H5T_set_loc(H5T_t *dt, H5F_t *f, H5T_loc_t loc)
 
                             /* Mark the VL, compound, enum or array type */
                             if((changed = H5T_set_loc(memb_type,f,loc)) < 0)
-                                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location");
+                                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location")
                             if(changed > 0)
                                 ret_value = changed;
 
@@ -5398,7 +5397,7 @@ H5T_set_loc(H5T_t *dt, H5F_t *f, H5T_loc_t loc)
 
                                 /* Fail if the old_size is zero */
                                 if (0 == old_size)
-                                    HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, FAIL, "old_size of zero would cause division by zero");
+                                    HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, FAIL, "old_size of zero would cause division by zero")
 
                                 /* Adjust the size of the member */
                                 dt->shared->u.compnd.memb[i].size = (dt->shared->u.compnd.memb[i].size*memb_type->shared->size)/old_size;
@@ -5411,7 +5410,7 @@ H5T_set_loc(H5T_t *dt, H5F_t *f, H5T_loc_t loc)
 
                     /* Range check against datatype size */
                     if ((accum_change < 0) && ((ssize_t) dt->shared->size < accum_change))
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, FAIL, "invalid field size in datatype");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_BADVALUE, FAIL, "invalid field size in datatype")
 
                     /* Apply the accumulated size change to the datatype */
                     dt->shared->size += (size_t) accum_change;
@@ -5423,14 +5422,14 @@ H5T_set_loc(H5T_t *dt, H5F_t *f, H5T_loc_t loc)
                 /* (If the force_conv flag is _not_ set, the type cannot change in size, so don't recurse) */
                 if(dt->shared->parent->shared->force_conv && H5T_IS_COMPLEX(dt->shared->parent->shared->type)) {
                     if((changed = H5T_set_loc(dt->shared->parent,f,loc)) < 0)
-                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location");
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location")
                     if(changed > 0)
                         ret_value = changed;
                 } /* end if */
 
                 /* Mark this VL sequence */
                 if((changed = H5T__vlen_set_loc(dt, f, loc)) < 0)
-                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location");
+                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "Unable to set VL location")
                 if(changed > 0)
                     ret_value = changed;
                 break;
diff --git a/src/H5Tcommit.c b/src/H5Tcommit.c
index 3eb9cd7..0e609ff 100644
--- a/src/H5Tcommit.c
+++ b/src/H5Tcommit.c
@@ -108,7 +108,6 @@ H5Tcommit2(hid_t loc_id, const char *name, hid_t type_id, hid_t lcpl_id,
     H5T_t *dt = NULL;                   /* High level datatype object that wraps the VOL object */
     H5VL_object_t *vol_obj = NULL;          /* object token of loc_id */
     H5VL_loc_params_t loc_params;
-    hbool_t         vol_wrapper_set = FALSE;            /* Whether the VOL object wrapping context was set up */
     herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_API(FAIL)
@@ -150,15 +149,8 @@ H5Tcommit2(hid_t loc_id, const char *name, hid_t type_id, hid_t lcpl_id,
     if(NULL == (vol_obj = (H5VL_object_t *)H5I_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid object identifier")
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* Commit the type */
-    if(NULL == (data = H5VL_datatype_commit(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                           name, type_id, lcpl_id, tcpl_id, tapl_id, 
-                                           H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (data = H5VL_datatype_commit(vol_obj, loc_params, name, type_id, lcpl_id, tcpl_id, tapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
     /* Set up VOL object */
@@ -172,10 +164,6 @@ H5Tcommit2(hid_t loc_id, const char *name, hid_t type_id, hid_t lcpl_id,
     dt->vol_obj = new_obj;
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't reset VOL wrapper info")
-
     FUNC_LEAVE_API(ret_value)
 } /* end H5Tcommit2() */
 
@@ -315,9 +303,7 @@ H5Tcommit_anon(hid_t loc_id, hid_t type_id, hid_t tcpl_id, hid_t tapl_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid file identifier")
 
     /* Commit the datatype */
-    if(NULL == (dt = H5VL_datatype_commit(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                           NULL, type_id, H5P_DEFAULT, tcpl_id, tapl_id, 
-                                           H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dt = H5VL_datatype_commit(vol_obj, loc_params, NULL, type_id, H5P_DEFAULT, tcpl_id, tapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
     /* Setup VOL object */
@@ -581,7 +567,6 @@ H5Topen2(hid_t loc_id, const char *name, hid_t tapl_id)
     void *dt = NULL;           /* datatype token created by VOL plugin */
     H5VL_object_t *vol_obj = NULL;     /* object token of loc_id */
     H5VL_loc_params_t loc_params;
-    hbool_t         vol_wrapper_set = FALSE;            /* Whether the VOL object wrapping context was set up */
     hid_t        ret_value = H5I_INVALID_HID;      /* Return value */
 
     FUNC_ENTER_API(H5I_INVALID_HID)
@@ -605,14 +590,8 @@ H5Topen2(hid_t loc_id, const char *name, hid_t tapl_id)
     if(NULL == (vol_obj = (H5VL_object_t *)H5I_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid file identifier")
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* Open the datatype */
-    if(NULL == (dt = H5VL_datatype_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                            name, tapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dt = H5VL_datatype_open(vol_obj, loc_params, name, tapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open named datatype")
 
     /* Register the type and return the ID */
@@ -620,13 +599,9 @@ H5Topen2(hid_t loc_id, const char *name, hid_t tapl_id)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTREGISTER, H5I_INVALID_HID, "unable to register named datatype")
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't reset VOL wrapper info")
-
     /* Cleanup on error */
     if(H5I_INVALID_HID == ret_value)
-        if(dt && H5VL_datatype_close(dt, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dt && H5VL_datatype_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to release datatype")
 
     FUNC_LEAVE_API(ret_value)
@@ -678,16 +653,15 @@ H5Tget_create_plist(hid_t dtype_id)
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "can't get default creation property list")
         if((ret_value = H5P_copy_plist(tcpl_plist, TRUE)) < 0)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTGET, H5I_INVALID_HID, "unable to copy the creation property list")
-    }
+    } /* end if */
     /* If the datatype is committed, retrieve further information */
     else {
         H5VL_object_t *vol_obj = type->vol_obj;
 
         /* Get the property list through the VOL */
-        if(H5VL_datatype_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATATYPE_GET_TCPL, 
-                             H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+        if(H5VL_datatype_get(vol_obj, H5VL_DATATYPE_GET_TCPL, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTGET, H5I_INVALID_HID, "can't get object creation info")
-    }
+    } /* end else */
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -727,8 +701,7 @@ H5Tflush(hid_t type_id)
 
     /* Flush metadata for named datatype */
     if(dt->vol_obj)
-        if((ret_value = H5VL_datatype_specific(dt->vol_obj->data, dt->vol_obj->plugin->cls, H5VL_DATATYPE_FLUSH, 
-                                          H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, type_id)) < 0)
+        if(H5VL_datatype_specific(dt->vol_obj, H5VL_DATATYPE_FLUSH, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, type_id) < 0)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTFLUSH, FAIL, "unable to flush datatype")
 
 done:
@@ -752,7 +725,6 @@ herr_t
 H5Trefresh(hid_t type_id)
 {
     H5T_t *dt;                          /* Datatype for this operation */
-    hbool_t             vol_wrapper_set = FALSE;        /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API(FAIL)
@@ -769,22 +741,11 @@ H5Trefresh(hid_t type_id)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTSET, FAIL, "can't set access property list info")
 
     /* Refresh the datatype's metadata */
-    if(dt->vol_obj) {
-        /* Set wrapper info in API context */
-        if(H5VL_set_vol_wrapper(dt->vol_obj->data, dt->vol_obj->plugin) < 0)
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
-        vol_wrapper_set = TRUE;
-
-        if((ret_value = H5VL_datatype_specific(dt->vol_obj->data, dt->vol_obj->plugin->cls, H5VL_DATATYPE_REFRESH, 
-                                          H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, type_id)) < 0)
+    if(dt->vol_obj)
+        if(H5VL_datatype_specific(dt->vol_obj, H5VL_DATATYPE_REFRESH, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, type_id) < 0)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTLOAD, FAIL, "unable to refresh datatype")
-    } /* end if */
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't reset VOL wrapper info")
-
     FUNC_LEAVE_API(ret_value)
 } /* H5Trefresh */
 
@@ -1137,8 +1098,7 @@ H5T_construct_datatype(H5VL_object_t *vol_obj)
     FUNC_ENTER_NOAPI(NULL)
 
     /* get required buf size for encoding the datatype */
-    if(H5VL_datatype_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATATYPE_GET_BINARY, 
-                         H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &nalloc, NULL, 0) < 0)
+    if(H5VL_datatype_get(vol_obj, H5VL_DATATYPE_GET_BINARY, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &nalloc, NULL, 0) < 0)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to get datatype serialized size")
 
     /* allocate buffer to store binary description of the datatype */
@@ -1146,8 +1106,7 @@ H5T_construct_datatype(H5VL_object_t *vol_obj)
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't allocate space for datatype")
 
     /* get binary description of the datatype */
-    if(H5VL_datatype_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATATYPE_GET_BINARY, 
-                         H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &nalloc, buf, (size_t)nalloc) < 0)
+    if(H5VL_datatype_get(vol_obj, H5VL_DATATYPE_GET_BINARY, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &nalloc, buf, (size_t)nalloc) < 0)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to get serialized datatype")
 
     if(NULL == (dt = H5T_decode((size_t)nalloc, (const unsigned char *)buf)))
diff --git a/src/H5Tdeprec.c b/src/H5Tdeprec.c
index 4cedbd3..69a52e1 100644
--- a/src/H5Tdeprec.c
+++ b/src/H5Tdeprec.c
@@ -137,10 +137,7 @@ H5Tcommit1(hid_t loc_id, const char *name, hid_t type_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid object identifier")
 
     /* Commit the datatype */
-    if(NULL == (data = H5VL_datatype_commit(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                           name, type_id, H5P_LINK_CREATE_DEFAULT,
-                                           H5P_DATATYPE_CREATE_DEFAULT, H5P_DATATYPE_ACCESS_DEFAULT, 
-                                           H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (data = H5VL_datatype_commit(vol_obj, loc_params, name, type_id, H5P_LINK_CREATE_DEFAULT, H5P_DATATYPE_CREATE_DEFAULT, H5P_DATATYPE_ACCESS_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
     /* Set up VOL object */
@@ -197,9 +194,7 @@ H5Topen1(hid_t loc_id, const char *name)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the datatype */
-    if(NULL == (dt = H5VL_datatype_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                            name, H5P_DATATYPE_ACCESS_DEFAULT, 
-                                            H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dt = H5VL_datatype_open(vol_obj, loc_params, name, H5P_DATATYPE_ACCESS_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open named datatype")
 
     /* Register the type and return the ID */
@@ -209,7 +204,7 @@ H5Topen1(hid_t loc_id, const char *name)
 done:
     /* Cleanup on error */
     if(H5I_INVALID_HID == ret_value)
-        if(dt && H5VL_datatype_close(dt, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dt && H5VL_datatype_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to close datatype")
 
     FUNC_LEAVE_API(ret_value)
diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index a820536..a6286c6 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -148,6 +148,21 @@ static herr_t H5VL__object_specific(void *obj, H5VL_loc_params_t loc_params,
     void **req, va_list arguments);
 static herr_t H5VL__object_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
     void **req, va_list arguments);
+static void * H5VL__datatype_commit(void *obj, H5VL_loc_params_t loc_params,
+    const H5VL_class_t *cls, const char *name, hid_t type_id, hid_t lcpl_id,
+    hid_t tcpl_id, hid_t tapl_id, hid_t dxpl_id, void **req);
+static void *H5VL__datatype_open(void *obj, H5VL_loc_params_t loc_params,
+    const H5VL_class_t *cls, const char *name, hid_t tapl_id, hid_t dxpl_id,
+    void **req);
+static herr_t H5VL__datatype_get(void *obj, const H5VL_class_t *cls,
+    H5VL_datatype_get_t get_type, hid_t dxpl_id, void **req, va_list arguments);
+static herr_t H5VL__datatype_specific(void *obj, const H5VL_class_t *cls,
+    H5VL_datatype_specific_t specific_type, hid_t dxpl_id, void **req,
+    va_list arguments);
+static herr_t H5VL__datatype_optional(void *obj, const H5VL_class_t *cls,
+    hid_t dxpl_id, void **req, va_list arguments);
+static herr_t H5VL__datatype_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req);
 
 
 /*********************/
@@ -4929,7 +4944,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_datatype_commit
+ * Function:	H5VL__datatype_commit
  *
  * Purpose:	Commits a datatype to the file through the VOL
  *
@@ -4938,14 +4953,14 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *
-H5VL_datatype_commit(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls,
+static void *
+H5VL__datatype_commit(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls,
     const char *name, hid_t type_id, hid_t lcpl_id, hid_t tcpl_id, hid_t tapl_id, 
     hid_t dxpl_id, void **req)
 {
-    void *ret_value = NULL;              /* Return value */
+    void *ret_value = NULL;             /* Return value */
 
-    FUNC_ENTER_NOAPI(NULL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->datatype_cls.commit)
@@ -4957,6 +4972,44 @@ H5VL_datatype_commit(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__datatype_commit() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_datatype_commit
+ *
+ * Purpose:	Commits a datatype to the file through the VOL
+ *
+ * Return:      Success:    Pointer to the new datatype
+ *              Failure:    NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5VL_datatype_commit(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params,
+    const char *name, hid_t type_id, hid_t lcpl_id, hid_t tcpl_id, hid_t tapl_id, 
+    hid_t dxpl_id, void **req)
+{
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
+    void *ret_value = NULL;             /* Return value */
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, NULL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if(NULL == (ret_value = H5VL__datatype_commit(vol_obj->data, loc_params, vol_obj->plugin->cls, name, type_id, lcpl_id, tcpl_id, tapl_id, dxpl_id, req)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "datatype commit failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, NULL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_datatype_commit() */
 
 
@@ -4989,7 +5042,7 @@ H5VLdatatype_commit(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(NULL == (ret_value = H5VL_datatype_commit(obj, loc_params, cls, name, type_id, lcpl_id, tcpl_id, tapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = H5VL__datatype_commit(obj, loc_params, cls, name, type_id, lcpl_id, tcpl_id, tapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "unable to commit datatype")
 
 done:
@@ -4998,7 +5051,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_datatype_open
+ * Function:	H5VL__datatype_open
  *
  * Purpose:	Opens a named datatype through the VOL
  *
@@ -5007,24 +5060,61 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *
-H5VL_datatype_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls,
+static void *
+H5VL__datatype_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls,
     const char *name, hid_t tapl_id, hid_t dxpl_id, void **req)
 {
-    void *ret_value = NULL;              /* Return value */
+    void *ret_value = NULL;             /* Return value */
 
-    FUNC_ENTER_NOAPI(NULL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->datatype_cls.open)
         HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, NULL, "no datatype open callback")
 
     /* Call the corresponding VOL callback */
-    if(NULL == (ret_value = (cls->datatype_cls.open) (obj, loc_params, name, tapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = (cls->datatype_cls.open)(obj, loc_params, name, tapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "open failed")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__datatype_open() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_datatype_open
+ *
+ * Purpose:	Opens a named datatype through the VOL
+ *
+ * Return:      Success:    Pointer to the datatype
+ *              Failure:    NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5VL_datatype_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params,
+    const char *name, hid_t tapl_id, hid_t dxpl_id, void **req)
+{
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
+    void *ret_value = NULL;             /* Return value */
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, NULL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if(NULL == (ret_value = H5VL__datatype_open(vol_obj->data, loc_params, vol_obj->plugin->cls, name, tapl_id, dxpl_id, req)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "open failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, NULL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_datatype_open() */
 
 
@@ -5056,7 +5146,7 @@ H5VLdatatype_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(NULL == (ret_value = H5VL_datatype_open(obj, loc_params, cls, name, tapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = H5VL__datatype_open(obj, loc_params, cls, name, tapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "unable to open datatype")
 
 done:
@@ -5065,6 +5155,37 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL__datatype_get
+ *
+ * Purpose:     Get specific information about the datatype through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__datatype_get(void *obj, const H5VL_class_t *cls, H5VL_datatype_get_t get_type, 
+    hid_t dxpl_id, void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->datatype_cls.get)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype get' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->datatype_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "datatype get failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__datatype_get() */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5VL_datatype_get
  *
  * Purpose:     Get specific information about the datatype through the VOL
@@ -5075,30 +5196,36 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_datatype_get(void *obj, const H5VL_class_t *cls, H5VL_datatype_get_t get_type, 
+H5VL_datatype_get(const H5VL_object_t *vol_obj, H5VL_datatype_get_t get_type, 
     hid_t dxpl_id, void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->datatype_cls.get)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype get' method")
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
 
-    /* Call the corresponding VOL callback */
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->datatype_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "get failed")
+    if(H5VL__datatype_get(vol_obj->data, vol_obj->plugin->cls, get_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "datatype get failed")
 
 done:
     /* End access to the va_list, if we started it */
     if(arg_started)
         va_end(arguments);
 
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_datatype_get() */
 
@@ -5133,8 +5260,8 @@ H5VLdatatype_get(void *obj, hid_t plugin_id, H5VL_datatype_get_t get_type,
     if(NULL == cls->datatype_cls.get)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `datatype get' method")
 
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->datatype_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__datatype_get(obj, cls, get_type, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "unable to execute datatype get callback")
 
 done:
@@ -5143,9 +5270,40 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__datatype_specific
+ *
+ * Purpose:	Specific operation on datatypes through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__datatype_specific(void *obj, const H5VL_class_t *cls, H5VL_datatype_specific_t specific_type, 
+    hid_t dxpl_id, void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->datatype_cls.specific)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype specific' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->datatype_cls.specific)(obj, specific_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute datatype specific callback")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__datatype_specific() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_datatype_specific
  *
- * Purpose:	specific operation on datatypes through the VOL
+ * Purpose:	Specific operation on datatypes through the VOL
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -5153,23 +5311,25 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_datatype_specific(void *obj, const H5VL_class_t *cls, H5VL_datatype_specific_t specific_type, 
+H5VL_datatype_specific(const H5VL_object_t *vol_obj, H5VL_datatype_specific_t specific_type, 
     hid_t dxpl_id, void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->datatype_cls.specific)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype specific' method")
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
 
-    /* Call the corresponding VOL callback */
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->datatype_cls.specific)(obj, specific_type, dxpl_id, req, arguments) < 0)
+    if(H5VL__datatype_specific(vol_obj->data, vol_obj->plugin->cls, specific_type, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute datatype specific callback")
 
 done:
@@ -5177,6 +5337,10 @@ done:
     if(arg_started)
         va_end(arguments);
 
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_datatype_specific() */
 
@@ -5208,12 +5372,8 @@ H5VLdatatype_specific(void *obj, hid_t plugin_id, H5VL_datatype_specific_t speci
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->datatype_cls.specific)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `datatype specific' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->datatype_cls.specific)(obj, specific_type, dxpl_id, req, arguments) < 0)
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__datatype_specific(obj, cls, specific_type, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute datatype specific callback")
 
 done:
@@ -5222,9 +5382,40 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__datatype_optional
+ *
+ * Purpose:	Optional operation specific to plugins.
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__datatype_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->datatype_cls.optional)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype optional' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->datatype_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute datatype optional callback")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__datatype_optional() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_datatype_optional
  *
- * Purpose:	optional operation specific to plugins.
+ * Purpose:	Optional operation specific to plugins.
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -5232,23 +5423,25 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_datatype_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+H5VL_datatype_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id,
     void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->datatype_cls.optional)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype optional' method")
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
 
-    /* Call the corresponding VOL callback */
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->datatype_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+    if(H5VL__datatype_optional(vol_obj->data, vol_obj->plugin->cls, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute datatype optional callback")
 
 done:
@@ -5256,6 +5449,10 @@ done:
     if(arg_started)
         va_end(arguments);
 
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_datatype_optional() */
 
@@ -5286,12 +5483,8 @@ H5VLdatatype_optional(void *obj, hid_t plugin_id, hid_t dxpl_id, void **req,
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->datatype_cls.optional)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `datatype optional' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->datatype_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__datatype_optional(obj, cls, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute datatype optional callback")
 
 done:
@@ -5300,7 +5493,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5VL_datatype_close
+ * Function:    H5VL__datatype_close
  *
  * Purpose:     Closes a datatype through the VOL
  *
@@ -5309,23 +5502,60 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t
-H5VL_datatype_close(void *dt, const H5VL_class_t *cls, hid_t dxpl_id, void **req)
+static herr_t
+H5VL__datatype_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->datatype_cls.close)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'datatype close' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->datatype_cls.close)(dt, dxpl_id, req) < 0)
+    if((cls->datatype_cls.close)(obj, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "datatype close failed")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__datatype_close() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5VL_datatype_close
+ *
+ * Purpose:     Closes a datatype through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_datatype_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req)
+{
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__datatype_close(vol_obj->data, vol_obj->plugin->cls, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "datatype close failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_datatype_close() */
 
 
@@ -5340,22 +5570,22 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdatatype_close(void *dt, hid_t plugin_id, hid_t dxpl_id, void **req)
+H5VLdatatype_close(void *obj, hid_t plugin_id, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE4("e", "*xii**x", dt, plugin_id, dxpl_id, req);
+    H5TRACE4("e", "*xii**x", obj, plugin_id, dxpl_id, req);
 
     /* Check args and get class pointer */
-    if(NULL == dt)
+    if(NULL == obj)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(H5VL_datatype_close(dt, cls, dxpl_id, req) < 0)
+    if(H5VL__datatype_close(obj, cls, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "unable to close datatype")
 
 done:
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index 7b2e590..a168b57 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -114,7 +114,7 @@ H5_DLL herr_t H5VL_attr_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void
 
 /* Dataset functions */
 H5_DLL void *H5VL_dataset_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req);
-H5_DLL void * H5VL_dataset_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t dapl_id, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_dataset_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t dapl_id, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_dataset_read(const H5VL_object_t *vol_obj, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id, hid_t plist_id, void *buf, void **req);
 H5_DLL herr_t H5VL_dataset_write(const H5VL_object_t *vol_obj, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id, hid_t plist_id, const void *buf, void **req);
 H5_DLL herr_t H5VL_dataset_get(const H5VL_object_t *vol_obj, H5VL_dataset_get_t get_type, hid_t dxpl_id, void **req, ...);
@@ -132,7 +132,7 @@ H5_DLL herr_t H5VL_file_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void
 
 /* Group functions */
 H5_DLL void *H5VL_group_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t gcpl_id, hid_t gapl_id, hid_t dxpl_id, void **req);
-H5_DLL void * H5VL_group_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t gapl_id, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_group_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t gapl_id, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_group_get(const H5VL_object_t *vol_obj, H5VL_group_get_t get_type, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_group_specific(const H5VL_object_t *vol_obj, H5VL_group_specific_t specific_type, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_group_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...);
@@ -147,19 +147,19 @@ H5_DLL herr_t H5VL_link_specific(const H5VL_object_t *vol_obj, H5VL_loc_params_t
 H5_DLL herr_t H5VL_link_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...);
 
 /* Object functions */
-H5_DLL void * H5VL_object_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t params, H5I_type_t *opened_type, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_object_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t params, H5I_type_t *opened_type, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_object_copy(const H5VL_object_t *src_obj, H5VL_loc_params_t src_loc_params, const char *src_name, const H5VL_object_t *dst_obj, H5VL_loc_params_t dst_loc_params, const char *dst_name, hid_t ocpypl_id, hid_t lcpl_id, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_object_get(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, H5VL_object_get_t get_type, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_object_specific(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, H5VL_object_specific_t specific_type, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_object_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...);
 
 /* Datatype functions */
-H5_DLL void *H5VL_datatype_commit(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, hid_t type_id, hid_t lcpl_id, hid_t tcpl_id, hid_t tapl_id, hid_t dxpl_id, void **req);
-H5_DLL void *H5VL_datatype_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, hid_t tapl_id, hid_t dxpl_id, void **req);
-H5_DLL herr_t H5VL_datatype_get(void *dt, const H5VL_class_t *cls, H5VL_datatype_get_t get_type, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_datatype_specific(void *obj, const H5VL_class_t *cls, H5VL_datatype_specific_t specific_type, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_datatype_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_datatype_close(void *dt, const H5VL_class_t *cls, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_datatype_commit(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t type_id, hid_t lcpl_id, hid_t tcpl_id, hid_t tapl_id, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_datatype_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t tapl_id, hid_t dxpl_id, void **req);
+H5_DLL herr_t H5VL_datatype_get(const H5VL_object_t *vol_obj, H5VL_datatype_get_t get_type, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_datatype_specific(const H5VL_object_t *vol_obj, H5VL_datatype_specific_t specific_type, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_datatype_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_datatype_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req);
 
 /* Asynchronous functions */
 H5_DLL herr_t H5VL_request_cancel(void **req, const H5VL_class_t *cls, H5ES_status_t *status);