Added 'notify' callback for async requests; switched VOL class and info

comparison to return comparison value as parameter, so they can return error
values; "cancelled" -> "canceled"; switched order of 'wrap_object' and
'free_wrap_ctx' management callbacks.

9 files changed, 256 insertions, 82 deletions

diff --git a/src/H5ESpublic.h b/src/H5ESpublic.h
index 2df1a6e..e3b1b56 100644
--- a/src/H5ESpublic.h
+++ b/src/H5ESpublic.h
@@ -29,7 +29,7 @@ typedef enum H5ES_status_t {
     H5ES_STATUS_IN_PROGRESS,   /* Operation has not yet completed                       */
     H5ES_STATUS_SUCCEED,       /* Operation has completed, successfully                 */
     H5ES_STATUS_FAIL,          /* Operation has completed, but failed                   */
-    H5ES_STATUS_CANCELLED      /* Operation has not completed and was cancelled         */
+    H5ES_STATUS_CANCELED       /* Operation has not completed and was canceled          */
 } H5ES_status_t;
 
 
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index a792e57..e802e3b 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -5309,7 +5309,8 @@ H5P__facc_vol_cmp(const void *_info1, const void *_info2, size_t H5_ATTR_UNUSED
     const H5VL_connector_prop_t *info1 = (const H5VL_connector_prop_t *)_info1; /* Create local aliases for values */
     const H5VL_connector_prop_t *info2 = (const H5VL_connector_prop_t *)_info2;
     H5VL_class_t *cls1, *cls2;  /* connector class for each property */
-    int cmp_value;              /* Value from comparison */
+    int cmp_value = 0;          /* Value from comparison */
+    herr_t status;              /* Status from info comparison */
     int ret_value = 0;          /* Return value */
 
     FUNC_ENTER_STATIC_NOERR
@@ -5324,7 +5325,9 @@ H5P__facc_vol_cmp(const void *_info1, const void *_info2, size_t H5_ATTR_UNUSED
         HGOTO_DONE(-1)
     if(NULL == (cls2 = (H5VL_class_t *)H5I_object(info2->connector_id)))
         HGOTO_DONE(1)
-    if(0 != (cmp_value = H5VL_cmp_connector_cls(cls1, cls2)))
+    status = H5VL_cmp_connector_cls(&cmp_value, cls1, cls2);
+    HDassert(status >= 0);
+    if(cmp_value != 0)
         HGOTO_DONE(cmp_value);
 
     /* At this point, we should be able to assume that we are dealing with
@@ -5336,8 +5339,11 @@ H5P__facc_vol_cmp(const void *_info1, const void *_info2, size_t H5_ATTR_UNUSED
      * info objects
      */
     HDassert(cls1->info_cmp == cls2->info_cmp);
-    if(0 != (cmp_value = H5VL_cmp_connector_info(cls1, info1->connector_info, info2->connector_info)))
-        HGOTO_DONE(cmp_value);
+    status = H5VL_cmp_connector_info(cls1, &cmp_value, info1->connector_info, info2->connector_info);
+    HDassert(status >= 0);
+
+    /* Set return value */
+    ret_value = cmp_value;
     
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5VL.c b/src/H5VL.c
index 5eeb201..268b9d2 100644
--- a/src/H5VL.c
+++ b/src/H5VL.c
@@ -512,7 +512,8 @@ H5VLcmp_connector_cls(int *cmp, hid_t connector_id1, hid_t connector_id2)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
 
     /* Compare the two VOL connector classes */
-    *cmp = H5VL_cmp_connector_cls(cls1, cls2);
+    if(H5VL_cmp_connector_cls(cmp, cls1, cls2) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCOMPARE, FAIL, "can't compare connector classes")
 
 done:
     FUNC_LEAVE_API(ret_value)
diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index 2c77416..74448af 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -171,6 +171,8 @@ static herr_t H5VL__datatype_close(void *obj, const H5VL_class_t *cls, hid_t dxp
     void **req);
 static herr_t H5VL__request_wait(void *req, const H5VL_class_t *cls,
     uint64_t timeout, H5ES_status_t *status);
+static herr_t H5VL__request_notify(void *req, const H5VL_class_t *cls,
+    H5VL_request_notify_t cb, void *ctx);
 static herr_t H5VL__request_cancel(void *req, const H5VL_class_t *cls);
 static herr_t H5VL__request_specific(void *req, const H5VL_class_t *cls,
     H5VL_request_specific_t specific_type, va_list arguments);
@@ -403,44 +405,53 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5VL_cmp_connector_info
  *
- * Purpose:     Compare VOL info for a connector
+ * Purpose:     Compare VOL info for a connector.  Sets *cmp_value to
+ *              positive if INFO1 is greater than INFO2, negative if
+ *              INFO2 is greater than INFO1 and zero if INFO1 and
+ *              INFO2 are equal.
  *
- * Return:      Positive if VALUE1 is greater than VALUE2, negative if
- *              VALUE2 is greater than VALUE1 and zero if VALUE1 and
- *              VALUE2 are equal.
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
  *
  *-------------------------------------------------------------------------
  */
-int
-H5VL_cmp_connector_info(const H5VL_class_t *connector, const void *info1,
-    const void *info2)
+herr_t
+H5VL_cmp_connector_info(const H5VL_class_t *connector, int *cmp_value,
+    const void *info1, const void *info2)
 {
-    int cmp_value;              /* Value from comparison */
-    int ret_value = 0;          /* Return value */
+    herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
     /* Sanity checks */
     HDassert(connector);
+    HDassert(cmp_value);
+
+    /* Take care of cases where one or both pointers is NULL */
+    if(info1 == NULL && info2 != NULL) {
+        *cmp_value = -1;
+        HGOTO_DONE(SUCCEED);
+    } /* end if */
+    if(info1 != NULL && info2 == NULL) {
+        *cmp_value = 1;
+        HGOTO_DONE(SUCCEED);
+    } /* end if */
+    if(info1 == NULL && info2 == NULL) {
+        *cmp_value = 0;
+        HGOTO_DONE(SUCCEED);
+    } /* end if */
 
     /* Use the class's info comparison routine to compare the info objects,
      * if there is a a callback, otherwise just compare the info objects as
      * memory buffers
      */
     if(connector->info_cmp) {
-        if(0 != (cmp_value = (connector->info_cmp)(info1, info2)))
-            HGOTO_DONE(cmp_value);
+        if((connector->info_cmp)(cmp_value, info1, info2) < 0)
+            HGOTO_ERROR(H5E_VOL, H5E_CANTCOMPARE, FAIL, "can't compare connector info")
     } /* end if */
     else {
-        if(info1 == NULL && info2 != NULL)
-            HGOTO_DONE(-1);
-        if(info1 != NULL && info2 == NULL)
-            HGOTO_DONE(1);
-        if(info1) {
-            HDassert(connector->info_size > 0);
-            if(0 != (cmp_value = HDmemcmp(info1, info2, connector->info_size)))
-                HGOTO_DONE(cmp_value);
-        } /* end if */
+        HDassert(connector->info_size > 0);
+        *cmp_value = HDmemcmp(info1, info2, connector->info_size);
     } /* end else */
 
 done:
@@ -478,7 +489,7 @@ H5VLcmp_connector_info(int *cmp, hid_t connector_id, const void *info1, const vo
 
     /* Compare the two VOL connector info objects */
     if(cmp)
-        *cmp = H5VL_cmp_connector_info(cls, info1, info2);
+        H5VL_cmp_connector_info(cls, cmp, info1, info2);
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -5846,6 +5857,9 @@ done:
  *
  * Purpose:     Waits on an asychronous request through the VOL
  *
+ * Note:	Releases the request if the operation has completed and the
+ *		connector callback succeeds
+ *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
  *
@@ -5882,6 +5896,9 @@ done:
  *
  * Purpose:     Waits on an asychronous request through the VOL
  *
+ * Note:	Releases the request if the operation has completed and the
+ *		connector callback succeeds
+ *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
  *
@@ -5922,6 +5939,9 @@ done:
  *
  * Purpose:     Waits on a request
  *
+ * Note:	Releases the request if the operation has completed and the
+ *		connector callback succeeds
+ *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
  *
@@ -5950,10 +5970,128 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL__request_notify
+ *
+ * Purpose:     Registers a user callback to be invoked when an asynchronous
+ *		operation completes
+ *
+ * Note:	Releases the request, if connector callback succeeds
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__request_notify(void *req, const H5VL_class_t *cls, H5VL_request_notify_t cb,
+    void *ctx)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Sanity check */
+    HDassert(req);
+    HDassert(cls);
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->request_cls.notify)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL connector has no 'async notify' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->request_cls.notify)(req, cb, ctx) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTRELEASE, FAIL, "request notify failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__request_notify() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5VL_request_notify
+ *
+ * Purpose:     Registers a user callback to be invoked when an asynchronous
+ *		operation completes
+ *
+ * Note:	Releases the request, if connector callback succeeds
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_request_notify(const H5VL_object_t *vol_obj, H5VL_request_notify_t cb,
+    void *ctx)
+{
+    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)
+
+    /* Sanity check */
+    HDassert(vol_obj);
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->connector) < 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__request_notify(vol_obj->data, vol_obj->connector->cls, cb, ctx) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "request notify 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_request_notify() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5VLrequest_notify
+ *
+ * Purpose:     Registers a user callback to be invoked when an asynchronous
+ *		operation completes
+ *
+ * Note:	Releases the request, if connector callback succeeds
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VLrequest_notify(void *req, hid_t connector_id, H5VL_request_notify_t cb,
+    void *ctx)
+{
+    H5VL_class_t *cls;                  /* VOL connector's class struct */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API_NOINIT
+
+    /* Get class pointer */
+    if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(connector_id, H5I_VOL)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
+
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__request_notify(req, cls, cb, ctx) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "unable to register notify callback for request")
+
+done:
+    FUNC_LEAVE_API_NOINIT(ret_value)
+} /* end H5VLrequest_notify() */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5VL__request_cancel
  *
  * Purpose:     Cancels an asynchronous request through the VOL
  *
+ * Note:	Releases the request, if connector callback succeeds
+ *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
  *
@@ -5988,6 +6126,8 @@ done:
  *
  * Purpose:     Cancels an asynchronous request through the VOL
  *
+ * Note:	Releases the request, if connector callback succeeds
+ *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
  *
@@ -6027,6 +6167,8 @@ done:
  *
  * Purpose:     Cancels a request
  *
+ * Note:	Releases the request, if connector callback succeeds
+ *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
  *
diff --git a/src/H5VLint.c b/src/H5VLint.c
index 167d098..82886cd 100644
--- a/src/H5VLint.c
+++ b/src/H5VLint.c
@@ -883,47 +883,65 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-int
-H5VL_cmp_connector_cls(const H5VL_class_t *cls1, const H5VL_class_t *cls2)
+herr_t
+H5VL_cmp_connector_cls(int *cmp_value, const H5VL_class_t *cls1, const H5VL_class_t *cls2)
 {
-    int cmp_value;              /* Value from comparison */
-    int ret_value = 0;          /* Return value */
+    herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
     /* Sanity checks */
     HDassert(cls1);
-    HDassert(cls1);
+    HDassert(cls2);
 
     /* Compare connector "values" */
-    if(cls1->value < cls2->value)
-        HGOTO_DONE(-1)
-    if(cls1->value > cls2->value)
-        HGOTO_DONE(1)
+    if(cls1->value < cls2->value) {
+        *cmp_value = -1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
+    if(cls1->value > cls2->value) {
+        *cmp_value = 1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
     HDassert(cls1->value == cls2->value);
 
     /* Compare connector names */
-    if(cls1->name == NULL && cls2->name != NULL)
-        HGOTO_DONE(-1);
-    if(cls1->name != NULL && cls2->name == NULL)
-        HGOTO_DONE(1);
-    if(0 != (cmp_value = HDstrcmp(cls1->name, cls2->name)))
-        HGOTO_DONE(cmp_value);
+    if(cls1->name == NULL && cls2->name != NULL) {
+        *cmp_value = -1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
+    if(cls1->name != NULL && cls2->name == NULL) {
+        *cmp_value = 1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
+    if(0 != (*cmp_value = HDstrcmp(cls1->name, cls2->name)))
+        HGOTO_DONE(SUCCEED)
 
     /* Compare connector VOL API versions */
-    if(cls1->version < cls2->version)
-        HGOTO_DONE(-1)
-    if(cls1->version > cls2->version)
-        HGOTO_DONE(1)
+    if(cls1->version < cls2->version) {
+        *cmp_value = -1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
+    if(cls1->version > cls2->version) {
+        *cmp_value = 1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
     HDassert(cls1->version == cls2->version);
 
     /* Compare connector info */
-    if(cls1->info_size < cls2->info_size)
-        HGOTO_DONE(-1)
-    if(cls1->info_size > cls2->info_size)
-        HGOTO_DONE(1)
+    if(cls1->info_size < cls2->info_size) {
+        *cmp_value = -1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
+    if(cls1->info_size > cls2->info_size) {
+        *cmp_value = 1;
+        HGOTO_DONE(SUCCEED)
+    } /* end if */
     HDassert(cls1->info_size == cls2->info_size);
 
+    /* Set comparison value to 'equal' */
+    *cmp_value = 0;
+
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_cmp_connector_cls() */
diff --git a/src/H5VLnative.c b/src/H5VLnative.c
index 3fad8e1..6c51d95 100644
--- a/src/H5VLnative.c
+++ b/src/H5VLnative.c
@@ -134,8 +134,8 @@ static H5VL_class_t H5VL_native_cls_g = {
     NULL,                                           /* str to info  */
     NULL,                                           /* get_object   */
     NULL,                                           /* get_wrap_ctx */
-    NULL,                                           /* free_wrap_ctx */
     NULL,                                           /* wrap_object  */
+    NULL,                                           /* free_wrap_ctx */
     {   /* attribute_cls */
         H5VL__native_attr_create,                   /* create       */
         H5VL__native_attr_open,                     /* open         */
@@ -197,6 +197,7 @@ static H5VL_class_t H5VL_native_cls_g = {
     },
     {   /* request_cls */
         NULL,                                       /* wait         */
+        NULL,                                       /* notify       */
         NULL,                                       /* cancel       */
         NULL,                                       /* specific     */
         NULL,                                       /* optional     */
@@ -292,7 +293,7 @@ done:
  *
  * Purpose:	Creates an attribute on an object.
  *
- * Return:	Success:	attr id. 
+ * Return:	Success:	Pointer to attribute object
  *		Failure:	NULL
  *
  *-------------------------------------------------------------------------
@@ -365,9 +366,9 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_attr_open
  *
- * Purpose:	Opens a attr inside a native h5 file.
+ * Purpose:	Opens an attr inside a native H5 file.
  *
- * Return:	Success:	attr id. 
+ * Return:	Success:	Pointer to attribute object
  *		Failure:	NULL
  *
  * Programmer:  Mohamad Chaarawi
@@ -423,9 +424,9 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_attr_read
  *
- * Purpose:	Reads in data from attribute.
+ * Purpose:	Reads data from attribute.
  *
- *              Non-negative on success/Negative on failure
+ * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:  Mohamad Chaarawi
  *              March, 2012
@@ -456,9 +457,9 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_attr_write
  *
- * Purpose:	Writes out data to attribute.
+ * Purpose:	Writes data to attribute.
  *
- *              Non-negative on success/Negative on failure
+ * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:  Mohamad Chaarawi
  *              March, 2012
@@ -489,7 +490,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_attr_get
  *
- * Purpose:	Gets certain information about an attribute
+ * Purpose:	Gets information about an attribute
  *
  * Return:	Success:	0
  *		Failure:	-1
@@ -673,7 +674,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_attr_specific
  *
- * Purpose:	Specific operations for attributes
+ * Purpose:	Specific operation on attribute
  *
  * Return:	Success:	0
  *		Failure:	-1
@@ -1176,7 +1177,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5VL__native_dataset_specific
  *
- * Purpose:     Specific operations for datasets
+ * Purpose:     Specific operation on dataset
  *
  * Return:      SUCCEED/FAIL
  *
@@ -1496,7 +1497,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5VL__native_file_get
  *
- * Purpose:     Gets certain data about a file
+ * Purpose:     Get info about a file
  *
  * Return:      SUCCEED/FAIL
  *
@@ -1648,7 +1649,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5VL__native_file_specific
  *
- * Purpose:     Perform an operation
+ * Purpose:	Specific operation on file
  *
  * Return:      SUCCEED/FAIL
  *
@@ -2307,7 +2308,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5VL__native_group_get
  *
- * Purpose:     Gets data about a group
+ * Purpose:     Get info about a group
  *
  * Return:      SUCCEED/FAIL
  *
@@ -2754,7 +2755,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_link_get
  *
- * Purpose:	Gets certain data about a link
+ * Purpose:	Get info about a link
  *
  * Return:	Success:	0
  *		Failure:	-1
@@ -2847,7 +2848,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_link_specific
  *
- * Purpose:	Specific operations with links
+ * Purpose:	Specific operation on a link
  *
  * Return:	Success:	0
  *		Failure:	-1
@@ -2959,7 +2960,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_object_open
  *
- * Purpose:	Opens a object inside a native h5 file.
+ * Purpose:	Opens an object inside a native h5 file.
  *
  * Return:	Success:	object id. 
  *		Failure:	NULL
@@ -3040,10 +3041,10 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_object_copy
  *
- * Purpose:	Copys a object inside a native h5 file.
+ * Purpose:	Copies an object inside a native h5 file.
  *
- * Return:	Success:	object id. 
- *		Failure:	NULL
+ * Return:	Success:	0
+ *		Failure:	-1
  *
  * Programmer:  Mohamad Chaarawi
  *              March, 2012
@@ -3174,7 +3175,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:    H5VL__native_object_specific
  *
- * Purpose:     Perform a connector-specific operation for an objectibute
+ * Purpose:	Specific operation on an object
  *
  * Return:      SUCCEED/FAIL
  *
@@ -3533,7 +3534,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_datatype_get
  *
- * Purpose:	Gets certain information about a datatype
+ * Purpose:	Get information about a datatype
  *
  * Return:	Success:	0
  *		Failure:	-1
@@ -3639,7 +3640,7 @@ done:
 /*-------------------------------------------------------------------------
  * Function:	H5VL__native_datatype_close
  *
- * Purpose:	Closes an datatype.
+ * Purpose:	Closes a datatype.
  *
  * Return:	Success:	0
  *		Failure:	-1, datatype not closed.
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index ca0c87e..ef5a81e 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -63,7 +63,7 @@ typedef enum H5VL_get_connector_kind_t {
 
 /* Utility functions */
 H5_DLL herr_t H5VL_init(void);
-H5_DLL int H5VL_cmp_connector_cls(const H5VL_class_t *cls1, const H5VL_class_t *cls);
+H5_DLL herr_t H5VL_cmp_connector_cls(int *cmp_value, const H5VL_class_t *cls1, const H5VL_class_t *cls2);
 H5_DLL herr_t H5VL_conn_copy(H5VL_connector_prop_t *value);
 H5_DLL herr_t H5VL_conn_free(const H5VL_connector_prop_t *info);
 
@@ -110,8 +110,8 @@ H5_DLL herr_t H5VL_register_using_existing_id(H5I_type_t type, void *object, H5V
 /* Connector "management" functions */
 H5_DLL int H5VL_copy_connector_info(const H5VL_class_t *connector, void **dst_info,
     const void *src_info);
-H5_DLL int H5VL_cmp_connector_info(const H5VL_class_t *connector, const void *info1,
-    const void *info2);
+H5_DLL herr_t H5VL_cmp_connector_info(const H5VL_class_t *connector, int *cmp_value,
+    const void *info1, const void *info2);
 H5_DLL herr_t H5VL_free_connector_info(const H5VL_class_t *connector, void *info);
 
 /* Attribute functions */
@@ -175,6 +175,7 @@ H5_DLL herr_t H5VL_datatype_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, v
 
 /* Asynchronous functions */
 H5_DLL herr_t H5VL_request_wait(const H5VL_object_t *vol_obj, uint64_t timeout, H5ES_status_t *status);
+H5_DLL herr_t H5VL_request_notify(const H5VL_object_t *vol_obj, H5VL_request_notify_t cb, void *ctx);
 H5_DLL herr_t H5VL_request_cancel(const H5VL_object_t *vol_obj);
 H5_DLL herr_t H5VL_request_specific(const H5VL_object_t *vol_obj, H5VL_request_specific_t specific_type, ...);
 H5_DLL herr_t H5VL_request_optional(const H5VL_object_t *vol_obj, ...);
diff --git a/src/H5VLpublic.h b/src/H5VLpublic.h
index 92664aa..b89946d 100644
--- a/src/H5VLpublic.h
+++ b/src/H5VLpublic.h
@@ -337,9 +337,13 @@ typedef struct H5VL_object_class_t {
     herr_t (*optional)(void *obj, hid_t dxpl_id, void **req, va_list arguments);
 } H5VL_object_class_t;
 
-/* Async operation routines */
+/* Asynchronous request 'notify' callback */
+typedef herr_t (*H5VL_request_notify_t)(void *ctx, H5ES_status_t status);
+
+/* Async request operation routines */
 typedef struct H5VL_request_class_t {
     herr_t (*wait)(void *req, uint64_t timeout, H5ES_status_t *status);
+    herr_t (*notify)(void *req, H5VL_request_notify_t cb, void *ctx);
     herr_t (*cancel)(void *req);
     herr_t (*specific)(void *req, H5VL_request_specific_t specific_type, va_list arguments);
     herr_t (*optional)(void *req, va_list arguments);
@@ -383,14 +387,14 @@ typedef struct H5VL_class_t {
     herr_t  (*terminate)(void);                     /* Connector termination callback               */
     size_t  info_size;                              /* size of the vol info                         */
     void *  (*info_copy)(const void *info);         /* Callback to create a copy of the vol info    */
-    int     (*info_cmp)(const void *info1, const void *info2); /* Callback to compare vol info      */
+    herr_t  (*info_cmp)(int *cmp_value, const void *info1, const void *info2); /* Callback to compare vol info      */
     herr_t  (*info_free)(void *info);               /* Callback to release the vol info copy        */
     herr_t  (*info_to_str)(const void *info, char **str); /* Callback to serialize connector's info into a string */
     herr_t  (*str_to_info)(const char *str, void **info); /* Callback to deserialize a string into connector's info */
     void *  (*get_object)(const void *obj);         /* Callback to retrieve underlying object       */
     herr_t  (*get_wrap_ctx)(const void *obj, void **wrap_ctx); /* Callback to retrieve the object wrapping context for the connector */
-    herr_t  (*free_wrap_ctx)(void *wrap_ctx);       /* Callback to release the object wrapping context for the connector */
     void*   (*wrap_object)(void *obj, void *wrap_ctx); /* Callback to wrap an object */
+    herr_t  (*free_wrap_ctx)(void *wrap_ctx);       /* Callback to release the object wrapping context for the connector */
 
     /* Data Model */
     H5VL_attr_class_t          attr_cls;            /* attribute class callbacks    */
@@ -454,8 +458,8 @@ H5_DLL herr_t H5VLconnector_info_to_str(const void *info, hid_t connector_id, ch
 H5_DLL herr_t H5VLconnector_str_to_info(const char *str, hid_t connector_id, void **info);
 H5_DLL void *H5VLget_object(void *obj, hid_t connector_id);
 H5_DLL herr_t H5VLget_wrap_ctx(void *obj, hid_t connector_id, void **wrap_ctx);
-H5_DLL herr_t H5VLfree_wrap_ctx(void *wrap_ctx, hid_t connector_id);
 H5_DLL void *H5VLwrap_object(void *obj, hid_t connector_id, void *wrap_ctx);
+H5_DLL herr_t H5VLfree_wrap_ctx(void *wrap_ctx, hid_t connector_id);
 
 /* Public wrappers for attribute callbacks */
 H5_DLL void *H5VLattr_create(void *obj, const H5VL_loc_params_t *loc_params, hid_t connector_id, const char *attr_name, hid_t acpl_id, hid_t aapl_id, hid_t dxpl_id, void **req);
@@ -524,6 +528,7 @@ H5_DLL herr_t H5VLdatatype_close(void *dt, hid_t connector_id, hid_t dxpl_id, vo
 
 /* Public wrappers for asynchronous request callbacks */
 H5_DLL herr_t H5VLrequest_wait(void *req, hid_t connector_id, uint64_t timeout, H5ES_status_t *status);
+H5_DLL herr_t H5VLrequest_notify(void *req, hid_t connector_id, H5VL_request_notify_t cb, void *ctx);
 H5_DLL herr_t H5VLrequest_cancel(void *req, hid_t connector_id);
 H5_DLL herr_t H5VLrequest_specific(void *req, hid_t connector_id, H5VL_request_specific_t specific_type, va_list arguments);
 H5_DLL herr_t H5VLrequest_optional(void *req, hid_t connector_id, va_list arguments);
diff --git a/src/H5trace.c b/src/H5trace.c
index db26d83..d69ab28 100644
--- a/src/H5trace.c
+++ b/src/H5trace.c
@@ -834,8 +834,8 @@ H5_trace(const double *returning, const char *func, const char *type, ...)
                                 case H5ES_STATUS_FAIL:
                                     HDfprintf(out, "H5ES_STATUS_FAIL");
                                     break;
-                                case H5ES_STATUS_CANCELLED:
-                                    HDfprintf(out, "H5ES_STATUS_CANCELLED");
+                                case H5ES_STATUS_CANCELED:
+                                    HDfprintf(out, "H5ES_STATUS_CANCELED");
                                     break;
 
                                 default: