Refactor all the 'H5VL_*_optional' callbacks to move the type of operation out

of the va_list, so it's at least possible for another connector to know what
the operation is and decide whether to implement it or not.

Added a new VOL sub-class called "introspect" where callbacks that report
information about the connector or container can be placed.  Added an
'opt_query' callback to this sub-class, for a connector to report back
to the library whether a particular optional callback operation is supported.
Also added a 'get_conn_cls' introspection callback, to retrieve the H5VL_class_t
of a connector (either the "current" connector, H5VL_GET_CONN_LVL_CURR, or
the terminal connector, H5VL_GET_CONN_LVL_TERM).

Moved the "post open" operation from a file 'specific' operation to a file
'optional' operation, now that it's possible to detect (with the 'opt_query'
introspection callback) whether a VOL connector implements an optional
operation, without just returning an error.

Added new internal VOL helper routines: H5VL_object_is_native, to determine
if an object is in (or is a) native file, and H5VL_file_is_same, to determine
if two objects are in (or are) the same terminal VOL connector's container.
(And moved the special handling for FILE_IS_EQUAL operation out of internal VOL
callback routine into H5VL_file_is_same)

Made new dataset 'get' operation for H5Dvlen_get_buf_size, aligning it better
with other 'get' operations in API.

Fixed several issues with pass-through connectors, which are now passing the
'make check-passthrough-vol' tests again.

A bunch of warning and style cleanups as well.

1 files changed, 35 insertions, 3 deletions

diff --git a/src/H5VLnative.c b/src/H5VLnative.c
index 78eaee4..0a3dacb 100644
--- a/src/H5VLnative.c
+++ b/src/H5VLnative.c
@@ -31,7 +31,7 @@ static hid_t H5VL_NATIVE_ID_g = H5I_INVALID_HID;
 static herr_t H5VL__native_term(void);
 
 /* Native VOL connector class struct */
-static H5VL_class_t H5VL_native_cls_g = {
+static const H5VL_class_t H5VL_native_cls_g = {
     H5VL_NATIVE_VERSION,                            /* version      */
     H5VL_NATIVE_VALUE,                              /* value        */
     H5VL_NATIVE_NAME,                               /* name         */
@@ -112,6 +112,10 @@ static H5VL_class_t H5VL_native_cls_g = {
         H5VL__native_object_specific,               /* specific     */
         H5VL__native_object_optional                /* optional     */
     },
+    {   /* introspect_cls */
+        H5VL__native_introspect_get_conn_cls,       /* get_conn_cls */
+        H5VL__native_introspect_opt_query,          /* opt_query    */
+    },
     {   /* request_cls */
         NULL,                                       /* wait         */
         NULL,                                       /* notify       */
@@ -148,8 +152,8 @@ H5VL_native_register(void)
     FUNC_ENTER_NOAPI(H5I_INVALID_HID)
 
     /* Register the native VOL connector, if it isn't already */
-    if(NULL == H5I_object_verify(H5VL_NATIVE_ID_g, H5I_VOL))
-        if((H5VL_NATIVE_ID_g = H5VL_register_connector((const H5VL_class_t *)&H5VL_native_cls_g, TRUE, H5P_DEFAULT)) < 0)
+    if(H5I_INVALID_HID == H5VL_NATIVE_ID_g)
+        if((H5VL_NATIVE_ID_g = H5VL_register_connector(&H5VL_native_cls_g, TRUE, H5P_DEFAULT)) < 0)
             HGOTO_ERROR(H5E_VOL, H5E_CANTINSERT, H5I_INVALID_HID, "can't create ID for native VOL connector")
 
     /* Set return value */
@@ -180,3 +184,31 @@ H5VL__native_term(void)
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5VL__native_term() */
 
+
+/*---------------------------------------------------------------------------
+ * Function:    H5VL__native_introspect_get_conn_cls
+ *
+ * Purpose:     Query the connector class.
+ *
+ * Note:        This routine is in this file so that it can return the address
+ *              of the staticly declared class struct.
+ *
+ * Returns:     SUCCEED (Can't fail)
+ *
+ *---------------------------------------------------------------------------
+ */
+herr_t
+H5VL__native_introspect_get_conn_cls(void H5_ATTR_UNUSED *obj,
+    H5VL_get_conn_lvl_t H5_ATTR_UNUSED lvl, const H5VL_class_t **conn_cls)
+{
+    FUNC_ENTER_PACKAGE_NOERR
+
+    /* Sanity check */
+    HDassert(conn_cls);
+
+    /* Retrieve the native VOL connector class */
+    *conn_cls = &H5VL_native_cls_g;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5VL__native_introspect_get_conn_cls() */
+