[svn-r13497] Description:

        Move ref. count of # of links to an object out of the object header's
prefix and make it a header message instead (since it's a "rare" occurence),
eliminating some more space for each object in the file.

        Inserting this "ref. count" message exposed a flaw in the library's
mechanism for locating a message to promote to another chunk and replace
with a continuation message, which required some additional work to fix.
It's still not completely robust, but it's working for more cases now and
detects failures robustly.

        Reduced the minimum size of an object header chunk to just enough to
contain a header message prefix and continuation message.

Tested on:
	FreeBSD/32 6.2 (duty)

1 files changed, 32 insertions, 2 deletions

diff --git a/src/H5O.c b/src/H5O.c
index d2ff41d..5f3e507 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -103,6 +103,7 @@ const H5O_msg_class_t *const H5O_msg_class_g[] = {
     H5O_MSG_BTREEK,		/*0x0013 Non-default v1 B-tree 'K' values */
     H5O_MSG_DRVINFO,		/*0x0014 Driver info settings		*/
     H5O_MSG_AINFO,		/*0x0015 Attribute information		*/
+    H5O_MSG_REFCOUNT,		/*0x0016 Object's ref. count		*/
 };
 
 /* Header object ID to class mapping */
@@ -989,8 +990,7 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
 	HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "no write intent on file")
 
     /* get header */
-    if(NULL == (oh = H5AC_protect(loc->file, dxpl_id, H5AC_OHDR, loc->addr,
-				   NULL, NULL, H5AC_WRITE)))
+    if(NULL == (oh = H5AC_protect(loc->file, dxpl_id, H5AC_OHDR, loc->addr, NULL, NULL, H5AC_WRITE)))
 	HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to load object header")
 
     /* adjust link count */
@@ -1033,6 +1033,36 @@ H5O_link(const H5O_loc_t *loc, int adjust, hid_t dxpl_id)
         oh_flags |= H5AC__DIRTIED_FLAG;
     } /* end if */
 
+    /* Check for operations on refcount message */
+    if(oh->version > H5O_VERSION_1) {
+        /* Check if the object has a refcount message already */
+        if(oh->has_refcount_msg) {
+            /* Check for removing refcount message */
+            if(oh->nlink <= 1) {
+                if(H5O_msg_remove_real(loc->file, oh, H5O_MSG_REFCOUNT, H5O_ALL, NULL, NULL, TRUE, dxpl_id) < 0)
+                    HGOTO_ERROR(H5E_ATTR, H5E_CANTDELETE, FAIL, "unable to delete refcount message")
+                oh->has_refcount_msg = FALSE;
+            } /* end if */
+            /* Update refcount message with new link count */
+            else {
+                H5O_refcount_t refcount = oh->nlink;
+
+                if(H5O_msg_write_real(loc->file, dxpl_id, oh, H5O_MSG_REFCOUNT, H5O_MSG_FLAG_DONTSHARE, 0, &refcount) < 0)
+                    HGOTO_ERROR(H5E_ATTR, H5E_CANTUPDATE, FAIL, "unable to update refcount message")
+            } /* end else */
+        } /* end if */
+        else {
+            /* Check for adding refcount message to object */
+            if(oh->nlink > 1) {
+                H5O_refcount_t refcount = oh->nlink;
+
+                if(H5O_msg_append_real(loc->file, dxpl_id, oh, H5O_MSG_REFCOUNT, H5O_MSG_FLAG_DONTSHARE, 0, &refcount) < 0)
+                    HGOTO_ERROR(H5E_ATTR, H5E_CANTINSERT, FAIL, "unable to create new refcount message")
+                oh->has_refcount_msg = TRUE;
+            } /* end if */
+        } /* end else */
+    } /* end if */
+
     /* Set return value */
     ret_value = oh->nlink;