[svn-r13135] Continuing code cleanup.

Moved SOHM table version out of table encoding and completely into superblock.
This is a file format change.
Added test that extends shared dataspaces.  Dynamically allocate arrays in
shared message cache code.  Clean up comments.

Tested on windows, kagiso, smirom.

12 files changed, 292 insertions, 146 deletions

diff --git a/src/H5F.c b/src/H5F.c
index 847d912..cb809e0 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -895,7 +895,7 @@ static H5F_t *
 H5F_new(H5F_file_t *shared, hid_t fcpl_id, hid_t fapl_id, H5FD_t *lf)
 {
     H5F_t	*f = NULL, *ret_value;
-    unsigned    sohm_indexes; /* JAMES: necessary? */
+    unsigned    sohm_indexes;
     unsigned    super_vers = HDF5_SUPERBLOCK_VERSION_DEF;
     H5P_genplist_t *plist;              /* Property list */
 
@@ -917,7 +917,7 @@ H5F_new(H5F_file_t *shared, hid_t fcpl_id, hid_t fapl_id, H5FD_t *lf)
 	f->shared->base_addr = HADDR_UNDEF;
 	f->shared->freespace_addr = HADDR_UNDEF;
 	f->shared->sohm_addr = HADDR_UNDEF;
-	f->shared->sohm_vers = 0;
+	f->shared->sohm_vers = HDF5_SHAREDHEADER_VERSION;
 	f->shared->sohm_nindexes = 0;
 	f->shared->driver_addr = HADDR_UNDEF;
         f->shared->lf = lf;
@@ -954,6 +954,8 @@ H5F_new(H5F_file_t *shared, hid_t fcpl_id, hid_t fapl_id, H5FD_t *lf)
          */
         if(H5P_get(plist, H5F_CRT_SHMSG_NINDEXES_NAME, &sohm_indexes)<0)
             HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get number of SOHM indexes")
+        HDassert(sohm_indexes < 255);
+        f->shared->sohm_nindexes = sohm_indexes;
 
         if(sohm_indexes > 0) {
             super_vers= HDF5_SUPERBLOCK_VERSION_2; /* Super block version 2 */
@@ -1249,9 +1251,7 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id, hid_t d
     unsigned            tent_flags;         /*tentative flags               */
     H5FD_class_t       *drvr;               /*file driver class info        */
     H5P_genplist_t     *a_plist;            /*file access property list     */
-    H5P_genplist_t     *c_plist;            /*file access property list     */
     H5F_close_degree_t  fc_degree;          /*file close degree             */
-    unsigned            num_sohm_indexes;   /*number of SOHM indexes        */
     H5F_t              *ret_value;          /*actual return value           */
 
     FUNC_ENTER_NOAPI(H5F_open, NULL)
@@ -1381,19 +1381,15 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id, hid_t d
         if(H5F_init_superblock(file, dxpl_id) == 0)
             HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to allocate file superblock")
 
-         /* Create the Shared Object Header Message table and register it with the
-          * metadata cache */
-         /* JAMES: hack.  Should check f->shared directly? */
-        if(NULL == (c_plist = H5P_object_verify(fcpl_id,H5P_FILE_CREATE)))
-            HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, NULL, "can't find object for ID");
+        /* Create the Shared Object Header Message table and register it with the
+         * metadata cache, if this file supports shared messages */
+        if(file->shared->sohm_nindexes > 0) {
+            H5P_genplist_t     *c_plist;            /*file creation property list     */
+            if(NULL == (c_plist = H5P_object_verify(fcpl_id,H5P_FILE_CREATE)))
+                HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, NULL, "can't find object for ID");
 
-        if(H5P_get(c_plist, H5F_CRT_SHMSG_NINDEXES_NAME, &num_sohm_indexes)<0)
-            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get SOHM information")
-
-        if(num_sohm_indexes > 0)
-        {
-          if(H5SM_init(file, c_plist, dxpl_id) <0)
-              HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create SOHM table")
+            if(H5SM_init(file, c_plist, dxpl_id) <0)
+                HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create SOHM table")
         }
 
         /* Create and open the root group */
diff --git a/src/H5Oattr.c b/src/H5Oattr.c
index 1358147..037239f 100644
--- a/src/H5Oattr.c
+++ b/src/H5Oattr.c
@@ -366,11 +366,7 @@ H5O_attr_encode(H5F_t *f, uint8_t *p, const void *mesg)
     UINT16ENCODE(p, attr->dt_size);
     UINT16ENCODE(p, attr->ds_size);
 
-    /*
-     * Encode the character encoding used for the attribute's name
-     * Also add several "reserved" fields to pad to 16 bytes.
-     */
-    /* JAMES: only do this if flag says to? */
+    /* The character encoding for the attribute's name, in later versions */
     if(version >= H5O_ATTR_VERSION_3)
         *p++ = attr->encoding;
 
@@ -873,7 +869,6 @@ H5O_attr_copy_file(H5F_t *file_src, const H5O_msg_class_t UNUSED *mesg_type,
     } /* end if */
 
     /* Copy the dataspace for the attribute */
-	/* JAMES: does this need to be copy_file? */
     attr_dst->ds = H5S_copy(attr_src->ds, FALSE);
     HDassert(attr_dst->ds);
 
diff --git a/src/H5Ocopy.c b/src/H5Ocopy.c
index df8fe01..4e457ac 100644
--- a/src/H5Ocopy.c
+++ b/src/H5Ocopy.c
@@ -579,22 +579,19 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
 
     current_pos = oh_dst->chunk[0].image;
 
-    /* Copy the message header.  Most of this will be overwritten when
-     * the header is flushed to disk, but later versions have a
-     * magic number that isn't.
+    /* Copy the header.  Most of this (number of messages, etc.) will be
+     * overwritten when the header is flushed to disk, but later versions have
+     * a magic number that isn't.
      */
     HDmemcpy(current_pos, oh_src->chunk[0].image,
             (size_t)(H5O_SIZEOF_HDR_OH(oh_dst) - H5O_SIZEOF_CHKSUM_OH(oh_dst)));
     current_pos += H5O_SIZEOF_HDR_OH(oh_dst) - H5O_SIZEOF_CHKSUM_OH(oh_dst);
 
-    /* JAMES: include this in loop above?  Doesn't take deleted messages
-     * into account
-     */
     /* Copy each message that wasn't dirtied above */
     null_msgs = 0;
     for(mesgno = 0; mesgno < oh_dst->nmesgs; mesgno++) {
         /* Skip any deleted or NULL messages in the source unless the
-         * preserve_null flag is set
+         * preserve_null flag is set.
          */
         if(FALSE == cpy_info->preserve_null) {
             while(deleted[mesgno + null_msgs]) {
diff --git a/src/H5Ofill.c b/src/H5Ofill.c
index 78b5c77..73732b2 100644
--- a/src/H5Ofill.c
+++ b/src/H5Ofill.c
@@ -634,7 +634,6 @@ H5O_fill_new_free (void *mesg)
 
     HDassert(mesg);
 
-    /* JAMES: should this free the O_loc? */
     H5FL_FREE(H5O_fill_new_t, mesg);
 
     FUNC_LEAVE_NOAPI(SUCCEED)
diff --git a/src/H5Omessage.c b/src/H5Omessage.c
index bcb3e6e..e1ae146 100644
--- a/src/H5Omessage.c
+++ b/src/H5Omessage.c
@@ -441,11 +441,13 @@ H5O_msg_write_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
          * though, and that the library doesn't try to reset the current
          * message like it would in a normal overwrite (this message is
          * realy a shared pointer, not a real message).
-         * JAMES: will this break if a shared message is overwritten with a larger
-         * non-shared message?
+         *
+         * Note that this only works when shared messages are replaced by other
+         * shared messages.  Currently, messages can't shrink once they've
+         * been written to object headers so this is a safe assumption (for
+         * now).
          */
-        HDassert(H5O_msg_is_shared(type->id, mesg) > 0); /* JAMES: this should work with
-                                                      * replacement messages that aren't shared, too. */
+        HDassert(H5O_msg_is_shared(type->id, mesg) > 0);
 
         /* Extract shared message info from current message */
         if(NULL == H5O_msg_get_share(type->id, mesg, &sh_mesg))
@@ -2007,9 +2009,10 @@ done:
  *
  * Purpose:     Calls a message's delete callback.
  *
- *              JAMES: this is mostly redundant with H5O_delete_mesg below,
+ *              This is mostly redundant with H5O_delete_mesg below,
  *              but H5O_delete_mesg only works on messages in object headers
- *              (i.e., not shared messages).
+ *              (while the shared message code needs to delete messages in
+ *              the heap).
  *
  * Return:      Success:        Non-negative
  *              Failure:        Negative
@@ -2084,11 +2087,10 @@ H5O_delete_mesg(H5F_t *f, hid_t dxpl_id, H5O_mesg_t *mesg, hbool_t adj_link)
                 HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "unable to decode message")
         } /* end if */
 
-        /* Check if this message needs to be removed from the SOHM table */
-        /* JAMES: there should be a callback, maybe in H5O_shared_delete, to fiddle w/ the ref. count.
-        * We shouldn't need to do a search in the SOHM table on delete. */
+        /* Check if this message needs to be removed from the SOHM table if
+         * it's a shared message.
+         */
         if(type == H5O_MSG_SHARED) {
-            /* The native message here is actually a shared message.    */
             if(H5SM_try_delete(f, dxpl_id, mesg->type->id, mesg->native) < 0)
                 HGOTO_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL, "unable to delete message from SOHM table")
         } /* end if */
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index 2d555e8..f40d28e 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -135,11 +135,14 @@ typedef struct H5O_copy_t {
  * Shared object message.
  * This needs to go first because other messages can be shared and
  * include a H5O_shared_t struct
+ * The oloc shouldn't ever be holding open a file; if it ever is (if
+ * H5O_loc_hold_file was ever called on it) it won't be closed properly,
+ * since shared messages don't close their olocs.
  */
 typedef struct H5O_shared_t {
     unsigned flags;             /* flags describing how message is shared */
     union {
-        H5O_loc_t	oloc;		/*object location info		     */
+        H5O_loc_t	oloc;		/* object location info		     */
         H5SM_fheap_id_t heap_id;        /* ID within the SOHM heap           */
     } u;
 } H5O_shared_t;
diff --git a/src/H5Oshared.c b/src/H5Oshared.c
index eef0bd8..d665742 100644
--- a/src/H5Oshared.c
+++ b/src/H5Oshared.c
@@ -207,8 +207,7 @@ done:
  *              reference count is stored in the file-wide shared message
  *              index and is changed in a different place in the code.
  *
- * Return:	Success:	New link count
- *
+ * Return:	Success:	New link count, or 1 for messages in heap
  *		Failure:	Negative
  *
  * Programmer:	Quincey Koziol
@@ -245,8 +244,11 @@ H5O_shared_link_adj(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared, int adj
     }
     else
     {
+        /* Messages in the heap don't have file object ref counts; they
+         * return 1 as a dummy value.
+         */
         HDassert(shared->flags & H5O_SHARED_IN_HEAP_FLAG);
-        ret_value = 1; /* JAMES temp refcount*/
+        ret_value = 1;
     }
 
 done:
diff --git a/src/H5SM.c b/src/H5SM.c
index 40e47c7..94d1d67 100755
--- a/src/H5SM.c
+++ b/src/H5SM.c
@@ -157,10 +157,6 @@ H5SM_init(H5F_t *f, H5P_genplist_t * fc_plist, hid_t dxpl_id)
      */
     HDassert(num_indexes < 256);
     table->num_indexes = num_indexes;
-    table->version = H5SM_MASTER_TABLE_VERSION;
-
-    f->shared->sohm_nindexes = table->num_indexes;
-    f->shared->sohm_vers = table->version;
 
     /* Check that list and btree cutoffs make sense.  There can't be any
      * values greater than the list max but less than the btree min; the
@@ -463,9 +459,6 @@ H5SM_create_index(H5F_t *f, H5SM_index_header_t *header, hid_t dxpl_id)
     }
 
     /* Create a heap to hold the shared messages that the list or B-tree will index */
-    /* JAMES: this should happen first, so that the list/btree size can scale depending
-     * on how big a heap pointer is.
-     */
     HDmemset(&fheap_cparam, 0, sizeof(fheap_cparam));
     fheap_cparam.managed.width = H5SM_FHEAP_MAN_WIDTH;
     fheap_cparam.managed.start_block_size = H5SM_FHEAP_MAN_START_BLOCK_SIZE;
@@ -828,6 +821,7 @@ H5SM_try_share(H5F_t *f, hid_t dxpl_id, unsigned type_id, void *mesg)
             HGOTO_ERROR(H5E_OHDR, H5E_BADTYPE, FAIL, "can't tell if datatype is immutable")
 
         /* Don't share committed datatypes */
+        /* JAMES: Quincey says this check isn't working! */
         if((tri_ret = H5T_committed((H5T_t*) mesg)) > 0)
             HGOTO_DONE(FALSE)
         else if(tri_ret < 0)
@@ -1421,6 +1415,64 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5SM_message_encode
+ *
+ * Purpose:	Serialize a H5SM_sohm_t struct into a buffer RAW.
+ *
+ * Return:	Non-negative on success
+ *              Negative on failure
+ *
+ * Programmer:	James Laird
+ *              Monday, November 6, 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5SM_message_encode(const H5F_t UNUSED *f, uint8_t *raw, const void *_nrecord)
+{
+    const H5SM_sohm_t *message = (const H5SM_sohm_t *)_nrecord;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5SM_message_encode)
+
+    /* Encode the SOHM's fields */
+    UINT32ENCODE(raw, message->hash);
+    UINT32ENCODE(raw, message->ref_count);
+    UINT64ENCODE(raw, message->fheap_id);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5SM_message_encode */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5SM_message_decode
+ *
+ * Purpose:	Read an encoded SOHM message from RAW into an H5SM_sohm_t struct.
+ *
+ * Return:	Non-negative on success
+ *              Negative on failure
+ *
+ * Programmer:	James Laird
+ *              Monday, November 6, 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5SM_message_decode(const H5F_t UNUSED *f, const uint8_t *raw, void *_nrecord)
+{
+    H5SM_sohm_t *message = (H5SM_sohm_t *)_nrecord;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5SM_message_decode)
+
+    /* Encode the SOHM's fields */
+    UINT32DECODE(raw, message->hash);
+    UINT32DECODE(raw, message->ref_count);
+    UINT64DECODE(raw, message->fheap_id);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5SM_message_decode */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5SM_reconstitute
  *
  * Purpose:     Reconstitute a shared object header message structure from
diff --git a/src/H5SMbtree2.c b/src/H5SMbtree2.c
index c6b0aa2..1b5cb98 100755
--- a/src/H5SMbtree2.c
+++ b/src/H5SMbtree2.c
@@ -244,65 +244,6 @@ H5SM_btree_retrieve(void *udata, const void *native)
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5SM_message_encode
- *
- * Purpose:	Serialize the SOHM message.
- *
- * Return:	Non-negative on success
- *              Negative on failure
- *
- * Programmer:	James Laird
- *              Monday, November 6, 2006
- *
- *-------------------------------------------------------------------------
- */
-herr_t
-H5SM_message_encode(const H5F_t UNUSED *f, uint8_t *raw, const void *_nrecord)
-{
-    const H5SM_sohm_t *message = (const H5SM_sohm_t *)_nrecord;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5SM_message_encode)
-
-    /* Encode the SOHM's fields */
-    UINT32ENCODE(raw, message->hash);
-    UINT32ENCODE(raw, message->ref_count);
-    UINT64ENCODE(raw, message->fheap_id);
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5SM_message_encode */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5SM_message_decode
- *
- * Purpose:	Read an encoded SOHM message into an H5SM_sohm_t struct.
- *
- * Return:	Non-negative on success
- *              Negative on failure
- *
- * Programmer:	James Laird
- *              Monday, November 6, 2006
- *
- *-------------------------------------------------------------------------
- */
-/* JAMES: move to H5SM.c or something */
-herr_t
-H5SM_message_decode(const H5F_t UNUSED *f, const uint8_t *raw, void *_nrecord)
-{
-    H5SM_sohm_t *message = (H5SM_sohm_t *)_nrecord;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5SM_message_decode)
-
-    /* Encode the SOHM's fields */
-    UINT32DECODE(raw, message->hash);
-    UINT32DECODE(raw, message->ref_count);
-    UINT64DECODE(raw, message->fheap_id);
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5SM_message_decode */
-
-
-/*-------------------------------------------------------------------------
  * Function:	H5SM_btree_debug
  *
  * Purpose:	Print debugging information for a H5SM_sohm_t.
diff --git a/src/H5SMcache.c b/src/H5SMcache.c
index c79c7d6..1031a5c 100644
--- a/src/H5SMcache.c
+++ b/src/H5SMcache.c
@@ -104,6 +104,7 @@ const H5AC_class_t H5AC_SOHM_LIST[1] = {{
 static herr_t
 H5SM_flush_table(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_master_table_t *table)
 {
+    uint8_t *buf=NULL;                /* Temporary buffer */
     herr_t          ret_value=SUCCEED;
 
     FUNC_ENTER_NOAPI(H5SM_flush_table, FAIL)
@@ -114,7 +115,6 @@ H5SM_flush_table(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_ma
     HDassert(table);
 
     if(table->cache_info.is_dirty) {
-        uint8_t *buf;                /* Temporary buffer */
         uint8_t  *p;                 /* Pointer into raw data buffer */
         size_t	 size;               /* Header size on disk */
         uint32_t computed_chksum;    /* Computed metadata checksum value */
@@ -134,8 +134,6 @@ H5SM_flush_table(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_ma
         HDmemcpy(p, H5SM_TABLE_MAGIC, (size_t)H5SM_TABLE_SIZEOF_MAGIC);
         p += H5SM_TABLE_SIZEOF_MAGIC;
 
-        *p++ = table->version; /* Version */
-
         /* Encode each index header */
         for(x=0; x<table->num_indexes; ++x) {
             *p++ = H5SM_LIST_VERSION;   /* Encode version for this list. */
@@ -161,8 +159,6 @@ H5SM_flush_table(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_ma
 
 	table->cache_info.is_dirty = FALSE;
 
-        /* Free buffer */
-        H5MM_xfree(buf);
     } /* end if */
 
     if(destroy)
@@ -170,6 +166,9 @@ H5SM_flush_table(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_ma
 	    HGOTO_ERROR(H5E_SOHM, H5E_CANTFREE, FAIL, "unable to destroy sohm table")
 
 done:
+    /* Free buffer if allocated */
+    buf = H5MM_xfree(buf);
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5SM_flush_table */
 
@@ -208,7 +207,6 @@ H5SM_load_table(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1
 
     /* Read number of indexes and version from file superblock */
     table->num_indexes = f->shared->sohm_nindexes;
-    table->version = f->shared->sohm_vers;
 
     HDassert(addr == f->shared->sohm_addr);
     HDassert(addr != HADDR_UNDEF);
@@ -219,8 +217,8 @@ H5SM_load_table(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1
      */
     table_size = H5SM_TABLE_SIZE(f) + (table->num_indexes * H5SM_INDEX_HEADER_SIZE(f));
 
-    /* Allocate temporary buffer */
-    if(NULL == (buf = HDmalloc(table_size)))
+    /* Allocate temporary buffer */ /* JAMES: FL_BLK? */
+    if(NULL == (buf = H5MM_malloc(table_size)))
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
     /* Read header from disk */
@@ -234,10 +232,6 @@ H5SM_load_table(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1
 	HGOTO_ERROR(H5E_SOHM, H5E_CANTLOAD, NULL, "bad SOHM table signature");
     p += H5SM_TABLE_SIZEOF_MAGIC;
 
-    /* Version number */
-    if (table->version != *p++)
-        HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "wrong SOHM table version number")
-
     /* Don't count the checksum in the table size yet, since it comes after
      * all of the index headers
      */
@@ -278,9 +272,8 @@ H5SM_load_table(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1
     ret_value = table;
 
 done:
-    /* Free buffer if it was allocated */
-    if(buf)
-        HDfree(buf);
+    /* Free buffer if allocated */
+    buf = H5MM_xfree(buf);
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5SM_load_table */ 
@@ -397,6 +390,7 @@ H5SM_table_size(const H5F_t *f, const H5SM_master_table_t *table, size_t *size_p
 static herr_t
 H5SM_flush_list(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_list_t *list)
 {
+    uint8_t *buf=NULL;               /* Temporary buffer */
     herr_t          ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI(H5SM_flush_list, FAIL)
@@ -408,18 +402,19 @@ H5SM_flush_list(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_lis
     HDassert(list->header);
 
     if (list->cache_info.is_dirty) {
-        uint8_t buf[H5F_LISTBUF_SIZE];  /* Temporary buffer */   /* JAMES Do I need to use H5FL_BLK_MALLOC instead? */
         uint8_t *p;                 /* Pointer into raw data buffer */
         size_t	size;               /* Header size on disk */
         uint32_t computed_chksum;   /* Computed metadata checksum value */
         hsize_t x;
         hsize_t mesgs_written;
 
-        /* JAMES: consider only writing as many messages as necessary, and then adding a
-         * blank "end of list" message or something?
-         */
         size = H5SM_LIST_SIZE(f, list->header->num_messages);
 
+        /* Allocate temporary buffer */
+        /* JAMES: is BLK_MALLOC somehow better for this? */
+        if(NULL == (buf = H5MM_malloc(size)))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
+
         /* Encode the list */
         p = buf;
 
@@ -431,12 +426,11 @@ H5SM_flush_list(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_lis
         mesgs_written = 0;
         for(x=0; x<list->header->list_max && mesgs_written < list->header->num_messages; x++) {
             if(list->messages[x].ref_count > 0) {
-              /* JAMES: use H5SM_message_encode here */
-              UINT32ENCODE(p, list->messages[x].hash);  /* Read the hash value for this message */
-              UINT32ENCODE(p, list->messages[x].ref_count);  /* Read the reference count for this message */
-              UINT64ENCODE(p, list->messages[x].fheap_id); /* Get the heap ID for the message */
+                if(H5SM_message_encode(f, p, &(list->messages[x]))< 0)
+                    HGOTO_ERROR(H5E_SOHM, H5E_CANTFLUSH, FAIL, "unable to write shared message to disk")
 
-              ++mesgs_written;
+                p+=H5SM_SOHM_ENTRY_SIZE(f);
+                ++mesgs_written;
             }
         }
 
@@ -459,6 +453,9 @@ H5SM_flush_list(H5F_t *f, hid_t dxpl_id, hbool_t destroy, haddr_t addr, H5SM_lis
 	    HGOTO_ERROR(H5E_SOHM, H5E_CANTFREE, FAIL, "unable to destroy list")
 
 done:
+    /* Free buffer if allocated */
+    buf = H5MM_xfree(buf);
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5SM_flush_list */
 
@@ -509,7 +506,7 @@ H5SM_load_list(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1,
 
     /* Allocate temporary buffer */
     /* JAMES: is BLK_MALLOC somehow better for this? */
-    if(NULL == (buf = HDmalloc(size)))
+    if(NULL == (buf = H5MM_malloc(size)))
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
     /* Read list from disk */
@@ -519,15 +516,15 @@ H5SM_load_list(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1,
 
     /* Check magic number */
     if(HDmemcmp(p, H5SM_LIST_MAGIC, (size_t)H5SM_LIST_SIZEOF_MAGIC))
-	HGOTO_ERROR(H5E_SOHM, H5E_CANTLOAD, NULL, "bad SOHM list signature");
+        HGOTO_ERROR(H5E_SOHM, H5E_CANTLOAD, NULL, "bad SOHM list signature");
     p += H5SM_LIST_SIZEOF_MAGIC;
 
     /* Read messages into the list array */
     for(x=0; x<header->num_messages; x++)
     {
-        UINT32DECODE(p, list->messages[x].hash);  /* Read the hash value for this message */
-        UINT32DECODE(p, list->messages[x].ref_count);  /* Read the reference count for this message */
-        UINT64DECODE(p, list->messages[x].fheap_id); /* Get the heap ID for the message */
+        if(H5SM_message_decode(f, p, &(list->messages[x])) < 0)
+            HGOTO_ERROR(H5E_SOHM, H5E_CANTLOAD, NULL, "can't decode shared message");
+        p += H5SM_SOHM_ENTRY_SIZE(f);
     }
 
     /* Read in checksum */
@@ -553,8 +550,8 @@ H5SM_load_list(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void UNUSED *udata1,
 
     ret_value = list;
 done:
-    if(buf)
-        HDfree(buf);
+    /* Free buffer if allocated */
+    buf = H5MM_xfree(buf);
 
     if(ret_value == NULL) {
         if(list) {
diff --git a/src/H5SMpkg.h b/src/H5SMpkg.h
index b771893..37a40a1 100755
--- a/src/H5SMpkg.h
+++ b/src/H5SMpkg.h
@@ -37,14 +37,11 @@
 #define H5SM_TABLE_SIZEOF_MAGIC 4
 #define H5SM_SIZEOF_CHECKSUM 4
 
-#define H5SM_MASTER_TABLE_VERSION	0	/* Version of the Shared Object Header Message Master Table*/
-
 #define H5SM_SOHM_ENTRY_SIZE(f) (4  /* Hash value */                         \
          + 4                        /* reference count*/                     \
          + sizeof(H5SM_fheap_id_t)) /* size of heap ID on disk */
 
 #define H5SM_TABLE_SIZE(f) ( H5SM_TABLE_SIZEOF_MAGIC                         \
-         + 1                                   /* Table version */           \
          + H5SM_SIZEOF_CHECKSUM)               /* Checksum */
 
 #define H5SM_INDEX_HEADER_SIZE(f) (1 /* Whether index is a list or B-tree */ \
@@ -145,7 +142,6 @@ typedef struct {
     /* Information for H5AC cache functions, _must_ be first field in structure */
     H5AC_info_t cache_info;
 
-    unsigned version;               /* Version of the table struct */
     uint8_t num_indexes;            /* Number of indexes */
     H5SM_index_header_t *indexes;   /* Array of num_indexes indexes */
 } H5SM_master_table_t;
diff --git a/test/tsohm.c b/test/tsohm.c
index 9fcbf41..4fe2d8b 100644
--- a/test/tsohm.c
+++ b/test/tsohm.c
@@ -3038,6 +3038,172 @@ test_sohm_extlink(void)
 }
 
 
+/*-------------------------------------------------------------------------
+ * Function:    test_sohm_extend_dset_helper
+ *
+ * Purpose:     Tests extending a dataset's dataspace.
+ *
+ * Programmer:  James Laird
+ *              Wednesday, January 10, 2007
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static void test_sohm_extend_dset_helper(hid_t fcpl_id)
+{
+    hid_t file_id = -1;
+    hid_t space_id = -1;
+    hid_t dcpl_id = -1;
+    hid_t dset_id = -1;
+    hsize_t dims1[] = {1, 2};
+    hsize_t max_dims1[] = {H5S_UNLIMITED, 2};
+    hsize_t dims2[] = {5, 2};
+    long data[10] = {0};
+    herr_t ret;
+
+    /* Create file */
+    file_id = H5Fcreate(FILENAME, H5F_ACC_TRUNC, fcpl_id, H5P_DEFAULT);
+    CHECK_I(file_id, "H5Fcreate");
+
+    /* Create property list with chunking */
+    dcpl_id = H5Pcreate(H5P_DATASET_CREATE);
+    CHECK_I(dcpl_id, "H5Pcreate");
+    ret = H5Pset_chunk(dcpl_id, 2, dims1);
+    CHECK_I(ret, "H5Pset_chunk");
+
+    /* Create a dataspace and a dataset*/
+    space_id = H5Screate_simple(2, dims1, max_dims1);
+    CHECK_I(space_id, "H5Screate_simple");
+    dset_id = H5Dcreate(file_id, "dataset", H5T_NATIVE_LONG, space_id, dcpl_id);
+    CHECK_I(dset_id, "H5Dcreate");
+
+    /* Extend the dataset */
+    ret = H5Dextend(dset_id, dims2);
+    CHECK_I(ret, "H5Dclose");
+
+    /* Write some garbage to the dataset */
+    ret = H5Dwrite(dset_id, H5T_NATIVE_LONG, H5S_ALL, H5S_ALL, H5P_DEFAULT, data);
+    CHECK_I(ret, "H5Dwrite");
+
+    /* Close the dataset and file */
+    ret = H5Dclose(dset_id);
+    CHECK_I(ret, "H5Dclose");
+    ret = H5Fclose(file_id);
+    CHECK_I(ret, "H5Fclose");
+
+
+    /* Create a new dataset in a new file, but this time close it before
+     * extending it to make sure that the old dataspace is written to
+     * disk.
+     */
+    file_id = H5Fcreate(FILENAME, H5F_ACC_TRUNC, fcpl_id, H5P_DEFAULT);
+    CHECK_I(file_id, "H5Fcreate");
+    dset_id = H5Dcreate(file_id, "dataset", H5T_NATIVE_LONG, space_id, dcpl_id);
+    CHECK_I(dset_id, "H5Dcreate");
+
+    /* Close and re-open file and dataset */
+    ret = H5Dclose(dset_id);
+    CHECK_I(ret, "H5Dclose");
+    ret = H5Fclose(file_id);
+    CHECK_I(ret, "H5Fclose");
+
+    file_id = H5Fopen(FILENAME, H5F_ACC_RDWR, H5P_DEFAULT);
+    CHECK_I(file_id, "H5Fopen");
+    dset_id = H5Dopen(file_id, "dataset");
+    CHECK_I(dset_id, "H5Dopen");
+
+    /* Extend the dataset */
+    ret = H5Dextend(dset_id, dims2);
+    CHECK_I(ret, "H5Dclose");
+
+    /* Write some garbage to the dataset */
+    ret = H5Dwrite(dset_id, H5T_NATIVE_LONG, H5S_ALL, H5S_ALL, H5P_DEFAULT, data);
+    CHECK_I(ret, "H5Dwrite");
+
+    /* Close the dataset and file */
+    ret = H5Dclose(dset_id);
+    CHECK_I(ret, "H5Dclose");
+    ret = H5Fclose(file_id);
+    CHECK_I(ret, "H5Fclose");
+
+    /* Cleanup */
+    ret = H5Sclose(space_id);
+    CHECK_I(ret, "H5Sclose");
+    ret = H5Pclose(dcpl_id);
+    CHECK_I(ret, "H5Pclose");
+}
+
+
+/*-------------------------------------------------------------------------
+ * Function:    test_sohm_extend_dset
+ *
+ * Purpose:     Test extended shared dataspaces.  An extended dataset's
+ *              dataspace will change, possibly confusing the shared message
+ *              code.
+ *
+ * Programmer:  James Laird
+ *              Wednesday, January 10, 2007
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static void
+test_sohm_extend_dset(void)
+{
+    hid_t fcpl_id = -1;
+    herr_t ret;
+
+    /* Create fcpl */
+    fcpl_id = H5Pcreate(H5P_FILE_CREATE);
+    CHECK_I(fcpl_id, "H5Pcreate");
+
+    /* Test extending datasets with different FCPLs */
+    ret = H5Pset_shared_mesg_nindexes(fcpl_id, 1);
+    CHECK_I(ret, "H5Pset_shared_mesg_nindexes");
+
+    /* No shared messages */
+    test_sohm_extend_dset_helper(fcpl_id);
+
+
+    /* Only dataspaces */
+    ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_SDSPACE_FLAG, 16);
+    CHECK_I(ret, "H5Pset_shared_mesg_index");
+
+    test_sohm_extend_dset_helper(fcpl_id);
+
+    /* All messages */
+    ret = H5Pset_shared_mesg_nindexes(fcpl_id, 1);
+    CHECK_I(ret, "H5Pset_shared_mesg_nindexes");
+    ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_ALL_FLAG, 16);
+    CHECK_I(ret, "H5Pset_shared_mesg_index");
+
+    test_sohm_extend_dset_helper(fcpl_id);
+
+
+    /* All messages in lists */
+    ret = H5Pset_shared_mesg_phase_change(fcpl_id, 100, 50);
+    CHECK_I(ret, "H5Pset_shared_mesg_phase_change");
+
+    test_sohm_extend_dset_helper(fcpl_id);
+
+
+    /* All messages in lists converted to B-trees */
+    ret = H5Pset_shared_mesg_phase_change(fcpl_id, 1, 0);
+    CHECK_I(ret, "H5Pset_shared_mesg_phase_change");
+
+    test_sohm_extend_dset_helper(fcpl_id);
+
+
+    /* All messages in B-trees */
+    ret = H5Pset_shared_mesg_phase_change(fcpl_id, 0, 0);
+    CHECK_I(ret, "H5Pset_shared_mesg_phase_change");
+
+    test_sohm_extend_dset_helper(fcpl_id);
+}
+
+
 
 /****************************************************************
 ** 
@@ -3061,7 +3227,7 @@ test_sohm(void)
     test_sohm_delete_revert();  /* Test that a file with SOHMs becomes an
                                  * empty file again when they are deleted. */
     test_sohm_extlink();        /* Test SOHMs when external links are used */
-    /* JAMES: try extending dataspaces, overwriting attributes */
+    test_sohm_extend_dset();    /* Test extending shared datasets */
 
 } /* test_sohm() */