[svn-r13232] Description:

	Remove the "scaffolding" for shared message method invocation and
simplify the way shared messages are dealt with in general.

Tested on:
	FreeBSD/32 6.2 (duty)
	Mac OS X/32 10.4.8 (amazon)

31 files changed, 621 insertions, 2087 deletions

diff --git a/src/H5Adense.c b/src/H5Adense.c
index 30229f4..b630166 100644
--- a/src/H5Adense.c
+++ b/src/H5Adense.c
@@ -388,7 +388,6 @@ H5A_dense_insert(H5F_t *f, hid_t dxpl_id, const H5O_t *oh, H5A_t *attr)
     H5A_bt2_ud_ins_t udata;             /* User data for v2 B-tree insertion */
     H5HF_t *fheap = NULL;               /* Fractal heap handle for attributes */
     H5HF_t *shared_fheap = NULL;        /* Fractal heap handle for shared header messages */
-    H5O_shared_t sh_mesg;               /* Shared object header message */
     uint8_t attr_buf[H5A_ATTR_BUF_SIZE]; /* Buffer for serializing message */
     void *attr_ptr = NULL;              /* Pointer to serialized message */
     unsigned mesg_flags = 0;            /* Flags for storing message */
@@ -414,7 +413,7 @@ H5A_dense_insert(H5F_t *f, hid_t dxpl_id, const H5O_t *oh, H5A_t *attr)
         htri_t shared_mesg;             /* Should this message be stored in the Shared Message table? */
 
         /* Check if message is already shared */
-        if((shared_mesg = H5O_attr_is_shared(attr)) < 0)
+        if((shared_mesg = H5O_msg_is_shared(H5O_ATTR_ID, attr)) < 0)
             HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "error determining if message is shared")
         else if(shared_mesg > 0)
             /* Mark the message as shared */
@@ -449,12 +448,8 @@ H5A_dense_insert(H5F_t *f, hid_t dxpl_id, const H5O_t *oh, H5A_t *attr)
         /* Sanity check */
         HDassert(attr_sharable);
 
-        /* Get the shared information for the attribute */
-        if(NULL == H5O_attr_get_share(attr, &sh_mesg))
-            HGOTO_ERROR(H5E_ATTR, H5E_BADMESG, FAIL, "can't get shared message")
-
         /* Use heap ID for shared message heap */
-        udata.id = sh_mesg.u.heap_id;
+        udata.id = attr->sh_loc.u.heap_id;
     } /* end if */
     else {
         size_t attr_size;                   /* Size of serialized attribute in the heap */
@@ -805,7 +800,7 @@ H5A_dense_rename(H5F_t *f, hid_t dxpl_id, const H5O_t *oh, const char *old_name,
     HDassert(attr_copy);
 
     /* Check if message is already shared */
-    if((shared_mesg = H5O_attr_is_shared(attr_copy)) < 0)
+    if((shared_mesg = H5O_msg_is_shared(H5O_ATTR_ID, attr_copy)) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "error determining if message is shared")
     else if(shared_mesg > 0) {
         /* Reset shared status of copy */
@@ -823,7 +818,7 @@ H5A_dense_rename(H5F_t *f, hid_t dxpl_id, const H5O_t *oh, const char *old_name,
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINSERT, FAIL, "unable to add to dense storage")
 
     /* Was this attribute shared? */
-    if((shared_mesg = H5O_attr_is_shared(attr_copy)) > 0) {
+    if((shared_mesg = H5O_msg_is_shared(H5O_ATTR_ID, attr_copy)) > 0) {
         hsize_t attr_rc;                /* Attribute's ref count in shared message storage */
 
         /* Retrieve ref count for shared attribute */
diff --git a/src/H5Apkg.h b/src/H5Apkg.h
index 3194494..9ac95cb 100644
--- a/src/H5Apkg.h
+++ b/src/H5Apkg.h
@@ -195,8 +195,6 @@ H5_DLL herr_t H5A_attr_release_table(H5A_attr_table_t *atable);
 H5_DLL herr_t H5O_attr_reset(void *_mesg);
 H5_DLL herr_t H5O_attr_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link);
 H5_DLL herr_t H5O_attr_link(H5F_t *f, hid_t dxpl_id, const void *_mesg);
-H5_DLL void *H5O_attr_get_share(const void *_mesg, H5O_shared_t *sh);
-H5_DLL htri_t H5O_attr_is_shared(const void *_mesg);
 
 /* Attribute operations */
 H5_DLL herr_t H5O_attr_update_shared(H5F_t *f, hid_t dxpl_id, H5A_t *attr, 
diff --git a/src/H5Atest.c b/src/H5Atest.c
index 13d13f1..3c1cfab 100644
--- a/src/H5Atest.c
+++ b/src/H5Atest.c
@@ -102,7 +102,7 @@ H5A_is_shared_test(hid_t attr_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not an attribute")
 
     /* Check if attribute is shared */
-    ret_value = H5O_attr_is_shared(attr);
+    ret_value = H5O_msg_is_shared(H5O_ATTR_ID, attr);
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -135,7 +135,7 @@ H5A_get_shared_rc_test(hid_t attr_id, hsize_t *ref_count)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not an attribute")
 
     /* Sanity check */
-    HDassert(H5O_attr_is_shared(attr));
+    HDassert(H5O_msg_is_shared(H5O_ATTR_ID, attr));
 
     /* Retrieve ref count for shared attribute */
     if(H5SM_get_refcount(attr->oloc.file, H5AC_ind_dxpl_id, H5O_ATTR_ID,
diff --git a/src/H5O.c b/src/H5O.c
index f1b579c..be16c6a 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -88,16 +88,16 @@ const H5O_msg_class_t *const H5O_msg_class_g[] = {
     H5O_MSG_EFL,		/*0x0007 Data storage -- external data files */
     H5O_MSG_LAYOUT,		/*0x0008 Data Layout			*/
 #ifdef H5O_ENABLE_BOGUS
-    H5O_MSG_BOGUS,		/*0x0009 "Bogus"			*/
+    H5O_MSG_BOGUS,		/*0x0009 "Bogus" (for testing)		*/
 #else /* H5O_ENABLE_BOGUS */
-    NULL,			/*0x0009 "Bogus"			*/
+    NULL,			/*0x0009 "Bogus" (for testing)		*/
 #endif /* H5O_ENABLE_BOGUS */
     H5O_MSG_GINFO,		/*0x000A Group Information		*/
     H5O_MSG_PLINE,		/*0x000B Data storage -- filter pipeline */
     H5O_MSG_ATTR,		/*0x000C Attribute list			*/
     H5O_MSG_NAME,		/*0x000D Object name			*/
     H5O_MSG_MTIME,		/*0x000E Object modification date and time */
-    H5O_MSG_SHARED,		/*0x000F Shared header message (shouldn't be in file) */
+    NULL,			/*0x000F UNUSED (used to be "Shared"    */
     H5O_MSG_CONT,		/*0x0010 Object header continuation	*/
     H5O_MSG_STAB,		/*0x0011 Symbol table			*/
     H5O_MSG_MTIME_NEW,		/*0x0012 New Object modification date and time */
@@ -1114,7 +1114,7 @@ H5O_touch_oh(H5F_t *f,
             if(!force)
                 HGOTO_DONE(SUCCEED);        /*nothing to do*/
 
-            size = (H5O_MSG_MTIME_NEW->raw_size)(f, &now);
+            size = (H5O_MSG_MTIME_NEW->raw_size)(f, FALSE, &now);
             if((idx = H5O_alloc(f, dxpl_id, oh, H5O_MSG_MTIME_NEW, size, oh_flags_ptr)) == UFAIL)
                 HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to allocate space for modification time message")
         } /* end if */
diff --git a/src/H5Oattr.c b/src/H5Oattr.c
index 2997705..35c52ef 100644
--- a/src/H5Oattr.c
+++ b/src/H5Oattr.c
@@ -33,12 +33,11 @@ static void *H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const
 static void *H5O_attr_copy(const void *_mesg, void *_dest);
 static size_t H5O_attr_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_attr_free(void *mesg);
-static herr_t H5O_attr_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
-    const void *mesg_src, hbool_t *deleted, const H5O_copy_t *cpy_info, void *udata);
+static herr_t H5O_attr_pre_copy_file(H5F_t *file_src, const void *mesg_src,
+    hbool_t *deleted, const H5O_copy_t *cpy_info, void *udata);
 static void *H5O_attr_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
     void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
     void *udata);
-static herr_t H5O_attr_set_share(void *_mesg, const H5O_shared_t *sh);
 static herr_t H5O_attr_get_crt_index(const void *_mesg, H5O_crt_idx_t *crt_idx);
 static herr_t H5O_attr_set_crt_index(void *_mesg, H5O_crt_idx_t crt_idx);
 static herr_t H5O_attr_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
@@ -58,6 +57,8 @@ static herr_t H5O_attr_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
 #define H5O_SHARED_LINK_REAL		H5O_attr_link
 #define H5O_SHARED_COPY_FILE		H5O_attr_shared_copy_file
 #define H5O_SHARED_COPY_FILE_REAL	H5O_attr_copy_file
+#define H5O_SHARED_DEBUG		H5O_attr_shared_debug
+#define H5O_SHARED_DEBUG_REAL		H5O_attr_debug
 #include "H5Oshared.h"			/* Shared Object Header Message Callbacks */
 
 /* This message derives from H5O message class */
@@ -65,24 +66,23 @@ const H5O_msg_class_t H5O_MSG_ATTR[1] = {{
     H5O_ATTR_ID,		/* message id number            */
     "attribute",		/* message name for debugging   */
     sizeof(H5A_t),		/* native message size          */
-    H5O_attr_shared_decode,		/* decode message               */
-    H5O_attr_shared_encode,		/* encode message               */
+    TRUE,			/* messages are sharable?       */
+    H5O_attr_shared_decode,	/* decode message               */
+    H5O_attr_shared_encode,	/* encode message               */
     H5O_attr_copy,		/* copy the native value        */
-    H5O_attr_shared_size,		/* size of raw message          */
+    H5O_attr_shared_size,	/* size of raw message          */
     H5O_attr_reset,		/* reset method                 */
     H5O_attr_free,	        /* free method			*/
-    H5O_attr_shared_delete,		/* file delete method		*/
-    H5O_attr_shared_link,		/* link method			*/
-    H5O_attr_get_share,		/* get share method		*/
-    H5O_attr_set_share,		/* set share method		*/
+    H5O_attr_shared_delete,	/* file delete method		*/
+    H5O_attr_shared_link,	/* link method			*/
+    H5O_shared_copy,		/* set share method		*/
     NULL,		    	/*can share method		*/
-    H5O_attr_is_shared,		/*is shared method		*/
     H5O_attr_pre_copy_file,	/* pre copy native value to file */
-    H5O_attr_shared_copy_file,		/* copy native value to file    */
+    H5O_attr_shared_copy_file,	/* copy native value to file    */
     NULL,			/* post copy native value to file    */
-    NULL /* H5O_attr_get_crt_index */,	/* get creation index		*/
-    NULL /* H5O_attr_set_crt_index */,	/* set creation index		*/
-    H5O_attr_debug		/* debug the message            */
+    H5O_attr_get_crt_index,	/* get creation index		*/
+    H5O_attr_set_crt_index,	/* set creation index		*/
+    H5O_attr_shared_debug	/* debug the message            */
 }};
 
 /* This is the initial version, which does not have support for shared datatypes */
@@ -132,7 +132,7 @@ H5FL_EXTERN(H5S_extent_t);
     function using malloc() and is returned to the caller.
 --------------------------------------------------------------------------*/
 static void *
-H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags,
+H5O_attr_decode(H5F_t *f, hid_t dxpl_id, unsigned UNUSED mesg_flags,
     const uint8_t *p)
 {
     H5A_t		*attr = NULL;
@@ -263,7 +263,7 @@ done:
  *	Added a version number at the beginning.
  *
  *	Raymond Lu, 8 April 2004
- *	For data space, changed the operation on H5S_simple_t to
+ *	For dataspace, changed the operation on H5S_simple_t to
  *	H5S_extent_t
  *
  *      James Laird, 15 November 2005
@@ -279,9 +279,8 @@ H5O_attr_encode(H5F_t *f, uint8_t *p, const void *mesg)
     unsigned    version;        /* Attribute version */
     hbool_t     type_shared;    /* Flag to indicate that a shared datatype is used for this attribute */
     hbool_t     space_shared;   /* Flag to indicate that a shared dataspace is used for this attribute */
-    H5O_shared_t sh_mesg;       /* Shared message location */
     hbool_t     use_latest_format;      /* Flag indicating the newest file format should be used */
-    unsigned     flags=0;        /* Attribute flags */
+    unsigned    flags = 0;      /* Attribute flags */
     herr_t      ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_attr_encode)
@@ -359,23 +358,8 @@ H5O_attr_encode(H5F_t *f, uint8_t *p, const void *mesg)
         p += name_len;
 
     /* encode the attribute datatype */
-    if(type_shared) {
-        /* Reset shared message information */
-        HDmemset(&sh_mesg, 0, sizeof(H5O_shared_t));
-
-        /* Get shared message information from datatype */
-        if(NULL == (H5O_MSG_DTYPE->get_share)(attr->dt, &sh_mesg/*out*/))
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode shared attribute datatype")
-
-        /* Encode shared message information for datatype */
-        if((H5O_MSG_SHARED->encode)(f, p, &sh_mesg) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode shared attribute datatype")
-    } /* end if */
-    else {
-        /* Encode datatype information */
-        if((H5O_MSG_DTYPE->encode)(f, p, attr->dt) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode attribute datatype")
-    } /* end else */
+    if((H5O_MSG_DTYPE->encode)(f, FALSE, p, attr->dt) < 0)
+        HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode attribute datatype")
 
     if(version < H5O_ATTR_VERSION_2) {
         HDmemset(p + attr->dt_size, 0, H5O_ALIGN_OLD(attr->dt_size) - attr->dt_size);
@@ -385,23 +369,8 @@ H5O_attr_encode(H5F_t *f, uint8_t *p, const void *mesg)
         p += attr->dt_size;
 
     /* encode the attribute dataspace */
-    if(space_shared) {
-        /* Reset shared message information */
-        HDmemset(&sh_mesg, 0, sizeof(H5O_shared_t));
-
-        /* Get shared message information from dataspace */
-        if(NULL == (H5O_MSG_SDSPACE->get_share)(attr->ds, &sh_mesg/*out*/))
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode shared attribute dataspace")
-
-        /* Encode shared message information for dataspace */
-        if((H5O_MSG_SHARED->encode)(f, p, &sh_mesg) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode shared attribute dataspace")
-    } /* end if */
-    else {
-        /* Encode non-shared dataspace information */
-        if((H5O_MSG_SDSPACE->encode)(f, p, &(attr->ds->extent)) < 0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode attribute dataspace")
-    } /* end else */
+    if((H5O_MSG_SDSPACE->encode)(f, FALSE, p, &(attr->ds->extent)) < 0)
+        HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't encode attribute dataspace")
 
     if(version < H5O_ATTR_VERSION_2) {
         HDmemset(p + attr->ds_size, 0, H5O_ALIGN_OLD(attr->ds_size) - attr->ds_size);
@@ -527,19 +496,19 @@ H5O_attr_size(const H5F_t *f, const void *_mesg)
     /* Version-specific size information */
     if(version == H5O_ATTR_VERSION_1)
         ret_value += H5O_ALIGN_OLD(name_len) +	/*attribute name	*/
-                    H5O_ALIGN_OLD(attr->dt_size) +	/*data type		*/
-                    H5O_ALIGN_OLD(attr->ds_size) +	/*data space		*/
+                    H5O_ALIGN_OLD(attr->dt_size) +	/*datatype		*/
+                    H5O_ALIGN_OLD(attr->ds_size) +	/*dataspace		*/
                     attr->data_size;		/*the data itself	*/
     else if(version == H5O_ATTR_VERSION_2)
         ret_value += name_len	+		/*attribute name	*/
-                    attr->dt_size +		/*data type		*/
-                    attr->ds_size +		/*data space		*/
+                    attr->dt_size +		/*datatype		*/
+                    attr->ds_size +		/*dataspace		*/
                     attr->data_size;		/*the data itself	*/
     else if(version == H5O_ATTR_VERSION_3 || version == H5O_ATTR_VERSION_4)
         ret_value += 1 +                        /*character encoding    */
                     name_len	+		/*attribute name	*/
-                    attr->dt_size +		/*data type		*/
-                    attr->ds_size +		/*data space		*/
+                    attr->dt_size +		/*datatype		*/
+                    attr->ds_size +		/*dataspace		*/
                     attr->data_size;		/*the data itself	*/
     else
         HDassert(0 && "Bad attribute version");
@@ -685,96 +654,6 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_attr_get_share
- *
- * Purpose:	Gets sharing information from the message
- *
- * Return:	Shared message on success/NULL on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 17, 2006
- *
- *-------------------------------------------------------------------------
- */
-void *
-H5O_attr_get_share(const void *_mesg, H5O_shared_t *sh /*out*/)
-{
-    const H5A_t  *mesg = (const H5A_t *)_mesg;
-    void         *ret_value = NULL;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_attr_get_share)
-
-    HDassert(mesg);
-
-    ret_value = H5O_msg_copy(H5O_SHARED_ID, &(mesg->sh_loc), sh);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_attr_get_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_attr_set_share
- *
- * Purpose:	Sets sharing information for the message
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_attr_set_share(void *_mesg/*in,out*/, const H5O_shared_t *sh)
-{
-    H5A_t  *mesg = (H5A_t *)_mesg;
-    herr_t       ret_value = SUCCEED;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_attr_set_share)
-
-    HDassert(mesg);
-    HDassert(sh);
-
-    if(NULL == H5O_msg_copy(H5O_SHARED_ID, sh, &(mesg->sh_loc)))
-        ret_value = FAIL;
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_attr_set_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_attr_is_shared
- *
- * Purpose:	Determines if this attribute is shared (committed or a SOHM)
- *              or not.
- *
- * Return:	TRUE if attribute is shared
- *              FALSE if attribute is not shared
- *              Negative on failure
- *
- * Programmer:	James Laird
- *		Tuesday, October 17, 2006
- *
- *-------------------------------------------------------------------------
- */
-htri_t
-H5O_attr_is_shared(const void *_mesg)
-{
-    const H5A_t  *mesg = (const H5A_t *)_mesg;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_attr_is_shared)
-
-    HDassert(mesg);
-
-    /* Attributes can't currently be committed, but this should let the
-     * library read a "committed attribute" if we ever create one in
-     * the future.
-     */
-    FUNC_LEAVE_NOAPI(H5O_IS_SHARED(mesg->sh_loc.flags))
-} /* end H5O_attr_is_shared */
-
-
-/*-------------------------------------------------------------------------
  * Function:    H5O_attr_pre_copy_file
  *
  * Purpose:     Perform any necessary actions before copying message between
@@ -790,9 +669,8 @@ H5O_attr_is_shared(const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_attr_pre_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *type,
-    const void UNUSED *native_src, hbool_t *deleted, const H5O_copy_t *cpy_info,
-    void UNUSED *udata)
+H5O_attr_pre_copy_file(H5F_t UNUSED *file_src, const void UNUSED *native_src,
+    hbool_t *deleted, const H5O_copy_t *cpy_info, void UNUSED *udata)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_attr_pre_copy_file)
 
@@ -1174,9 +1052,6 @@ H5O_attr_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream, int in
 	       int fwidth)
 {
     const H5A_t *mesg = (const H5A_t *)_mesg;
-    H5O_shared_t	sh_mesg;        /* Shared message information */
-    void *dt_mesg;                      /* Pointer to datatype message to dump */
-    herr_t      (*debug)(H5F_t*, hid_t, const void*, FILE*, int, int)=NULL;
     herr_t ret_value = SUCCEED;   /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_attr_debug)
@@ -1200,39 +1075,19 @@ H5O_attr_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream, int in
 	    "Object:",
 	    mesg->oloc.addr);
 
-    fprintf(stream, "%*sData type...\n", indent, "");
+    fprintf(stream, "%*sDatatype...\n", indent, "");
     fprintf(stream, "%*s%-*s %lu\n", indent+3, "", MAX(0,fwidth-3),
-	    "Size:",
+	    "Encoded Size:",
 	    (unsigned long)(mesg->dt_size));
-    fprintf (stream, "%*s%-*s %s\n", indent+3, "", MAX(0,fwidth-3),
-               "Shared:",
-               (H5T_committed(mesg->dt) ? "Yes" : "No")
-               );
-    if(H5T_committed(mesg->dt)) {
-        /* Reset shared message information */
-        HDmemset(&sh_mesg, 0, sizeof(H5O_shared_t));
-
-        /* Get shared message information from datatype */
-        if(NULL == (H5O_MSG_DTYPE->get_share)(mesg->dt, &sh_mesg/*out*/))
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTENCODE, FAIL, "can't retrieve shared message information")
-
-        debug = H5O_MSG_SHARED->debug;
-        dt_mesg = &sh_mesg;
-    } /* end if */
-    else {
-        debug = H5O_MSG_DTYPE->debug;
-        dt_mesg = mesg->dt;
-    } /* end else */
-    if(debug)
-        (debug)(f, dxpl_id, dt_mesg, stream, indent+3, MAX(0, fwidth-3));
-    else
-        fprintf(stream, "%*s<No info for this message>\n", indent + 6, "");
+    if((H5O_MSG_DTYPE->debug)(f, dxpl_id, mesg->dt, stream, indent + 3, MAX(0, fwidth - 3)) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "unable to display datatype message info")
 
-    fprintf(stream, "%*sData space...\n", indent, "");
+    fprintf(stream, "%*sDataspace...\n", indent, "");
     fprintf(stream, "%*s%-*s %lu\n", indent+3, "", MAX(0, fwidth - 3),
-	    "Size:",
+	    "Encoded Size:",
 	    (unsigned long)(mesg->ds_size));
-    H5S_debug(f, dxpl_id, mesg->ds, stream, indent+3, MAX(0, fwidth - 3));
+    if(H5S_debug(f, dxpl_id, mesg->ds, stream, indent+3, MAX(0, fwidth - 3)) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "unable to display dataspace message info")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5Oattribute.c b/src/H5Oattribute.c
index 5d6d1aa..5e2c4df 100644
--- a/src/H5Oattribute.c
+++ b/src/H5Oattribute.c
@@ -263,7 +263,7 @@ H5O_attr_create(const H5O_loc_t *loc, hid_t dxpl_id, H5A_t *attr)
     } /* end else */
 
     /* Was new attribugte shared? */
-    if((shared_mesg = H5O_attr_is_shared(attr)) > 0) {
+    if((shared_mesg = H5O_msg_is_shared(H5O_ATTR_ID, attr)) > 0) {
         hsize_t attr_rc;                /* Attribute's ref count in shared message storage */
 
         /* Retrieve ref count for shared attribute */
@@ -524,8 +524,8 @@ H5O_attr_update_shared(H5F_t *f, hid_t dxpl_id, H5A_t *attr,
     HDassert(attr);
 
     /* Extract shared message info from current attribute (for later use) */
-    if(NULL == H5O_attr_get_share(attr, &sh_mesg))
-        HGOTO_ERROR(H5E_ATTR, H5E_BADMESG, FAIL, "can't get shared info")
+    if(H5O_shared_copy(&sh_mesg, &(attr->sh_loc)) < 0)
+        HGOTO_ERROR(H5E_ATTR, H5E_CANTCOPY, FAIL, "can't get shared message")
 
     /* Store new version of message as a SOHM */
     /* (should always work, since we're not changing the size of the attribute) */
@@ -557,8 +557,8 @@ H5O_attr_update_shared(H5F_t *f, hid_t dxpl_id, H5A_t *attr,
 
     /* Extract updated shared message info from modified attribute, if requested */
     if(update_sh_mesg)
-        if(NULL == H5O_attr_get_share(attr, update_sh_mesg))
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "can't get shared info")
+        if(H5O_shared_copy(update_sh_mesg, &(attr->sh_loc)) < 0)
+            HGOTO_ERROR(H5E_ATTR, H5E_CANTCOPY, FAIL, "can't get shared message")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -785,7 +785,7 @@ H5O_attr_rename_mod_cb(H5O_t *oh, H5O_mesg_t *mesg/*in,out*/,
         } /* end if */
         else {
             /* Sanity check */
-            HDassert(H5O_attr_is_shared((H5A_t *)mesg->native) == FALSE);
+            HDassert(H5O_msg_is_shared(H5O_ATTR_ID, (H5A_t *)mesg->native) == FALSE);
 
             /* Check for attribute message changing size */
             if(HDstrlen(udata->new_name) != HDstrlen(udata->old_name)) {
@@ -831,7 +831,7 @@ H5O_attr_rename_mod_cb(H5O_t *oh, H5O_mesg_t *mesg/*in,out*/,
                     HGOTO_ERROR(H5E_ATTR, H5E_CANTINSERT, H5_ITER_ERROR, "unable to relocate renamed attribute in header")
 
                 /* Sanity check */
-                HDassert(H5O_attr_is_shared(attr) == FALSE);
+                HDassert(H5O_msg_is_shared(H5O_ATTR_ID, attr) == FALSE);
 
                 /* Release the local copy of the attribute */
                 H5O_msg_free_real(H5O_MSG_ATTR, attr);
@@ -1164,7 +1164,7 @@ H5O_attr_remove(const H5O_loc_t *loc, const char *name, hid_t dxpl_id)
                     htri_t shared_mesg;             /* Should this message be stored in the Shared Message table? */
 
                     /* Check if attribute is shared */
-                    if((shared_mesg = H5O_attr_is_shared(&(atable.attrs[u]))) < 0)
+                    if((shared_mesg = H5O_msg_is_shared(H5O_ATTR_ID, &(atable.attrs[u]))) < 0)
                         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "error determining if message is shared")
                     else if(shared_mesg == 0) {
                         /* Increment reference count on attribute components */
diff --git a/src/H5Obogus.c b/src/H5Obogus.c
index 93475cd..39ba18f 100644
--- a/src/H5Obogus.c
+++ b/src/H5Obogus.c
@@ -37,9 +37,9 @@
 #ifdef H5O_ENABLE_BOGUS
 
 /* PRIVATE PROTOTYPES */
-static void *H5O_bogus_decode(H5F_t *f, hid_t dxpl_id, unsigned UNUSED mesg_flags, const uint8_t *p);
-static herr_t H5O_bogus_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static size_t H5O_bogus_size(const H5F_t *f, const void *_mesg);
+static void *H5O_bogus_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
+static herr_t H5O_bogus_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
+static size_t H5O_bogus_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_bogus_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
 			     int indent, int fwidth);
 
@@ -48,6 +48,7 @@ const H5O_msg_class_t H5O_MSG_BOGUS[1] = {{
     H5O_BOGUS_ID,            	/*message id number             */
     "bogus",                 	/*message name for debugging    */
     0,     	                /*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_bogus_decode,        	/*decode message                */
     H5O_bogus_encode,        	/*encode message                */
     NULL,          	        /*copy the native value         */
@@ -56,8 +57,8 @@ const H5O_msg_class_t H5O_MSG_BOGUS[1] = {{
     NULL,		        /*free method			*/
     NULL,		        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL,			/*set share method		*/
+    NULL,		    	/*can share method		*/
     NULL,			/* pre copy native value to file */
     NULL,			/* copy native value to file    */
     NULL,			/* post copy native value to file    */
@@ -129,12 +130,10 @@ done:
  *              koziol@ncsa.uiuc.edu
  *              Jan 21 2003
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_bogus_encode(H5F_t UNUSED *f, uint8_t *p, const void UNUSED *mesg)
+H5O_bogus_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, const void UNUSED *mesg)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_encode);
 
@@ -166,12 +165,10 @@ H5O_bogus_encode(H5F_t UNUSED *f, uint8_t *p, const void UNUSED *mesg)
  *              koziol@ncsa.uiuc.edu
  *              Jan 21 2003
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_bogus_size(const H5F_t UNUSED *f, const void UNUSED *mesg)
+H5O_bogus_size(const H5F_t UNUSED *f, hbool_t UNUSED disable_shared, const void UNUSED *mesg)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_bogus_size);
 
diff --git a/src/H5Ocache.c b/src/H5Ocache.c
index 02c8975..64f23d5 100644
--- a/src/H5Ocache.c
+++ b/src/H5Ocache.c
@@ -156,10 +156,6 @@ H5O_flush_msgs(H5F_t *f, H5O_t *oh)
 
             /* Encode the message itself */
             if(curr_msg->native) {
-                herr_t	(*encode)(H5F_t*, uint8_t*, const void*);
-
-                HDassert(curr_msg->type->encode);
-
                 /*
                  * Encode the message.  If the message is shared then we
                  * encode a Shared Object message instead of the object
@@ -169,21 +165,18 @@ H5O_flush_msgs(H5F_t *f, H5O_t *oh)
                 HDassert(curr_msg->raw_size == H5O_ALIGN_OH(oh, curr_msg->raw_size));
                 HDassert(curr_msg->raw + curr_msg->raw_size <=
                        oh->chunk[curr_msg->chunkno].image + (oh->chunk[curr_msg->chunkno].size - H5O_SIZEOF_CHKSUM_OH(oh)));
-                if((curr_msg->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(curr_msg->type))
-                    encode = H5O_MSG_SHARED->encode;
-                else
-                    encode = curr_msg->type->encode;
 #ifndef NDEBUG
 /* Sanity check that the message won't overwrite past it's allocated space */
-if(!(curr_msg->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(curr_msg->type)) {
+{
     size_t msg_size;
 
-    msg_size = curr_msg->type->raw_size(f, curr_msg->native);
+    msg_size = curr_msg->type->raw_size(f, FALSE, curr_msg->native);
     msg_size = H5O_ALIGN_OH(oh, msg_size);
     HDassert(msg_size <= curr_msg->raw_size);
-} /* end if */
+}
 #endif /* NDEBUG */
-                if((encode)(f, curr_msg->raw, curr_msg->native) < 0)
+                HDassert(curr_msg->type->encode);
+                if((curr_msg->type->encode)(f, FALSE, curr_msg->raw, curr_msg->native) < 0)
                     HGOTO_ERROR(H5E_OHDR, H5E_CANTENCODE, FAIL, "unable to encode object header message")
             } /* end if */
 
diff --git a/src/H5Ocont.c b/src/H5Ocont.c
index 6146df8..f378611 100644
--- a/src/H5Ocont.c
+++ b/src/H5Ocont.c
@@ -37,8 +37,8 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_cont_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_cont_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static size_t H5O_cont_size(const H5F_t *f, const void *_mesg);
+static herr_t H5O_cont_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
+static size_t H5O_cont_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_cont_free(void *mesg);
 static herr_t H5O_cont_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link);
 static herr_t H5O_cont_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
@@ -49,6 +49,7 @@ const H5O_msg_class_t H5O_MSG_CONT[1] = {{
     H5O_CONT_ID,            	/*message id number             */
     "hdr continuation",     	/*message name for debugging    */
     sizeof(H5O_cont_t),     	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_cont_decode,        	/*decode message                */
     H5O_cont_encode,        	/*encode message                */
     NULL,                   	/*no copy method                */
@@ -57,10 +58,8 @@ const H5O_msg_class_t H5O_MSG_CONT[1] = {{
     H5O_cont_free,	        /* free method			*/
     H5O_cont_delete,		/* file delete method		*/
     NULL,			/* link method			*/
-    NULL, 		    	/*get share method		*/
-    NULL,		    	/*can share method		*/
     NULL,		    	/*set share method		*/
-    NULL, 			/*is shared method		*/
+    NULL,		    	/*can share method		*/
     NULL,			/* pre copy native value to file */
     NULL,			/* copy native value to file    */
     NULL, 		 	/* post copy native value to file    */
@@ -129,12 +128,10 @@ done:
  *              matzke@llnl.gov
  *              Aug  7 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_cont_encode(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_cont_encode(H5F_t *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_cont_t       *cont = (const H5O_cont_t *) _mesg;
 
@@ -170,12 +167,10 @@ H5O_cont_encode(H5F_t *f, uint8_t *p, const void *_mesg)
  *              koziol@ncsa.uiuc.edu
  *              Sep  6 2005
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_cont_size(const H5F_t *f, const void UNUSED *_mesg)
+H5O_cont_size(const H5F_t *f, hbool_t UNUSED disable_shared, const void UNUSED *_mesg)
 {
     size_t ret_value;   /* Return value */
 
@@ -199,20 +194,18 @@ H5O_cont_size(const H5F_t *f, const void UNUSED *_mesg)
  * Programmer:	Quincey Koziol
  *              Monday, November 15, 2004
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_cont_free (void *mesg)
+H5O_cont_free(void *mesg)
 {
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_cont_free);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_cont_free)
 
-    assert (mesg);
+    HDassert(mesg);
 
-    H5FL_FREE(H5O_cont_t,mesg);
+    H5FL_FREE(H5O_cont_t, mesg);
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
+    FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_cont_free() */
 
 
@@ -270,14 +263,14 @@ H5O_cont_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE *
 {
     const H5O_cont_t       *cont = (const H5O_cont_t *) _mesg;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_cont_debug);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_cont_debug)
 
     /* check args */
-    assert(f);
-    assert(cont);
-    assert(stream);
-    assert(indent >= 0);
-    assert(fwidth >= 0);
+    HDassert(f);
+    HDassert(cont);
+    HDassert(stream);
+    HDassert(indent >= 0);
+    HDassert(fwidth >= 0);
 
     HDfprintf(stream, "%*s%-*s %a\n", indent, "", fwidth,
 	      "Continuation address:", cont->addr);
@@ -289,5 +282,5 @@ H5O_cont_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE *
 	      "Points to chunk number:",
 	      (int) (cont->chunkno));
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
-}
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5O_cont_debug() */
diff --git a/src/H5Ocopy.c b/src/H5Ocopy.c
index a93b321..b50ecd9 100644
--- a/src/H5Ocopy.c
+++ b/src/H5Ocopy.c
@@ -357,7 +357,7 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
     } /* end if */
     else {
         oh_dst->nattrs = oh_src->nattrs;
-        /* XXX: Bail out for now, if the source object has densely stored attributes */
+/* XXX: Bail out for now, if the source object has densely stored attributes */
         if(H5F_addr_defined(oh_src->attr_fheap_addr))
             HGOTO_ERROR(H5E_OHDR, H5E_UNSUPPORTED, FAIL, "densely stored attributes not supported yet")
         else {
@@ -396,11 +396,8 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
         /* Sanity check */
         HDassert(!mesg_src->dirty);     /* Should be cleared by earlier call to flush messages */
 
-        /* Check for shared message to operate on */
-        if((mesg_src->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(mesg_src->type))
-            copy_type = H5O_MSG_SHARED;
-        else
-            copy_type = mesg_src->type;
+        /* Get message class to operate on */
+        copy_type = mesg_src->type;
 
         /* Check for continuation message; these are converted to NULL
          * messages because the destination OH will have only one chunk
@@ -409,30 +406,21 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
             deleted[mesgno] = TRUE;
             ++null_msgs;
             copy_type = H5O_MSG_NULL;
-        }
+        } /* end if */
         HDassert(copy_type);
 
         if(copy_type->pre_copy_file) {
-            /*
-             * Decode the message if necessary.  If the message is shared then do
-             * a shared message, ignoring the message type.
-             */
-            if(NULL == mesg_src->native) {
-                /* Decode the message if necessary */
-                HDassert(copy_type->decode);
-                if(NULL == (mesg_src->native = (copy_type->decode)(oloc_src->file, dxpl_id, mesg_src->flags, mesg_src->raw)))
-                    HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "unable to decode a message")
-            } /* end if (NULL == mesg_src->native) */
+            /* Decode the message if necessary. */
+            H5O_LOAD_NATIVE(oloc_src->file, dxpl_id, mesg_src, FAIL)
 
             /* Perform "pre copy" operation on message */
-            if((copy_type->pre_copy_file)(oloc_src->file, mesg_src->type, mesg_src->native, &(deleted[mesgno]), cpy_info, udata) < 0)
+            if((copy_type->pre_copy_file)(oloc_src->file, mesg_src->native, &(deleted[mesgno]), cpy_info, udata) < 0)
                 HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to perform 'pre copy' operation on message")
 
             /* Check if the message should be deleted in the destination */
-            if(deleted[mesgno]) {
+            if(deleted[mesgno])
                 /* Mark message as deleted */
                 ++null_msgs;
-            } /* end if(deleted) */
         } /* end if(copy_type->pre_copy_file) */
     } /* end for */
 
@@ -459,8 +447,8 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
             while(deleted[mesgno + null_msgs]) {
                 ++null_msgs;
                 HDassert(mesgno + null_msgs < oh_src->nmesgs);
-            }
-        }
+            } /* end while */
+        } /* end if */
 
         /* Set up convenience variables */
         mesg_src = &(oh_src->mesg[mesgno + null_msgs]);
@@ -482,33 +470,22 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
             mesg_dst->type = H5O_MSG_NULL;
             mesg_dst->flags = 0;
             mesg_dst->dirty = 1;
-        }
+        } /* end if */
 
-        /* Check for shared message to operate on */
+        /* Check for message class to operate on */
         /* (Use destination message, in case the message has been removed (i.e
-            *      converted to a nil message) in the destination -QAK)
-            */
-        if((mesg_dst->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(mesg_dst->type))
-            copy_type = H5O_MSG_SHARED;
-        else
-            copy_type = mesg_dst->type;
+         *      converted to a nil message) in the destination -QAK)
+         */
+        copy_type = mesg_dst->type;
         HDassert(copy_type);
 
         /* copy this message into destination file */
         if(copy_type->copy_file) {
-            /*
-             * Decode the message if necessary.  If the message is shared then do
-             * a shared message, ignoring the message type.
-             */
-            if(NULL == mesg_src->native) {
-                /* Decode the message if necessary */
-                HDassert(copy_type->decode);
-                if(NULL == (mesg_src->native = (copy_type->decode)(oloc_src->file, dxpl_id, mesg_dst->flags, mesg_src->raw)))
-                    HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "unable to decode a message")
-            } /* end if (NULL == mesg_src->native) */
+            /* Decode the message if necessary. */
+            H5O_LOAD_NATIVE(oloc_src->file, dxpl_id, mesg_src, FAIL)
 
             /* Copy the source message */
-            if((mesg_dst->native = H5O_msg_copy_file(copy_type, mesg_dst->type,
+            if((mesg_dst->native = H5O_msg_copy_file(copy_type, 
                     oloc_src->file, mesg_src->native, oloc_dst->file, dxpl_id,
                     &shared, cpy_info, udata)) == NULL)
                 HGOTO_ERROR(H5E_OHDR, H5E_CANTCOPY, FAIL, "unable to copy object header message")
@@ -522,21 +499,17 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
                 mesg_dst->flags |= H5O_MSG_FLAG_SHARED;
 
                 /* Recompute shared message size (mesg_dst->native is really
-                 * an H5O_shared_t)
+                 * shared)
                  */
-                if(H5O_NEW_SHARED(mesg_dst->type))
-                    mesg_dst->raw_size = H5O_ALIGN_OH(oh_dst,
-                            H5O_msg_raw_size(oloc_dst->file, mesg_dst->type->id, FALSE, mesg_dst->native));
-                else
-                    mesg_dst->raw_size = H5O_ALIGN_OH(oh_dst,
-                            H5O_msg_raw_size(oloc_dst->file, H5O_SHARED_ID, FALSE, mesg_dst->native));
+                mesg_dst->raw_size = H5O_ALIGN_OH(oh_dst,
+                        H5O_msg_raw_size(oloc_dst->file, mesg_dst->type->id, FALSE, mesg_dst->native));
             } /* end if */
             else if(shared == FALSE && (mesg_dst->flags & H5O_MSG_FLAG_SHARED)) {
                 /* Unset shared flag */
                 mesg_dst->flags &= ~H5O_MSG_FLAG_SHARED;
 
                 /* Recompute native message size (msg_dest->native is no longer
-                 * an H5O_shared_t)
+                 * shared)
                  */
                 mesg_dst->raw_size = H5O_ALIGN_OH(oh_dst,
                         H5O_msg_raw_size(oloc_dst->file, mesg_dst->type->id, FALSE, mesg_dst->native));
@@ -661,14 +634,11 @@ H5O_copy_header_real(const H5O_loc_t *oloc_src, H5O_loc_t *oloc_dst /*out */,
         mesg_src = &(oh_src->mesg[mesgno + null_msgs]);
         mesg_dst = &(oh_dst->mesg[mesgno]);
 
-        /* Check for shared message to operate on */
+        /* Check for message class to operate on */
         /* (Use destination message, in case the message has been removed (i.e
          *      converted to a nil message) in the destination -QAK)
          */
-        if((mesg_dst->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(mesg_dst->type))
-            copy_type = H5O_MSG_SHARED;
-        else
-            copy_type = mesg_dst->type;
+        copy_type = mesg_dst->type;
         HDassert(copy_type);
 
         if(copy_type->post_copy_file && mesg_src->native) {
diff --git a/src/H5Odbg.c b/src/H5Odbg.c
index 13428cf..a53493e 100644
--- a/src/H5Odbg.c
+++ b/src/H5Odbg.c
@@ -247,8 +247,7 @@ H5O_debug_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, haddr_t addr, FILE *stream, i
 {
     unsigned	i, chunkno;
     size_t	mesg_total = 0, chunk_total = 0;
-    int		*sequence;
-    const H5O_msg_class_t  *debug_type;              /* Type of message to use for callbacks */
+    unsigned	*sequence;
     herr_t	ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI(H5O_debug_real, FAIL)
@@ -356,9 +355,11 @@ H5O_debug_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, haddr_t addr, FILE *stream, i
     } /* end for */
 
     /* debug each message */
-    if(NULL == (sequence = H5MM_calloc(NELMTS(H5O_msg_class_g) * sizeof(int))))
+    if(NULL == (sequence = H5MM_calloc(NELMTS(H5O_msg_class_g) * sizeof(unsigned))))
 	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
     for(i = 0, mesg_total = 0; i < oh->nmesgs; i++) {
+        const H5O_msg_class_t  *debug_type;              /* Type of message to use for callbacks */
+
 	mesg_total += H5O_SIZEOF_MSGHDR_OH(oh) + oh->mesg[i].raw_size;
 	HDfprintf(stream, "%*sMessage %d...\n", indent, "", i);
 
@@ -410,13 +411,9 @@ H5O_debug_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, haddr_t addr, FILE *stream, i
 	    HDfprintf(stream, "*** BAD MESSAGE RAW ADDRESS\n");
 
 	/* decode the message */
-	if((oh->mesg[i].flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(oh->mesg[i].type)) {
-            debug_type = H5O_MSG_SHARED;
-	} else {
-            debug_type = oh->mesg[i].type;
-	} /* end else */
-	if(NULL==oh->mesg[i].native && debug_type->decode)
-            oh->mesg[i].native = (debug_type->decode)(f, dxpl_id, oh->mesg[i].flags, oh->mesg[i].raw);
+	debug_type = oh->mesg[i].type;
+	if(NULL == oh->mesg[i].native && debug_type->decode)
+            H5O_LOAD_NATIVE(f, dxpl_id, &oh->mesg[i], FAIL)
 
 	/* print the message */
 	HDfprintf(stream, "%*s%-*s\n", indent + 3, "", MAX(0, fwidth - 3),
@@ -425,17 +422,6 @@ H5O_debug_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, haddr_t addr, FILE *stream, i
 	    (debug_type->debug)(f, dxpl_id, oh->mesg[i].native, stream, indent + 6, MAX(0, fwidth - 6));
 	else
 	    HDfprintf(stream, "%*s<No info for this message>\n", indent + 6, "");
-
-	/* If the message is shared then also print the pointed-to message */
-	if((oh->mesg[i].flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(oh->mesg[i].type)) {
-	    H5O_shared_t *shared = (H5O_shared_t*)(oh->mesg[i].native);
-	    void *mesg;
-
-            mesg = H5O_shared_read(f, dxpl_id, shared, oh->mesg[i].type, NULL);
-	    if(oh->mesg[i].type->debug)
-		(oh->mesg[i].type->debug)(f, dxpl_id, mesg, stream, indent + 3, MAX (0, fwidth - 3));
-	    H5O_msg_free_real(oh->mesg[i].type, mesg);
-	} /* end if */
     } /* end for */
     sequence = H5MM_xfree(sequence);
 
diff --git a/src/H5Odtype.c b/src/H5Odtype.c
index 31de559..c060ad5 100644
--- a/src/H5Odtype.c
+++ b/src/H5Odtype.c
@@ -33,12 +33,10 @@ static void *H5O_dtype_copy(const void *_mesg, void *_dest);
 static size_t H5O_dtype_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_dtype_reset(void *_mesg);
 static herr_t H5O_dtype_free(void *_mesg);
-static void *H5O_dtype_get_share(const void *_mesg, H5O_shared_t *sh);
 static herr_t H5O_dtype_set_share(void *_mesg, const H5O_shared_t *sh);
 static htri_t H5O_dtype_can_share(const void *_mesg);
-static htri_t H5O_dtype_is_shared(const void *_mesg);
-static herr_t H5O_dtype_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
-    const void *mesg_src, hbool_t *deleted, const H5O_copy_t *cpy_info, void *_udata);
+static herr_t H5O_dtype_pre_copy_file(H5F_t *file_src, const void *mesg_src,
+    hbool_t *deleted, const H5O_copy_t *cpy_info, void *_udata);
 static void *H5O_dtype_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
     void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
 
@@ -59,6 +57,8 @@ static herr_t H5O_dtype_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
 #undef H5O_SHARED_LINK_REAL
 #define H5O_SHARED_COPY_FILE		H5O_dtype_shared_copy_file
 #define H5O_SHARED_COPY_FILE_REAL	H5O_dtype_copy_file
+#define H5O_SHARED_DEBUG		H5O_dtype_shared_debug
+#define H5O_SHARED_DEBUG_REAL		H5O_dtype_debug
 #include "H5Oshared.h"			/* Shared Object Header Message Callbacks */
 
 /* This message derives from H5O message class */
@@ -66,6 +66,7 @@ const H5O_msg_class_t H5O_MSG_DTYPE[1] = {{
     H5O_DTYPE_ID,		/* message id number		*/
     "datatype",			/* message name for debugging	*/
     sizeof(H5T_t),		/* native message size		*/
+    TRUE,			/* messages are sharable?       */
     H5O_dtype_shared_decode,	/* decode message		*/
     H5O_dtype_shared_encode,	/* encode message		*/
     H5O_dtype_copy,		/* copy the native value	*/
@@ -74,16 +75,14 @@ const H5O_msg_class_t H5O_MSG_DTYPE[1] = {{
     H5O_dtype_free,		/* free method			*/
     H5O_dtype_shared_delete,	/* file delete method		*/
     H5O_dtype_shared_link,	/* link method			*/
-    H5O_dtype_get_share,	/* get share method		*/
     H5O_dtype_set_share,	/* set share method		*/
     H5O_dtype_can_share,	/* can share method		*/
-    H5O_dtype_is_shared,	/* is shared method		*/
     H5O_dtype_pre_copy_file,	/* pre copy native value to file */
     H5O_dtype_shared_copy_file,	/* copy native value to file    */
     NULL,			/* post copy native value to file */
     NULL,			/* get creation index		*/
     NULL,			/* set creation index		*/
-    H5O_dtype_debug		/* debug the message		*/
+    H5O_dtype_shared_debug	/* debug the message		*/
 }};
 
 /* This is the version to create all datatypes which don't contain
@@ -1274,49 +1273,6 @@ H5O_dtype_free(void *mesg)
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_dtype_get_share
- *
- * Purpose:	Returns information about where the shared message is located
- *		by filling in the SH shared message struct.
- *
- * Return:	Shared message on success/NULL on failure
- *
- * Programmer:	Robb Matzke
- *		Monday, June  1, 1998
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_dtype_get_share(const void *_mesg, H5O_shared_t *sh/*out*/)
-{
-    const H5T_t	*dt = (const H5T_t *)_mesg;
-    void      *ret_value = NULL;       /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_dtype_get_share)
-
-    HDassert(dt);
-
-    /* Make sure the shared struct is initialized to some reasonable value */
-    HDassert((dt->sh_loc.flags & (H5O_SHARED_IN_HEAP_FLAG | H5O_COMMITTED_FLAG)) || dt->sh_loc.flags == H5O_NOT_SHARED);
-
-#ifndef NDEBUG
-    /* Make sure datatype state is correct: committed datatypes must have
-     * state NAMED or OPEN and neither unshared datatypes nor datatypes
-     * shared in the heap can be NAMED or OPEN. */
-    if(dt->sh_loc.flags & H5O_COMMITTED_FLAG)
-        HDassert(H5T_STATE_NAMED == dt->shared->state || H5T_STATE_OPEN == dt->shared->state);
-    else
-        HDassert(! (H5T_STATE_NAMED == dt->shared->state || H5T_STATE_OPEN == dt->shared->state));
-#endif /* NDEBUG */
-
-    /* Do actual copy of shared information */
-    ret_value = H5O_msg_copy(H5O_SHARED_ID, &(dt->sh_loc), sh);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_dtype_get_share() */
-
-
-/*-------------------------------------------------------------------------
  * Function:	H5O_dtype_set_share
  *
  * Purpose:	Copies sharing information from SH into the message.
@@ -1334,7 +1290,7 @@ H5O_dtype_set_share(void *_mesg/*in,out*/, const H5O_shared_t *sh)
     H5T_t	*dt = (H5T_t *)_mesg;
     herr_t       ret_value = SUCCEED;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_dtype_set_share)
+    FUNC_ENTER_NOAPI_NOINIT(H5O_dtype_set_share)
 
     HDassert(dt);
     HDassert(sh);
@@ -1349,13 +1305,14 @@ H5O_dtype_set_share(void *_mesg/*in,out*/, const H5O_shared_t *sh)
         (dt->shared->state != H5T_STATE_OPEN && dt->shared->state != H5T_STATE_NAMED));
 
     /* Copy the shared information */
-    if(NULL == H5O_msg_copy(H5O_SHARED_ID, sh, &(dt->sh_loc)))
-        ret_value = FAIL;
+    if(H5O_shared_copy(&(dt->sh_loc), sh) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTCOPY, FAIL, "unable to copy shared message info")
 
     /* If this is now a committed datatype, set its state properly. */
     if(sh->flags & H5O_COMMITTED_FLAG)
         dt->shared->state = H5T_STATE_NAMED;
 
+done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_dtype_set_share() */
 
@@ -1403,35 +1360,6 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_dtype_can_share() */
 
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_dtype_is_shared
- *
- * Purpose:	Determines if this datatype is shared (committed or a SOHM)
- *              or not.
- *
- * Return:	TRUE if datatype is shared
- *              FALSE if datatype is not shared
- *              Negative on failure
- *
- * Programmer:	James Laird
- *		Monday, October 16, 2006
- *
- *-------------------------------------------------------------------------
- */
-static htri_t
-H5O_dtype_is_shared(const void *_mesg)
-{
-    const H5T_t	*mesg = (const H5T_t *)_mesg;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_dtype_is_shared)
-
-    HDassert(mesg);
-
-    FUNC_LEAVE_NOAPI(H5O_IS_SHARED(mesg->sh_loc.flags))
-} /* end H5O_dtype_is_shared() */
-
 
 /*-------------------------------------------------------------------------
  * Function:    H5O_dtype_pre_copy_file
@@ -1449,8 +1377,8 @@ H5O_dtype_is_shared(const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_dtype_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t UNUSED *type,
-    const void *mesg_src, hbool_t UNUSED *deleted, const H5O_copy_t UNUSED *cpy_info,
+H5O_dtype_pre_copy_file(H5F_t *file_src, const void *mesg_src,
+    hbool_t UNUSED *deleted, const H5O_copy_t UNUSED *cpy_info,
     void *_udata)
 {
     const H5T_t	   *dt_src = (const H5T_t *)mesg_src;  /* Source datatype */
diff --git a/src/H5Oefl.c b/src/H5Oefl.c
index ce6a9e5..fbf3806 100644
--- a/src/H5Oefl.c
+++ b/src/H5Oefl.c
@@ -29,12 +29,12 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_efl_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_efl_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_efl_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_efl_copy(const void *_mesg, void *_dest);
-static size_t H5O_efl_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_efl_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_efl_reset(void *_mesg);
-static void *H5O_efl_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
-    void *mesg_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
+static void *H5O_efl_copy_file(H5F_t *file_src, void *mesg_src,
+    H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
 static herr_t H5O_efl_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
 			    int indent, int fwidth);
 
@@ -43,6 +43,7 @@ const H5O_msg_class_t H5O_MSG_EFL[1] = {{
     H5O_EFL_ID,		    	/*message id number		*/
     "external file list",   	/*message name for debugging    */
     sizeof(H5O_efl_t),	    	/*native message size	    	*/
+    FALSE,			/* messages are sharable?       */
     H5O_efl_decode,	    	/*decode message		*/
     H5O_efl_encode,	    	/*encode message		*/
     H5O_efl_copy,	    	/*copy native value		*/
@@ -51,10 +52,8 @@ const H5O_msg_class_t H5O_MSG_EFL[1] = {{
     NULL,		            /* free method			*/
     NULL,		        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,	  	    	/*get share method		*/
     NULL,			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     H5O_efl_copy_file,		/* copy native value to file    */
     NULL,			/* post copy native value to file    */
@@ -183,29 +182,20 @@ done:
  * Programmer:	Robb Matzke
  *		Tuesday, November 25, 1997
  *
- * Modifications:
- *	Robb Matzke, 1998-07-20
- *	Rearranged the message to add a version number near the beginning.
- *
- * 	Robb Matzke, 1999-10-14
- *	Entering the name into the local heap happens when the dataset is
- *	created. Otherwise we could end up in infinite recursion if the heap
- *	happens to hash to the same cache slot as the object header.
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_efl_encode(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_efl_encode(H5F_t *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_efl_t	*mesg = (const H5O_efl_t *)_mesg;
     size_t		u;      /* Local index variable */
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_encode);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_encode)
 
     /* check args */
-    assert(f);
-    assert(mesg);
-    assert(p);
+    HDassert(f);
+    HDassert(mesg);
+    HDassert(p);
 
     /* Version */
     *p++ = H5O_EFL_VERSION;
@@ -216,29 +206,29 @@ H5O_efl_encode(H5F_t *f, uint8_t *p, const void *_mesg)
     *p++ = 0;
 
     /* Number of slots */
-    assert (mesg->nalloc>0);
+    HDassert(mesg->nalloc > 0);
     UINT16ENCODE(p, mesg->nused); /*yes, twice*/
-    assert (mesg->nused>0 && mesg->nused<=mesg->nalloc);
+    HDassert(mesg->nused > 0 && mesg->nused <= mesg->nalloc);
     UINT16ENCODE(p, mesg->nused);
 
     /* Heap address */
-    assert (H5F_addr_defined(mesg->heap_addr));
+    HDassert(H5F_addr_defined(mesg->heap_addr));
     H5F_addr_encode(f, &p, mesg->heap_addr);
 
     /* Encode file list */
-    for (u=0; u<mesg->nused; u++) {
+    for(u = 0; u < mesg->nused; u++) {
 	/*
 	 * The name should have been added to the heap when the dataset was
 	 * created.
 	 */
-	assert(mesg->slot[u].name_offset);
-	H5F_ENCODE_LENGTH (f, p, mesg->slot[u].name_offset);
-	H5F_ENCODE_LENGTH (f, p, mesg->slot[u].offset);
-	H5F_ENCODE_LENGTH (f, p, mesg->slot[u].size);
-    }
+	HDassert(mesg->slot[u].name_offset);
+	H5F_ENCODE_LENGTH(f, p, mesg->slot[u].name_offset);
+	H5F_ENCODE_LENGTH(f, p, mesg->slot[u].offset);
+	H5F_ENCODE_LENGTH(f, p, mesg->slot[u].size);
+    } /* end for */
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
-}
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5O_efl_encode() */
 
 
 /*-------------------------------------------------------------------------
@@ -254,8 +244,6 @@ H5O_efl_encode(H5F_t *f, uint8_t *p, const void *_mesg)
  * Programmer:	Robb Matzke
  *		Tuesday, November 25, 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static void *
@@ -311,21 +299,19 @@ done:
  * Programmer:	Robb Matzke
  *		Tuesday, November 25, 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_efl_size(const H5F_t *f, const void *_mesg)
+H5O_efl_size(const H5F_t *f, hbool_t UNUSED disable_shared, const void *_mesg)
 {
     const H5O_efl_t	*mesg = (const H5O_efl_t *) _mesg;
     size_t		ret_value = 0;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_size);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_size)
 
     /* check args */
-    assert(f);
-    assert(mesg);
+    HDassert(f);
+    HDassert(mesg);
 
     ret_value = H5F_SIZEOF_ADDR(f) +			/*heap address	*/
 		2 +					/*slots allocated*/
@@ -335,8 +321,8 @@ H5O_efl_size(const H5F_t *f, const void *_mesg)
 			       H5F_SIZEOF_SIZE(f) +	/*file offset	*/
 			       H5F_SIZEOF_SIZE(f));	/*file size	*/
 
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_efl_size() */
 
 
 /*-------------------------------------------------------------------------
@@ -350,8 +336,6 @@ H5O_efl_size(const H5F_t *f, const void *_mesg)
  * Programmer:	Robb Matzke
  *		Tuesday, November 25, 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
@@ -360,21 +344,21 @@ H5O_efl_reset(void *_mesg)
     H5O_efl_t	*mesg = (H5O_efl_t *) _mesg;
     size_t	u;              /* Local index variable */
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_reset);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_reset)
 
     /* check args */
-    assert(mesg);
+    HDassert(mesg);
 
     /* reset */
-    for (u=0; u<mesg->nused; u++)
-	mesg->slot[u].name = H5MM_xfree (mesg->slot[u].name);
+    for(u = 0; u < mesg->nused; u++)
+	mesg->slot[u].name = H5MM_xfree(mesg->slot[u].name);
     mesg->heap_addr = HADDR_UNDEF;
     mesg->nused = mesg->nalloc = 0;
     if(mesg->slot)
         mesg->slot = H5MM_xfree(mesg->slot);
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
-}
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5O_efl_reset() */
 
 
 /*-------------------------------------------------------------------------
@@ -390,8 +374,6 @@ H5O_efl_reset(void *_mesg)
  * Programmer:	Robb Matzke
  *              Tuesday, March  3, 1998
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 hsize_t
@@ -399,24 +381,23 @@ H5O_efl_total_size (H5O_efl_t *efl)
 {
     hsize_t	ret_value = 0, tmp;
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_efl_total_size);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_efl_total_size)
 
-    if (efl->nused>0 &&
-	H5O_EFL_UNLIMITED==efl->slot[efl->nused-1].size) {
+    if(efl->nused > 0 && H5O_EFL_UNLIMITED == efl->slot[efl->nused - 1].size)
 	ret_value = H5O_EFL_UNLIMITED;
-    } else {
+    else {
         size_t		u;      /* Local index variable */
 
-	for (u=0; u<efl->nused; u++, ret_value=tmp) {
+	for(u = 0; u < efl->nused; u++, ret_value = tmp) {
 	    tmp = ret_value + efl->slot[u].size;
-	    if (tmp<=ret_value)
-		HGOTO_ERROR (H5E_EFL, H5E_OVERFLOW, 0, "total external storage size overflowed");
-	}
-    }
+	    if(tmp <= ret_value)
+		HGOTO_ERROR(H5E_EFL, H5E_OVERFLOW, 0, "total external storage size overflowed");
+	} /* end for */
+    } /* end else */
 
 done:
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_efl_total_size() */
 
 
 /*-------------------------------------------------------------------------
@@ -431,14 +412,11 @@ done:
  * Programmer:  Peter Cao
  *              September 29, 2005
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_efl_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *mesg_type,
-    void *mesg_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t UNUSED *cpy_info,
-    void UNUSED *_udata)
+H5O_efl_copy_file(H5F_t UNUSED *file_src, void *mesg_src, H5F_t *file_dst,
+    hid_t dxpl_id, H5O_copy_t UNUSED *cpy_info, void UNUSED *_udata)
 {
     H5O_efl_t     *efl_src = (H5O_efl_t *) mesg_src;
     H5O_efl_t     *efl_dst = NULL;
@@ -479,14 +457,14 @@ H5O_efl_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *mesg_typ
 
         /* copy content from the source. Need to update later */
         HDmemcpy(efl_dst->slot, efl_src->slot, size);
-    }
+    } /* end if */
 
     /* copy the name from the source */
     for(idx = 0; idx < efl_src->nused; idx++) {
         efl_dst->slot[idx].name = H5MM_xstrdup(efl_src->slot[idx].name);
         efl_dst->slot[idx].name_offset = H5HL_insert(file_dst, dxpl_id, efl_dst->heap_addr,
-            HDstrlen(efl_dst->slot[idx].name)+1, efl_dst->slot[idx].name);
-    }
+            HDstrlen(efl_dst->slot[idx].name) + 1, efl_dst->slot[idx].name);
+    } /* end for */
 
     /* Set return value */
     ret_value = efl_dst;
@@ -497,7 +475,7 @@ done:
             H5MM_xfree(efl_dst);
 
     FUNC_LEAVE_NOAPI(ret_value)
-}
+} /* end H5O_efl_copy_file() */
 
 
 /*-------------------------------------------------------------------------
@@ -510,8 +488,6 @@ done:
  * Programmer:	Robb Matzke
  *		Tuesday, November 25, 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
@@ -522,14 +498,14 @@ H5O_efl_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE * s
     char		    buf[64];
     size_t		    u;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_debug);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_efl_debug)
 
     /* check args */
-    assert(f);
-    assert(mesg);
-    assert(stream);
-    assert(indent >= 0);
-    assert(fwidth >= 0);
+    HDassert(f);
+    HDassert(mesg);
+    HDassert(stream);
+    HDassert(indent >= 0);
+    HDassert(fwidth >= 0);
 
     HDfprintf(stream, "%*s%-*s %a\n", indent, "", fwidth,
 	      "Heap address:", mesg->heap_addr);
@@ -538,7 +514,7 @@ H5O_efl_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE * s
 	      "Slots used/allocated:",
 	      mesg->nused, mesg->nalloc);
 
-    for (u = 0; u < mesg->nused; u++) {
+    for(u = 0; u < mesg->nused; u++) {
 	sprintf (buf, "File %u", (unsigned)u);
 	HDfprintf (stream, "%*s%s:\n", indent, "", buf);
 
@@ -557,8 +533,8 @@ H5O_efl_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE * s
 	HDfprintf (stream, "%*s%-*s %lu\n", indent+3, "", MAX (fwidth-3, 0),
 		   "Bytes reserved for data:",
 		   (unsigned long)(mesg->slot[u].size));
-    }
+    } /* end for */
 
-    FUNC_LEAVE_NOAPI(SUCCEED);
-}
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5O_efl_debug() */
 
diff --git a/src/H5Ofill.c b/src/H5Ofill.c
index 091f810..b68967b 100644
--- a/src/H5Ofill.c
+++ b/src/H5Ofill.c
@@ -41,9 +41,6 @@ static void  *H5O_fill_new_copy(const void *_mesg, void *_dest);
 static size_t H5O_fill_new_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_fill_new_reset(void *_mesg);
 static herr_t H5O_fill_new_free(void *_mesg);
-static void  *H5O_fill_new_get_share(const void *_mesg, H5O_shared_t *sh);
-static herr_t H5O_fill_new_set_share(void *_mesg, const H5O_shared_t *sh);
-static htri_t H5O_fill_new_is_shared(const void *_mesg);
 static herr_t H5O_fill_new_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE *stream,
 			     int indent, int fwidth);
 
@@ -61,6 +58,8 @@ static herr_t H5O_fill_new_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FIL
 #undef H5O_SHARED_LINK_REAL
 #define H5O_SHARED_COPY_FILE		H5O_fill_shared_copy_file
 #undef H5O_SHARED_COPY_FILE_REAL
+#define H5O_SHARED_DEBUG		H5O_fill_shared_debug
+#define H5O_SHARED_DEBUG_REAL		H5O_fill_debug
 #include "H5Oshared.h"			/* Shared Object Header Message Callbacks */
 
 /* Set up & include shared message "interface" info */
@@ -88,6 +87,10 @@ static herr_t H5O_fill_new_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FIL
 #undef H5O_SHARED_COPY_FILE
 #define H5O_SHARED_COPY_FILE		H5O_fill_new_shared_copy_file
 #undef H5O_SHARED_COPY_FILE_REAL
+#undef H5O_SHARED_DEBUG
+#define H5O_SHARED_DEBUG		H5O_fill_new_shared_debug
+#undef H5O_SHARED_DEBUG_REAL
+#define H5O_SHARED_DEBUG_REAL		H5O_fill_new_debug
 #undef H5Oshared_H
 #include "H5Oshared.h"			/* Shared Object Header Message Callbacks */
 
@@ -96,24 +99,23 @@ const H5O_msg_class_t H5O_MSG_FILL[1] = {{
     H5O_FILL_ID,                /*message id number                     */
     "fill",                     /*message name for debugging            */
     sizeof(H5O_fill_t),		/*native message size                   */
-    H5O_fill_shared_decode,		/*decode message                        */
-    H5O_fill_shared_encode,		/*encode message                        */
+    TRUE,			/* messages are sharable?       */
+    H5O_fill_shared_decode,	/*decode message                        */
+    H5O_fill_shared_encode,	/*encode message                        */
     H5O_fill_new_copy,          /*copy the native value                 */
-    H5O_fill_shared_size,		/*raw message size			*/
+    H5O_fill_shared_size,	/*raw message size			*/
     H5O_fill_new_reset,         /*free internal memory			*/
     H5O_fill_new_free,		/* free method				*/
     H5O_fill_shared_delete,	/* file delete method			*/
     H5O_fill_shared_link,	/* link method				*/
-    H5O_fill_new_get_share,	/* get share method			*/
-    H5O_fill_new_set_share,	/* set share method			*/
+    H5O_shared_copy,		/* set share method			*/
     NULL,		    	/*can share method		*/
-    H5O_fill_new_is_shared,	/* is shared method			*/
     NULL,			/* pre copy native value to file	*/
     H5O_fill_shared_copy_file,	/* copy native value to file		*/
     NULL,			/* post copy native value to file	*/
     NULL,			/* get creation index		*/
     NULL,			/* set creation index		*/
-    H5O_fill_debug              /*debug the message			*/
+    H5O_fill_shared_debug       /*debug the message			*/
 }};
 
 /* This message derives from H5O message class, for new fill value after version 1.4  */
@@ -121,6 +123,7 @@ const H5O_msg_class_t H5O_MSG_FILL_NEW[1] = {{
     H5O_FILL_NEW_ID,		/*message id number			*/
     "fill_new", 		/*message name for debugging		*/
     sizeof(H5O_fill_t),		/*native message size			*/
+    TRUE,			/* messages are sharable?       */
     H5O_fill_new_shared_decode,	/*decode message			*/
     H5O_fill_new_shared_encode,	/*encode message			*/
     H5O_fill_new_copy,		/*copy the native value			*/
@@ -129,16 +132,14 @@ const H5O_msg_class_t H5O_MSG_FILL_NEW[1] = {{
     H5O_fill_new_free,		/* free method				*/
     H5O_fill_new_shared_delete,	/* file delete method			*/
     H5O_fill_new_shared_link,	/* link method				*/
-    H5O_fill_new_get_share,	/* get share method			*/
-    H5O_fill_new_set_share,	/* set share method			*/
+    H5O_shared_copy,		/* set share method			*/
     NULL,		    	/*can share method		*/
-    H5O_fill_new_is_shared,	/* is shared method			*/
     NULL,			/* pre copy native value to file	*/
     H5O_fill_new_shared_copy_file, /* copy native value to file		*/
     NULL,			/* post copy native value to file	*/
     NULL,			/* get creation index		*/
     NULL,			/* set creation index		*/
-    H5O_fill_new_debug		/*debug the message			*/
+    H5O_fill_new_shared_debug	/*debug the message			*/
 }};
 
 /* Initial version of the "old" fill value information */
@@ -600,96 +601,6 @@ H5O_fill_new_free(void *mesg)
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_fill_new_get_share
- *
- * Purpose:	Gets sharing information from the message
- *
- * Return:	Shared message on success/NULL on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_fill_new_get_share(const void *_mesg, H5O_shared_t *sh /*out*/)
-{
-    const H5O_fill_t  *mesg = (const H5O_fill_t *)_mesg;
-    void       *ret_value;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_fill_new_get_share)
-
-    HDassert(mesg);
-
-    ret_value = H5O_msg_copy(H5O_SHARED_ID, &(mesg->sh_loc), sh);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_fill_new_get_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_fill_new_set_share
- *
- * Purpose:	Sets sharing information for the message
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_fill_new_set_share(void *_mesg/*in,out*/, const H5O_shared_t *sh)
-{
-    H5O_fill_t  *mesg = (H5O_fill_t *)_mesg;
-    herr_t       ret_value = SUCCEED;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_fill_new_set_share)
-
-    HDassert(mesg);
-    HDassert(sh);
-
-    if(NULL == H5O_msg_copy(H5O_SHARED_ID, sh, &(mesg->sh_loc)))
-        ret_value = FAIL;
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_fill_new_set_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_fill_new_is_shared
- *
- * Purpose:	Determines if this fill value is shared (committed or a SOHM)
- *              or not.
- *
- * Return:	TRUE if fill value is shared
- *              FALSE if fill value is not shared
- *              Negative on failure
- *
- * Programmer:	James Laird
- *		Monday, October 16, 2006
- *
- *-------------------------------------------------------------------------
- */
-static htri_t
-H5O_fill_new_is_shared(const void *_mesg)
-{
-    const H5O_fill_t  *mesg = (const H5O_fill_t *)_mesg;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_fill_new_is_shared)
-
-    HDassert(mesg);
-
-    /* Fill values can't currently be committed, but this should let the
-     * library read a "committed fill value" if we ever create one in
-     * the future.
-     */
-    FUNC_LEAVE_NOAPI(H5O_IS_SHARED(mesg->sh_loc.flags))
-} /* end H5O_fill_new_is_shared() */
-
-
-/*-------------------------------------------------------------------------
  * Function:	H5O_fill_new_debug
  *
  * Purpose:	Prints debugging info for the message.
@@ -707,7 +618,7 @@ static herr_t
 H5O_fill_new_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE *stream,
 	       int indent, int fwidth)
 {
-    const H5O_fill_t	*mesg = (const H5O_fill_t *)_mesg;
+    const H5O_fill_t *mesg = (const H5O_fill_t *)_mesg;
     H5D_fill_value_t fill_status;       /* Whether the fill value is defined */
 
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_fill_new_debug)
@@ -715,8 +626,8 @@ H5O_fill_new_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FIL
     HDassert(f);
     HDassert(mesg);
     HDassert(stream);
-    HDassert(indent>=0);
-    HDassert(fwidth>=0);
+    HDassert(indent >= 0);
+    HDassert(fwidth >= 0);
 
     HDfprintf(stream, "%*s%-*s %u\n", indent, "", fwidth,
 	      "Version:", (unsigned)H5O_FILL_VERSION);
@@ -847,8 +758,6 @@ H5O_fill_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg, FILE *s
  * Programmer:	Robb Matzke
  *              Thursday, October  1, 1998
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 herr_t
diff --git a/src/H5Oginfo.c b/src/H5Oginfo.c
index d0fb5da..12a4646 100644
--- a/src/H5Oginfo.c
+++ b/src/H5Oginfo.c
@@ -33,9 +33,9 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_ginfo_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_ginfo_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_ginfo_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_ginfo_copy(const void *_mesg, void *_dest);
-static size_t H5O_ginfo_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_ginfo_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_ginfo_free(void *_mesg);
 static herr_t H5O_ginfo_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
 			     FILE * stream, int indent, int fwidth);
@@ -45,6 +45,7 @@ const H5O_msg_class_t H5O_MSG_GINFO[1] = {{
     H5O_GINFO_ID,            	/*message id number             */
     "ginfo",                 	/*message name for debugging    */
     sizeof(H5O_ginfo_t),     	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_ginfo_decode,        	/*decode message                */
     H5O_ginfo_encode,        	/*encode message                */
     H5O_ginfo_copy,          	/*copy the native value         */
@@ -53,10 +54,8 @@ const H5O_msg_class_t H5O_MSG_GINFO[1] = {{
     H5O_ginfo_free,	        /* free method			*/
     NULL,	        	/* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL, 			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     NULL,			/* copy native value to file    */
     NULL,			/* post copy native value to file    */
@@ -149,12 +148,10 @@ done:
  *              koziol@ncsa.uiuc.edu
  *              Aug 30 2005
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_ginfo_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
+H5O_ginfo_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_ginfo_t  *ginfo = (const H5O_ginfo_t *) _mesg;
     unsigned char       flags;          /* Flags for encoding group info */
@@ -199,8 +196,6 @@ H5O_ginfo_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
  *              koziol@ncsa.uiuc.edu
  *              Aug 30 2005
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static void *
@@ -248,7 +243,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_ginfo_size(const H5F_t UNUSED *f, const void UNUSED *_mesg)
+H5O_ginfo_size(const H5F_t UNUSED *f, hbool_t UNUSED disable_shared, const void UNUSED *_mesg)
 {
     size_t ret_value;   /* Return value */
 
diff --git a/src/H5Olayout.c b/src/H5Olayout.c
index 6e9a71f..a542a7d 100644
--- a/src/H5Olayout.c
+++ b/src/H5Olayout.c
@@ -33,15 +33,15 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_layout_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_layout_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_layout_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_layout_copy(const void *_mesg, void *_dest);
-static size_t H5O_layout_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_layout_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_layout_reset(void *_mesg);
 static herr_t H5O_layout_free(void *_mesg);
 static herr_t H5O_layout_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg,
     hbool_t adj_link);
-static void *H5O_layout_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
-    void *mesg_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
+static void *H5O_layout_copy_file(H5F_t *file_src, void *mesg_src,
+    H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
 static herr_t H5O_layout_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
 			       int indent, int fwidth);
 
@@ -50,6 +50,7 @@ const H5O_msg_class_t H5O_MSG_LAYOUT[1] = {{
     H5O_LAYOUT_ID,          	/*message id number             */
     "layout",               	/*message name for debugging    */
     sizeof(H5O_layout_t),   	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_layout_decode,      	/*decode message                */
     H5O_layout_encode,      	/*encode message                */
     H5O_layout_copy,        	/*copy the native value         */
@@ -58,10 +59,8 @@ const H5O_msg_class_t H5O_MSG_LAYOUT[1] = {{
     H5O_layout_free,        	/*free the struct		*/
     H5O_layout_delete,	        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL,			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     H5O_layout_copy_file,       /* copy native value to file    */
     NULL,		        /* post copy native value to file    */
@@ -261,7 +260,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_layout_encode(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_layout_encode(H5F_t *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_layout_t     *mesg = (const H5O_layout_t *) _mesg;
     unsigned               u;
@@ -319,7 +318,7 @@ H5O_layout_encode(H5F_t *f, uint8_t *p, const void *_mesg)
     } /* end switch */
 
 done:
-    FUNC_LEAVE_NOAPI(ret_value);
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_layout_encode() */
 
 
@@ -336,8 +335,6 @@ done:
  * Programmer:  Robb Matzke
  *              Wednesday, October  8, 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static void *
@@ -347,32 +344,32 @@ H5O_layout_copy(const void *_mesg, void *_dest)
     H5O_layout_t           *dest = (H5O_layout_t *) _dest;
     void                   *ret_value;          /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_layout_copy);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_layout_copy)
 
     /* check args */
-    assert(mesg);
-    if (!dest && NULL==(dest=H5FL_MALLOC(H5O_layout_t)))
+    HDassert(mesg);
+    if(!dest && NULL == (dest = H5FL_MALLOC(H5O_layout_t)))
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
     /* copy */
     *dest = *mesg;
 
     /* Deep copy the buffer for compact datasets also */
-    if(mesg->type==H5D_COMPACT) {
+    if(mesg->type == H5D_COMPACT) {
         /* Allocate memory for the raw data */
-        if (NULL==(dest->u.compact.buf=H5MM_malloc(dest->u.compact.size)))
+        if(NULL == (dest->u.compact.buf = H5MM_malloc(dest->u.compact.size)))
             HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "unable to allocate memory for compact dataset")
 
         /* Copy over the raw data */
-        HDmemcpy(dest->u.compact.buf,mesg->u.compact.buf,dest->u.compact.size);
+        HDmemcpy(dest->u.compact.buf, mesg->u.compact.buf, dest->u.compact.size);
     } /* end if */
 
     /* Set return value */
-    ret_value=dest;
+    ret_value = dest;
 
 done:
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_layout_copy() */
 
 
 /*-------------------------------------------------------------------------
@@ -389,8 +386,6 @@ done:
  * Programmer:  Raymond Lu
  *              August 14, 2002
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 size_t
@@ -399,11 +394,11 @@ H5O_layout_meta_size(const H5F_t *f, const void *_mesg)
     const H5O_layout_t      *mesg = (const H5O_layout_t *) _mesg;
     size_t                  ret_value;
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_layout_meta_size);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_layout_meta_size)
 
     /* check args */
-    assert(f);
-    assert(mesg);
+    HDassert(f);
+    HDassert(mesg);
 
     ret_value = 1 +                     /* Version number                       */
                 1;                      /* layout class type                    */
@@ -436,8 +431,8 @@ H5O_layout_meta_size(const H5F_t *f, const void *_mesg)
     } /* end switch */
 
 done:
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_layout_meta_size() */
 
 
 /*-------------------------------------------------------------------------
@@ -454,28 +449,26 @@ done:
  * Programmer:  Robb Matzke
  *              Wednesday, October  8, 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_layout_size(const H5F_t *f, const void *_mesg)
+H5O_layout_size(const H5F_t *f, hbool_t UNUSED disable_shared, const void *_mesg)
 {
     const H5O_layout_t     *mesg = (const H5O_layout_t *) _mesg;
     size_t                  ret_value;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_layout_size);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_layout_size)
 
     /* check args */
-    assert(f);
-    assert(mesg);
+    HDassert(f);
+    HDassert(mesg);
 
     ret_value = H5O_layout_meta_size(f, mesg);
-    if(mesg->type==H5D_COMPACT)
+    if(mesg->type == H5D_COMPACT)
         ret_value += mesg->u.compact.size;/* data for compact dataset             */
 
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_layout_size() */
 
 
 /*-------------------------------------------------------------------------
@@ -612,14 +605,11 @@ done:
  * Programmer:  Peter Cao
  *              July 23, 2005
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_layout_copy_file(H5F_t *file_src, const H5O_msg_class_t UNUSED *mesg_type,
-    void *mesg_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
-    void *_udata)
+H5O_layout_copy_file(H5F_t *file_src, void *mesg_src, H5F_t *file_dst,
+    hid_t dxpl_id, H5O_copy_t *cpy_info, void *_udata)
 {
     H5D_copy_file_ud_t *udata = (H5D_copy_file_ud_t *)_udata;   /* Dataset copying user data */
     H5O_layout_t       *layout_src = (H5O_layout_t *) mesg_src;
diff --git a/src/H5Olinfo.c b/src/H5Olinfo.c
index 6b286d9..b5c4041 100644
--- a/src/H5Olinfo.c
+++ b/src/H5Olinfo.c
@@ -35,12 +35,12 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_linfo_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_linfo_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_linfo_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_linfo_copy(const void *_mesg, void *_dest);
-static size_t H5O_linfo_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_linfo_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_linfo_free(void *_mesg);
 static herr_t H5O_linfo_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link);
-static void *H5O_linfo_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
+static void *H5O_linfo_copy_file(H5F_t *file_src, 
     void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
     void *udata);
 static herr_t H5O_linfo_post_copy_file(const H5O_loc_t *parent_src_oloc, const void *mesg_src, H5O_loc_t *dst_oloc,
@@ -53,6 +53,7 @@ const H5O_msg_class_t H5O_MSG_LINFO[1] = {{
     H5O_LINFO_ID,            	/*message id number             */
     "linfo",                 	/*message name for debugging    */
     sizeof(H5O_linfo_t),     	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_linfo_decode,        	/*decode message                */
     H5O_linfo_encode,        	/*encode message                */
     H5O_linfo_copy,          	/*copy the native value         */
@@ -61,10 +62,8 @@ const H5O_msg_class_t H5O_MSG_LINFO[1] = {{
     H5O_linfo_free,	        /* free method			*/
     H5O_linfo_delete,	        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL, 			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     H5O_linfo_copy_file,	/* copy native value to file    */
     H5O_linfo_post_copy_file,	/* post copy native value to file */
@@ -181,7 +180,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_linfo_encode(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_linfo_encode(H5F_t *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_linfo_t   *linfo = (const H5O_linfo_t *)_mesg;
     unsigned char       index_flags;          /* Flags for encoding link index info */
@@ -283,7 +282,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_linfo_size(const H5F_t *f, const void *_mesg)
+H5O_linfo_size(const H5F_t *f, hbool_t UNUSED disable_shared, const void *_mesg)
 {
     const H5O_linfo_t   *linfo = (const H5O_linfo_t *)_mesg;
     size_t ret_value;   /* Return value */
@@ -378,9 +377,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_linfo_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *mesg_type, 
-    void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
-    void UNUSED *udata)
+H5O_linfo_copy_file(H5F_t UNUSED *file_src, void *native_src, H5F_t *file_dst,
+    hid_t dxpl_id, H5O_copy_t *cpy_info, void UNUSED *udata)
 {
     H5O_linfo_t          *linfo_src = (H5O_linfo_t *) native_src;
     H5O_linfo_t          *linfo_dst = NULL;
diff --git a/src/H5Olink.c b/src/H5Olink.c
index b77446e..47ebfdb 100644
--- a/src/H5Olink.c
+++ b/src/H5Olink.c
@@ -38,17 +38,16 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_link_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_link_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_link_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_link_copy(const void *_mesg, void *_dest);
-static size_t H5O_link_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_link_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_link_reset(void *_mesg);
 static herr_t H5O_link_free(void *_mesg);
 /* static herr_t H5O_link_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link); */
-static herr_t H5O_link_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
-    const void *mesg_src, hbool_t *deleted, const H5O_copy_t *cpy_info, void *udata);
-static void *H5O_link_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
-    void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
-    void *udata);
+static herr_t H5O_link_pre_copy_file(H5F_t *file_src, const void *mesg_src,
+    hbool_t *deleted, const H5O_copy_t *cpy_info, void *udata);
+static void *H5O_link_copy_file(H5F_t *file_src, void *native_src,
+    H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
 static herr_t H5O_link_post_copy_file(const H5O_loc_t *src_oloc, const void *mesg_src, H5O_loc_t *dst_oloc,
     void *mesg_dst, hid_t dxpl_id, H5O_copy_t *cpy_info);
 static herr_t H5O_link_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
@@ -59,6 +58,7 @@ const H5O_msg_class_t H5O_MSG_LINK[1] = {{
     H5O_LINK_ID,            	/*message id number             */
     "link",                 	/*message name for debugging    */
     sizeof(H5O_link_t),     	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_link_decode,        	/*decode message                */
     H5O_link_encode,        	/*encode message                */
     H5O_link_copy,          	/*copy the native value         */
@@ -67,10 +67,8 @@ const H5O_msg_class_t H5O_MSG_LINK[1] = {{
     H5O_link_free,	        /* free method			*/
     H5O_link_delete,	       	/* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL, 			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     H5O_link_pre_copy_file,	/* pre copy native value to file */
     H5O_link_copy_file,		/* copy native value to file    */
     H5O_link_post_copy_file,	/* post copy native value to file    */
@@ -232,7 +230,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_link_encode(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_link_encode(H5F_t *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_link_t       *lnk = (const H5O_link_t *) _mesg;
     size_t                  len;            /* Length of a string in the message */
@@ -381,7 +379,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_link_size(const H5F_t *f, const void *_mesg)
+H5O_link_size(const H5F_t *f, hbool_t UNUSED disable_shared, const void *_mesg)
 {
     const H5O_link_t *lnk = (const H5O_link_t *)_mesg;
     size_t ret_value;   /* Return value */
@@ -573,9 +571,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_link_pre_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *type,
-    const void UNUSED *native_src, hbool_t *deleted, const H5O_copy_t *cpy_info,
-    void UNUSED *udata)
+H5O_link_pre_copy_file(H5F_t UNUSED *file_src, const void UNUSED *native_src,
+    hbool_t *deleted, const H5O_copy_t *cpy_info, void UNUSED *udata)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_link_pre_copy_file)
 
@@ -610,9 +607,8 @@ H5O_link_pre_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *typ
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_link_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *mesg_type,
-    void *native_src, H5F_t UNUSED *file_dst, hid_t UNUSED dxpl_id,
-    H5O_copy_t UNUSED *cpy_info, void UNUSED *udata)
+H5O_link_copy_file(H5F_t UNUSED *file_src, void *native_src, H5F_t UNUSED *file_dst,
+    hid_t UNUSED dxpl_id, H5O_copy_t UNUSED *cpy_info, void UNUSED *udata)
 {
     H5O_link_t  *link_src = (H5O_link_t *)native_src;
     H5O_link_t  *link_dst = NULL;
diff --git a/src/H5Omessage.c b/src/H5Omessage.c
index 1c9235e..99cbed6 100644
--- a/src/H5Omessage.c
+++ b/src/H5Omessage.c
@@ -45,31 +45,6 @@
 /* Local Macros */
 /****************/
 
-/* Load native information for a message, if it's not already present */
-/* (Only works for messages with decode callback) */
-#define H5O_LOAD_NATIVE(F, DXPL, MSG, ERR)                                        \
-    if(NULL == (MSG)->native) {                                               \
-        const H5O_msg_class_t	*decode_type;                                 \
-                                                                              \
-        /* Check for shared message */                                        \
-        if(((MSG)->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED((MSG)->type))                                \
-            decode_type = H5O_MSG_SHARED;                                     \
-        else                                                                  \
-            decode_type = (MSG)->type;                                        \
-                                                                              \
-        /* Decode the message */                                              \
-        HDassert(decode_type->decode);                                        \
-        if(NULL == ((MSG)->native = (decode_type->decode)((F), (DXPL), (MSG)->flags, (MSG)->raw))) \
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, ERR, "unable to decode message") \
-                                                                              \
-        /* Set the message's "creation index", if it has one */		      \
-        if((MSG)->type->set_crt_index) {				      \
-            /* Set the creation index for the message */		      \
-            if(((MSG)->type->set_crt_index)((MSG)->native, (MSG)->crt_idx) < 0) \
-                HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, ERR, "unable to set creation index") \
-        } /* end if */							      \
-    } /* end if */
-
 
 /******************/
 /* Local Typedefs */
@@ -100,16 +75,12 @@ static herr_t H5O_msg_write_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *typ
     unsigned overwrite, unsigned mesg_flags, unsigned update_flags,
     void *mesg, hid_t dxpl_id, unsigned *oh_flags_ptr);
 static herr_t H5O_msg_reset_real(const H5O_msg_class_t *type, void *native);
-static void *H5O_msg_copy_real(const H5O_msg_class_t *type, const void *mesg,
-        void *dst);
 static herr_t H5O_msg_remove_real(const H5O_loc_t *loc, const H5O_msg_class_t *type,
     int sequence, H5O_operator_t op, void *op_data, hbool_t adj_link, hid_t dxpl_id);
 static herr_t H5O_msg_remove_cb(H5O_t *oh, H5O_mesg_t *mesg/*in,out*/, 
     unsigned sequence, unsigned *oh_flags_ptr, void *_udata/*in,out*/);
 static unsigned H5O_new_mesg(H5F_t *f, H5O_t *oh, unsigned *flags,
-    const H5O_msg_class_t *orig_type, void *orig_mesg, H5O_shared_t *sh_mesg,
-    const H5O_msg_class_t **new_type, void **new_mesg, hid_t dxpl_id,
-    unsigned *oh_flags_ptr);
+    const H5O_msg_class_t *type, void *mesg, hid_t dxpl_id, unsigned *oh_flags_ptr);
 static herr_t H5O_copy_mesg(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned idx,
     const H5O_msg_class_t *type, const void *mesg, unsigned flags,
     unsigned update_flags, unsigned *oh_flags_ptr);
@@ -220,24 +191,6 @@ H5O_msg_append(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned type_id,
     HDassert(mesg);
     HDassert(oh_flags_ptr);
 
-    /* Should this message be written as a SOHM? */
-    if(!(mesg_flags & H5O_MSG_FLAG_DONTSHARE) && !H5O_NEW_SHARED(type)) {
-        htri_t shared_mesg;                 /* Should this message be stored in the Shared Message table? */
-
-        /* Check if message is already shared */
-        if((shared_mesg = H5O_msg_is_shared(type_id, mesg)) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "error determining if message is shared")
-        else if(shared_mesg > 0)
-            mesg_flags |= H5O_MSG_FLAG_SHARED;
-        else {
-            if((shared_mesg = H5SM_try_share(f, dxpl_id, type_id, mesg)) > 0)
-                /* Mark the message as shared */
-                mesg_flags |= H5O_MSG_FLAG_SHARED;
-            else if(shared_mesg < 0)
-                HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "error determining if message should be shared")
-        } /* end else */
-    } /* end if */
-
     /* Append new message to object header */
     if(H5O_msg_append_real(f, dxpl_id, oh, type, mesg_flags, update_flags, mesg, oh_flags_ptr) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINSERT, FAIL, "unable to create new message in header")
@@ -264,12 +217,8 @@ done:
  */
 herr_t
 H5O_msg_append_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, const H5O_msg_class_t *type,
-    unsigned mesg_flags, unsigned update_flags, void *mesg,
-    unsigned *oh_flags_ptr)
+    unsigned mesg_flags, unsigned update_flags, void *mesg, unsigned *oh_flags_ptr)
 {
-    const H5O_msg_class_t *new_type;    /* Actual H5O class type for the ID */
-    void *new_mesg;                     /* Actual message to write */
-    H5O_shared_t sh_mesg;               /* Shared object header info */
     unsigned idx;                       /* Index of message to modify */
     herr_t ret_value = SUCCEED;         /* Return value */
 
@@ -284,11 +233,11 @@ H5O_msg_append_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, const H5O_msg_class_t *t
     HDassert(oh_flags_ptr);
 
     /* Create a new message */
-    if((idx = H5O_new_mesg(f, oh, &mesg_flags, type, mesg, &sh_mesg, &new_type, &new_mesg, dxpl_id, oh_flags_ptr)) == UFAIL)
+    if((idx = H5O_new_mesg(f, oh, &mesg_flags, type, mesg, dxpl_id, oh_flags_ptr)) == UFAIL)
         HGOTO_ERROR(H5E_OHDR, H5E_NOSPACE, FAIL, "unable to create new message")
 
     /* Copy the information for the message */
-    if(H5O_copy_mesg(f, dxpl_id, oh, idx, new_type, new_mesg, mesg_flags, update_flags, oh_flags_ptr) < 0)
+    if(H5O_copy_mesg(f, dxpl_id, oh, idx, type, mesg, mesg_flags, update_flags, oh_flags_ptr) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCOPY, FAIL, "unable to write message")
 #ifdef H5O_DEBUG
 H5O_assert(oh);
@@ -350,19 +299,6 @@ H5O_msg_write(H5O_loc_t *loc, unsigned type_id, unsigned overwrite,
     if(0 == (H5F_INTENT(loc->file) & H5F_ACC_RDWR))
 	HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "no write intent on file")
 
-    if(!H5O_NEW_SHARED(type)) {
-        /* Should this message be written as a SOHM? */
-        if(!(mesg_flags & H5O_MSG_FLAG_DONTSHARE)) {
-            htri_t shared_mesg;                 /* Whether the message should be shared */
-
-            if((shared_mesg = H5SM_try_share(loc->file, dxpl_id, type_id, mesg)) > 0)
-                /* Mark the message as shared */
-                mesg_flags |= H5O_MSG_FLAG_SHARED;
-            else if(shared_mesg < 0)
-                HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, FAIL, "error while trying to share message")
-        } /* end if */
-    } /* end if */
-
     /* Protect the object header */
     if(NULL == (oh = (H5O_t *)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")
@@ -409,12 +345,9 @@ H5O_msg_write_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
     unsigned overwrite, unsigned mesg_flags, unsigned update_flags,
     void *mesg, hid_t dxpl_id, unsigned *oh_flags_ptr)
 {
+    H5O_mesg_t         *idx_msg;        /* Pointer to message to modify */
     int	        	sequence;       /* Sequence # of message type to modify */
     unsigned		idx;            /* Index of message to modify */
-    H5O_mesg_t         *idx_msg;        /* Pointer to message to modify */
-    H5O_shared_t	sh_mesg;        /* Shared message to store */
-    const H5O_msg_class_t *write_type = type;   /* Type of message to be written */
-    const void          *write_mesg = mesg;     /* Actual message being written */
     herr_t	        ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_msg_write_real)
@@ -440,9 +373,9 @@ H5O_msg_write_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
         HGOTO_ERROR(H5E_OHDR, H5E_NOTFOUND, FAIL, "message not found")
 
     /* Check for modifying a constant message */
-    if(idx_msg->flags & H5O_MSG_FLAG_CONSTANT) {
+    if(idx_msg->flags & H5O_MSG_FLAG_CONSTANT)
 	HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "unable to modify constant message")
-    } else if(idx_msg->flags & H5O_MSG_FLAG_SHARED) {
+    else if(idx_msg->flags & H5O_MSG_FLAG_SHARED) {
         /* This message is shared, but it's being modified.  This is valid if
          * it's shared in the heap .
          * First, make sure it's not a committed message; these can't ever
@@ -454,46 +387,22 @@ H5O_msg_write_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
         if(H5SM_try_delete(f, dxpl_id, idx_msg->type->id, (H5O_shared_t *)idx_msg->native) < 0)
             HGOTO_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL, "unable to delete message from SOHM table")
 
-        if(H5O_NEW_SHARED(type)) {
-            /* Should this message be written as a SOHM? */
-            if(!(mesg_flags & H5O_MSG_FLAG_DONTSHARE)) {
-                htri_t shared_mesg;                 /* Whether the message should be shared */
+        /* Should this message be written as a SOHM? */
+        if(!(mesg_flags & H5O_MSG_FLAG_DONTSHARE)) {
+            htri_t shared_mesg;                 /* Whether the message should be shared */
 
 /* XXX: Maybe this should be before the "try_delete" call? */
 /*      (and the try_delete would need to use a copy of the message's shared info) */
-                if((shared_mesg = H5SM_try_share(f, dxpl_id, idx_msg->type->id, mesg)) > 0)
-                    /* Mark the message as shared */
-                    mesg_flags |= H5O_MSG_FLAG_SHARED;
-                else if(shared_mesg < 0)
-                    HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, FAIL, "error while trying to share message")
-            } /* end if */
+            if((shared_mesg = H5SM_try_share(f, dxpl_id, idx_msg->type->id, mesg)) > 0)
+                /* Mark the message as shared */
+                mesg_flags |= H5O_MSG_FLAG_SHARED;
+            else if(shared_mesg < 0)
+                HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, FAIL, "error while trying to share message")
         } /* end if */
-        else {
-            /* Now this message is no longer shared and we can safely overwrite it.
-             * We need to make sure that the message we're writing is shared,
-             * though, and that the library doesn't try to reset the current
-             * message like it would in a normal overwrite (this message is
-             * really a shared pointer, not a real 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);
-
-            /* Extract shared message info from current message */
-            if(NULL == H5O_msg_get_share(type->id, mesg, &sh_mesg))
-                HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, FAIL, "can't get shared message")
-
-            /* Instead of writing the original message, write a shared message */
-            write_type = H5O_MSG_SHARED;
-            write_mesg = &sh_mesg;
-        } /* end else */
     } /* end if */
 
     /* Copy the information for the message */
-    if(H5O_copy_mesg(f, dxpl_id, oh, idx, write_type, write_mesg, mesg_flags, update_flags, oh_flags_ptr) < 0)
+    if(H5O_copy_mesg(f, dxpl_id, oh, idx, type, mesg, mesg_flags, update_flags, oh_flags_ptr) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to write message")
 #ifdef H5O_DEBUG
 H5O_assert(oh);
@@ -611,30 +520,18 @@ H5O_msg_read_real(H5F_t *f, H5O_t *oh, unsigned type_id, int sequence,
 	HGOTO_ERROR(H5E_OHDR, H5E_NOTFOUND, NULL, "unable to find object header message")
 
     /*
-     * Decode the message if necessary.  If the message is shared then decode
-     * a shared message, ignoring the message type.
+     * Decode the message if necessary.  If the message is shared then retrieve
+     * native message through the shared interface.
      */
     H5O_LOAD_NATIVE(f, dxpl_id, &(oh->mesg[idx]), NULL)
 
-    /* Read the message in */
-    if((oh->mesg[idx].flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(type)) {
-	/*
-	 * If the message is shared then then the native pointer points to an
-	 * H5O_MSG_SHARED message.  We use that information to look up the real
-	 * message in the global heap or some other object header.
-	 */
-        if(NULL == (ret_value = H5O_shared_read(f, dxpl_id, (const H5O_shared_t *)oh->mesg[idx].native, type, mesg)))
-	    HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy message to user space")
-    } else {
-	/*
-	 * The message is not shared, but rather exists in the object
-	 * header.  The object header caches the native message (along with
-	 * the raw message) so we must copy the native message before
-	 * returning.
-	 */
-	if(NULL == (ret_value = (type->copy)(oh->mesg[idx].native, mesg)))
-	    HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy message to user space")
-    } /* end else */
+    /*
+     * The object header caches the native message (along with
+     * the raw message) so we must copy the native message before
+     * returning.
+     */
+    if(NULL == (ret_value = (type->copy)(oh->mesg[idx].native, mesg)))
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy message to user space")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -772,10 +669,7 @@ H5O_msg_free_mesg(H5O_mesg_t *mesg)
     HDassert(mesg);
 
     /* Free any native information */
-    if((mesg->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(mesg->type))
-        mesg->native = H5O_msg_free_real(H5O_MSG_SHARED, mesg->native);
-    else
-        mesg->native = H5O_msg_free_real(mesg->type, mesg->native);
+    mesg->native = H5O_msg_free_real(mesg->type, mesg->native);
 
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_msg_free_mesg() */
@@ -840,13 +734,14 @@ H5O_msg_copy(unsigned type_id, const void *mesg, void *dst)
     FUNC_ENTER_NOAPI(H5O_msg_copy, NULL)
 
     /* check args */
+    HDassert(mesg);
     HDassert(type_id < NELMTS(H5O_msg_class_g));
     type = H5O_msg_class_g[type_id];    /* map the type ID to the actual type object */
     HDassert(type);
 
-    /* Call the "real" copy routine */
-    if((ret_value = H5O_msg_copy_real(type, mesg, dst)) == NULL)
-	HGOTO_ERROR(H5E_OHDR, H5E_CANTCOPY, NULL, "unable to copy object header message")
+    /* Call the message class's copy routine */
+    if(NULL == (ret_value = (type->copy)(mesg, dst)))
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy object header message")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -854,41 +749,6 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_msg_copy_real
- *
- * Purpose:	Copies a message.  If MESG is is the null pointer then a null
- *		pointer is returned with no error.
- *
- * Return:	Success:	Ptr to the new message
- *
- *		Failure:	NULL
- *
- * Programmer:	Robb Matzke
- *              Thursday, May 21, 1998
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_msg_copy_real(const H5O_msg_class_t *type, const void *mesg, void *dst)
-{
-    void	*ret_value = NULL;
-
-    FUNC_ENTER_NOAPI_NOINIT(H5O_msg_copy_real)
-
-    /* check args */
-    HDassert(type);
-    HDassert(type->copy);
-
-    if(mesg)
-	if(NULL == (ret_value = (type->copy)(mesg, dst)))
-	    HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy object header message")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_msg_copy_real() */
-
-
-/*-------------------------------------------------------------------------
  * Function:	H5O_msg_count
  *
  * Purpose:	Counts the number of messages in an object header which are a
@@ -1370,11 +1230,9 @@ H5O_msg_iterate_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
     hbool_t internal, H5O_mesg_operator_t op, void *op_data, hid_t dxpl_id,
     unsigned *oh_flags_ptr)
 {
+    H5O_mesg_t         *idx_msg;        /* Pointer to current message */
     unsigned		idx;            /* Absolute index of current message in all messages */
     unsigned		sequence;       /* Relative index of current message for messages of type */
-    H5O_mesg_t         *idx_msg;        /* Pointer to current message */
-    void               *native_mesg=NULL; /* Native, readable message */
-    hbool_t             native_mesg_alloc = FALSE;  /* True if native_mesg needs to be freed */
     herr_t              ret_value = H5_ITER_CONT;      /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_msg_iterate_real)
@@ -1393,31 +1251,14 @@ H5O_msg_iterate_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
             H5O_LOAD_NATIVE(f, dxpl_id, idx_msg, FAIL)
 
             /* Check for making an "internal" (i.e. within the H5O package) callback */
-            if(internal) {
-                /* Call the "internal" iterator callback */
-                if((ret_value = (op.lib_op)(oh, idx_msg, sequence, oh_flags_ptr, op_data)) != 0)
-                    break;
-            } /* end if */
-            else {
-                /* If the message is shared, get the real message it points to */
-                if((idx_msg->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(idx_msg->type)) {
-                    if(NULL == (native_mesg = H5O_shared_read(f, dxpl_id, (const H5O_shared_t *)idx_msg->native, idx_msg->type, NULL)))
-                        HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, FAIL, "unable to read shared message")
-                    native_mesg_alloc = TRUE;
-                } /* end if */
-                else
-                    native_mesg = idx_msg->native;
-
-                /* Call the iterator callback */
-                if((ret_value = (op.app_op)(native_mesg, sequence, op_data)) != 0)
-                    break;
-
-                /* Free the "real" message if it was allocated */
-                if(native_mesg_alloc) {
-                    H5O_msg_free(idx_msg->type->id, native_mesg);
-                    native_mesg_alloc = FALSE;
-                } /* end if */
-            } /* end else */
+            if(internal)
+                ret_value = (op.lib_op)(oh, idx_msg, sequence, oh_flags_ptr, op_data);
+            else
+                ret_value = (op.app_op)(idx_msg->native, sequence, op_data);
+
+            /* Check for iterator callback indicating to get out of loop */
+            if(ret_value != 0)
+                break;
 
             /* Increment sequence value for message type */
             sequence++;
@@ -1429,10 +1270,6 @@ H5O_msg_iterate_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
         HERROR(H5E_OHDR, H5E_CANTLIST, "iterator function failed");
 
 done:
-    /* Free the native message if it was allocated */
-    if(native_mesg_alloc)
-        H5O_msg_free(idx_msg->type->id, native_mesg);
-
     /* Check if object message was modified */
     if(*oh_flags_ptr & H5AC__DIRTIED_FLAG) {
         /* Try to condense object header info */
@@ -1470,7 +1307,6 @@ H5O_msg_raw_size(const H5F_t *f, unsigned type_id, hbool_t disable_shared,
     const void *mesg)
 {
     const H5O_msg_class_t *type;        /* Actual H5O class type for the ID */
-    unsigned old_sh_mesg_flags = 0;     /* Message's current shared message flags */
     size_t ret_value;                   /* Return value */
 
     FUNC_ENTER_NOAPI(H5O_msg_raw_size, 0)
@@ -1483,32 +1319,10 @@ H5O_msg_raw_size(const H5F_t *f, unsigned type_id, hbool_t disable_shared,
     HDassert(f);
     HDassert(mesg);
 
-    /* Check for disabling shared message encoding, to encode the "base" type */
-    if(disable_shared) {
-        H5O_shared_t *sh_mesg = (H5O_shared_t *)mesg;       /* Pointer to message's shared message info */
-
-        /* Try to make certain that this routine doesn't get invoked for
-         *      unsharable message classes
-         */
-        HDassert(type->is_shared);
-
-        /* Preserve message's shared message info while getting the
-         *  "real" encoded size & buffer (*ick* - QAK)
-         *  (XXX: Harmless but ugly for message classes that aren't using shared
-         *          message method interface yet - QAK)
-         */
-        old_sh_mesg_flags = sh_mesg->flags;
-        sh_mesg->flags = 0;
-    } /* end if */
-
     /* Compute the raw data size for the mesg */
-    if((ret_value = (type->raw_size)(f, mesg)) == 0)
+    if((ret_value = (type->raw_size)(f, disable_shared, mesg)) == 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCOUNT, 0, "unable to determine size of message")
 
-    /* Restore message's shared message info, if appropriate (*ick* - QAK) */
-    if(disable_shared)
-        ((H5O_shared_t *)mesg)->flags = old_sh_mesg_flags;
-
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_msg_raw_size() */
@@ -1548,7 +1362,7 @@ H5O_msg_mesg_size(const H5F_t *f, unsigned type_id, const void *mesg, size_t ext
     HDassert(mesg);
 
     /* Compute the raw data size for the mesg */
-    if((ret_value = (type->raw_size)(f, mesg)) == 0)
+    if((ret_value = (type->raw_size)(f, FALSE, mesg)) == 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCOUNT, 0, "unable to determine size of message")
 
     /* Add in "extra" raw space */
@@ -1566,53 +1380,6 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_msg_get_share
- *
- * Purpose:	Call the 'get_share' method for a
- *              particular class of object header.  Fills SHARE
- *              with the shared object, or allocated an H5O_shared_t
- *              message and returns it.
- *
- *              If SHARE is NULL, the return value must be freed
- *              with H5O_msg_free.
- *
- * Return:	Success:	H5O_shared_t describing the shared information
- *                              for the message.
- *
- *		Failure:	NULL
- *
- * Programmer:	Quincey Koziol
- *		koziol@ncsa.uiuc.edu
- *		Oct  2 2003
- *
- *-------------------------------------------------------------------------
- */
-void *
-H5O_msg_get_share(unsigned type_id, const void *mesg, H5O_shared_t *share)
-{
-    const H5O_msg_class_t *type;        /* Actual H5O class type for the ID */
-    void  *ret_value;                   /* Return value */
-
-    FUNC_ENTER_NOAPI(H5O_msg_get_share, NULL)
-
-    /* Check args */
-    HDassert(type_id < NELMTS(H5O_msg_class_g));
-    HDassert(type_id != H5O_SHARED_ID);
-    type = H5O_msg_class_g[type_id];    /* map the type ID to the actual type object */
-    HDassert(type);
-    HDassert(type->get_share);
-    HDassert(mesg);
-
-    /* Get shared data for the mesg */
-    if((ret_value = (type->get_share)(mesg, share)) == NULL)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, NULL, "unable to retrieve shared message information")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_msg_get_share() */
-
-
-/*-------------------------------------------------------------------------
  * Function:    H5O_msg_can_share
  *
  * Purpose:     Call the 'can share' method for a
@@ -1644,9 +1411,6 @@ H5O_msg_can_share(unsigned type_id, const void *mesg)
     HDassert(type);
     HDassert(mesg);
 
-    /* If the message doesn't have an is_shared callback, it's not sharable
-     * and thus can't be shared.
-     */
     /* If there is a can_share callback, use it */
     if((type->can_share))
         ret_value = (type->can_share)(mesg);
@@ -1658,7 +1422,7 @@ H5O_msg_can_share(unsigned type_id, const void *mesg)
             ret_value = TRUE;
         else
             ret_value = FALSE;
-    }
+    } /* end else */
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_msg_can_share() */
@@ -1694,11 +1458,11 @@ H5O_msg_is_shared(unsigned type_id, const void *mesg)
     HDassert(type);
     HDassert(mesg);
 
-    /* If there is no is_shared function, then obviously it's not a shared message! */
-    if(!(type->is_shared))
+    /* If message class isn't sharable, then obviously it's not a shared message! */
+    if(!(type->is_sharable))
         ret_value = FALSE;
     else
-        ret_value = (type->is_shared)(mesg);
+        ret_value = H5O_IS_SHARED(((const H5O_shared_t *)mesg)->flags);
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_msg_is_shared() */
@@ -1813,7 +1577,6 @@ H5O_msg_encode(H5F_t *f, unsigned type_id, hbool_t disable_shared,
     unsigned char *buf, const void *mesg)
 {
     const H5O_msg_class_t *type;        /* Actual H5O class type for the ID */
-    unsigned old_sh_mesg_flags = 0;     /* Message's current shared message flags */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(H5O_msg_encode,FAIL)
@@ -1824,32 +1587,10 @@ H5O_msg_encode(H5F_t *f, unsigned type_id, hbool_t disable_shared,
     type = H5O_msg_class_g[type_id];    /* map the type ID to the actual type object */
     HDassert(type);
 
-    /* Check for disabling shared message encoding, to encode the "base" type */
-    if(disable_shared) {
-        H5O_shared_t *sh_mesg = (H5O_shared_t *)mesg;       /* Pointer to message's shared message info */
-
-        /* Try to make certain that this routine doesn't get invoked for
-         *      unsharable message classes
-         */
-        HDassert(type->is_shared);
-
-        /* Preserve message's shared message info while getting the
-         *  "real" encoded size & buffer (*ick* - QAK)
-         *  (XXX: Harmless but ugly for message classes that aren't using shared
-         *          message method interface yet - QAK)
-         */
-        old_sh_mesg_flags = sh_mesg->flags;
-        sh_mesg->flags = 0;
-    } /* end if */
-
     /* Encode */
-    if((type->encode)(f, buf, mesg) < 0)
+    if((type->encode)(f, disable_shared, buf, mesg) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTENCODE, FAIL, "unable to encode message")
 
-    /* Restore message's shared message info, if appropriate (*ick* - QAK) */
-    if(disable_shared)
-        ((H5O_shared_t *)mesg)->flags = old_sh_mesg_flags;
-
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_msg_encode() */
@@ -1916,98 +1657,41 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5O_msg_copy_file(const H5O_msg_class_t *copy_type, const H5O_msg_class_t *mesg_type,
-    H5F_t *file_src, void *native_src, H5F_t *file_dst, hid_t dxpl_id,
+H5O_msg_copy_file(const H5O_msg_class_t *type, H5F_t *file_src,
+    void *native_src, H5F_t *file_dst, hid_t dxpl_id,
     hbool_t *shared, H5O_copy_t *cpy_info, void *udata)
 {
+    htri_t is_shared;     /* Whether message is shared */
     void        *native_mesg = NULL;
-    void        *shared_mesg = NULL;
-    hbool_t      committed;         /* TRUE if message is a committed message */
     void        *ret_value;
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_msg_copy_file)
 
     /* check args */
-    HDassert(copy_type);
-    HDassert(copy_type->copy_file);
-    HDassert(mesg_type);
+    HDassert(type);
+    HDassert(type->copy_file);
     HDassert(file_src);
     HDassert(native_src);
     HDassert(file_dst);
     HDassert(cpy_info);
 
-    /* Check if this message is committed.  We'll need to know this later. */
-    committed = FALSE;
-    if(copy_type->id == H5O_SHARED_ID) {
-        H5O_shared_t *tmp_shared_mesg = (H5O_shared_t *)native_src;
-
-        if(tmp_shared_mesg->flags & H5O_COMMITTED_FLAG) {
-            HDassert(!(tmp_shared_mesg->flags & H5O_SHARED_IN_HEAP_FLAG));
-            committed = TRUE;
-        } /* end if */
-    } /* end if */
-
     /* The copy_file callback will return an H5O_shared_t only if the message
      * to be copied is a committed datatype.
      */
-    if(NULL == (native_mesg = (copy_type->copy_file)(file_src, mesg_type, native_src, file_dst, dxpl_id, cpy_info, udata)))
+    if(NULL == (native_mesg = (type->copy_file)(file_src, native_src, file_dst, dxpl_id, cpy_info, udata)))
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCOPY, NULL, "unable to copy object header message to file")
 
-    /* Committed messages are always committed in the destination.  Messages in
-     * the heap are not shared by default--they need to be "re-shared" in the
-     * destination.
-     */
-    if(committed == TRUE)
-        *shared = TRUE;
-    else {
-        if(!H5O_NEW_SHARED(copy_type)) {
-            *shared = FALSE;
-
-            /* If message isn't committed but can be shared, handle with implicit sharing. */
-            if(mesg_type->set_share) {
-                htri_t       try_share_ret;     /* Value returned from H5SM_try_share */
-
-                /* Try to share it in the destination file. */
-                if((try_share_ret = H5SM_try_share(file_dst, dxpl_id, mesg_type->id, native_mesg)) < 0)
-                    HGOTO_ERROR(H5E_SOHM, H5E_WRITEERROR, NULL, "unable to determine if message should be shared")
-
-                /* If it isn't shared, reset its sharing information.  If it is
-                 * shared, its sharing information will have been overwritten by
-                 * H5SM_try_share.
-                 */
-                if(try_share_ret == FALSE) {
-                    if(H5O_msg_reset_share(mesg_type->id, native_mesg) < 0)
-                        HGOTO_ERROR(H5E_SOHM, H5E_WRITEERROR, NULL, "unable to reset sharing information in message")
-                } /* end if */
-                else {
-                    /* Get shared message from native message */
-                    if(NULL == (shared_mesg = H5O_msg_get_share(mesg_type->id, native_mesg, NULL)))
-                        HGOTO_ERROR(H5E_SOHM, H5E_READERROR, NULL, "unable to get shared location from message")
-
-                    /* Free native message; the shared message is all we need to return */
-                    H5O_msg_free(mesg_type->id, native_mesg);
-
-                    native_mesg = shared_mesg;
-                    *shared = TRUE;
-                } /* end else */
-            } /* end if */
-        } /* end if */
-        else {
-            htri_t is_shared;     /* Whether new message is shared */
-
-            /* Check if new message is shared */
-            if((is_shared = H5O_msg_is_shared(copy_type->id, native_mesg)) < 0)
-                HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, NULL, "unable to query message's shared status")
-            *shared = is_shared;
-        } /* end else */
-    } /* end else */
+    /* Check if new message is shared */
+    if((is_shared = H5O_msg_is_shared(type->id, native_mesg)) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, NULL, "unable to query message's shared status")
+    *shared = is_shared;
 
     /* Set return value */
     ret_value = native_mesg;
 
 done:
-    if(NULL == ret_value)
-        H5O_msg_free(mesg_type->id, native_mesg);
+    if(NULL == ret_value && native_mesg)
+        H5O_msg_free(type->id, native_mesg);
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_msg_copy_file() */
@@ -2027,11 +1711,11 @@ done:
  *-------------------------------------------------------------------------
  */
 static unsigned
-H5O_new_mesg(H5F_t *f, H5O_t *oh, unsigned *mesg_flags, const H5O_msg_class_t *orig_type,
-    void *orig_mesg, H5O_shared_t *sh_mesg, const H5O_msg_class_t **new_type,
-    void **new_mesg, hid_t dxpl_id, unsigned *oh_flags_ptr)
+H5O_new_mesg(H5F_t *f, H5O_t *oh, unsigned *mesg_flags, const H5O_msg_class_t *type,
+    void *mesg, hid_t dxpl_id, unsigned *oh_flags_ptr)
 {
     size_t	size;                   /* Size of space allocated for object header */
+    htri_t shared_mesg;                 /* Should this message be stored in the Shared Message table? */
     unsigned    ret_value = UFAIL;      /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_new_mesg)
@@ -2040,93 +1724,47 @@ H5O_new_mesg(H5F_t *f, H5O_t *oh, unsigned *mesg_flags, const H5O_msg_class_t *o
     HDassert(f);
     HDassert(oh);
     HDassert(mesg_flags);
-    HDassert(orig_type);
-    HDassert(orig_mesg);
-    HDassert(sh_mesg);
-    HDassert(new_type);
-    HDassert(new_mesg);
+    HDassert(!(*mesg_flags & H5O_MSG_FLAG_SHARED));
+    HDassert(type);
+    HDassert(mesg);
     HDassert(oh_flags_ptr);
 
-    /* Check for shared message */
-    if((*mesg_flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(orig_type)) {
-        htri_t      is_shared;              /* Is this a shared message? */
-
-        if((NULL == orig_type->is_shared) || (NULL == orig_type->get_share))
-            HGOTO_ERROR(H5E_OHDR, H5E_UNSUPPORTED, UFAIL, "message class is not sharable")
-        if((is_shared = (orig_type->is_shared)(orig_mesg)) == FALSE) {
-            /*
-             * If the message isn't shared then turn off the shared bit
-             * and treat it as an unshared message.
-             */
-            *mesg_flags &= ~H5O_MSG_FLAG_SHARED;
-            *new_type = orig_type;
-            *new_mesg = orig_mesg;
-        } else if(is_shared > 0) {
-            /* Message is shared. Get shared message, change message type,
-             * and use shared information */
-            HDmemset(sh_mesg, 0, sizeof(H5O_shared_t));
-            if(NULL == (orig_type->get_share)(orig_mesg, sh_mesg/*out*/))
-                HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, UFAIL, "can't get shared message")
-
-            *new_type = H5O_MSG_SHARED;
-            *new_mesg = sh_mesg;
-        } else {
-            HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, UFAIL, "can't determine if message is shared")
-        } /* end else */
+    /* Check if message is already shared */
+    if((shared_mesg = H5O_msg_is_shared(type->id, mesg)) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, UFAIL, "error determining if message is shared")
+    else if(shared_mesg > 0) {
+        /* Increment message's reference count */
+        if(type->link && (type->link)(f, dxpl_id, mesg) < 0)
+            HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, UFAIL, "unable to adjust shared message ref count")
+        *mesg_flags |= H5O_MSG_FLAG_SHARED;
     } /* end if */
     else {
-        *new_type = orig_type;
-        *new_mesg = orig_mesg;
-    } /* end else */
-
-    if(H5O_NEW_SHARED(orig_type)) {
-        htri_t shared_mesg;                 /* Should this message be stored in the Shared Message table? */
-
-        HDassert(!(*mesg_flags & H5O_MSG_FLAG_SHARED));
-
-        /* Check if message is already shared */
-        if((shared_mesg = H5O_msg_is_shared((*new_type)->id, (*new_mesg))) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, UFAIL, "error determining if message is shared")
-        else if(shared_mesg > 0) {
-            /* Increment message's reference count */
-            if((*new_type)->link && ((*new_type)->link)(f, dxpl_id, (*new_mesg)) < 0)
-                HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, UFAIL, "unable to adjust shared message ref count")
-            *mesg_flags |= H5O_MSG_FLAG_SHARED;
+        /* Avoid unsharable messages */
+        if(!(*mesg_flags & H5O_MSG_FLAG_DONTSHARE)) {
+            /* Attempt to share message */
+            if((shared_mesg = H5SM_try_share(f, dxpl_id, type->id, mesg)) > 0)
+                /* Mark the message as shared */
+                *mesg_flags |= H5O_MSG_FLAG_SHARED;
+            else if(shared_mesg < 0)
+                HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, UFAIL, "error determining if message should be shared")
         } /* end if */
-        else {
-            /* Avoid unsharable messages */
-            if(!(*mesg_flags & H5O_MSG_FLAG_DONTSHARE)) {
-                /* Attempt to share message */
-                if((shared_mesg = H5SM_try_share(f, dxpl_id, (*new_type)->id, (*new_mesg))) > 0)
-                    /* Mark the message as shared */
-                    *mesg_flags |= H5O_MSG_FLAG_SHARED;
-                else if(shared_mesg < 0)
-                    HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, UFAIL, "error determining if message should be shared")
-            } /* end if */
-        } /* end else */
-    } /* end if */
+    } /* end else */
 
     /* Compute the size needed to store the message on disk */
-    if((size = ((*new_type)->raw_size)(f, *new_mesg)) >= H5O_MESG_MAX_SIZE)
+    if((size = (type->raw_size)(f, FALSE, mesg)) >= H5O_MESG_MAX_SIZE)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, UFAIL, "object header message is too large")
 
     /* Allocate space in the object header for the message */
-    if((ret_value = H5O_alloc(f, dxpl_id, oh, orig_type, size, oh_flags_ptr)) == UFAIL)
+    if((ret_value = H5O_alloc(f, dxpl_id, oh, type, size, oh_flags_ptr)) == UFAIL)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, UFAIL, "unable to allocate space for message")
 
     /* Get the message's "creation index", if it has one */
-    if(orig_type->get_crt_index) {
+    if(type->get_crt_index) {
         /* Retrieve the creation index for the message */
-        if((orig_type->get_crt_index)(orig_mesg, &oh->mesg[ret_value].crt_idx) < 0)
+        if((type->get_crt_index)(mesg, &oh->mesg[ret_value].crt_idx) < 0)
             HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, UFAIL, "unable to retrieve creation index")
     } /* end if */
 
-    if(!H5O_NEW_SHARED(orig_type)) {
-        /* Increment any links in message */
-        if((*new_type)->link && ((*new_type)->link)(f, dxpl_id, (*new_mesg)) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, UFAIL, "unable to adjust shared object link count")
-    } /* end if */
-
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_new_mesg() */
@@ -2150,8 +1788,8 @@ H5O_copy_mesg(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned idx,
     const H5O_msg_class_t *type, const void *mesg, unsigned mesg_flags,
     unsigned update_flags, unsigned *oh_flags_ptr)
 {
-    H5O_mesg_t         *idx_msg;        /* Pointer to message to modify */
-    herr_t      ret_value = SUCCEED;    /* Return value */
+    H5O_mesg_t *idx_msg = &oh->mesg[idx];       /* Pointer to message to modify */
+    herr_t      ret_value = SUCCEED;            /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_copy_mesg)
 
@@ -2162,9 +1800,6 @@ H5O_copy_mesg(H5F_t *f, hid_t dxpl_id, H5O_t *oh, unsigned idx,
     HDassert(mesg);
     HDassert(oh_flags_ptr);
 
-    /* Set pointer to the correct message */
-    idx_msg = &oh->mesg[idx];
-
     /* Reset existing native information for the header's message */
     H5O_msg_reset_real(type, idx_msg->native);
 
@@ -2248,7 +1883,7 @@ done:
 herr_t
 H5O_delete_mesg(H5F_t *f, hid_t dxpl_id, H5O_mesg_t *mesg, hbool_t adj_link)
 {
-    const H5O_msg_class_t *type;  /* Type of object to free */
+    const H5O_msg_class_t *type = mesg->type;  /* Type of object to free */
     herr_t ret_value = SUCCEED;   /* Return value */
 
     FUNC_ENTER_NOAPI(H5O_delete_mesg, FAIL)
@@ -2257,35 +1892,10 @@ H5O_delete_mesg(H5F_t *f, hid_t dxpl_id, H5O_mesg_t *mesg, hbool_t adj_link)
     HDassert(f);
     HDassert(mesg);
 
-    /* Get the message to free's type */
-    if((mesg->flags & H5O_MSG_FLAG_SHARED) && !H5O_NEW_SHARED(mesg->type))
-        type = H5O_MSG_SHARED;
-    else
-        type = mesg->type;
-
     /* Check if there is a file space deletion callback for this type of message */
     if(type->del) {
         /* Decode the message if necessary. */
-        if(NULL == mesg->native) {
-            HDassert(type->decode);
-            if(NULL == (mesg->native = (type->decode)(f, dxpl_id, mesg->flags, mesg->raw)))
-                HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "unable to decode message")
-
-            /* Set the message's "creation index", if it has one */
-            if(mesg->type->set_crt_index) {
-                /* Set the creation index for the message */
-                if((mesg->type->set_crt_index)(mesg->native, mesg->crt_idx) < 0)
-                    HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "unable to set creation index")
-            } /* end if */
-        } /* end if */
-
-        /* Check if this message needs to be removed from the SOHM table if
-         * it's a shared message.
-         */
-        if(type == H5O_MSG_SHARED) {
-            if(H5SM_try_delete(f, dxpl_id, mesg->type->id, (H5O_shared_t *)mesg->native) < 0)
-                HGOTO_ERROR(H5E_OHDR, H5E_CANTFREE, FAIL, "unable to delete message from SOHM table")
-        } /* end if */
+        H5O_LOAD_NATIVE(f, dxpl_id, mesg, FAIL)
 
         if((type->del)(f, dxpl_id, mesg->native, adj_link) < 0)
             HGOTO_ERROR(H5E_OHDR, H5E_CANTDELETE, FAIL, "unable to delete file space for object header message")
diff --git a/src/H5Omtime.c b/src/H5Omtime.c
index 5015264..d180cc6 100644
--- a/src/H5Omtime.c
+++ b/src/H5Omtime.c
@@ -33,13 +33,13 @@
 
 
 static void *H5O_mtime_new_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_mtime_new_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static size_t H5O_mtime_new_size(const H5F_t *f, const void *_mesg);
+static herr_t H5O_mtime_new_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
+static size_t H5O_mtime_new_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 
 static void *H5O_mtime_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_mtime_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_mtime_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_mtime_copy(const void *_mesg, void *_dest);
-static size_t H5O_mtime_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_mtime_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_mtime_reset(void *_mesg);
 static herr_t H5O_mtime_free(void *_mesg);
 static herr_t H5O_mtime_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE *stream,
@@ -50,6 +50,7 @@ const H5O_msg_class_t H5O_MSG_MTIME[1] = {{
     H5O_MTIME_ID,		/*message id number		*/
     "mtime",			/*message name for debugging	*/
     sizeof(time_t),		/*native message size		*/
+    FALSE,			/* messages are sharable?       */
     H5O_mtime_decode,		/*decode message		*/
     H5O_mtime_encode,		/*encode message		*/
     H5O_mtime_copy,		/*copy the native value		*/
@@ -58,10 +59,8 @@ const H5O_msg_class_t H5O_MSG_MTIME[1] = {{
     H5O_mtime_free,		/* free method			*/
     NULL,		        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,			/*get share method		*/
     NULL,			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     NULL,			/* copy native value to file    */
     NULL,			/* post copy native value to file    */
@@ -76,6 +75,7 @@ const H5O_msg_class_t H5O_MSG_MTIME_NEW[1] = {{
     H5O_MTIME_NEW_ID,		/*message id number		*/
     "mtime_new",		/*message name for debugging	*/
     sizeof(time_t),		/*native message size		*/
+    FALSE,			/* messages are sharable?       */
     H5O_mtime_new_decode,	/*decode message		*/
     H5O_mtime_new_encode,	/*encode message		*/
     H5O_mtime_copy,		/*copy the native value		*/
@@ -84,10 +84,8 @@ const H5O_msg_class_t H5O_MSG_MTIME_NEW[1] = {{
     H5O_mtime_free,		/* free method			*/
     NULL,		        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,			/*get share method		*/
     NULL,			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL,			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     NULL,			/* copy native value to file    */
     NULL,			/* post copy native value to file    */
@@ -302,12 +300,10 @@ done:
  *		koziol@ncsa.uiuc.edu
  *		Jan  3 2002
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_mtime_new_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
+H5O_mtime_new_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const time_t	*mesg = (const time_t *) _mesg;
 
@@ -349,7 +345,7 @@ H5O_mtime_new_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_mtime_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
+H5O_mtime_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const time_t	*mesg = (const time_t *) _mesg;
     struct tm		*tm;
@@ -435,7 +431,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_mtime_new_size(const H5F_t UNUSED * f, const void UNUSED * mesg)
+H5O_mtime_new_size(const H5F_t UNUSED * f, hbool_t UNUSED disable_shared, const void UNUSED * mesg)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_mtime_new_size);
 
@@ -468,7 +464,7 @@ H5O_mtime_new_size(const H5F_t UNUSED * f, const void UNUSED * mesg)
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_mtime_size(const H5F_t UNUSED * f, const void UNUSED * mesg)
+H5O_mtime_size(const H5F_t UNUSED * f, hbool_t UNUSED disable_shared, const void UNUSED * mesg)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_mtime_size);
 
diff --git a/src/H5Oname.c b/src/H5Oname.c
index 4b528b8..3402690 100644
--- a/src/H5Oname.c
+++ b/src/H5Oname.c
@@ -33,9 +33,9 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_name_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_name_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_name_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_name_copy(const void *_mesg, void *_dest);
-static size_t H5O_name_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_name_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_name_reset(void *_mesg);
 static herr_t H5O_name_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
 			     int indent, int fwidth);
@@ -45,18 +45,17 @@ const H5O_msg_class_t H5O_MSG_NAME[1] = {{
     H5O_NAME_ID,            	/*message id number             */
     "name",                 	/*message name for debugging    */
     sizeof(H5O_name_t),     	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_name_decode,        	/*decode message                */
     H5O_name_encode,        	/*encode message                */
     H5O_name_copy,          	/*copy the native value         */
     H5O_name_size,          	/*raw message size              */
     H5O_name_reset,         	/*free internal memory          */
-    NULL,		            /* free method			*/
+    NULL,			/* free method			*/
     NULL,		        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL,			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     NULL,			/* copy native value to file    */
     NULL,			/* post copy native value to file    */
@@ -130,7 +129,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_name_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
+H5O_name_encode(H5F_t UNUSED *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_name_t       *mesg = (const H5O_name_t *) _mesg;
 
@@ -214,7 +213,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_name_size(const H5F_t UNUSED *f, const void *_mesg)
+H5O_name_size(const H5F_t UNUSED *f, hbool_t UNUSED disable_shared, const void *_mesg)
 {
     const H5O_name_t       *mesg = (const H5O_name_t *) _mesg;
     size_t                  ret_value;
diff --git a/src/H5Onull.c b/src/H5Onull.c
index 914d8be..98049d8 100644
--- a/src/H5Onull.c
+++ b/src/H5Onull.c
@@ -34,6 +34,7 @@ const H5O_msg_class_t H5O_MSG_NULL[1] = {{
     H5O_NULL_ID,            	/*message id number             */
     "null",                 	/*message name for debugging    */
     0,                      	/*native message size           */
+    FALSE,			/*messages are sharable?        */
     NULL,                   	/*no decode method              */
     NULL,                   	/*no encode method              */
     NULL,                   	/*no copy method                */
@@ -42,10 +43,8 @@ const H5O_msg_class_t H5O_MSG_NULL[1] = {{
     NULL,                   	/*no free method                */
     NULL,		    	/*no file delete method         */
     NULL,		    	/*no link method		*/
-    NULL,		    	/*no get share method	        */
     NULL,	            	/*no set share method	        */
     NULL,		    	/*no can share method		*/
-    NULL,	            	/*no is_shared method	        */
     NULL,		    	/*no pre copy native value to file */
     NULL,		    	/*no copy native value to file  */
     NULL,		    	/*no post copy native value to file */
diff --git a/src/H5Opkg.h b/src/H5Opkg.h
index 0a0310d..0f5a7ae 100644
--- a/src/H5Opkg.h
+++ b/src/H5Opkg.h
@@ -157,10 +157,24 @@
 #define H5O_SIZEOF_CHKSUM_OH(O)						      \
     H5O_SIZEOF_CHKSUM_VERS((O)->version)
 
-/* Temporary macro to define which message classes are using the "new"
- * shared message "interface" for their methods.
- */
-#define H5O_NEW_SHARED(T)       ((T) == H5O_MSG_PLINE || (T) == H5O_MSG_FILL_NEW || (T) == H5O_MSG_FILL || (T) == H5O_MSG_SDSPACE || (T) == H5O_MSG_DTYPE || (T) == H5O_MSG_ATTR)
+/* Load native information for a message, if it's not already present */
+/* (Only works for messages with decode callback) */
+#define H5O_LOAD_NATIVE(F, DXPL, MSG, ERR)                                        \
+    if(NULL == (MSG)->native) {                                               \
+        const H5O_msg_class_t	*decode_type = (MSG)->type;                   \
+                                                                              \
+        /* Decode the message */                                              \
+        HDassert(decode_type->decode);                                        \
+        if(NULL == ((MSG)->native = (decode_type->decode)((F), (DXPL), (MSG)->flags, (MSG)->raw))) \
+            HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, ERR, "unable to decode message") \
+                                                                              \
+        /* Set the message's "creation index", if it has one */		      \
+        if((MSG)->type->set_crt_index) {				      \
+            /* Set the creation index for the message */		      \
+            if((decode_type->set_crt_index)((MSG)->native, (MSG)->crt_idx) < 0) \
+                HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, ERR, "unable to set creation index") \
+        } /* end if */							      \
+    } /* end if */
 
 
 /* The "message class" type */
@@ -168,20 +182,19 @@ struct H5O_msg_class_t {
     unsigned	id;				/*message type ID on disk   */
     const char	*name;				/*for debugging             */
     size_t	native_size;			/*size of native message    */
+    hbool_t     is_sharable;			/*are messages of this class sharable? */
     void	*(*decode)(H5F_t*, hid_t, unsigned, const uint8_t *);
-    herr_t	(*encode)(H5F_t*, uint8_t*, const void *);
+    herr_t	(*encode)(H5F_t*, hbool_t, uint8_t*, const void *);
     void	*(*copy)(const void *, void *);	/*copy native value         */
-    size_t	(*raw_size)(const H5F_t *, const void *);/*sizeof encoded message	*/
+    size_t	(*raw_size)(const H5F_t *, hbool_t, const void *);/*sizeof encoded message	*/
     herr_t	(*reset)(void *);		/*free nested data structs  */
     herr_t	(*free)(void *);		/*free main data struct  */
     herr_t	(*del)(H5F_t *, hid_t, const void *, hbool_t); /* Delete space in file referenced by this message */
     herr_t	(*link)(H5F_t *, hid_t, const void *); /* Increment any links in file reference by this message */
-    void	*(*get_share)(const void*, struct H5O_shared_t*);    /* Get shared information */
-    herr_t	(*set_share)(void*, const struct H5O_shared_t*);    /* Set shared information */
+    herr_t	(*set_share)(void*, const H5O_shared_t*);    /* Set shared information */
     htri_t	(*can_share)(const void *);	/* Is message allowed to be shared? */
-    htri_t	(*is_shared)(const void *);	/* Is message shared? */
-    herr_t	(*pre_copy_file)(H5F_t *, const H5O_msg_class_t *, const void *, hbool_t *, const H5O_copy_t *, void *); /*"pre copy" action when copying native value to file */
-    void	*(*copy_file)(H5F_t *, const H5O_msg_class_t *, void *, H5F_t *, hid_t, H5O_copy_t *, void *); /*copy native value to file */
+    herr_t	(*pre_copy_file)(H5F_t *, const void *, hbool_t *, const H5O_copy_t *, void *); /*"pre copy" action when copying native value to file */
+    void	*(*copy_file)(H5F_t *, void *, H5F_t *, hid_t, H5O_copy_t *, void *); /*copy native value to file */
     herr_t	(*post_copy_file)(const H5O_loc_t *, const void *, H5O_loc_t *, void *, hid_t, H5O_copy_t *); /*"post copy" action when copying native value to file */
     herr_t      (*get_crt_index)(const void *, H5O_crt_idx_t *);	/* Get message's creation index */
     herr_t      (*set_crt_index)(void *, H5O_crt_idx_t);	/* Set message's creation index */
@@ -418,9 +431,9 @@ H5_DLL void *H5O_msg_read_real(H5F_t *f, H5O_t *oh, unsigned type_id,
 H5_DLL void *H5O_msg_free_real(const H5O_msg_class_t *type, void *mesg);
 H5_DLL herr_t H5O_msg_free_mesg(H5O_mesg_t *mesg);
 H5_DLL htri_t H5O_msg_exists_oh(struct H5O_t *oh, unsigned type_id, int sequence);
-H5_DLL void * H5O_msg_copy_file(const H5O_msg_class_t *copy_type,
-    const H5O_msg_class_t *mesg_type, H5F_t *file_src, void *mesg_src,
-    H5F_t *file_dst, hid_t dxpl_id, hbool_t *shared, H5O_copy_t *cpy_info, void *udata);
+H5_DLL void *H5O_msg_copy_file(const H5O_msg_class_t *type, H5F_t *file_src,
+    void *mesg_src, H5F_t *file_dst, hid_t dxpl_id, hbool_t *shared,
+    H5O_copy_t *cpy_info, void *udata);
 H5_DLL herr_t H5O_msg_iterate_real(H5F_t *f, H5O_t *oh, const H5O_msg_class_t *type,
     hbool_t internal, H5O_mesg_operator_t op, void *op_data, hid_t dxpl_id,
     unsigned *oh_flags_ptr);
@@ -433,19 +446,18 @@ H5_DLL herr_t H5O_release_mesg(H5F_t *f, hid_t dxpl_id, H5O_t *oh,
     H5O_mesg_t *mesg, hbool_t delete_mesg, hbool_t adj_link);
 
 /* Shared object operators */
-H5_DLL void * H5O_shared_read(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared,
-    const H5O_msg_class_t *type, void *mesg);
-H5_DLL void * H5O_shared_decode_new(H5F_t *f, hid_t dxpl_id, const uint8_t *buf, const H5O_msg_class_t *type);
-H5_DLL herr_t H5O_shared_encode_new(const H5F_t *f, uint8_t *buf/*out*/, const H5O_shared_t *sh_mesg);
-H5_DLL size_t H5O_shared_size_new(const H5F_t *f, const H5O_shared_t *sh_mesg);
-H5_DLL herr_t H5O_shared_delete_new(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
+H5_DLL void * H5O_shared_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *buf, const H5O_msg_class_t *type);
+H5_DLL herr_t H5O_shared_encode(const H5F_t *f, uint8_t *buf/*out*/, const H5O_shared_t *sh_mesg);
+H5_DLL size_t H5O_shared_size(const H5F_t *f, const H5O_shared_t *sh_mesg);
+H5_DLL herr_t H5O_shared_delete(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
     const H5O_msg_class_t *mesg_type, hbool_t adj_link);
-H5_DLL herr_t H5O_shared_link_new(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
+H5_DLL herr_t H5O_shared_link(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
     const H5O_msg_class_t *mesg_type);
-H5_DLL herr_t H5O_shared_copy_file_new(H5F_t *file_src, H5F_t *file_dst, hid_t dxpl_id,
+H5_DLL herr_t H5O_shared_copy_file(H5F_t *file_src, H5F_t *file_dst, hid_t dxpl_id,
     const H5O_msg_class_t *mesg_type, const void *_native_src, void *_native_dst,
     H5O_copy_t *cpy_info, void *udata);
-
+H5_DLL herr_t H5O_shared_debug(const H5O_shared_t *mesg, FILE *stream,
+    int indent, int fwidth);
 
 /* Attribute operations */
 H5_DLL herr_t H5O_attr_create(const H5O_loc_t *loc, hid_t dxpl_id, H5A_t *attr);
diff --git a/src/H5Opline.c b/src/H5Opline.c
index d87c781..c2201c1 100644
--- a/src/H5Opline.c
+++ b/src/H5Opline.c
@@ -35,10 +35,7 @@ static void *H5O_pline_copy(const void *_mesg, void *_dest);
 static size_t H5O_pline_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_pline_reset(void *_mesg);
 static herr_t H5O_pline_free(void *_mesg);
-static void *H5O_pline_get_share(const void *_mesg, H5O_shared_t *sh);
-static herr_t H5O_pline_set_share(void *_mesg, const H5O_shared_t *sh);
-static htri_t H5O_pline_is_shared(const void *_mesg);
-static herr_t H5O_pline_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
+static herr_t H5O_pline_pre_copy_file(H5F_t *file_src, 
     const void *mesg_src, hbool_t *deleted, const H5O_copy_t *cpy_info, void *_udata);
 static herr_t H5O_pline_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
     FILE * stream, int indent, int fwidth);
@@ -57,6 +54,8 @@ static herr_t H5O_pline_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
 #undef H5O_SHARED_LINK_REAL
 #define H5O_SHARED_COPY_FILE		H5O_pline_shared_copy_file
 #undef H5O_SHARED_COPY_FILE_REAL
+#define H5O_SHARED_DEBUG		H5O_pline_shared_debug
+#define H5O_SHARED_DEBUG_REAL		H5O_pline_debug
 #include "H5Oshared.h"			/* Shared Object Header Message Callbacks */
 
 /* This message derives from H5O message class */
@@ -64,6 +63,7 @@ const H5O_msg_class_t H5O_MSG_PLINE[1] = {{
     H5O_PLINE_ID,		/* message id number		*/
     "filter pipeline",		/* message name for debugging	*/
     sizeof(H5O_pline_t),	/* native message size		*/
+    TRUE,			/* messages are sharable?       */
     H5O_pline_shared_decode,	/* decode message		*/
     H5O_pline_shared_encode,	/* encode message		*/
     H5O_pline_copy,		/* copy the native value	*/
@@ -72,16 +72,14 @@ const H5O_msg_class_t H5O_MSG_PLINE[1] = {{
     H5O_pline_free,		/* free method			*/
     H5O_pline_shared_delete,    /* file delete method		*/
     H5O_pline_shared_link,	/* link method			*/
-    H5O_pline_get_share,	/* get share method		*/
-    H5O_pline_set_share,	/* set share method		*/
+    H5O_shared_copy,		/* set share method			*/
     NULL,		    	/*can share method		*/
-    H5O_pline_is_shared,	/* is shared method		*/
     H5O_pline_pre_copy_file,	/* pre copy native value to file */
     H5O_pline_shared_copy_file,	/* copy native value to file    */
     NULL,			/* post copy native value to file    */
     NULL,			/* get creation index		*/
     NULL,			/* set creation index		*/
-    H5O_pline_debug		/* debug the message		*/
+    H5O_pline_shared_debug	/* debug the message		*/
 }};
 
 
@@ -588,9 +586,8 @@ H5O_pline_free(void *mesg)
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_pline_pre_copy_file(H5F_t UNUSED *file_src, const H5O_msg_class_t UNUSED *type,
-    const void *mesg_src, hbool_t UNUSED *deleted, const H5O_copy_t UNUSED *cpy_info,
-    void *_udata)
+H5O_pline_pre_copy_file(H5F_t UNUSED *file_src, const void *mesg_src,
+    hbool_t UNUSED *deleted, const H5O_copy_t UNUSED *cpy_info, void *_udata)
 {
     const H5O_pline_t *pline_src = (const H5O_pline_t *)mesg_src;    /* Source datatype */
     H5D_copy_file_ud_t *udata = (H5D_copy_file_ud_t *)_udata;   /* Dataset copying user data */
@@ -615,98 +612,6 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_pline_get_share
- *
- * Purpose:	Gets sharing information from the message
- *
- * Return:	Shared message on success/NULL on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_pline_get_share(const void *_mesg, H5O_shared_t *sh /*out*/)
-{
-    const H5O_pline_t  *mesg = (const H5O_pline_t *)_mesg;
-    void       *ret_value = NULL;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_pline_get_share)
-
-    HDassert (mesg);
-
-    ret_value = H5O_msg_copy(H5O_SHARED_ID, &(mesg->sh_loc), sh);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_pline_get_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_pline_set_share
- *
- * Purpose:	Sets sharing information for the message
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- * Modifications:
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_pline_set_share(void *_mesg/*in,out*/, const H5O_shared_t *sh)
-{
-    H5O_pline_t  *mesg = (H5O_pline_t *)_mesg;
-    herr_t       ret_value = SUCCEED;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_pline_set_share)
-
-    HDassert (mesg);
-    HDassert (sh);
-
-    if(NULL == H5O_msg_copy(H5O_SHARED_ID, sh, &(mesg->sh_loc)))
-        ret_value = FAIL;
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_pline_set_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_pline_is_shared
- *
- * Purpose:	Determines if this fill value is shared (committed or a SOHM)
- *              or not.
- *
- * Return:	TRUE if fill value is shared
- *              FALSE if fill value is not shared
- *              Negative on failure
- *
- * Programmer:	James Laird
- *		Monday, October 16, 2006
- *
- *-------------------------------------------------------------------------
- */
-static htri_t
-H5O_pline_is_shared(const void *_mesg)
-{
-    const H5O_pline_t  *mesg = (const H5O_pline_t *)_mesg;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_pline_is_shared)
-
-    HDassert(mesg);
-
-    /* I/O pipelines can't currently be committed, but this should let the
-     * library read a "committed I/O pipeline" if we ever create one in
-     * the future.
-     */
-    FUNC_LEAVE_NOAPI(H5O_IS_SHARED(mesg->sh_loc.flags))
-} /* end H5O_pline_is_shared() */
-
-
-/*-------------------------------------------------------------------------
  * Function:	H5O_pline_debug
  *
  * Purpose:	Prints debugging information for filter pipeline message MESG
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index 62285e1..76d5dd0 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -426,7 +426,6 @@ H5_DLL size_t H5O_msg_raw_size(const H5F_t *f, unsigned type_id,
     hbool_t disable_shared, const void *mesg);
 H5_DLL size_t H5O_msg_mesg_size(const H5F_t *f, unsigned type_id, const void *mesg,
     size_t extra_raw);
-H5_DLL void *H5O_msg_get_share(unsigned type_id, const void *mesg, H5O_shared_t *share);
 H5_DLL htri_t H5O_msg_is_shared(unsigned type_id, const void *mesg);
 H5_DLL htri_t H5O_msg_can_share(unsigned type_id, const void *mesg);
 H5_DLL herr_t H5O_msg_set_share(unsigned type_id, H5O_shared_t *share, void *mesg);
@@ -468,5 +467,8 @@ H5_DLL herr_t H5O_fill_convert(H5O_fill_t *fill, H5T_t *type, hbool_t *fill_chan
 /* Link operators */
 H5_DLL herr_t H5O_link_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link);
 
+/* Shared message operators */
+H5_DLL herr_t H5O_shared_copy(void *dst, const H5O_shared_t *src);
+
 #endif /* _H5Oprivate_H */
 
diff --git a/src/H5Osdspace.c b/src/H5Osdspace.c
index 1d406d9..c111824 100644
--- a/src/H5Osdspace.c
+++ b/src/H5Osdspace.c
@@ -31,11 +31,8 @@ static void *H5O_sdspace_copy(const void *_mesg, void *_dest);
 static size_t H5O_sdspace_size(const H5F_t *f, const void *_mesg);
 static herr_t H5O_sdspace_reset(void *_mesg);
 static herr_t H5O_sdspace_free(void *_mesg);
-static void *H5O_sdspace_get_share(const void *_mesg, H5O_shared_t *sh);
-static herr_t H5O_sdspace_set_share(void *_mesg, const H5O_shared_t *sh);
-static htri_t H5O_sdspace_is_shared(const void *_mesg);
-static herr_t H5O_sdspace_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
-    const void *mesg_src, hbool_t *deleted, const H5O_copy_t *cpy_info, void *_udata);
+static herr_t H5O_sdspace_pre_copy_file(H5F_t *file_src, const void *mesg_src,
+    hbool_t *deleted, const H5O_copy_t *cpy_info, void *_udata);
 static herr_t H5O_sdspace_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
 				FILE * stream, int indent, int fwidth);
 
@@ -53,6 +50,8 @@ static herr_t H5O_sdspace_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
 #undef H5O_SHARED_LINK_REAL
 #define H5O_SHARED_COPY_FILE		H5O_sdspace_shared_copy_file
 #undef H5O_SHARED_COPY_FILE_REAL
+#define H5O_SHARED_DEBUG		H5O_sdspace_shared_debug
+#define H5O_SHARED_DEBUG_REAL		H5O_sdspace_debug
 #include "H5Oshared.h"			/* Shared Object Header Message Callbacks */
 
 /* This message derives from H5O message class */
@@ -60,6 +59,7 @@ const H5O_msg_class_t H5O_MSG_SDSPACE[1] = {{
     H5O_SDSPACE_ID,	    	/* message id number		    	*/
     "dataspace",	    	/* message name for debugging	   	*/
     sizeof(H5S_extent_t),   	/* native message size		    	*/
+    TRUE,			/* messages are sharable?       */
     H5O_sdspace_shared_decode,	/* decode message			*/
     H5O_sdspace_shared_encode,	/* encode message			*/
     H5O_sdspace_copy,	    	/* copy the native value		*/
@@ -68,16 +68,14 @@ const H5O_msg_class_t H5O_MSG_SDSPACE[1] = {{
     H5O_sdspace_free,		/* free method				*/
     H5O_sdspace_shared_delete,	/* file delete method		*/
     H5O_sdspace_shared_link,	/* link method			*/
-    H5O_sdspace_get_share,    	/* get share method			*/
-    H5O_sdspace_set_share,	/* set share method			*/
+    H5O_shared_copy,		/* set share method			*/
     NULL,		    	/*can share method		*/
-    H5O_sdspace_is_shared,	/* is shared method			*/
     H5O_sdspace_pre_copy_file,	/* pre copy native value to file */
     H5O_sdspace_shared_copy_file,/* copy native value to file    */
     NULL,			/* post copy native value to file    */
     NULL,			/* get creation index		*/
     NULL,			/* set creation index		*/
-    H5O_sdspace_debug	        /* debug the message		    	*/
+    H5O_sdspace_shared_debug	/* debug the message		    	*/
 }};
 
 /* Initial version of the dataspace information */
@@ -437,111 +435,19 @@ H5O_sdspace_reset(void *_mesg)
  * Programmer:	Quincey Koziol
  *              Thursday, March 30, 2000
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_sdspace_free (void *mesg)
+H5O_sdspace_free(void *mesg)
 {
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_sdspace_free)
 
-    assert (mesg);
+    HDassert(mesg);
 
-    H5FL_FREE(H5S_extent_t,mesg);
+    H5FL_FREE(H5S_extent_t, mesg);
 
     FUNC_LEAVE_NOAPI(SUCCEED)
-}
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_sdspace_get_share
- *
- * Purpose:	Gets sharing information from the message
- *
- * Return:	Shared message on success/NULL on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_sdspace_get_share(const void *_mesg, H5O_shared_t *sh /*out*/)
-{
-    const H5S_extent_t  *mesg = (const H5S_extent_t *)_mesg;
-    void       *ret_value = NULL;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_sdspace_get_share)
-
-    HDassert (mesg);
-
-    ret_value = H5O_msg_copy(H5O_SHARED_ID, &(mesg->sh_loc), sh);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_sdspace_get_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_sdspace_set_share
- *
- * Purpose:	Sets sharing information for the message
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	James Laird
- *              Tuesday, October 10, 2006
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_sdspace_set_share(void *_mesg/*in,out*/, const H5O_shared_t *sh)
-{
-    H5S_extent_t  *mesg = (H5S_extent_t *)_mesg;
-    herr_t       ret_value = SUCCEED;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_sdspace_set_share)
-
-    HDassert (mesg);
-    HDassert (sh);
-
-    if(NULL == H5O_msg_copy(H5O_SHARED_ID, sh, &(mesg->sh_loc)))
-        ret_value = FAIL;
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_sdspace_set_share() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_sdspace_is_shared
- *
- * Purpose:	Determines if this dataspace is shared (committed or a SOHM)
- *              or not.
- *
- * Return:	TRUE if dataspace is shared
- *              FALSE if dataspace is not shared
- *              Negative on failure
- *
- * Programmer:	James Laird
- *		Monday, October 16, 2006
- *
- *-------------------------------------------------------------------------
- */
-static htri_t
-H5O_sdspace_is_shared(const void *_mesg)
-{
-    const H5S_extent_t  *mesg = (const H5S_extent_t *)_mesg;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_sdspace_is_shared)
-
-    HDassert(mesg);
-
-    /* Dataspaces can't currently be committed, but this should let the
-     * library read a "committed dataspace" if we ever create one in
-     * the future.
-     */
-    FUNC_LEAVE_NOAPI(H5O_IS_SHARED(mesg->sh_loc.flags))
-} /* end H5O_sdspace_is_shared() */
+} /* end H5O_sdspace_free() */
 
 
 /*-------------------------------------------------------------------------
@@ -560,9 +466,8 @@ H5O_sdspace_is_shared(const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_sdspace_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t UNUSED *type,
-    const void *mesg_src, hbool_t UNUSED *deleted, const H5O_copy_t UNUSED *cpy_info,
-    void *_udata)
+H5O_sdspace_pre_copy_file(H5F_t *file_src, const void *mesg_src,
+    hbool_t UNUSED *deleted, const H5O_copy_t UNUSED *cpy_info, void *_udata)
 {
     const H5S_extent_t *src_space_extent = (const H5S_extent_t *)mesg_src;  /* Source dataspace extent */
     H5D_copy_file_ud_t *udata = (H5D_copy_file_ud_t *)_udata;   /* Dataset copying user data */
@@ -617,44 +522,44 @@ static herr_t
 H5O_sdspace_debug(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *mesg,
 		  FILE * stream, int indent, int fwidth)
 {
-    const H5S_extent_t	   *sdim = (const H5S_extent_t *) mesg;
-    unsigned		    u;	/* local counting variable */
+    const H5S_extent_t	   *sdim = (const H5S_extent_t *)mesg;
 
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_sdspace_debug)
 
     /* check args */
-    assert(f);
-    assert(sdim);
-    assert(stream);
-    assert(indent >= 0);
-    assert(fwidth >= 0);
+    HDassert(f);
+    HDassert(sdim);
+    HDassert(stream);
+    HDassert(indent >= 0);
+    HDassert(fwidth >= 0);
 
     HDfprintf(stream, "%*s%-*s %lu\n", indent, "", fwidth,
 	    "Rank:",
 	    (unsigned long) (sdim->rank));
 
-    if(sdim->rank>0) {
+    if(sdim->rank > 0) {
+        unsigned		    u;	/* local counting variable */
+
         HDfprintf(stream, "%*s%-*s {", indent, "", fwidth, "Dim Size:");
-        for (u = 0; u < sdim->rank; u++)
+        for(u = 0; u < sdim->rank; u++)
             HDfprintf (stream, "%s%Hu", u?", ":"", sdim->size[u]);
         HDfprintf (stream, "}\n");
 
         HDfprintf(stream, "%*s%-*s ", indent, "", fwidth, "Dim Max:");
-        if (sdim->max) {
+        if(sdim->max) {
             HDfprintf (stream, "{");
-            for (u = 0; u < sdim->rank; u++) {
-                if (H5S_UNLIMITED==sdim->max[u]) {
+            for(u = 0; u < sdim->rank; u++) {
+                if(H5S_UNLIMITED==sdim->max[u])
                     HDfprintf (stream, "%sINF", u?", ":"");
-                } else {
+                else
                     HDfprintf (stream, "%s%Hu", u?", ":"", sdim->max[u]);
-                }
-            }
+            } /* end for */
             HDfprintf (stream, "}\n");
-        } else {
+        } /* end if */
+        else
             HDfprintf (stream, "CONSTANT\n");
-        }
     } /* end if */
 
     FUNC_LEAVE_NOAPI(SUCCEED)
-}
+} /* end H5O_sdspace_debug() */
 
diff --git a/src/H5Oshared.c b/src/H5Oshared.c
index 8a77744..dafe3d2 100644
--- a/src/H5Oshared.c
+++ b/src/H5Oshared.c
@@ -39,44 +39,6 @@
 #include "H5Opkg.h"             /* Object headers			*/
 #include "H5SMprivate.h"        /* Shared object header messages        */
 
-static void *H5O_shared_decode(H5F_t*, hid_t dxpl_id, unsigned mesg_flags, const uint8_t*);
-static herr_t H5O_shared_encode(H5F_t*, uint8_t*, const void*);
-static void *H5O_shared_copy(const void *_mesg, void *_dest);
-static size_t H5O_shared_size(const H5F_t*, const void *_mesg);
-static herr_t H5O_shared_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg,
-    hbool_t adj_link);
-static herr_t H5O_shared_link(H5F_t *f, hid_t dxpl_id, const void *_mesg);
-static herr_t H5O_shared_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
-    const void *mesg_src, hbool_t *deleted, const H5O_copy_t *cpy_info, void *_udata);
-static void *H5O_shared_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
-    void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
-static herr_t H5O_shared_debug(H5F_t*, hid_t dxpl_id, const void*, FILE*, int, int);
-
-/* This message derives from H5O message class */
-const H5O_msg_class_t H5O_MSG_SHARED[1] = {{
-    H5O_SHARED_ID,	    	/*message id number			*/
-    "shared",		    	/*message name for debugging		*/
-    sizeof(H5O_shared_t), 	/*native message size			*/
-    H5O_shared_decode,	    	/*decode method				*/
-    H5O_shared_encode,	    	/*encode method				*/
-    H5O_shared_copy,		/*copy the native value			*/
-    H5O_shared_size,	    	/*size method				*/
-    NULL,		    	/*no reset method			*/
-    NULL,		        /*no free method			*/
-    H5O_shared_delete,		/*file delete method			*/
-    H5O_shared_link,		/*link method				*/
-    NULL,			/*get share method			*/
-    NULL, 			/*set share method			*/
-    NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
-    H5O_shared_pre_copy_file,	/* pre copy native value to file */
-    H5O_shared_copy_file,	/* copy native value to file    */
-    NULL,			/* post copy native value to file    */
-    NULL,			/* get creation index		*/
-    NULL,			/* set creation index		*/
-    H5O_shared_debug	    	/*debug method				*/
-}};
-
 /* First version, with full symbol table entry as link for object header sharing */
 #define H5O_SHARED_VERSION_1	1
 
@@ -113,14 +75,13 @@ H5FL_BLK_DEFINE(ser_mesg);
  *
  *-------------------------------------------------------------------------
  */
-void *
+static void *
 H5O_shared_read(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared,
-    const H5O_msg_class_t *type, void *mesg)
+    const H5O_msg_class_t *type)
 {
     H5HF_t *fheap = NULL;
     uint8_t mesg_buf[H5O_MESG_BUF_SIZE]; /* Buffer for deserializing messages */
     uint8_t *buf = NULL;        /* Pointer to raw message in heap */
-    void *native_mesg = NULL;   /* Used for messages shared in heap */
     void *ret_value = NULL;     /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5O_shared_read)
@@ -166,39 +127,25 @@ H5O_shared_read(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared,
             HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "can't read message from fractal heap.")
 
         /* Decode the message */
-        if(NULL == (native_mesg = H5O_msg_decode(f, dxpl_id, type->id, buf)))
+        if(NULL == (ret_value = H5O_msg_decode(f, dxpl_id, type->id, buf)))
             HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, NULL, "can't decode shared message.")
-
-        /* Check if there is a user buffer to fill */
-        if(mesg) {
-            /* Copy this message to the user's buffer */
-            if(NULL == (ret_value = (type->copy)(native_mesg, mesg)))
-                HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy message to user space")
-        } /* end if */
-        else {
-            /* Otherwise, take ownership of the decoded native message */
-            ret_value = native_mesg;
-            native_mesg = NULL;
-        } /* end else */
     } /* end if */
     else {
         HDassert(shared->flags & H5O_COMMITTED_FLAG);
 
         /* Get the shared message from an object header */
-        if(NULL == (ret_value = H5O_msg_read(&(shared->u.oloc), type->id, 0, mesg, dxpl_id)))
+        if(NULL == (ret_value = H5O_msg_read(&(shared->u.oloc), type->id, 0, NULL, dxpl_id)))
             HGOTO_ERROR(H5E_OHDR, H5E_READERROR, NULL, "unable to read message")
     } /* end else */
 
     /* Mark the message as shared */
-    if(type->set_share && (type->set_share)(ret_value, shared) < 0)
+    if((type->set_share)(ret_value, shared) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, NULL, "unable to set sharing information")
 
 done:
     /* Release resources */
     if(buf && buf != mesg_buf)
         buf = H5FL_BLK_FREE(ser_mesg, buf);
-    if(native_mesg)
-        H5O_msg_free(type->id, native_mesg);
     if(fheap && H5HF_close(fheap, dxpl_id) < 0)
         HDONE_ERROR(H5E_HEAP, H5E_CANTFREE, NULL, "can't close fractal heap")
 
@@ -207,7 +154,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_shared_link_adj_new
+ * Function:	H5O_shared_link_adj
  *
  * Purpose:	Changes the link count for the object referenced by a shared
  *              message.
@@ -228,12 +175,12 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_shared_link_adj_new(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared,
+H5O_shared_link_adj(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared,
     const H5O_msg_class_t *type, int adjust)
 {
     herr_t ret_value = SUCCEED;     /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_link_adj_new)
+    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_link_adj)
 
     /* check args */
     HDassert(f);
@@ -270,70 +217,11 @@ H5O_shared_link_adj_new(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared,
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_shared_link_adj_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_shared_link_adj
- *
- * Purpose:	Changes the link count for the object referenced by a shared
- *              message.
- *
- *              This function changes the object header link count and is
- *              only relevant for committed messages.  Messages shared in
- *              the heap are re-shared each time they're written, so their
- *              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, or 1 for messages in heap
- *		Failure:	Negative
- *
- * Programmer:	Quincey Koziol
- *		koziol@ncsa.uiuc.edu
- *		Sep 26 2003
- *
- * Modifications:
- *
- *-------------------------------------------------------------------------
- */
-static int
-H5O_shared_link_adj(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *shared, int adjust)
-{
-    int ret_value;     /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_link_adj)
-
-    /* check args */
-    HDassert(f);
-    HDassert(shared);
-
-    /*
-     * The shared message is stored in some other object header.
-     * The other object header must be in the same file as the
-     * new object header. Adjust the reference count on that
-     * object header.
-     */
-    if(shared->flags & H5O_COMMITTED_FLAG) {
-        if(shared->u.oloc.file->shared != f->shared)
-            HGOTO_ERROR(H5E_LINK, H5E_CANTINIT, FAIL, "interfile hard links are not allowed")
-        if((ret_value = H5O_link(&(shared->u.oloc), adjust, dxpl_id)) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
-    } /* end if */
-    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;
-    } /* end else */
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_shared_link_adj() */
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_shared_decode_new
+ * Function:	H5O_shared_decode
  *
  * Purpose:	Decodes a shared object message
  *
@@ -345,13 +233,13 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5O_shared_decode_new(H5F_t *f, hid_t dxpl_id, const uint8_t *buf, const H5O_msg_class_t *type)
+H5O_shared_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *buf, const H5O_msg_class_t *type)
 {
     H5O_shared_t sh_mesg;       /* Shared message info */
     unsigned version;           /* Shared message version */
     void *ret_value;            /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_decode_new)
+    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_decode)
 
     /* Check args */
     HDassert(f);
@@ -404,104 +292,16 @@ H5O_shared_decode_new(H5F_t *f, hid_t dxpl_id, const uint8_t *buf, const H5O_msg
     } /* end else if */
 
     /* Retrieve actual message, through decoded shared message info */
-    if(NULL == (ret_value = H5O_shared_read(f, dxpl_id, &sh_mesg, type, NULL)))
+    if(NULL == (ret_value = H5O_shared_read(f, dxpl_id, &sh_mesg, type)))
         HGOTO_ERROR(H5E_OHDR, H5E_READERROR, NULL, "unable to retrieve native message")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_shared_decode_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_shared_decode
- *
- * Purpose:	Decodes a shared object message and returns it.
- *
- * Return:	Success:	Ptr to a new shared object message.
- *
- *		Failure:	NULL
- *
- * Programmer:	Robb Matzke
- *              Thursday, April  2, 1998
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_shared_decode(H5F_t *f, hid_t UNUSED dxpl_id, unsigned UNUSED mesg_flags,
-    const uint8_t *buf)
-{
-    H5O_shared_t	*mesg = NULL;
-    unsigned		version;
-    void                *ret_value;     /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_decode)
-
-    /* Check args */
-    HDassert(f);
-    HDassert(buf);
-
-    /* Decode */
-    if(NULL == (mesg = (H5O_shared_t *)H5MM_calloc(sizeof(H5O_shared_t))))
-	HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
-
-    /* Version */
-    version = *buf++;
-    if(version < H5O_SHARED_VERSION_1 || version > H5O_SHARED_VERSION_LATEST)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, NULL, "bad version number for shared object message")
-
-    /* Get the shared information flags
-     * Flags are unused before version 3.
-     */
-    if(version >= H5O_SHARED_VERSION_2)
-        mesg->flags = *buf++;
-    else {
-        mesg->flags = H5O_COMMITTED_FLAG;
-        buf++;
-    } /* end else */
-
-    /* Skip reserved bytes (for version 1) */
-    if(version == H5O_SHARED_VERSION_1)
-        buf += 6;
-
-    /* Body */
-    if(version == H5O_SHARED_VERSION_1)
-        H5G_obj_ent_decode(f, &buf, &(mesg->u.oloc));
-    else if (version >= H5O_SHARED_VERSION_2) {
-        /* If this message is in the heap, copy a heap ID.
-         * Otherwise, it is a named datatype, so copy an H5O_loc_t.
-         */
-        if(mesg->flags & H5O_SHARED_IN_HEAP_FLAG) {
-            HDassert(version >= H5O_SHARED_VERSION_3 );
-            HDmemcpy(&(mesg->u.heap_id), buf, sizeof(mesg->u.heap_id));
-        }
-        else {
-            /* The H5O_COMMITTED_FLAG should be set if this message
-             * is from an older version before the flag existed.
-             */
-            if(version < H5O_SHARED_VERSION_3)
-                mesg->flags = H5O_COMMITTED_FLAG;
-
-            HDassert(mesg->flags & H5O_COMMITTED_FLAG);
-
-            H5F_addr_decode(f, &buf, &(mesg->u.oloc.addr));
-            mesg->u.oloc.file = f;
-        } /* end else */
-    } /* end else if */
-
-    /* Set return value */
-    ret_value = mesg;
-
-done:
-    if(ret_value == NULL)
-        if(mesg != NULL)
-            H5MM_xfree(mesg);
-
-    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_shared_decode() */
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_shared_encode_new
+ * Function:	H5O_shared_encode
  *
  * Purpose:	Encodes message _MESG into buffer BUF.
  *
@@ -513,11 +313,11 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_shared_encode_new(const H5F_t *f, uint8_t *buf/*out*/, const H5O_shared_t *sh_mesg)
+H5O_shared_encode(const H5F_t *f, uint8_t *buf/*out*/, const H5O_shared_t *sh_mesg)
 {
     unsigned    version;
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_encode_new)
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_encode)
 
     /* Check args */
     HDassert(f);
@@ -546,60 +346,6 @@ H5O_shared_encode_new(const H5F_t *f, uint8_t *buf/*out*/, const H5O_shared_t *s
         H5F_addr_encode(f, &buf, sh_mesg->u.oloc.addr);
 
     FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5O_shared_encode_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_shared_encode
- *
- * Purpose:	Encodes message _MESG into buffer BUF.
- *
- * Return:	Non-negative on success/Negative on failure
- *
- * Programmer:	Robb Matzke
- *              Thursday, April  2, 1998
- *
- * Modifications:
- *	Robb Matzke, 1998-07-20
- *	Added a version number to the beginning of the message.
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_shared_encode(H5F_t *f, uint8_t *buf/*out*/, const void *_mesg)
-{
-    const H5O_shared_t	*mesg = (const H5O_shared_t *)_mesg;
-    unsigned    version;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_encode)
-
-    /* Check args */
-    HDassert(f);
-    HDassert(buf);
-    HDassert(mesg);
-
-    /* If this message is shared in the heap, we need to use version 3 of the
-     * encoding and encode the SHARED_IN_HEAP flag.
-     */
-    if(mesg->flags & H5O_SHARED_IN_HEAP_FLAG || H5F_USE_LATEST_FORMAT(f))
-        version = H5O_SHARED_VERSION_LATEST;
-    else {
-        HDassert(mesg->flags & H5O_COMMITTED_FLAG);
-        version = H5O_SHARED_VERSION_2; /* version 1 is no longer used */
-    } /* end else */
-
-    *buf++ = version;
-    *buf++ = (unsigned)mesg->flags;
-
-    /* Encode either the heap ID of the message or the address of the
-     * object header that holds it.
-     */
-    if(mesg->flags & H5O_SHARED_IN_HEAP_FLAG)
-        HDmemcpy(buf, &(mesg->u.heap_id), sizeof(mesg->u.heap_id));
-    else
-        H5F_addr_encode(f, &buf, mesg->u.oloc.addr);
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_shared_encode() */
 
 
@@ -619,40 +365,33 @@ H5O_shared_encode(H5F_t *f, uint8_t *buf/*out*/, const void *_mesg)
  *
  *-------------------------------------------------------------------------
  */
-static void *
-H5O_shared_copy(const void *_mesg, void *_dest)
+herr_t
+H5O_shared_copy(void *_dst, const H5O_shared_t *src)
 {
-    const H5O_shared_t  *mesg = (const H5O_shared_t *) _mesg;
-    H5O_shared_t	*dest = (H5O_shared_t *) _dest;
-    void        *ret_value;     /* Return value */
+    H5O_shared_t *dst = (H5O_shared_t *)_dst;
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_copy)
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_copy)
 
     /* check args */
-    HDassert(mesg);
-    if(!dest && NULL == (dest = (H5O_shared_t *)H5MM_malloc(sizeof(H5O_shared_t))))
-        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
+    HDassert(dst);
+    HDassert(src);
 
     /* copy */
-    dest->flags = mesg->flags;
-    if(mesg->flags & H5O_COMMITTED_FLAG)
-        H5O_loc_copy(&(dest->u.oloc), &(mesg->u.oloc), H5_COPY_DEEP);
-    else if(mesg->flags & H5O_SHARED_IN_HEAP_FLAG)
-        dest->u.heap_id = mesg->u.heap_id;
+    dst->flags = src->flags;
+    if(src->flags & H5O_COMMITTED_FLAG)
+        H5O_loc_copy(&(dst->u.oloc), &(src->u.oloc), H5_COPY_DEEP);
+    else if(src->flags & H5O_SHARED_IN_HEAP_FLAG)
+        dst->u.heap_id = src->u.heap_id;
     else
         /* This message's sharing information is being reset */
-        HDassert(mesg->flags == H5O_NOT_SHARED);
-
-    /* Set return value */
-    ret_value = dest;
+        HDassert(src->flags == H5O_NOT_SHARED);
 
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
+    FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_shared_copy() */
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5O_shared_size_new
+ * Function:	H5O_shared_size
  *
  * Purpose:	Returns the length of a shared object message.
  *
@@ -665,11 +404,11 @@ done:
  *-------------------------------------------------------------------------
  */
 size_t
-H5O_shared_size_new(const H5F_t *f, const H5O_shared_t *sh_mesg)
+H5O_shared_size(const H5F_t *f, const H5O_shared_t *sh_mesg)
 {
     size_t ret_value;           /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_size_new)
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_size)
 
     if(sh_mesg->flags & H5O_COMMITTED_FLAG) {
         ret_value = 1 +			/*version			*/
@@ -684,49 +423,11 @@ H5O_shared_size_new(const H5F_t *f, const H5O_shared_t *sh_mesg)
     } /* end else */
 
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_shared_size_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:	H5O_shared_size
- *
- * Purpose:	Returns the length of a shared object message.
- *
- * Return:	Success:	Length
- *
- *		Failure:	0
- *
- * Programmer:	Robb Matzke
- *              Thursday, April  2, 1998
- *
- *-------------------------------------------------------------------------
- */
-static size_t
-H5O_shared_size(const H5F_t *f, const void *_mesg)
-{
-    const H5O_shared_t *shared = (const H5O_shared_t *)_mesg;
-    size_t ret_value;           /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_size)
-
-    if(shared->flags & H5O_COMMITTED_FLAG) {
-        ret_value = 1 +			/*version			*/
-            1 +				/*the flags field		*/
-            H5F_SIZEOF_ADDR(f);		/*sharing by another obj hdr	*/
-    } /* end if */
-    else {
-        HDassert(shared->flags & H5O_SHARED_IN_HEAP_FLAG);
-        ret_value = 1 +			/*version			*/
-            1 +				/*the flags field	*/
-            H5O_FHEAP_ID_LEN;		/* Shared in the heap   */
-    } /* end else */
-
-    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_shared_size() */
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5O_shared_delete_new
+ * Function:    H5O_shared_delete
  *
  * Purpose:     Free file space referenced by message
  *
@@ -738,61 +439,16 @@ H5O_shared_size(const H5F_t *f, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_shared_delete_new(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
+H5O_shared_delete(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
     const H5O_msg_class_t *type, hbool_t adj_link)
 {
     herr_t ret_value = SUCCEED;   /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_delete_new)
-
-    /* check args */
-    HDassert(f);
-    HDassert(sh_mesg);
-
-    /* 
-     * Committed datatypes increment the OH of the original message when they
-     * are written (in H5O_shared_link) and decrement it here.
-     * SOHMs in the heap behave differently; their refcount is incremented
-     * during H5SM_share when they are going to be written (in H5O_msg_append
-     * or H5O_msg_write). Their refcount in the SOHM indexes still needs to
-     * be decremented when they're deleted (in H5O_shared_link_adj).
-     */
-
-    /* Decrement the reference count on the shared object, if requested */
-    if(adj_link)
-        if(H5O_shared_link_adj_new(f, dxpl_id, sh_mesg, type, -1) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_shared_delete_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5O_shared_delete
- *
- * Purpose:     Free file space referenced by message
- *
- * Return:      Non-negative on success/Negative on failure
- *
- * Programmer:  Quincey Koziol
- *              Friday, September 26, 2003
- *
- * Modifications:
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_shared_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link)
-{
-    const H5O_shared_t       *shared = (const H5O_shared_t *) _mesg;
-    herr_t ret_value = SUCCEED;   /* Return value */
-
     FUNC_ENTER_NOAPI_NOINIT(H5O_shared_delete)
 
     /* check args */
     HDassert(f);
-    HDassert(shared);
+    HDassert(sh_mesg);
 
     /* 
      * Committed datatypes increment the OH of the original message when they
@@ -805,7 +461,7 @@ H5O_shared_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link)
 
     /* Decrement the reference count on the shared object, if requested */
     if(adj_link)
-        if(H5O_shared_link_adj(f, dxpl_id, shared, -1) < 0)
+        if(H5O_shared_link_adj(f, dxpl_id, sh_mesg, type, -1) < 0)
             HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
 
 done:
@@ -814,7 +470,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5O_shared_link_new
+ * Function:    H5O_shared_link
  *
  * Purpose:     Increment reference count on any objects referenced by
  *              message
@@ -827,53 +483,19 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_shared_link_new(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
+H5O_shared_link(H5F_t *f, hid_t dxpl_id, const H5O_shared_t *sh_mesg,
     const H5O_msg_class_t *type)
 {
     herr_t ret_value = SUCCEED;   /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_link_new)
-
-    /* check args */
-    HDassert(f);
-    HDassert(sh_mesg);
-
-    /* Increment the reference count on the shared object */
-    if(H5O_shared_link_adj_new(f, dxpl_id, sh_mesg, type, 1) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_shared_link_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5O_shared_link
- *
- * Purpose:     Increment reference count on any objects referenced by
- *              message
- *
- * Return:      Non-negative on success/Negative on failure
- *
- * Programmer:  Quincey Koziol
- *              Friday, September 26, 2003
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_shared_link(H5F_t *f, hid_t dxpl_id, const void *_mesg)
-{
-    const H5O_shared_t       *shared = (const H5O_shared_t *) _mesg;
-    herr_t ret_value = SUCCEED;   /* Return value */
-
     FUNC_ENTER_NOAPI_NOINIT(H5O_shared_link)
 
     /* check args */
     HDassert(f);
-    HDassert(shared);
+    HDassert(sh_mesg);
 
     /* Increment the reference count on the shared object */
-    if(H5O_shared_link_adj(f, dxpl_id, shared, 1) < 0)
+    if(H5O_shared_link_adj(f, dxpl_id, sh_mesg, type, 1) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "unable to adjust shared object link count")
 
 done:
@@ -882,55 +504,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5O_shared_pre_copy_file
- *
- * Purpose:     Perform any necessary actions before copying message between
- *              files for shared messages.
- *
- * Return:      Success:        Non-negative
- *
- *              Failure:        Negative
- *
- * Programmer:  Peter Cao
- *              Saturday, February 11, 2006
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5O_shared_pre_copy_file(H5F_t *file_src, const H5O_msg_class_t *type,
-    const void *native_src, hbool_t *deleted, const H5O_copy_t *cpy_info,
-    void *udata)
-{
-    const H5O_shared_t   *shared_src = (const H5O_shared_t *)native_src;
-    void           *mesg_native = NULL;
-    herr_t         ret_value = SUCCEED;          /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_pre_copy_file)
-
-    /* check args */
-    HDassert(file_src);
-    HDassert(type);
-
-    if(type->pre_copy_file) {
-        /* Go get the actual shared message */
-        if(NULL == (mesg_native = H5O_shared_read(file_src, H5AC_dxpl_id, shared_src, type, NULL)))
-            HGOTO_ERROR(H5E_OHDR, H5E_READERROR, FAIL, "unable to load object header")
-
-        /* Perform "pre copy" operation on messge */
-        if((type->pre_copy_file)(file_src, type, mesg_native, deleted, cpy_info, udata) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to perform 'pre copy' operation on message")
-    } /* end of if */
-
-done:
-    if(mesg_native)
-        H5O_msg_free_real(type, mesg_native);
-
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5O_shared_pre_copy_file() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5O_shared_copy_file_new
+ * Function:    H5O_shared_copy_file
  *
  * Purpose:     Copies a message from _MESG to _DEST in file
  *
@@ -943,7 +517,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_shared_copy_file_new(H5F_t *file_src, H5F_t *file_dst, hid_t dxpl_id,
+H5O_shared_copy_file(H5F_t *file_src, H5F_t *file_dst, hid_t dxpl_id,
     const H5O_msg_class_t *mesg_type, const void *_native_src, void *_native_dst,
     H5O_copy_t *cpy_info, void UNUSED *udata)
 {
@@ -951,7 +525,7 @@ H5O_shared_copy_file_new(H5F_t *file_src, H5F_t *file_dst, hid_t dxpl_id,
     H5O_shared_t        *shared_dst = (H5O_shared_t *)_native_dst; /* Alias to shared info in native destination message */
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_copy_file_new)
+    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_copy_file)
 
     /* check args */
     HDassert(file_src);
@@ -983,90 +557,6 @@ H5O_shared_copy_file_new(H5F_t *file_src, H5F_t *file_dst, hid_t dxpl_id,
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* H5O_shared_copy_file_new() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5O_shared_copy_file
- *
- * Purpose:     Copies a message from _MESG to _DEST in file
- *
- * Return:      Success:        Ptr to _DEST
- *
- *              Failure:        NULL
- *
- * Programmer:  Quincey Koziol
- *              November 1, 2005
- *
- *-------------------------------------------------------------------------
- */
-static void *
-H5O_shared_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
-    void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
-    void *udata)
-{
-    H5O_shared_t        *shared_src = (H5O_shared_t *)native_src;
-    H5O_shared_t        *shared_dst = NULL;     /* The destination message if
-                                                 * it is a shared message */
-    void                *dst_mesg = NULL;       /* The destination message if
-                                                 * it's an unshared message */
-    void                *ret_value;             /* Return value */
-
-    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_copy_file)
-
-    /* check args */
-    HDassert(shared_src);
-    HDassert(file_dst);
-    HDassert(cpy_info);
-
-    /* Committed shared messages create a shared message at the destination
-     * and also copy the committed object that they point to.
-     * SOHMs actually write a non-shared message at the destination.
-     */
-    if(shared_src->flags & H5O_COMMITTED_FLAG) {
-        /* Allocate space for the destination message */
-        if(NULL == (shared_dst = (H5O_shared_t *)H5MM_malloc(sizeof(H5O_shared_t))))
-            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
-
-        /* Reset group entry for new object */
-        H5O_loc_reset(&(shared_dst->u.oloc));
-        shared_dst->u.oloc.file = file_dst;
-    
-        /* Set flags for new shared object */
-        shared_dst->flags = shared_src->flags;
-
-        /* Copy the shared object from source to destination */
-        if(H5O_copy_header_map(&(shared_src->u.oloc), &(shared_dst->u.oloc), dxpl_id, cpy_info, FALSE) < 0)
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTCOPY, NULL, "unable to copy object")
-
-        /* Set return value */
-        ret_value = shared_dst;
-    } /* end if */
-    else {
-        HDassert(shared_src->flags & H5O_SHARED_IN_HEAP_FLAG);
-
-        /* Read the shared message to get the original message */
-        if(NULL == (dst_mesg = H5O_shared_read(file_src, dxpl_id, shared_src, mesg_type, NULL)))
-            HGOTO_ERROR(H5E_OHDR, H5E_BADMESG, NULL, "unable to read shared message")
-
-        if(mesg_type->copy_file) {
-            /* Copy the original, un-shared message and return it */
-            ret_value = (mesg_type->copy_file)(file_src, mesg_type, dst_mesg, file_dst, dxpl_id, cpy_info, udata);
-            H5O_msg_free(mesg_type->id, dst_mesg);
-        } /* end else */
-        else
-            ret_value = dst_mesg;
-    } /* end else */
-
-done:
-    if(!ret_value) {
-        if(shared_dst)
-            H5O_msg_free(H5O_SHARED_ID, shared_dst);
-        if(dst_mesg)
-            H5O_msg_free(mesg_type->id, dst_mesg);
-    } /* end if */
-
-    FUNC_LEAVE_NOAPI(ret_value)
 } /* H5O_shared_copy_file() */
 
 
@@ -1080,43 +570,39 @@ done:
  * Programmer:	Robb Matzke
  *              Thursday, April  2, 1998
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
-static herr_t
-H5O_shared_debug (H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const void *_mesg,
-		  FILE *stream, int indent, int fwidth)
+herr_t
+H5O_shared_debug(const H5O_shared_t *mesg, FILE *stream, int indent, int fwidth)
 {
-    const H5O_shared_t	*mesg = (const H5O_shared_t *)_mesg;
-
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_shared_debug)
 
     /* Check args */
-    HDassert(f);
     HDassert(mesg);
     HDassert(stream);
     HDassert(indent >= 0);
     HDassert(fwidth >= 0);
 
-    if(mesg->flags & H5O_COMMITTED_FLAG)
-    {
+    HDfprintf(stream, "%*s%-*s %x\n", indent, "", fwidth,
+            "Shared Message Flags:",
+            mesg->flags);
+    if(mesg->flags & H5O_COMMITTED_FLAG) {
         HDfprintf(stream, "%*s%-*s %s\n", indent, "", fwidth,
                 "Sharing method:",
                 "Obj Hdr");
         HDfprintf(stream, "%*s%-*s %a\n", indent, "", fwidth,
                 "Object address:",
                 mesg->u.oloc.addr);
-    }
-    else
-    {
+    } /* end if */
+    else {
+        HDassert(mesg->flags & H5O_SHARED_IN_HEAP_FLAG);
         HDfprintf(stream, "%*s%-*s %s\n", indent, "", fwidth,
                 "Sharing method:",
                 "SOHM Heap");
         HDfprintf(stream, "%*s%-*s %a\n", indent, "", fwidth,
                 "Heap ID:",
                 mesg->u.heap_id);
-    }
+    } /* end else */
 
     FUNC_LEAVE_NOAPI(SUCCEED)
 } /* end H5O_shared_debug() */
diff --git a/src/H5Oshared.h b/src/H5Oshared.h
index 70049c7..96fb938 100644
--- a/src/H5Oshared.h
+++ b/src/H5Oshared.h
@@ -66,7 +66,7 @@ H5O_SHARED_DECODE(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p
     /* Check for shared message */
     if(mesg_flags & H5O_MSG_FLAG_SHARED) {
         /* Retrieve native message info indirectly through shared message */
-        if(NULL == (ret_value = H5O_shared_decode_new(f, dxpl_id, p, H5O_SHARED_TYPE)))
+        if(NULL == (ret_value = H5O_shared_decode(f, dxpl_id, p, H5O_SHARED_TYPE)))
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, NULL, "unable to decode shared message")
     } /* end if */
     else {
@@ -98,7 +98,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static H5_inline herr_t
-H5O_SHARED_ENCODE(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_SHARED_ENCODE(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_shared_t *sh_mesg = (const H5O_shared_t *)_mesg;     /* Pointer to shared message portion of actual message */
     herr_t ret_value = SUCCEED;         /* Return value */
@@ -116,9 +116,9 @@ H5O_SHARED_ENCODE(H5F_t *f, uint8_t *p, const void *_mesg)
 #endif /* H5O_SHARED_ENCODE_REAL */
 
     /* Check for shared message */
-    if(H5O_IS_SHARED(sh_mesg->flags)) {
+    if(H5O_IS_SHARED(sh_mesg->flags) && !disable_shared) {
         /* Encode shared message into buffer */
-        if(H5O_shared_encode_new(f, p, sh_mesg) < 0)
+        if(H5O_shared_encode(f, p, sh_mesg) < 0)
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTENCODE, FAIL, "unable to encode shared message")
     } /* end if */
     else {
@@ -150,7 +150,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static H5_inline size_t
-H5O_SHARED_SIZE(const H5F_t *f, const void *_mesg)
+H5O_SHARED_SIZE(const H5F_t *f, hbool_t disable_shared, const void *_mesg)
 {
     const H5O_shared_t *sh_mesg = (const H5O_shared_t *)_mesg;     /* Pointer to shared message portion of actual message */
     size_t ret_value;           /* Return value */
@@ -168,9 +168,9 @@ H5O_SHARED_SIZE(const H5F_t *f, const void *_mesg)
 #endif /* H5O_SHARED_SIZE_REAL */
 
     /* Check for shared message */
-    if(H5O_IS_SHARED(sh_mesg->flags)) {
+    if(H5O_IS_SHARED(sh_mesg->flags) && !disable_shared) {
         /* Retrieve encoded size of shared message */
-        if(0 == (ret_value = H5O_shared_size_new(f, sh_mesg)))
+        if(0 == (ret_value = H5O_shared_size(f, sh_mesg)))
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, 0, "unable to retrieve encoded size of shared message")
     } /* end if */
     else {
@@ -220,7 +220,7 @@ H5O_SHARED_DELETE(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link)
     /* Check for shared message */
     if(H5O_IS_SHARED(sh_mesg->flags)) {
         /* Decrement the reference count on the shared message/object */
-        if(H5O_shared_delete_new(f, dxpl_id, sh_mesg, H5O_SHARED_TYPE, adj_link) < 0)
+        if(H5O_shared_delete(f, dxpl_id, sh_mesg, H5O_SHARED_TYPE, adj_link) < 0)
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTDEC, FAIL, "unable to decrement ref count for shared message")
     } /* end if */
 #ifdef H5O_SHARED_DELETE_REAL
@@ -272,7 +272,7 @@ H5O_SHARED_LINK(H5F_t *f, hid_t dxpl_id, const void *_mesg)
     /* Check for shared message */
     if(H5O_IS_SHARED(sh_mesg->flags)) {
         /* Increment the reference count on the shared message/object */
-        if(H5O_shared_link_new(f, dxpl_id, sh_mesg, H5O_SHARED_TYPE) < 0)
+        if(H5O_shared_link(f, dxpl_id, sh_mesg, H5O_SHARED_TYPE) < 0)
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTINC, FAIL, "unable to increment ref count for shared message")
     } /* end if */
 #ifdef H5O_SHARED_LINK_REAL
@@ -306,7 +306,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static H5_inline void *
-H5O_SHARED_COPY_FILE(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
+H5O_SHARED_COPY_FILE(H5F_t *file_src,
     void *_native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info,
     void *udata)
 {
@@ -336,7 +336,7 @@ H5O_SHARED_COPY_FILE(H5F_t *file_src, const H5O_msg_class_t *mesg_type,
     HDmemset(dst_mesg, 0, sizeof(H5O_shared_t));
 
     /* Handle sharing destination message */
-    if(H5O_shared_copy_file_new(file_src, file_dst, dxpl_id, H5O_SHARED_TYPE,
+    if(H5O_shared_copy_file(file_src, file_dst, dxpl_id, H5O_SHARED_TYPE,
             _native_src, dst_mesg, cpy_info, udata) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, NULL, "unable to determine if message should be shared")
 
@@ -351,5 +351,58 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5O_SHARED_COPY_FILE() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5O_SHARED_DEBUG
+ *
+ * Purpose:     Prints debugging info for a potentially shared message.
+ *
+ * Note:	The actual name of this routine can be different in each source
+ *		file that this header file is included in, and must be defined
+ *		prior to including this header file.
+ *
+ * Return:	Success:	Non-negative
+ *		Failure:	Negative
+ *
+ * Programmer:  Quincey Koziol
+ *              Saturday, February  3, 2007
+ *
+ *-------------------------------------------------------------------------
+ */
+static H5_inline herr_t
+H5O_SHARED_DEBUG(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE *stream,
+    int indent, int fwidth)
+{
+    const H5O_shared_t *sh_mesg = (const H5O_shared_t *)_mesg;     /* Pointer to shared message portion of actual message */
+    herr_t ret_value = SUCCEED;           /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT(H5O_SHARED_DEBUG)
+
+#ifndef H5O_SHARED_TYPE
+#error "Need to define H5O_SHARED_TYPE macro!"
+#endif /* H5O_SHARED_TYPE */
+#ifndef H5O_SHARED_DEBUG
+#error "Need to define H5O_SHARED_DEBUG macro!"
+#endif /* H5O_SHARED_DEBUG */
+#ifndef H5O_SHARED_DEBUG_REAL
+#error "Need to define H5O_SHARED_DEBUG_REAL macro!"
+#endif /* H5O_SHARED_DEBUG_REAL */
+
+    /* Check for shared message */
+    if(H5O_IS_SHARED(sh_mesg->flags)) {
+        /* Print shared message information */
+        if(H5O_shared_debug(sh_mesg, stream, indent, fwidth) < 0)
+            HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "unable to display shared message info")
+    } /* end if */
+
+    /* Call native message's debug callback */
+    if(H5O_SHARED_DEBUG_REAL(f, dxpl_id, _mesg, stream, indent, fwidth) < 0)
+        HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "unable to display native message info")
+
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_SHARED_DEBUG() */
+
 #endif /* H5Oshared_H */
 
diff --git a/src/H5Ostab.c b/src/H5Ostab.c
index eb04b95..822e7a3 100644
--- a/src/H5Ostab.c
+++ b/src/H5Ostab.c
@@ -36,13 +36,13 @@
 
 /* PRIVATE PROTOTYPES */
 static void *H5O_stab_decode(H5F_t *f, hid_t dxpl_id, unsigned mesg_flags, const uint8_t *p);
-static herr_t H5O_stab_encode(H5F_t *f, uint8_t *p, const void *_mesg);
+static herr_t H5O_stab_encode(H5F_t *f, hbool_t disable_shared, uint8_t *p, const void *_mesg);
 static void *H5O_stab_copy(const void *_mesg, void *_dest);
-static size_t H5O_stab_size(const H5F_t *f, const void *_mesg);
+static size_t H5O_stab_size(const H5F_t *f, hbool_t disable_shared, const void *_mesg);
 static herr_t H5O_stab_free(void *_mesg);
 static herr_t H5O_stab_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg, hbool_t adj_link);
-static void *H5O_stab_copy_file(H5F_t *file_src, const H5O_msg_class_t *mesg_type, 
-    void *native_src, H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
+static void *H5O_stab_copy_file(H5F_t *file_src, void *native_src,
+    H5F_t *file_dst, hid_t dxpl_id, H5O_copy_t *cpy_info, void *udata);
 static herr_t H5O_stab_post_copy_file(const H5O_loc_t *src_oloc, const void *mesg_src, H5O_loc_t *dst_oloc,
     void *mesg_dst, hid_t dxpl_id, H5O_copy_t *cpy_info);
 static herr_t H5O_stab_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg,
@@ -53,6 +53,7 @@ const H5O_msg_class_t H5O_MSG_STAB[1] = {{
     H5O_STAB_ID,            	/*message id number             */
     "stab",                 	/*message name for debugging    */
     sizeof(H5O_stab_t),     	/*native message size           */
+    FALSE,			/* messages are sharable?       */
     H5O_stab_decode,        	/*decode message                */
     H5O_stab_encode,        	/*encode message                */
     H5O_stab_copy,          	/*copy the native value         */
@@ -61,10 +62,8 @@ const H5O_msg_class_t H5O_MSG_STAB[1] = {{
     H5O_stab_free,	        /* free method			*/
     H5O_stab_delete,	        /* file delete method		*/
     NULL,			/* link method			*/
-    NULL,		    	/*get share method		*/
     NULL, 			/*set share method		*/
     NULL,		    	/*can share method		*/
-    NULL, 			/*is shared method		*/
     NULL,			/* pre copy native value to file */
     H5O_stab_copy_file,		/* copy native value to file    */
     H5O_stab_post_copy_file,	/* post copy native value to file    */
@@ -136,12 +135,10 @@ done:
  *              matzke@llnl.gov
  *              Aug  6 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5O_stab_encode(H5F_t *f, uint8_t *p, const void *_mesg)
+H5O_stab_encode(H5F_t *f, hbool_t UNUSED disable_shared, uint8_t *p, const void *_mesg)
 {
     const H5O_stab_t       *stab = (const H5O_stab_t *) _mesg;
 
@@ -174,8 +171,6 @@ H5O_stab_encode(H5F_t *f, uint8_t *p, const void *_mesg)
  *              matzke@llnl.gov
  *              Aug  6 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static void *
@@ -185,22 +180,22 @@ H5O_stab_copy(const void *_mesg, void *_dest)
     H5O_stab_t             *dest = (H5O_stab_t *) _dest;
     void                *ret_value;     /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_stab_copy);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_stab_copy)
 
     /* check args */
-    assert(stab);
-    if (!dest && NULL==(dest = H5FL_MALLOC(H5O_stab_t)))
+    HDassert(stab);
+    if(!dest && NULL == (dest = H5FL_MALLOC(H5O_stab_t)))
 	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
 
     /* copy */
     *dest = *stab;
 
     /* Set return value */
-    ret_value=dest;
+    ret_value = dest;
 
 done:
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5O_stab_copy() */
 
 
 /*-------------------------------------------------------------------------
@@ -218,12 +213,10 @@ done:
  *              matzke@llnl.gov
  *              Aug  6 1997
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 static size_t
-H5O_stab_size(const H5F_t *f, const void UNUSED *_mesg)
+H5O_stab_size(const H5F_t *f, hbool_t UNUSED disable_shared, const void UNUSED *_mesg)
 {
     size_t ret_value;   /* Return value */
 
@@ -310,9 +303,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_stab_copy_file(H5F_t *file_src, const H5O_msg_class_t UNUSED *mesg_type, 
-    void *native_src, H5F_t *file_dst, hid_t dxpl_id,
-    H5O_copy_t UNUSED *cpy_info, void UNUSED *udata)
+H5O_stab_copy_file(H5F_t *file_src, void *native_src, H5F_t *file_dst,
+    hid_t dxpl_id, H5O_copy_t UNUSED *cpy_info, void UNUSED *udata)
 {
     H5O_stab_t          *stab_src = (H5O_stab_t *) native_src;
     H5O_stab_t          *stab_dst = NULL;
diff --git a/src/H5S.c b/src/H5S.c
index 8604750..6cfb635 100644
--- a/src/H5S.c
+++ b/src/H5S.c
@@ -641,7 +641,7 @@ H5S_extent_copy(H5S_extent_t *dst, const H5S_extent_t *src)
     } /* end switch */
 
     /* Copy the shared object info */
-    if(NULL == H5O_msg_copy(H5O_SHARED_ID, &(src->sh_loc), &(dst->sh_loc)))
+    if(H5O_shared_copy(&(dst->sh_loc), &(src->sh_loc)) < 0)
         HGOTO_ERROR(H5E_DATASPACE, H5E_CANTCOPY, FAIL, "can't copy shared information")
 
 done:
@@ -2326,11 +2326,10 @@ herr_t
 H5S_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE *stream, int indent, int fwidth)
 {
     const H5S_t	*mesg = (const H5S_t*)_mesg;
-    herr_t ret_value=SUCCEED;   /* Return value */
 
-    FUNC_ENTER_NOAPI(H5S_debug, FAIL);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5S_debug)
 
-    switch (H5S_GET_EXTENT_TYPE(mesg)) {
+    switch(H5S_GET_EXTENT_TYPE(mesg)) {
         case H5S_NULL:
             fprintf(stream, "%*s%-*s H5S_NULL\n", indent, "", fwidth,
                     "Space class:");
@@ -2345,16 +2344,15 @@ H5S_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE *stream, int indent,
             fprintf(stream, "%*s%-*s H5S_SIMPLE\n", indent, "", fwidth,
                     "Space class:");
             H5O_debug_id(H5O_SDSPACE_ID, f, dxpl_id, &(mesg->extent), stream,
-                                 indent+3, MAX(0, fwidth-3));
+                                 indent + 3, MAX(0, fwidth - 3));
             break;
 
         default:
             fprintf(stream, "%*s%-*s **UNKNOWN-%ld**\n", indent, "", fwidth,
                     "Space class:", (long)(H5S_GET_EXTENT_TYPE(mesg)));
             break;
-    }
+    } /* end switch */
 
-done:
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5S_debug() */
 
diff --git a/src/H5T.c b/src/H5T.c
index b3395de..f0cea46 100644
--- a/src/H5T.c
+++ b/src/H5T.c
@@ -3057,28 +3057,28 @@ done:
 H5T_t *
 H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
 {
-    H5T_t	*new_dt=NULL, *tmp=NULL;
+    H5T_t	*new_dt = NULL, *tmp = NULL;
     H5T_shared_t    *reopened_fo;
     unsigned	i;
     char	*s;
     H5T_t	*ret_value;
 
-    FUNC_ENTER_NOAPI(H5T_copy, NULL);
+    FUNC_ENTER_NOAPI(H5T_copy, NULL)
 
     /* check args */
-    assert(old_dt);
+    HDassert(old_dt);
 
     /* Allocate space */
-    if (NULL==(new_dt = H5FL_MALLOC(H5T_t)))
+    if(NULL == (new_dt = H5FL_MALLOC(H5T_t)))
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
-    if (NULL==(new_dt->shared = H5FL_MALLOC(H5T_shared_t)))
+    if(NULL == (new_dt->shared = H5FL_MALLOC(H5T_shared_t)))
         HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
 
     /* Copy shared information (entry information is copied last) */
     *(new_dt->shared) = *(old_dt->shared);
 
     /* Copy parent information */
-    if (new_dt->shared->parent)
+    if(new_dt->shared->parent)
         new_dt->shared->parent = H5T_copy(new_dt->shared->parent, method);
 
     /* Check what sort of copy we are making */
@@ -3095,11 +3095,10 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
              * Return a transient type (locked or unlocked) or an unopened named
              * type.  Immutable transient types are degraded to read-only.
              */
-            if (H5T_STATE_OPEN==old_dt->shared->state) {
+            if(H5T_STATE_OPEN==old_dt->shared->state)
                 new_dt->shared->state = H5T_STATE_NAMED;
-            } else if (H5T_STATE_IMMUTABLE==old_dt->shared->state) {
+            else if(H5T_STATE_IMMUTABLE==old_dt->shared->state)
                 new_dt->shared->state = H5T_STATE_RDONLY;
-            }
             break;
 
         case H5T_COPY_REOPEN:
@@ -3109,7 +3108,7 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
              */
             if(old_dt->sh_loc.flags & H5O_COMMITTED_FLAG) {
                 /* Check if the object is already open */
-                if((reopened_fo=H5FO_opened(old_dt->sh_loc.u.oloc.file, old_dt->sh_loc.u.oloc.addr))==NULL) {
+                if((reopened_fo = H5FO_opened(old_dt->sh_loc.u.oloc.file, old_dt->sh_loc.u.oloc.addr)) == NULL) {
                     /* Clear any errors from H5FO_opened() */
                     H5E_clear_stack(NULL);
 
@@ -3125,7 +3124,7 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
                     if(H5FO_top_incr(old_dt->sh_loc.u.oloc.file, old_dt->sh_loc.u.oloc.addr) < 0)
                         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINC, NULL, "can't increment object count")
 
-                    new_dt->shared->fo_count=1;
+                    new_dt->shared->fo_count = 1;
                 } else {
                     /* The object is already open.  Free the H5T_shared_t struct
                      * we had been using and use the one that already exists.
@@ -3145,9 +3144,9 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
                     /* Increment object count for the object in the top file */
                     if(H5FO_top_incr(old_dt->sh_loc.u.oloc.file, old_dt->sh_loc.u.oloc.addr) < 0)
                         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINC, NULL, "can't increment object count")
-                }
+                } /* end else */
                 new_dt->shared->state = H5T_STATE_OPEN;
-            } else if (H5T_STATE_IMMUTABLE==old_dt->shared->state) {
+            } else if(H5T_STATE_IMMUTABLE == old_dt->shared->state) {
                 new_dt->shared->state = H5T_STATE_RDONLY;
             }
             break;
@@ -3156,7 +3155,7 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
     switch(new_dt->shared->type) {
         case H5T_COMPOUND:
             {
-            int accum_change=0;    /* Amount of change in the offset of the fields */
+            int accum_change = 0;    /* Amount of change in the offset of the fields */
 
             /*
              * Copy all member fields to new type, then overwrite the
@@ -3171,7 +3170,7 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
             HDmemcpy(new_dt->shared->u.compnd.memb, old_dt->shared->u.compnd.memb,
                  new_dt->shared->u.compnd.nmembs * sizeof(H5T_cmemb_t));
 
-            for (i=0; i<new_dt->shared->u.compnd.nmembs; i++) {
+            for(i = 0; i < new_dt->shared->u.compnd.nmembs; i++) {
                 unsigned	j;
                 int    old_match;
 
@@ -3185,20 +3184,19 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
                 new_dt->shared->u.compnd.memb[i].offset += accum_change;
 
                 if(old_dt->shared->u.compnd.sorted != H5T_SORT_VALUE) {
-                    for (old_match=-1, j=0; j<old_dt->shared->u.compnd.nmembs; j++) {
-                        if(!HDstrcmp(new_dt->shared->u.compnd.memb[i].name,old_dt->shared->u.compnd.memb[j].name)) {
-                            old_match=j;
+                    for(old_match = -1, j = 0; j < old_dt->shared->u.compnd.nmembs; j++) {
+                        if(!HDstrcmp(new_dt->shared->u.compnd.memb[i].name, old_dt->shared->u.compnd.memb[j].name)) {
+                            old_match = j;
                             break;
                         } /* end if */
                     } /* end for */
 
                     /* check if we couldn't find a match */
-                    if(old_match<0)
+                    if(old_match < 0)
                         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "fields in datatype corrupted");
                 } /* end if */
-                else {
-                    old_match=i;
-                } /* end else */
+                else
+                    old_match = i;
 
                 /* If the field changed size, add that change to the accumulated size change */
                 if(new_dt->shared->u.compnd.memb[i].type->shared->size != old_dt->shared->u.compnd.memb[old_match].type->shared->size) {
@@ -3225,23 +3223,23 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
                                 sizeof(char*));
             new_dt->shared->u.enumer.value = H5MM_malloc(new_dt->shared->u.enumer.nalloc *
                                  new_dt->shared->size);
-            if (NULL==new_dt->shared->u.enumer.value)
+            if(NULL == new_dt->shared->u.enumer.value)
                 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++) {
+            for(i = 0; i < new_dt->shared->u.enumer.nmembs; i++) {
                 s = old_dt->shared->u.enumer.name[i];
                 new_dt->shared->u.enumer.name[i] = H5MM_xstrdup(s);
-            }
+            } /* end for */
             break;
 
         case H5T_VLEN:
         case H5T_REFERENCE:
-            if(method==H5T_COPY_TRANSIENT || method==H5T_COPY_REOPEN) {
+            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)
+                if(H5T_set_loc(new_dt, NULL, H5T_LOC_MEMORY) < 0)
                     HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "invalid datatype location");
-            }
+            } /* end if */
             break;
 
         case H5T_OPAQUE:
@@ -3269,33 +3267,33 @@ H5T_copy(const H5T_t *old_dt, H5T_copy_t method)
     if(new_dt->shared->state == H5T_STATE_NAMED || new_dt->shared->state == H5T_STATE_OPEN) {
         if(H5G_name_copy(&(new_dt->path), &(old_dt->path), H5_COPY_DEEP) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, NULL, "unable to copy path")
-    }
+    } /* end if */
 
     /* Copy shared location information if the new type is named or if it is
      * shared in the heap.
      */
     if(old_dt->sh_loc.flags & H5O_SHARED_IN_HEAP_FLAG ||
-        new_dt->shared->state == H5T_STATE_NAMED || new_dt->shared->state == H5T_STATE_OPEN)
+            new_dt->shared->state == H5T_STATE_NAMED || new_dt->shared->state == H5T_STATE_OPEN)
     {
-        if(NULL == H5O_msg_copy(H5O_SHARED_ID, &(old_dt->sh_loc), &(new_dt->sh_loc)))
-            HGOTO_ERROR(H5E_OHDR, H5E_CANTOPENOBJ, NULL, "unable to copy shared location")
-    }
+        if(H5O_shared_copy(&(new_dt->sh_loc), &(old_dt->sh_loc)) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "can't copy shared information")
+    } /* end if */
     else
         new_dt->sh_loc.flags = H5O_NOT_SHARED;
 
     /* Set return value */
-    ret_value=new_dt;
+    ret_value = new_dt;
 
 done:
-    if(ret_value==NULL) {
+    if(ret_value == NULL) {
         if(new_dt->shared != NULL)
             H5FL_FREE(H5T_shared_t, new_dt->shared);
-        if(new_dt!=NULL)
-            H5FL_FREE (H5T_t,new_dt);
+        if(new_dt != NULL)
+            H5FL_FREE(H5T_t, new_dt);
     } /* end if */
 
-    FUNC_LEAVE_NOAPI(ret_value);
-}
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5T_copy() */
 
 
 /*-------------------------------------------------------------------------