[svn-r9556] Purpose:

    Code cleanup & optimization

Description:
    Improve ADF/CGNS benchmark by reducing the number of internal attribute
copies made during creations, opens and writes.

    Added new H5O_iterate() routine for iterating through messages of a certain
type in the object header (attributes are the only message currently that can
have multiple instances in the object header).

    Cross-pollinated various minor code cleanups to reduce diffs between
branches.


Platforms tested:
    FreeBSD 4.10 (sleipnir) w/parallel
    Solaris 2.7 (arabica)
    Too minor to require h5committest

21 files changed, 272 insertions, 145 deletions

diff --git a/src/H5A.c b/src/H5A.c
index 1874187..a1e631b 100644
--- a/src/H5A.c
+++ b/src/H5A.c
@@ -41,6 +41,14 @@ static int H5A_get_index(H5G_entry_t *ent, const char *name, hid_t dxpl_id);
 static hsize_t H5A_get_storage_size(const H5A_t *attr);
 static herr_t H5A_rename(H5G_entry_t *ent, const char *old_name, const char *new_name, hid_t dxpl_id);
 
+/* Object header iterator callbacks */
+/* Data structure for callback for locating the index by name */
+typedef struct H5A_iter_cb1 {
+    const char *name;
+    int idx;
+} H5A_iter_cb1;
+static herr_t H5A_find_idx_by_name(const void *mesg, unsigned idx, void *op_data);
+
 /* The number of reserved IDs in dataset ID group */
 #define H5A_RESERVED_ATOMS  0
 
@@ -216,8 +224,7 @@ H5A_create(const H5G_entry_t *ent, const char *name, const H5T_t *type,
 	   const H5S_t *space, hid_t dxpl_id)
 {
     H5A_t	*attr = NULL;
-    H5A_t	found_attr;
-    int	seq=0;
+    H5A_iter_cb1 cb;                    /* Iterator callback */
     hid_t	ret_value = FAIL;
 
     FUNC_ENTER_NOAPI_NOINIT(H5A_create)
@@ -228,6 +235,14 @@ H5A_create(const H5G_entry_t *ent, const char *name, const H5T_t *type,
     assert(type);
     assert(space);
 
+    /* Iterate over the existing attributes to check for duplicates */
+    cb.name=name;
+    cb.idx=(-1);
+    if((ret_value=H5O_iterate(ent,H5O_ATTR_ID,H5A_find_idx_by_name,&cb,dxpl_id))<0)
+        HGOTO_ERROR(H5E_ATTR, H5E_NOTFOUND, FAIL, "error iterating over attributes")
+    if(ret_value>0)
+        HGOTO_ERROR(H5E_ATTR, H5E_ALREADYEXISTS, FAIL, "attribute already exists")
+
     /* Check if the dataspace has an extent set (or is NULL) */
     if( !(H5S_has_extent(space)) )
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "dataspace extent has not been set")
@@ -282,25 +297,8 @@ H5A_create(const H5G_entry_t *ent, const char *name, const H5T_t *type,
         HGOTO_ERROR(H5E_ATTR, H5E_CANTOPENOBJ, FAIL, "unable to open")
     attr->ent_opened=1;
 
-    /* Read in the existing attributes to check for duplicates */
-    seq=0;
-    while(H5O_read(&(attr->ent), H5O_ATTR_ID, seq, &found_attr, dxpl_id)!=NULL) {
-        /*
-	 * Compare found attribute name to new attribute name reject creation
-	 * if names are the same.
-	 */
-	if(HDstrcmp(found_attr.name,attr->name)==0) {
-	    (void)H5O_reset (H5O_ATTR_ID, &found_attr);
-	    HGOTO_ERROR(H5E_ATTR, H5E_ALREADYEXISTS, FAIL, "attribute already exists")
-	}
-	if(H5O_reset (H5O_ATTR_ID, &found_attr)<0)
-	    HGOTO_ERROR(H5E_ATTR, H5E_CANTFREE, FAIL, "can't release attribute info")
-	seq++;
-    }
-    H5E_clear_stack(NULL);
-
     /* Create the attribute message and save the attribute index */
-    if (H5O_modify(&(attr->ent), H5O_ATTR_ID, H5O_NEW_MESG, 0, 1, attr, dxpl_id) < 0) 
+    if (H5O_modify(&(attr->ent), H5O_ATTR_ID, H5O_NEW_MESG, 0, H5O_UPDATE_TIME, attr, dxpl_id) < 0) 
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "unable to update attribute header messages")
 
     /* Register the new attribute and get an ID for it */
@@ -322,6 +320,52 @@ done:
 
 /*--------------------------------------------------------------------------
  NAME
+    H5A_find_idx_by_name
+ PURPOSE
+    Iterator callback to determine the index of a attribute
+ USAGE
+    herr_t H5A_find_idx_by_name (mesg, idx, op_data)
+        const H5A_t *mesg;      IN: Pointer to attribute
+        unsigned idx;           IN: Index of attribute
+        void *op_data;          IN: Op data passed in
+ RETURNS
+    Non-negative on success, negative on failure
+ 
+ ERRORS
+
+ DESCRIPTION
+        This function determines if an attribute matches the name to search
+    for (from the 'op_data') and sets the index value in the 'op_data'.
+--------------------------------------------------------------------------*/
+static herr_t
+H5A_find_idx_by_name(const void *_mesg, unsigned idx, void *_op_data)
+{
+    const H5A_t *mesg = (const H5A_t *)_mesg;   /* Pointer to attribute */
+    H5A_iter_cb1 *op_data = (H5A_iter_cb1 *)_op_data;   /* Pointer to op data */
+    int		ret_value;         /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5A_find_idx_by_name)
+
+    assert(mesg);
+    assert(op_data);
+
+    /*
+     * Compare found attribute name to queried name and set the idx in the
+     * callback info if names are the same.
+     */
+    if(HDstrcmp(mesg->name,op_data->name)==0) {
+        op_data->idx=idx;
+        ret_value=1;
+    } /* end if */
+    else
+        ret_value=0;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5A_find_idx_by_name() */
+
+
+/*--------------------------------------------------------------------------
+ NAME
     H5A_get_index
  PURPOSE
     Determine the index of an attribute in an object header
@@ -343,8 +387,7 @@ done:
 static int
 H5A_get_index(H5G_entry_t *ent, const char *name, hid_t dxpl_id)
 {
-    H5A_t      	found_attr;
-    int		i;                      /* Index variable */
+    H5A_iter_cb1 cb;                    /* Iterator callback */
     int		ret_value=FAIL;         /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5A_get_index)
@@ -352,25 +395,13 @@ H5A_get_index(H5G_entry_t *ent, const char *name, hid_t dxpl_id)
     assert(ent);
     assert(name);
 
-    /* Look up the attribute for the object */
-    i=0;
-    while(H5O_read(ent, H5O_ATTR_ID, i, &found_attr, dxpl_id)!=NULL) {
-	/*
-	 * Compare found attribute name to new attribute name reject creation
-	 * if names are the same.
-	 */
-	if(HDstrcmp(found_attr.name,name)==0) {
-	    if(H5O_reset (H5O_ATTR_ID, &found_attr)<0)
-                HGOTO_ERROR(H5E_ATTR, H5E_CANTFREE, FAIL, "can't release attribute info")
-            HGOTO_DONE(i);
-	}
-	if(H5O_reset (H5O_ATTR_ID, &found_attr)<0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTFREE, FAIL, "can't release attribute info")
-	i++;
-    }
-    H5E_clear_stack(NULL);
-    
-    if(ret_value<0)
+    cb.name=name;
+    cb.idx=(-1);
+    if((ret_value=H5O_iterate(ent,H5O_ATTR_ID,H5A_find_idx_by_name,&cb,dxpl_id))<0)
+        HGOTO_ERROR(H5E_ATTR, H5E_NOTFOUND, FAIL, "error iterating over attributes")
+    if(ret_value>0)
+        ret_value=cb.idx;
+    else
         HGOTO_ERROR(H5E_ATTR, H5E_NOTFOUND, FAIL, "attribute not found")
 
 done:
@@ -690,7 +721,7 @@ H5A_write(H5A_t *attr, const H5T_t *mem_type, const void *buf, hid_t dxpl_id)
             HGOTO_ERROR(H5E_ATTR, H5E_BADVALUE, FAIL, "attribute not found")
 
         /* Modify the attribute data */
-        if (H5O_modify(&(attr->ent), H5O_ATTR_ID, idx, 0, 1, attr, dxpl_id) < 0) 
+        if (H5O_modify(&(attr->ent), H5O_ATTR_ID, idx, 0, H5O_UPDATE_DATA_ONLY|H5O_UPDATE_TIME, attr, dxpl_id) < 0) 
             HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "unable to update attribute header messages")
     } /* end if */
 
@@ -1267,7 +1298,7 @@ H5A_rename(H5G_entry_t *ent, const char *old_name, const char *new_name, hid_t d
     found_attr.initialized=TRUE;
 
     /* Modify the attribute message */
-    if (H5O_modify(ent, H5O_ATTR_ID, idx, 0, 1, &found_attr, dxpl_id) < 0) 
+    if (H5O_modify(ent, H5O_ATTR_ID, idx, 0, H5O_UPDATE_TIME, &found_attr, dxpl_id) < 0) 
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, FAIL, "unable to update attribute header messages")
    
     /* Close the attribute */
@@ -1405,9 +1436,8 @@ done:
 herr_t
 H5Adelete(hid_t loc_id, const char *name)
 {
-    H5A_t       found_attr;
     H5G_entry_t	*ent = NULL;		/*symtab ent of object to attribute */
-    int        idx=0, found=-1;
+    int         found;
     herr_t	ret_value;
 
     FUNC_ENTER_API(H5Adelete, FAIL)
@@ -1421,25 +1451,8 @@ H5Adelete(hid_t loc_id, const char *name)
     if (!name || !*name)
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
 
-    /* Look up the attribute for the object */
-    idx=0;
-    while(H5O_read(ent, H5O_ATTR_ID, idx, &found_attr, H5AC_dxpl_id)!=NULL) {
-	/*
-	 * Compare found attribute name to new attribute name reject
-	 * creation if names are the same.
-	 */
-	if(HDstrcmp(found_attr.name,name)==0) {
-	    if(H5O_reset (H5O_ATTR_ID, &found_attr)<0)
-                HGOTO_ERROR(H5E_ATTR, H5E_CANTFREE, FAIL, "can't release attribute info")
-	    found = idx;
-	    break;
-	}
-	if(H5O_reset (H5O_ATTR_ID, &found_attr)<0)
-            HGOTO_ERROR(H5E_ATTR, H5E_CANTFREE, FAIL, "can't release attribute info")
-	idx++;
-    }
-    H5E_clear_stack(NULL);
-    if (found<0)
+    /* Look up the attribute index for the object */
+    if((found=H5A_get_index(ent,name,H5AC_dxpl_id))<0)
         HGOTO_ERROR(H5E_ATTR, H5E_NOTFOUND, FAIL, "attribute not found")
 
     /* Delete the attribute from the location */
@@ -1506,7 +1519,7 @@ done:
  *-------------------------------------------------------------------------
  */
 H5A_t *
-H5A_copy(H5A_t *_new_attr, const H5A_t *old_attr)
+H5A_copy(H5A_t *_new_attr, const H5A_t *old_attr, unsigned update_flags)
 {
     H5A_t	*new_attr=NULL;
     hbool_t     allocated_attr=FALSE;   /* Whether the attribute was allocated */
@@ -1519,6 +1532,9 @@ H5A_copy(H5A_t *_new_attr, const H5A_t *old_attr)
 
     /* get space */
     if(_new_attr==NULL) {
+        /* Sanity check - We should not be only updating data if we don'y have anything */
+        HDassert(!(update_flags&H5O_UPDATE_DATA_ONLY));
+
         if (NULL==(new_attr = H5FL_MALLOC(H5A_t)))
             HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
         allocated_attr=TRUE;
@@ -1526,19 +1542,23 @@ H5A_copy(H5A_t *_new_attr, const H5A_t *old_attr)
     else
         new_attr=_new_attr;
 
-    /* Copy the top level of the attribute */
-    *new_attr = *old_attr;
+    if(!(update_flags&H5O_UPDATE_DATA_ONLY)) {
+        /* Copy the top level of the attribute */
+        *new_attr = *old_attr;
 
-    /* Don't open the object header for a copy */
-    new_attr->ent_opened=0;
+        /* Don't open the object header for a copy */
+        new_attr->ent_opened=0;
 
-    /* Copy the guts of the attribute */
-    new_attr->name=HDstrdup(old_attr->name);
-    new_attr->dt=H5T_copy(old_attr->dt, H5T_COPY_ALL);
-    new_attr->ds=H5S_copy(old_attr->ds, FALSE);
+        /* Copy the guts of the attribute */
+        new_attr->name=HDstrdup(old_attr->name);
+        new_attr->dt=H5T_copy(old_attr->dt, H5T_COPY_ALL);
+        new_attr->ds=H5S_copy(old_attr->ds, FALSE);
+    } /* end if */
     if(old_attr->data) {
-        if (NULL==(new_attr->data=H5MM_malloc(old_attr->data_size)))
-	    HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
+        if(!(update_flags&H5O_UPDATE_DATA_ONLY) || new_attr->data==NULL) {
+            if (NULL==(new_attr->data=H5MM_malloc(old_attr->data_size)))
+                HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
+        } /* end if */
         HDmemcpy(new_attr->data,old_attr->data,old_attr->data_size);
     } /* end if */
 
diff --git a/src/H5Apkg.h b/src/H5Apkg.h
index a354a48..976340d 100644
--- a/src/H5Apkg.h
+++ b/src/H5Apkg.h
@@ -55,7 +55,7 @@ struct H5A_t {
 };
 
 /* Function prototypes for H5A package scope */
-H5_DLL H5A_t       *H5A_copy(H5A_t *new_attr, const H5A_t *old_attr);
+H5_DLL H5A_t       *H5A_copy(H5A_t *new_attr, const H5A_t *old_attr, unsigned update_flags);
 H5_DLL herr_t      H5A_free(H5A_t *attr);
 H5_DLL herr_t      H5A_close(H5A_t *attr);
 
diff --git a/src/H5D.c b/src/H5D.c
index 456020b..c388184 100644
--- a/src/H5D.c
+++ b/src/H5D.c
@@ -2891,7 +2891,7 @@ H5D_close(H5D_t *dataset)
             case H5D_COMPACT:               
                 /* Update header message of layout for compact dataset. */
                 if(dataset->shared->layout.u.compact.dirty) {
-                    if(H5O_modify(&(dataset->ent), H5O_LAYOUT_ID, 0, 0, 1, &(dataset->shared->layout), H5AC_dxpl_id)<0)
+                    if(H5O_modify(&(dataset->ent), H5O_LAYOUT_ID, 0, 0, H5O_UPDATE_TIME, &(dataset->shared->layout), H5AC_dxpl_id)<0)
                         HGOTO_ERROR(H5E_DATASET, H5E_CANTRELEASE, FAIL, "unable to update layout message")
                     dataset->shared->layout.u.compact.dirty = FALSE;
                 } /* end if */
@@ -4134,7 +4134,7 @@ H5D_flush(H5F_t *f, hid_t dxpl_id, unsigned flags)
 
                 case H5D_COMPACT:               
                     if(dataset->shared->layout.u.compact.dirty) {
-                        if(H5O_modify(&(dataset->ent), H5O_LAYOUT_ID, 0, 0, 1, &(dataset->shared->layout), dxpl_id)<0)
+                        if(H5O_modify(&(dataset->ent), H5O_LAYOUT_ID, 0, 0, H5O_UPDATE_TIME, &(dataset->shared->layout), dxpl_id)<0)
                             HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "unable to update layout message")
                         dataset->shared->layout.u.compact.dirty = FALSE;
                     } /* end if */
diff --git a/src/H5G.c b/src/H5G.c
index d30f6f0..23405d6 100644
--- a/src/H5G.c
+++ b/src/H5G.c
@@ -281,7 +281,7 @@ done:
 hid_t
 H5Gopen(hid_t loc_id, const char *name)
 {
-    hid_t        ret_value = FAIL;
+    hid_t       ret_value = FAIL;
     H5G_t       *grp = NULL;
     H5G_entry_t	*loc = NULL;
     H5G_entry_t	 ent;
@@ -402,9 +402,9 @@ H5Giterate(hid_t loc_id, const char *name, int *idx_p,
     if (!idx_p)
         idx_p = &idx;
     if (idx<0)
-        HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index specified");
+	HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index specified");
     if (!op)
-        HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "no operator specified");
+	HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "no operator specified");
 
     /*
      * Open the group on which to operate.  We also create a group ID which
@@ -416,7 +416,7 @@ H5Giterate(hid_t loc_id, const char *name, int *idx_p,
         H5Gclose(udata.group_id);
         HGOTO_ERROR (H5E_ATOM, H5E_BADATOM, FAIL, "bad group atom");
     }
-    
+
     /* Build udata to pass through H5B_iterate() to H5G_node_iterate() */
     udata.skip = idx;
     udata.ent = &(grp->ent);
@@ -1544,7 +1544,7 @@ H5G_namei(H5G_entry_t *loc_ent, const char *name, const char **rest/*out*/,
 
     /* If this was an insert, make sure that the insert function was actually
      * called (this catches no-op names like "." and "/") */
-     if( action== H5G_NAMEI_INSERT && !did_insert)
+     if(action == H5G_NAMEI_INSERT && !did_insert)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "group already exists");
 
 done:
@@ -1793,7 +1793,6 @@ H5G_create(H5G_entry_t *loc, const char *name, size_t size_hint, hid_t dxpl_id)
     if (NULL==(grp->shared = H5FL_CALLOC(H5G_t)))
         HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed");
 
-
     /* What file is the group being added to? */
     if (NULL==(file=H5G_insertion_file(loc, name, dxpl_id)))
         HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, NULL, "unable to locate insertion point");
@@ -1825,10 +1824,11 @@ done:
             if(H5O_delete(file, dxpl_id,grp->ent.header)<0)
                 HDONE_ERROR(H5E_SYM, H5E_CANTDELETE, NULL, "unable to delete object header");
         } /* end if */
-        if(grp!=NULL)
+        if(grp!=NULL) {
             if(grp->shared != NULL)
                 H5FL_FREE(H5G_shared_t, grp->shared);
             H5FL_FREE(H5G_t,grp);
+        }
     } /* end if */
 
     FUNC_LEAVE_NOAPI(ret_value);
@@ -2988,7 +2988,7 @@ H5G_set_comment(H5G_entry_t *loc, const char *name, const char *buf, hid_t dxpl_
     /* Add the new message */
     if (buf && *buf) {
 	comment.s = H5MM_xstrdup(buf);
-	if (H5O_modify(&obj_ent, H5O_NAME_ID, H5O_NEW_MESG, 0, 1, &comment, dxpl_id)<0)
+	if (H5O_modify(&obj_ent, H5O_NAME_ID, H5O_NEW_MESG, 0, H5O_UPDATE_TIME, &comment, dxpl_id)<0)
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to set comment object header message");
 	H5O_reset(H5O_NAME_ID, &comment);
     }
diff --git a/src/H5Gstab.c b/src/H5Gstab.c
index d270ceb..71b5603 100644
--- a/src/H5Gstab.c
+++ b/src/H5Gstab.c
@@ -109,7 +109,7 @@ H5G_stab_create(H5F_t *f, hid_t dxpl_id, size_t init, H5G_entry_t *self/*out*/)
      * Insert the symbol table message into the object header and the symbol
      * table entry.
      */
-    if (H5O_modify(self, H5O_STAB_ID, H5O_NEW_MESG, H5O_FLAG_CONSTANT, 1, &stab, dxpl_id)<0) {
+    if (H5O_modify(self, H5O_STAB_ID, H5O_NEW_MESG, H5O_FLAG_CONSTANT, H5O_UPDATE_TIME, &stab, dxpl_id)<0) {
 	H5O_close(self);
 	HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't create message");
     }
diff --git a/src/H5O.c b/src/H5O.c
index 7cf7893..6c84e26 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -67,7 +67,7 @@ static herr_t H5O_share(H5F_t *f, hid_t dxpl_id, const H5O_class_t *type, const
 static unsigned H5O_find_in_ohdr(H5F_t *f, hid_t dxpl_id, H5O_t *oh,
                                  const H5O_class_t **type_p, int sequence);
 static int H5O_modify_real(H5G_entry_t *ent, const H5O_class_t *type,
-    int overwrite, unsigned flags, unsigned update_time, const void *mesg,
+    int overwrite, unsigned flags, unsigned update_flags, const void *mesg,
     hid_t dxpl_id);
 static int H5O_append_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh,
     const H5O_class_t *type, unsigned flags, const void *mesg);
@@ -83,7 +83,7 @@ static unsigned H5O_new_mesg(H5F_t *f, H5O_t *oh, unsigned *flags,
     const H5O_class_t *orig_type, const void *orig_mesg, H5O_shared_t *sh_mesg,
     const H5O_class_t **new_type, const void **new_mesg, hid_t dxpl_id);
 static herr_t H5O_write_mesg(H5O_t *oh, unsigned idx, const H5O_class_t *type,
-    const void *mesg, unsigned flags);
+    const void *mesg, unsigned flags, unsigned update_flags);
 
 /* Metadata cache callbacks */
 static H5O_t *H5O_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void *_udata1,
@@ -1183,7 +1183,7 @@ H5O_copy_real (const H5O_class_t *type, const void *mesg, void *dst)
     assert (type->copy);
 
     if (mesg) {
-	if (NULL==(ret_value=(type->copy)(mesg, dst)))
+	if (NULL==(ret_value=(type->copy)(mesg, dst, 0)))
 	    HGOTO_ERROR (H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy object header message");
     }
 
@@ -1629,7 +1629,7 @@ H5O_read_real(H5G_entry_t *ent, const H5O_class_t *type, int sequence, void *mes
 	 * the raw message) so we must copy the native message before
 	 * returning.
 	 */
-	if (NULL==(ret_value = (type->copy) (oh->mesg[idx].native, mesg)))
+	if (NULL==(ret_value = (type->copy) (oh->mesg[idx].native, mesg, 0)))
 	    HGOTO_ERROR (H5E_OHDR, H5E_CANTINIT, NULL, "unable to copy message to user space");
     }
 
@@ -1692,11 +1692,10 @@ H5O_find_in_ohdr(H5F_t *f, hid_t dxpl_id, H5O_t *oh, const H5O_class_t **type_p,
      * Decode the message if necessary.  If the message is shared then decode
      * a shared message, ignoring the message type.
      */
-    if (oh->mesg[u].flags & H5O_FLAG_SHARED) {
+    if (oh->mesg[u].flags & H5O_FLAG_SHARED)
 	type = H5O_SHARED;
-    } else {
+    else
 	type = oh->mesg[u].type;
-    }
 
     if (NULL == oh->mesg[u].native) {
 	assert(type->decode);
@@ -1767,7 +1766,7 @@ done:
  */
 int
 H5O_modify(H5G_entry_t *ent, unsigned type_id, int overwrite,
-   unsigned flags, unsigned update_time, const void *mesg, hid_t dxpl_id)
+   unsigned flags, unsigned update_flags, const void *mesg, hid_t dxpl_id)
 {
     const H5O_class_t *type;            /* Actual H5O class type for the ID */
     int	ret_value;              /* Return value */
@@ -1785,7 +1784,7 @@ H5O_modify(H5G_entry_t *ent, unsigned type_id, int overwrite,
     assert (0==(flags & ~H5O_FLAG_BITS));
 
     /* Call the "real" modify routine */
-    if((ret_value= H5O_modify_real(ent, type, overwrite, flags, update_time, mesg, dxpl_id))<0)
+    if((ret_value= H5O_modify_real(ent, type, overwrite, flags, update_flags, mesg, dxpl_id))<0)
 	HGOTO_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL, "unable to write object header");
 
 done:
@@ -1836,7 +1835,7 @@ done:
  */
 static int
 H5O_modify_real(H5G_entry_t *ent, const H5O_class_t *type, int overwrite,
-   unsigned flags, unsigned update_time, const void *mesg, hid_t dxpl_id)
+   unsigned flags, unsigned update_flags, const void *mesg, hid_t dxpl_id)
 {
     H5O_t		*oh=NULL;
     int		        sequence;
@@ -1894,11 +1893,11 @@ H5O_modify_real(H5G_entry_t *ent, const H5O_class_t *type, int overwrite,
     }
     
     /* Write the information to the message */
-    if(H5O_write_mesg(oh,idx,type,mesg,flags)<0)
+    if(H5O_write_mesg(oh,idx,type,mesg,flags,update_flags)<0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to write message");
 
     /* Update the modification time message if any */
-    if(update_time)
+    if(update_flags&H5O_UPDATE_TIME)
         H5O_touch_oh(ent->file, oh, FALSE);
     
     /* Set return value */
@@ -2086,7 +2085,7 @@ H5O_append_real(H5F_t *f, hid_t dxpl_id, H5O_t *oh, const H5O_class_t *type,
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to create new message");
 
     /* Write the information to the message */
-    if(H5O_write_mesg(oh,idx,type,mesg,flags)<0)
+    if(H5O_write_mesg(oh,idx,type,mesg,flags,0)<0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to write message");
 
     /* Set return value */
@@ -2189,7 +2188,7 @@ done:
  */
 static herr_t
 H5O_write_mesg(H5O_t *oh, unsigned idx, const H5O_class_t *type,
-    const void *mesg, unsigned flags)
+    const void *mesg, unsigned flags, unsigned update_flags)
 {
     H5O_mesg_t         *idx_msg;        /* Pointer to message to modify */
     herr_t      ret_value=SUCCEED;      /* Return value */
@@ -2205,10 +2204,11 @@ H5O_write_mesg(H5O_t *oh, unsigned idx, const H5O_class_t *type,
     idx_msg=&oh->mesg[idx];
 
     /* Reset existing native information */
-    H5O_reset_real(type, idx_msg->native);
+    if(!(update_flags&H5O_UPDATE_DATA_ONLY))
+        H5O_reset_real(type, idx_msg->native);
 
     /* Copy the native value for the message */
-    if (NULL == (idx_msg->native = (type->copy) (mesg, idx_msg->native)))
+    if (NULL == (idx_msg->native = (type->copy) (mesg, idx_msg->native, update_flags)))
         HGOTO_ERROR(H5E_OHDR, H5E_CANTINIT, FAIL, "unable to copy message to object header");
 
     idx_msg->flags = flags;
@@ -3509,6 +3509,102 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5O_iterate
+ *
+ * Purpose:	Iterate through object headers of a certain type.
+ *
+ * Return:	Returns a negative value if something is wrong, the return
+ *      value of the last operator if it was non-zero, or zero if all
+ *      object headers were processed.
+ *
+ * Programmer:	Quincey Koziol
+ *		koziol@ncsa.uiuc.edu
+ *		Nov 19 2004
+ *
+ * Description:
+ *      This function interates over the object headers of an object
+ *  specified with 'ent' of type 'type_id'.  For each object header of the
+ *  object, the 'op_data' and some additional information (specified below) are
+ *  passed to the 'op' function.
+ *      The operation receives a pointer to the object header message for the
+ *  object being iterated over ('mesg'), and the pointer to the operator data
+ *  passed in to H5O_iterate ('op_data').  The return values from an operator
+ *  are:
+ *      A. Zero causes the iterator to continue, returning zero when all 
+ *          object headers of that type have been processed.
+ *      B. Positive causes the iterator to immediately return that positive
+ *          value, indicating short-circuit success.
+ *      C. Negative causes the iterator to immediately return that value,
+ *          indicating failure.
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5O_iterate(const H5G_entry_t *ent, unsigned type_id, H5O_operator_t op,
+    void *op_data, hid_t dxpl_id)
+{
+    H5O_t		*oh=NULL;       /* Pointer to actual object header */
+    const H5O_class_t *type;            /* Actual H5O class type for the ID */
+    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 */
+    herr_t              ret_value=0;    /* Return value */
+
+    FUNC_ENTER_NOAPI(H5O_iterate, FAIL);
+
+    /* check args */
+    assert(ent);
+    assert(ent->file);
+    assert(H5F_addr_defined(ent->header));
+    assert(type_id<NELMTS(message_type_g));
+    type=message_type_g[type_id];    /* map the type ID to the actual type object */
+    assert(type);
+
+    /* Protect the object header to iterate over */
+    if (NULL == (oh = H5AC_protect(ent->file, dxpl_id, H5AC_OHDR, ent->header, NULL, NULL, H5AC_READ)))
+	HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to load object header");
+
+    /* Iterate over messages */
+    for (sequence=0, idx = 0, idx_msg=&oh->mesg[0]; idx < oh->nmesgs; idx++, idx_msg++) {
+	if (type->id == idx_msg->type->id) {
+            /*
+             * Decode the message if necessary.  If the message is shared then decode
+             * a shared message, ignoring the message type.
+             */
+            if (NULL == idx_msg->native) {
+                const H5O_class_t	*decode_type;
+
+                if (idx_msg->flags & H5O_FLAG_SHARED)
+                    decode_type = H5O_SHARED;
+                else
+                    decode_type = type;
+
+                /* Decode the message if necessary */
+                assert(decode_type->decode);
+                if (NULL == (idx_msg->native = (decode_type->decode) (ent->file, dxpl_id, idx_msg->raw, NULL)))
+                    HGOTO_ERROR(H5E_OHDR, H5E_CANTDECODE, FAIL, "unable to decode message");
+            } /* end if */
+
+            /* Call the iterator callback */
+	    if((ret_value=(op)(idx_msg->native,sequence,op_data))!=0)
+		break;
+
+            /* Increment sequence value for message type */
+            sequence++;
+        } /* end if */
+    } /* end for */
+
+done:
+    if (oh && H5AC_unprotect(ent->file, dxpl_id, H5AC_OHDR, ent->header, oh, FALSE) < 0)
+	HDONE_ERROR(H5E_OHDR, H5E_PROTECT, FAIL, "unable to release object header");
+
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* end H5O_iterate() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5O_debug_id
  *
  * Purpose:	Act as a proxy for calling the 'debug' method for a
diff --git a/src/H5Oattr.c b/src/H5Oattr.c
index 9f92c87..28da005 100644
--- a/src/H5Oattr.c
+++ b/src/H5Oattr.c
@@ -32,7 +32,7 @@
 /* PRIVATE PROTOTYPES */
 static herr_t H5O_attr_encode (H5F_t *f, uint8_t *p, const void *mesg);
 static void *H5O_attr_decode (H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
-static void *H5O_attr_copy (const void *_mesg, void *_dest);
+static void *H5O_attr_copy (const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_attr_size (H5F_t *f, const void *_mesg);
 static herr_t H5O_attr_reset (void *_mesg);
 static herr_t H5O_attr_free (void *mesg);
@@ -368,8 +368,8 @@ done:
         This function copies a native (memory) attribute message,
     allocating the destination structure if necessary.
 --------------------------------------------------------------------------*/
-static void            *
-H5O_attr_copy(const void *_src, void *_dst)
+static void *
+H5O_attr_copy(const void *_src, void *_dst, unsigned update_flags)
 {
     const H5A_t            *src = (const H5A_t *) _src;
     void                   *ret_value;  /* Return value */
@@ -380,7 +380,7 @@ H5O_attr_copy(const void *_src, void *_dst)
     assert(src);
 
     /* copy */
-    if (NULL == (ret_value = H5A_copy(_dst,src)))
+    if (NULL == (ret_value = H5A_copy(_dst,src,update_flags)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, NULL, "can't copy attribute");
 
 done:
@@ -481,7 +481,7 @@ H5O_attr_reset(void *_mesg)
     H5A_t                  *attr = (H5A_t *) _mesg;
     herr_t      ret_value=SUCCEED;       /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT(H5O_attr_reset);
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_attr_reset);
 
     if (attr)
         H5A_free(attr);
diff --git a/src/H5Odtype.c b/src/H5Odtype.c
index 4aee2b9..25b9c05 100644
--- a/src/H5Odtype.c
+++ b/src/H5Odtype.c
@@ -28,7 +28,7 @@
 /* PRIVATE PROTOTYPES */
 static herr_t H5O_dtype_encode (H5F_t *f, uint8_t *p, const void *mesg);
 static void *H5O_dtype_decode (H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
-static void *H5O_dtype_copy (const void *_mesg, void *_dest);
+static void *H5O_dtype_copy (const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_dtype_size (H5F_t *f, const void *_mesg);
 static herr_t H5O_dtype_reset (void *_mesg);
 static herr_t H5O_dtype_free (void *_mesg);
@@ -904,7 +904,7 @@ H5O_dtype_encode(H5F_t UNUSED *f, uint8_t *p, const void *mesg)
     FUNC_ENTER_NOAPI_NOINIT(H5O_dtype_encode);
 
     /* check args */
-    /*assert(f);*/
+    assert(f);
     assert(p);
     assert(dt);
 
@@ -935,7 +935,7 @@ done:
     allocating the destination structure if necessary.
 --------------------------------------------------------------------------*/
 static void *
-H5O_dtype_copy(const void *_src, void *_dst)
+H5O_dtype_copy(const void *_src, void *_dst, unsigned UNUSED update_flags)
 {
     const H5T_t		   *src = (const H5T_t *) _src;
     H5T_t		   *dst = NULL;
diff --git a/src/H5Oefl.c b/src/H5Oefl.c
index c795956..7472084 100644
--- a/src/H5Oefl.c
+++ b/src/H5Oefl.c
@@ -33,7 +33,7 @@
 /* PRIVATE PROTOTYPES */
 static void *H5O_efl_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_efl_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void *H5O_efl_copy(const void *_mesg, void *_dest);
+static void *H5O_efl_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_efl_size(H5F_t *f, const void *_mesg);
 static herr_t H5O_efl_reset(void *_mesg);
 static herr_t H5O_efl_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FILE * stream,
@@ -255,7 +255,7 @@ H5O_efl_encode(H5F_t *f, uint8_t *p, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_efl_copy(const void *_mesg, void *_dest)
+H5O_efl_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_efl_t	*mesg = (const H5O_efl_t *) _mesg;
     H5O_efl_t		*dest = (H5O_efl_t *) _dest;
diff --git a/src/H5Ofill.c b/src/H5Ofill.c
index f79c2d1..c1d1fd1 100644
--- a/src/H5Ofill.c
+++ b/src/H5Ofill.c
@@ -33,7 +33,7 @@
 
 static void  *H5O_fill_new_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_fill_new_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void  *H5O_fill_new_copy(const void *_mesg, void *_dest);
+static void  *H5O_fill_new_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_fill_new_size(H5F_t *f, const void *_mesg);
 static herr_t H5O_fill_new_reset(void *_mesg);
 static herr_t H5O_fill_new_free(void *_mesg);
@@ -42,7 +42,7 @@ static herr_t H5O_fill_new_debug(H5F_t *f, hid_t dxpl_id, const void *_mesg, FIL
 
 static void  *H5O_fill_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_fill_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void  *H5O_fill_copy(const void *_mesg, void *_dest);
+static void  *H5O_fill_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_fill_size(H5F_t *f, const void *_mesg);
 static herr_t H5O_fill_reset(void *_mesg);
 static herr_t H5O_fill_free(void *_mesg);
@@ -158,7 +158,7 @@ H5O_fill_new_decode(H5F_t UNUSED *f, hid_t UNUSED dxpl_id, const uint8_t *p,
     } /* end if */
     else
         mesg->size=(-1);
-    
+
     /* Set return value */
     ret_value = (void*)mesg;
     
@@ -293,7 +293,7 @@ static herr_t
 H5O_fill_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
 {
     const H5O_fill_t    *mesg = (const H5O_fill_t *)_mesg;
-    
+
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_fill_encode);
 
     assert(f);
@@ -328,7 +328,7 @@ H5O_fill_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_fill_new_copy(const void *_mesg, void *_dest)
+H5O_fill_new_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_fill_new_t	*mesg = (const H5O_fill_new_t *)_mesg;
     H5O_fill_new_t		*dest = (H5O_fill_new_t *)_dest;
@@ -400,7 +400,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_fill_copy(const void *_mesg, void *_dest)
+H5O_fill_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_fill_t    *mesg = (const H5O_fill_t *)_mesg;
     H5O_fill_t          *dest = (H5O_fill_t *)_dest;
@@ -555,7 +555,7 @@ H5O_fill_new_reset(void *_mesg)
     }
     mesg->alloc_time   = (H5D_alloc_time_t)0;
     mesg->fill_time    = (H5D_fill_time_t)0;
-    mesg->fill_defined = FALSE; 
+    mesg->fill_defined = FALSE;
 
     FUNC_LEAVE_NOAPI(SUCCEED);
 }
@@ -579,6 +579,7 @@ static herr_t
 H5O_fill_reset(void *_mesg)
 {
     H5O_fill_t  *mesg = (H5O_fill_t *)_mesg;
+    herr_t ret_value=SUCCEED;   /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5O_fill_reset);
 
@@ -818,10 +819,10 @@ H5O_fill_convert(void *_fill, H5T_t *dset_type, hid_t dxpl_id)
     H5O_fill_new_t	*fill = _fill;
     H5T_path_t		*tpath=NULL;		/*type conversion info	*/
     void		*buf=NULL, *bkg=NULL;	/*conversion buffers	*/
-    hid_t		src_id=-1, dst_id=-1;	/*data type identifiers	*/
+    hid_t		src_id=-1, dst_id=-1;	/*datatype identifiers	*/
     herr_t      ret_value=SUCCEED;       /* Return value */
 
-    FUNC_ENTER_NOAPI(H5O_fill_convert, FAIL);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_fill_convert);
 
     assert(fill);
     assert(dset_type);
@@ -838,7 +839,7 @@ H5O_fill_convert(void *_fill, H5T_t *dset_type, hid_t dxpl_id)
      * Can we convert between source and destination data types?
      */
     if (NULL==(tpath=H5T_path_find(fill->type, dset_type, NULL, NULL, dxpl_id)))
-	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to convert between src and dst data types")
+	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to convert between src and dst datatypes")
 
     /* Don't bother doing anything if there will be no actual conversion */
     if (!H5T_path_noop(tpath)) {
@@ -849,7 +850,7 @@ H5O_fill_convert(void *_fill, H5T_t *dset_type, hid_t dxpl_id)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to copy/register data type");
 
         /*
-         * Data type conversions are always done in place, so we need a buffer
+         * Datatype conversions are always done in place, so we need a buffer
          * that is large enough for both source and destination.
          */
         if (H5T_get_size(fill->type)>=H5T_get_size(dset_type)) {
@@ -864,7 +865,7 @@ H5O_fill_convert(void *_fill, H5T_t *dset_type, hid_t dxpl_id)
 
         /* Do the conversion */
         if (H5T_convert(tpath, src_id, dst_id, 1, 0, 0, buf, bkg, dxpl_id)<0)
-            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "data type conversion failed");
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "datatype conversion failed");
 
         /* Update the fill message */
         if (buf!=fill->buf) {
diff --git a/src/H5Olayout.c b/src/H5Olayout.c
index e829606..28db75c 100644
--- a/src/H5Olayout.c
+++ b/src/H5Olayout.c
@@ -35,7 +35,7 @@
 /* PRIVATE PROTOTYPES */
 static void *H5O_layout_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_layout_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void *H5O_layout_copy(const void *_mesg, void *_dest);
+static void *H5O_layout_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_layout_size(H5F_t *f, const void *_mesg);
 static herr_t H5O_layout_reset (void *_mesg);
 static herr_t H5O_layout_free (void *_mesg);
@@ -343,7 +343,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_layout_copy(const void *_mesg, void *_dest)
+H5O_layout_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_layout_t     *mesg = (const H5O_layout_t *) _mesg;
     H5O_layout_t           *dest = (H5O_layout_t *) _dest;
diff --git a/src/H5Omtime.c b/src/H5Omtime.c
index 6044988..57e1de1 100644
--- a/src/H5Omtime.c
+++ b/src/H5Omtime.c
@@ -39,7 +39,7 @@ static size_t H5O_mtime_new_size(H5F_t *f, const void *_mesg);
 
 static void *H5O_mtime_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_mtime_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void *H5O_mtime_copy(const void *_mesg, void *_dest);
+static void *H5O_mtime_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_mtime_size(H5F_t *f, const void *_mesg);
 static herr_t H5O_mtime_reset(void *_mesg);
 static herr_t H5O_mtime_free(void *_mesg);
@@ -385,7 +385,7 @@ H5O_mtime_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_mtime_copy(const void *_mesg, void *_dest)
+H5O_mtime_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const time_t	*mesg = (const time_t *) _mesg;
     time_t		*dest = (time_t *) _dest;
diff --git a/src/H5Oname.c b/src/H5Oname.c
index 0f1893d..b58246a 100644
--- a/src/H5Oname.c
+++ b/src/H5Oname.c
@@ -37,7 +37,7 @@
 /* PRIVATE PROTOTYPES */
 static void *H5O_name_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_name_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void *H5O_name_copy(const void *_mesg, void *_dest);
+static void *H5O_name_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_name_size(H5F_t *f, 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,
@@ -166,7 +166,7 @@ H5O_name_encode(H5F_t UNUSED *f, uint8_t *p, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_name_copy(const void *_mesg, void *_dest)
+H5O_name_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_name_t       *mesg = (const H5O_name_t *) _mesg;
     H5O_name_t             *dest = (H5O_name_t *) _dest;
diff --git a/src/H5Opkg.h b/src/H5Opkg.h
index 866e1b7..6ddfd92 100644
--- a/src/H5Opkg.h
+++ b/src/H5Opkg.h
@@ -62,7 +62,7 @@ typedef struct H5O_class_t {
     size_t	native_size;			 /*size of native message    */
     void	*(*decode)(H5F_t*, hid_t, const uint8_t*, struct H5O_shared_t*);
     herr_t	(*encode)(H5F_t*, uint8_t*, const void*);
-    void	*(*copy)(const void*, void*);    /*copy native value         */
+    void	*(*copy)(const void*, void*, unsigned);    /*copy native value         */
     size_t	(*raw_size)(H5F_t*, const void*);/*sizeof raw val	     */
     herr_t	(*reset)(void *);		 /*free nested data structs  */
     herr_t	(*free)(void *);		 /*free main data struct  */
diff --git a/src/H5Opline.c b/src/H5Opline.c
index 3485968..5319a92 100644
--- a/src/H5Opline.c
+++ b/src/H5Opline.c
@@ -34,7 +34,7 @@
 
 static herr_t H5O_pline_encode (H5F_t *f, uint8_t *p, const void *mesg);
 static void *H5O_pline_decode (H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
-static void *H5O_pline_copy (const void *_mesg, void *_dest);
+static void *H5O_pline_copy (const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_pline_size (H5F_t *f, const void *_mesg);
 static herr_t H5O_pline_reset (void *_mesg);
 static herr_t H5O_pline_free (void *_mesg);
@@ -247,7 +247,7 @@ H5O_pline_encode (H5F_t UNUSED *f, uint8_t *p/*out*/, const void *mesg)
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_pline_copy (const void *_src, void *_dst/*out*/)
+H5O_pline_copy (const void *_src, void *_dst/*out*/, unsigned UNUSED update_flags)
 {
     const H5O_pline_t	*src = (const H5O_pline_t *)_src;
     H5O_pline_t		*dst = (H5O_pline_t *)_dst;
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index f70443a..3e256e2 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -49,6 +49,10 @@
 #define H5O_FLAG_SHARED		0x02u
 #define H5O_FLAG_BITS		(H5O_FLAG_CONSTANT|H5O_FLAG_SHARED)
 
+/* Flags for updating messages */
+#define H5O_UPDATE_TIME         0x01u
+#define H5O_UPDATE_DATA_ONLY    0x02u
+
 /* Header message IDs */
 #define H5O_NULL_ID	0x0000          /* Null Message.  */
 #define H5O_SDSPACE_ID	0x0001          /* Simple Dataspace Message.  */
@@ -220,6 +224,10 @@ typedef struct H5O_stab_t {
     haddr_t	heap_addr;		/*address of name heap		     */
 } H5O_stab_t;
 
+/* Typedef for iteration operations */
+typedef herr_t (*H5O_operator_t)(const void *mesg/*in*/, unsigned idx,
+    void *operator_data/*in,out*/);
+
 /* General message operators */
 H5_DLL herr_t H5O_create(H5F_t *f, hid_t dxpl_id, size_t size_hint,
 			  H5G_entry_t *ent/*out*/);
@@ -232,7 +240,7 @@ H5_DLL htri_t H5O_exists(H5G_entry_t *ent, unsigned type_id, int sequence,
 H5_DLL void *H5O_read(H5G_entry_t *ent, unsigned type_id, int sequence,
     void *mesg, hid_t dxpl_id);
 H5_DLL int H5O_modify(H5G_entry_t *ent, unsigned type_id,
-    int overwrite, unsigned flags, unsigned update_time, const void *mesg, hid_t dxpl_id);
+    int overwrite, unsigned flags, unsigned update_flags, const void *mesg, hid_t dxpl_id);
 H5_DLL struct H5O_t * H5O_protect(H5G_entry_t *ent, hid_t dxpl_id);
 H5_DLL herr_t H5O_unprotect(H5G_entry_t *ent, struct H5O_t *oh, hid_t dxpl_id);
 H5_DLL int H5O_append(H5F_t *f, hid_t dxpl_id, struct H5O_t *oh, unsigned type_id, 
@@ -254,6 +262,8 @@ H5_DLL size_t H5O_raw_size(unsigned type_id, H5F_t *f, const void *mesg);
 H5_DLL herr_t H5O_get_share(unsigned type_id, H5F_t *f, const void *mesg, H5O_shared_t *share);
 H5_DLL herr_t H5O_delete(H5F_t *f, hid_t dxpl_id, haddr_t addr);
 H5_DLL herr_t H5O_get_info(H5G_entry_t *ent, H5O_stat_t *ostat, hid_t dxpl_id);
+H5_DLL herr_t H5O_iterate(const H5G_entry_t *ent, unsigned type_id, H5O_operator_t op,
+    void *op_data, hid_t dxpl_id);
 H5_DLL herr_t H5O_debug_id(hid_t type_id, H5F_t *f, hid_t dxpl_id, const void *mesg, FILE *stream, int indent, int fwidth);
 H5_DLL herr_t H5O_debug(H5F_t *f, hid_t dxpl_id, haddr_t addr, FILE * stream, int indent,
 			 int fwidth);
diff --git a/src/H5Osdspace.c b/src/H5Osdspace.c
index e130977..53f8c80 100644
--- a/src/H5Osdspace.c
+++ b/src/H5Osdspace.c
@@ -28,7 +28,7 @@
 /* PRIVATE PROTOTYPES */
 static void *H5O_sdspace_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_sdspace_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void *H5O_sdspace_copy(const void *_mesg, void *_dest);
+static void *H5O_sdspace_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_sdspace_size(H5F_t *f, const void *_mesg);
 static herr_t H5O_sdspace_reset(void *_mesg);
 static herr_t H5O_sdspace_free (void *_mesg);
@@ -277,7 +277,7 @@ H5O_sdspace_encode(H5F_t *f, uint8_t *p, const void *mesg)
 
 --------------------------------------------------------------------------*/
 static void *
-H5O_sdspace_copy(const void *mesg, void *dest)
+H5O_sdspace_copy(const void *mesg, void *dest, unsigned UNUSED update_flags)
 {
     const H5S_extent_t	   *src = (const H5S_extent_t *) mesg;
     H5S_extent_t	   *dst = (H5S_extent_t *) dest;
diff --git a/src/H5Oshared.c b/src/H5Oshared.c
index 0024d8d..59c8278 100644
--- a/src/H5Oshared.c
+++ b/src/H5Oshared.c
@@ -41,7 +41,7 @@
 
 static void *H5O_shared_decode (H5F_t*, hid_t dxpl_id, const uint8_t*, H5O_shared_t *sh);
 static herr_t H5O_shared_encode (H5F_t*, uint8_t*, const void*);
-static void *H5O_shared_copy(const void *_mesg, void *_dest);
+static void *H5O_shared_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_shared_size (H5F_t*, const void *_mesg);
 static herr_t H5O_shared_delete(H5F_t *f, hid_t dxpl_id, const void *_mesg);
 static herr_t H5O_shared_link(H5F_t *f, hid_t dxpl_id, const void *_mesg);
@@ -98,7 +98,7 @@ H5O_shared_read(H5F_t *f, hid_t dxpl_id, H5O_shared_t *shared, const H5O_class_t
 {
     void *ret_value = NULL;     /* Return value */
 
-    FUNC_ENTER_NOAPI(H5O_shared_read,NULL);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_shared_read);
 
     /* check args */
     assert(f);
@@ -344,7 +344,7 @@ H5O_shared_encode (H5F_t *f, uint8_t *buf/*out*/, const void *_mesg)
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_shared_copy(const void *_mesg, void *_dest)
+H5O_shared_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_shared_t  *mesg = (const H5O_shared_t *) _mesg;
     H5O_shared_t	*dest = (H5O_shared_t *) _dest;
diff --git a/src/H5Ostab.c b/src/H5Ostab.c
index b47ad3b..4b061df 100644
--- a/src/H5Ostab.c
+++ b/src/H5Ostab.c
@@ -40,7 +40,7 @@
 /* PRIVATE PROTOTYPES */
 static void *H5O_stab_decode(H5F_t *f, hid_t dxpl_id, const uint8_t *p, H5O_shared_t *sh);
 static herr_t H5O_stab_encode(H5F_t *f, uint8_t *p, const void *_mesg);
-static void *H5O_stab_copy(const void *_mesg, void *_dest);
+static void *H5O_stab_copy(const void *_mesg, void *_dest, unsigned update_flags);
 static size_t H5O_stab_size(H5F_t *f, 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);
@@ -179,7 +179,7 @@ H5O_stab_fast(const H5G_cache_t *cache, const H5O_class_t *type, void *_mesg)
     H5O_stab_t          *stab = NULL;
     void                *ret_value;     /* Return value */
 
-    FUNC_ENTER_NOAPI(H5O_stab_fast, NULL);
+    FUNC_ENTER_NOAPI_NOINIT(H5O_stab_fast);
 
     /* check args */
     assert(cache);
@@ -222,7 +222,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static void *
-H5O_stab_copy(const void *_mesg, void *_dest)
+H5O_stab_copy(const void *_mesg, void *_dest, unsigned UNUSED update_flags)
 {
     const H5O_stab_t       *stab = (const H5O_stab_t *) _mesg;
     H5O_stab_t             *dest = (H5O_stab_t *) _dest;
diff --git a/src/H5Tcommit.c b/src/H5Tcommit.c
index a3b5c80..75e8b8f 100644
--- a/src/H5Tcommit.c
+++ b/src/H5Tcommit.c
@@ -157,7 +157,7 @@ H5T_commit (H5G_entry_t *loc, const char *name, H5T_t *type, hid_t dxpl_id)
      */
     if (H5O_create (file, dxpl_id, 64, &(type->ent))<0)
 	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to create data type object header");
-    if (H5O_modify (&(type->ent), H5O_DTYPE_ID, 0, H5O_FLAG_CONSTANT, 1, type, dxpl_id)<0)
+    if (H5O_modify (&(type->ent), H5O_DTYPE_ID, 0, H5O_FLAG_CONSTANT, H5O_UPDATE_TIME, type, dxpl_id)<0)
 	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to update type header message");
     if (H5G_insert (loc, name, &(type->ent), dxpl_id)<0)
 	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to name data type");
diff --git a/src/H5Zszip.c b/src/H5Zszip.c
index 5d0282a..42e588c 100644
--- a/src/H5Zszip.c
+++ b/src/H5Zszip.c
@@ -84,7 +84,7 @@ H5Z_class_t H5Z_SZIP[1] = {{
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5Z_can_apply_szip(hid_t dcpl_id, hid_t type_id, hid_t space_id)
+H5Z_can_apply_szip(hid_t UNUSED dcpl_id, hid_t type_id, hid_t UNUSED space_id)
 {
     unsigned dtype_size;                /* Datatype's size (in bits) */
     H5T_order_t dtype_order;            /* Datatype's endianness order */