[svn-r11712] Purpose:

    New feature

Description:
    Check in baseline for compact group revisions, which radically revises the
source code for managing groups and object headers.

WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!
WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!

    This initiates the "unstable" phase of the 1.7.x branch, leading up
to the 1.8.0 release.  Please test this code, but do _NOT_ keep files created
with it - the format will change again before the release and you will not
be able to read your old files!!!

WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!
WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!  WARNING!!!!


Solution:
    There's too many changes to really describe them all, but some of them
include:
    - Stop abusing the H5G_entry_t structure and split it into two separate
        structures for non-symbol table node use within the library: H5O_loc_t
        for object locations in a file and H5G_name_t to store the path to
        an opened object.  H5G_entry_t is now only used for storing symbol
        table entries on disk.

    - Retire H5G_namei() in favor of a more general mechanism for traversing
        group paths and issuing callbacks on objects located.  This gets us out
        of the business of hacking H5G_namei() for new features, generally.

    - Revised H5O* routines to take a H5O_loc_t instead of H5G_entry_t

    - Lots more...

Platforms tested:
    h5committested and maybe another dozen configurations.... :-)

1 files changed, 291 insertions, 78 deletions

diff --git a/src/H5Tcommit.c b/src/H5Tcommit.c
index 098450d..c42b9dd 100644
--- a/src/H5Tcommit.c
+++ b/src/H5Tcommit.c
@@ -25,6 +25,7 @@
 
 #include "H5private.h"		/* Generic Functions			*/
 #include "H5Eprivate.h"		/* Error handling			*/
+#include "H5FLprivate.h"	/* Free Lists				*/
 #include "H5FOprivate.h"	/* File objects				*/
 #include "H5Iprivate.h"		/* IDs					*/
 #include "H5Oprivate.h"		/* Object headers			*/
@@ -32,8 +33,9 @@
 #include "H5Tpkg.h"		/* Datatypes				*/
 
 /* Static local functions */
-static herr_t H5T_commit(H5G_entry_t *loc, const char *name, H5T_t *type,
+static herr_t H5T_commit(H5G_loc_t *loc, const char *name, H5T_t *type,
     hid_t dxpl_id, hid_t tcpl_id, hid_t tapl_id);
+static H5T_t *H5T_open_oid(H5G_loc_t *loc, hid_t dxpl_id);
 
 
 /*--------------------------------------------------------------------------
@@ -69,36 +71,33 @@ H5T_init_commit_interface(void)
  * Programmer:	Robb Matzke
  *              Monday, June  1, 1998
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 herr_t
 H5Tcommit(hid_t loc_id, const char *name, hid_t type_id)
 {
-    H5G_entry_t	*loc = NULL;
+    H5G_loc_t	loc;
     H5T_t	*type = NULL;
-    herr_t      ret_value=SUCCEED;       /* Return value */
+    herr_t      ret_value = SUCCEED;       /* Return value */
 
     FUNC_ENTER_API(H5Tcommit, FAIL)
     H5TRACE3("e","isi",loc_id,name,type_id);
 
     /* Check arguments */
-    if (NULL==(loc=H5G_loc (loc_id)))
-	HGOTO_ERROR (H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
-    if (!name || !*name)
-	HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
-    if (NULL==(type=H5I_object_verify(type_id, H5I_DATATYPE)))
-	HGOTO_ERROR (H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
+    if(H5G_loc(loc_id, &loc) < 0)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
+    if(!name || !*name)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
+    if(NULL == (type = H5I_object_verify(type_id, H5I_DATATYPE)))
+	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
 
     /* Commit the type */
-    if (H5T_commit(loc, name, type, H5AC_dxpl_id, H5P_DATATYPE_CREATE_DEFAULT,
-            H5P_DEFAULT)<0)
-	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
+    if(H5T_commit(&loc, name, type, H5AC_dxpl_id, H5P_DATATYPE_CREATE_DEFAULT, H5P_DEFAULT) < 0)
+	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
 done:
     FUNC_LEAVE_API(ret_value)
-}
+} /* end H5Tcommit() */
 
 
 /*-------------------------------------------------------------------------
@@ -113,26 +112,24 @@ done:
  * Programmer:  Peter Cao
  *              May 17, 2005
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 herr_t
 H5Tcommit_expand(hid_t loc_id, const char *name, hid_t type_id, hid_t tcpl_id, hid_t tapl_id)
 {
-    H5G_entry_t	*loc = NULL;
+    H5G_loc_t	loc;
     H5T_t	*type = NULL;
     herr_t      ret_value=SUCCEED;       /* Return value */
 
     FUNC_ENTER_API(H5Tcommit_expand, FAIL)
 
     /* Check arguments */
-    if (NULL==(loc=H5G_loc (loc_id)))
-	HGOTO_ERROR (H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
-    if (!name || !*name)
-	HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
-    if (NULL==(type=H5I_object_verify(type_id, H5I_DATATYPE)))
-	HGOTO_ERROR (H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
+    if(H5G_loc (loc_id, &loc) < 0)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
+    if(!name || !*name)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
+    if(NULL == (type = H5I_object_verify(type_id, H5I_DATATYPE)))
+	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
 
     /* Get correct property list */
     if(H5P_DEFAULT == tcpl_id)
@@ -151,12 +148,12 @@ H5Tcommit_expand(hid_t loc_id, const char *name, hid_t type_id, hid_t tcpl_id, h
 #endif /* LATER */
 
     /* Commit the type */
-    if (H5T_commit(loc, name, type, H5AC_dxpl_id, tcpl_id, tapl_id)<0)
+    if(H5T_commit(&loc, name, type, H5AC_dxpl_id, tcpl_id, tapl_id) < 0)
 	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
 done:
     FUNC_LEAVE_API(ret_value)
-}
+} /* end H5Tcommit_expand() */
 
 
 /*-------------------------------------------------------------------------
@@ -170,29 +167,25 @@ done:
  * Programmer:	Robb Matzke
  *              Monday, June  1, 1998
  *
- * Modifications:
- *              Added datatype creation & access property lists
- *              Peter Cao
- *              May 17, 2005
- *
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5T_commit(H5G_entry_t *loc, const char *name, H5T_t *type, hid_t dxpl_id,
+H5T_commit(H5G_loc_t *loc, const char *name, H5T_t *type, hid_t dxpl_id,
     hid_t tcpl_id, hid_t UNUSED tapl_id)
 {
     H5F_t	*file = NULL;
     H5P_genplist_t  *tc_plist;          /* Property list created */
-    herr_t      ret_value=SUCCEED;      /* Return value */
+    H5G_loc_t   type_loc;               /* Dataset location */
+    herr_t      ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5T_commit)
 
-    HDassert (loc);
-    HDassert (name && *name);
-    HDassert (type);
-    HDassert (tcpl_id != H5P_DEFAULT);
+    HDassert(loc);
+    HDassert(name && *name);
+    HDassert(type);
+    HDassert(tcpl_id != H5P_DEFAULT);
 #ifdef LATER
-    HDassert (tapl_id != H5P_DEFAULT);
+    HDassert(tapl_id != H5P_DEFAULT);
 #endif /* LATER */
 
     /*
@@ -200,51 +193,56 @@ H5T_commit(H5G_entry_t *loc, const char *name, H5T_t *type, hid_t dxpl_id,
      * normally fails on such types (try H5Tclose(H5T_NATIVE_INT)) but closing
      * a named type should always succeed.
      */
-    if (H5T_STATE_NAMED==type->shared->state || H5T_STATE_OPEN==type->shared->state)
-	HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "datatype is already committed")
-    if (H5T_STATE_IMMUTABLE==type->shared->state)
-	HGOTO_ERROR (H5E_ARGS, H5E_BADVALUE, FAIL, "datatype is immutable")
+    if(H5T_STATE_NAMED == type->shared->state || H5T_STATE_OPEN == type->shared->state)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "datatype is already committed")
+    if(H5T_STATE_IMMUTABLE == type->shared->state)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "datatype is immutable")
 
     /* Find the insertion file */
-    if (NULL==(file=H5G_insertion_file(loc, name, dxpl_id)))
+    if(NULL == (file = H5G_insertion_file(loc, name, dxpl_id)))
 	HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "unable to find insertion point")
 
     /* Check for a "sensible" datatype to store on disk */
-    if(H5T_is_sensible(type)<=0)
+    if(H5T_is_sensible(type) <= 0)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "datatype is not sensible")
 
     /* Mark datatype as being on disk now.  This step changes the size of datatype as
      * stored on disk. */
-    if(H5T_set_loc(type, file, H5T_LOC_DISK)<0)
+    if(H5T_set_loc(type, file, H5T_LOC_DISK) < 0)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "cannot mark datatype on disk")
 
+    /* Set up & reset datatype location */
+    type_loc.oloc = &(type->oloc);
+    type_loc.path = &(type->path);
+    H5G_loc_reset(&type_loc);
+
     /*
      * Create the object header and open it for write access. Insert the data
      * type message and then give the object header a name.
      */
-    if (H5O_create (file, dxpl_id, 64, &(type->ent))<0)
-	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to create datatype object header")
-    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(H5O_create(file, dxpl_id, 64, &(type->oloc)) < 0)
+	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to create datatype object header")
+    if(H5O_modify(&(type->oloc), 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")
 
     /* Get the property list */
-    if (NULL == (tc_plist = H5I_object(tcpl_id)))
+    if(NULL == (tc_plist = H5I_object(tcpl_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a property list")
 
     /*
      * Give the datatype a name.  That is, create and add a new object to the
      * group this datatype is being initially created in.
      */
-    if (H5G_insert (loc, name, &(type->ent), dxpl_id, tc_plist)<0)
-	HGOTO_ERROR (H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to name datatype")
+    if(H5G_insert(loc, name, &type_loc, dxpl_id, tc_plist) < 0)
+	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to name datatype")
 
     type->shared->state = H5T_STATE_OPEN;
     type->shared->fo_count=1;
 
     /* Add datatype to the list of open objects in the file */
-    if(H5FO_top_incr(type->ent.file, type->ent.header)<0)
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINC, NULL, "can't incr object ref. count")
-    if(H5FO_insert(type->ent.file, type->ent.header, type->shared)<0)
+    if(H5FO_top_incr(type->oloc.file, type->oloc.addr) < 0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINC, FAIL, "can't incr object ref. count")
+    if(H5FO_insert(type->oloc.file, type->oloc.addr, type->shared) < 0)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINSERT, FAIL, "can't insert datatype into list of open objects")
 
     /* Mark datatype as being on memory now.  Since this datatype may still be used in memory
@@ -253,18 +251,18 @@ H5T_commit(H5G_entry_t *loc, const char *name, H5T_t *type, hid_t dxpl_id,
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "cannot mark datatype in memory")
 
 done:
-    if (ret_value<0) {
-	if ((type->shared->state==H5T_STATE_TRANSIENT || type->shared->state==H5T_STATE_RDONLY) && H5F_addr_defined(type->ent.header)) {
-	    if(H5O_close(&(type->ent))<0)
+    if(ret_value < 0) {
+	if((type->shared->state == H5T_STATE_TRANSIENT || type->shared->state == H5T_STATE_RDONLY) && H5F_addr_defined(type->oloc.addr)) {
+	    if(H5O_close(&(type->oloc)) < 0)
                 HDONE_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to release object header")
-            if(H5O_delete(file, dxpl_id,type->ent.header)<0)
+            if(H5O_delete(file, dxpl_id, type->oloc.addr) < 0)
                 HDONE_ERROR(H5E_DATATYPE, H5E_CANTDELETE, FAIL, "unable to delete object header")
-	    type->ent.header = HADDR_UNDEF;
-	}
-    }
+	    type->oloc.addr = HADDR_UNDEF;
+	} /* end if */
+    } /* end if */
 
     FUNC_LEAVE_NOAPI(ret_value)
-}
+} /* H5T_commit() */
 
 
 /*-------------------------------------------------------------------------
@@ -279,8 +277,6 @@ done:
  * Programmer:	Robb Matzke
  *              Thursday, June  4, 1998
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 htri_t
@@ -293,15 +289,15 @@ H5Tcommitted(hid_t type_id)
     H5TRACE1("t","i",type_id);
 
     /* Check arguments */
-    if (NULL==(type=H5I_object_verify(type_id,H5I_DATATYPE)))
-	HGOTO_ERROR (H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
+    if(NULL == (type = H5I_object_verify(type_id,H5I_DATATYPE)))
+	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a datatype")
 
     /* Set return value */
-    ret_value= H5T_committed(type);
+    ret_value = H5T_committed(type);
 
 done:
     FUNC_LEAVE_API(ret_value)
-}
+} /* end H5Tcommitted() */
 
 
 /*-------------------------------------------------------------------------
@@ -314,8 +310,6 @@ done:
  * Programmer:	Quincey Koziol
  *              Wednesday, September 24, 2003
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 htri_t
@@ -324,9 +318,9 @@ H5T_committed(const H5T_t *type)
     /* Use no-init for efficiency */
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5T_committed)
 
-    assert (type);
+    HDassert(type);
 
-    FUNC_LEAVE_NOAPI(H5T_STATE_OPEN==type->shared->state || H5T_STATE_NAMED==type->shared->state)
+    FUNC_LEAVE_NOAPI(H5T_STATE_OPEN == type->shared->state || H5T_STATE_NAMED == type->shared->state)
 } /* end H5T_committed() */
 
 
@@ -343,8 +337,6 @@ H5T_committed(const H5T_t *type)
  * Programmer:	Quincey Koziol
  *              Friday, September 26, 2003
  *
- * Modifications:
- *
  *-------------------------------------------------------------------------
  */
 int
@@ -355,13 +347,234 @@ H5T_link(const H5T_t *type, int adjust, hid_t dxpl_id)
     /* Use no-init for efficiency */
     FUNC_ENTER_NOAPI(H5T_link,FAIL)
 
-    assert (type);
+    HDassert(type);
 
     /* Adjust the link count on the named datatype */
-    if((ret_value=H5O_link(&(type->ent),adjust,dxpl_id))<0)
-        HGOTO_ERROR (H5E_DATATYPE, H5E_LINK, FAIL, "unable to adjust named datatype link count")
+    if((ret_value = H5O_link(&(type->oloc), adjust, dxpl_id)) < 0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_LINK, FAIL, "unable to adjust named datatype link count")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5T_link() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:	H5Topen
+ *
+ * Purpose:	Opens a named datatype.
+ *
+ * Return:	Success:	Object ID of the named datatype.
+ *
+ *		Failure:	Negative
+ *
+ * Programmer:	Robb Matzke
+ *              Monday, June  1, 1998
+ *
+ *-------------------------------------------------------------------------
+ */
+hid_t
+H5Topen(hid_t loc_id, const char *name)
+{
+    H5T_t       *type = NULL;
+    H5G_loc_t	 loc;
+    H5G_name_t   path;            	/* Datatype group hier. path */
+    H5O_loc_t    oloc;            	/* Datatype object location */
+    H5G_loc_t    type_loc;              /* Group object for datatype */
+    hbool_t      obj_found = FALSE;     /* Object at 'name' found */
+    hid_t        dxpl_id = H5AC_dxpl_id; /* dxpl to use to open datatype */
+    hid_t        ret_value = FAIL;
+
+    FUNC_ENTER_API(H5Topen, FAIL)
+    H5TRACE2("i","is",loc_id,name);
+
+    /* Check args */
+    if(H5G_loc(loc_id, &loc) < 0)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
+    if(!name || !*name)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
+
+    /* Set up datatype location to fill in */
+    type_loc.oloc = &oloc;
+    type_loc.path = &path;
+    H5G_loc_reset(&type_loc);
+
+    /*
+     * Find the named datatype object header and read the datatype message
+     * from it.
+     */
+    if(H5G_loc_find(&loc, name, &type_loc/*out*/, dxpl_id) < 0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_NOTFOUND, FAIL, "not found")
+    obj_found = TRUE;
+
+    /* Check that the object found is the correct type */
+    if(H5O_obj_type(&oloc, dxpl_id) != H5G_TYPE)
+        HGOTO_ERROR(H5E_DATASET, H5E_BADTYPE, FAIL, "not a named datatype")
+
+    /* Open it */
+    if((type = H5T_open(&type_loc, dxpl_id)) == NULL)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, FAIL, "unable to open named datatype")
+
+    /* Register the type and return the ID */
+    if((ret_value = H5I_register(H5I_DATATYPE, type)) < 0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTREGISTER, FAIL, "unable to register named datatype")
+
+done:
+    if(ret_value < 0) {
+        if(type != NULL)
+            H5T_close(type);
+        else {
+            if(obj_found && H5F_addr_defined(type_loc.oloc->addr))
+                H5G_name_free(type_loc.path);
+        } /* end else */
+    } /* end if */
+
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Topen() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5T_open
+ *
+ * Purpose:	Open a named datatype.
+ *
+ * Return:	Success:	Ptr to a new datatype.
+ *
+ *		Failure:	NULL
+ *
+ * Programmer:	Robb Matzke
+ *              Monday, June  1, 1998
+ *
+ *-------------------------------------------------------------------------
+ */
+H5T_t *
+H5T_open(H5G_loc_t *loc, hid_t dxpl_id)
+{
+    H5T_shared_t   *shared_fo = NULL;
+    H5T_t          *dt = NULL;
+    H5T_t          *ret_value;
+
+    FUNC_ENTER_NOAPI(H5T_open, NULL)
+
+    HDassert(loc);
+
+    /* Check if datatype was already open */
+    if((shared_fo = H5FO_opened(loc->oloc->file, loc->oloc->addr)) == NULL) {
+        /* Clear any errors from H5FO_opened() */
+        H5E_clear_stack(NULL);
+
+        /* Open the datatype object */
+        if((dt = H5T_open_oid(loc, dxpl_id)) == NULL)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_NOTFOUND, NULL, "not found")
+
+        /* Add the datatype to the list of opened objects in the file */
+        if(H5FO_insert(dt->oloc.file, dt->oloc.addr, dt->shared) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINSERT, NULL, "can't insert datatype into list of open objects")
+
+        /* Increment object count for the object in the top file */
+        if(H5FO_top_incr(dt->oloc.file, dt->oloc.addr) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINC, NULL, "can't increment object count")
+
+        /* Mark any datatypes as being in memory now */
+        if(H5T_set_loc(dt, NULL, H5T_LOC_MEMORY) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "invalid datatype location")
+
+        dt->shared->fo_count = 1;
+    } /* end if */
+    else {
+        if(NULL == (dt = H5FL_MALLOC(H5T_t)))
+            HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "can't allocate space for datatype")
+
+        /* Shallow copy (take ownership) of the object location object */
+        if(H5O_loc_copy(&(dt->oloc), loc->oloc, H5O_COPY_SHALLOW) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "can't copy object location")
+
+        /* Shallow copy (take ownership) of the group hier. path */
+        if(H5G_name_copy(&(dt->path), loc->path, H5G_COPY_SHALLOW) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "can't copy path")
+
+        dt->shared = shared_fo;
+
+        shared_fo->fo_count++;
+
+        /* Check if the object has been opened through the top file yet */
+        if(H5FO_top_count(dt->oloc.file, dt->oloc.addr) == 0) {
+            /* Open the object through this top file */
+            if(H5O_open(&(dt->oloc)) < 0)
+                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, NULL, "unable to open object header")
+        } /* end if */
+
+        /* Increment object count for the object in the top file */
+        if(H5FO_top_incr(dt->oloc.file, dt->oloc.addr) < 0)
+            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINC, NULL, "can't increment object count")
+    } /* end else */
+
+    ret_value = dt;
+
+done:
+    if(ret_value == NULL) {
+        if(dt) {
+            if(shared_fo == NULL)   /* Need to free shared fo */
+                H5FL_FREE(H5T_shared_t, dt->shared);
+            H5FL_FREE(H5T_t, dt);
+        } /* end if */
+
+        if(shared_fo)
+            shared_fo->fo_count--;
+    } /* end if */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5T_open() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5T_open_oid
+ *
+ * Purpose:	Open a named datatype.
+ *
+ * Return:	Success:	Ptr to a new datatype.
+ *
+ *		Failure:	NULL
+ *
+ * Programmer:	Quincey Koziol
+ *              Wednesday, March 17, 1999
+ *
+ *-------------------------------------------------------------------------
+ */
+static H5T_t *
+H5T_open_oid(H5G_loc_t *loc, hid_t dxpl_id)
+{
+    H5T_t	*dt = NULL;
+    H5T_t	*ret_value;
+
+    FUNC_ENTER_NOAPI(H5T_open_oid, NULL)
+
+    HDassert(loc);
+
+    if(H5O_open(loc->oloc) < 0)
+	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, NULL, "unable to open named datatype")
+    if(NULL == (dt = H5O_read(loc->oloc, H5O_DTYPE_ID, 0, NULL, dxpl_id)))
+	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, NULL, "unable to load type message from object header")
+
+    /* Mark the type as named and open */
+    dt->shared->state = H5T_STATE_OPEN;
+
+    /* Shallow copy (take ownership) of the object location object */
+    if(H5O_loc_copy(&(dt->oloc), loc->oloc, H5O_COPY_SHALLOW) < 0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "can't copy object location")
+
+    /* Shallow copy (take ownership) of the group hier. path */
+    if(H5G_name_copy(&(dt->path), loc->path, H5G_COPY_SHALLOW) < 0)
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCOPY, NULL, "can't copy path")
+
+    /* Set return value */
+    ret_value = dt;
+
+done:
+    if(ret_value == NULL) {
+        if(dt == NULL)
+            H5O_close(loc->oloc);
+    } /* end if */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5T_open_oid() */
+