path: root/src/H5Tcommit.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the files COPYING and Copyright.html.  COPYING can be found at the root   *
 * of the source code distribution tree; Copyright.html can be found at the  *
 * root level of an installed copy of the electronic HDF5 document set and   *
 * is linked from the top-level documents page.  It can also be found at     *
 * http://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html.  If you do not have     *
 * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * Module Info: This module contains the functionality for committing datatypes
 *      to a file for the H5T interface.
 */

#define H5T_PACKAGE		/*suppress error about including H5Tpkg	  */

/* Interface initialization */
#define H5_INTERFACE_INIT_FUNC	H5T_init_commit_interface


#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 "H5Lprivate.h"		/* Links				*/
#include "H5Oprivate.h"		/* Object headers			*/
#include "H5Pprivate.h"         /* Property lists                       */
#include "H5Tpkg.h"		/* Datatypes				*/

/* Static local functions */
static herr_t H5T_commit(H5F_t *file, 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);


/*--------------------------------------------------------------------------
NAME
   H5T_init_commit_interface -- Initialize interface-specific information
USAGE
    herr_t H5T_init_commit_interface()

RETURNS
    Non-negative on success/Negative on failure
DESCRIPTION
    Initializes any interface-specific data or routines.  (Just calls
    H5T_init_iterface currently).

--------------------------------------------------------------------------*/
static herr_t
H5T_init_commit_interface(void)
{
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5T_init_commit_interface)

    FUNC_LEAVE_NOAPI(H5T_init())
} /* H5T_init_commit_interface() */


/*-------------------------------------------------------------------------
 * Function:	H5Tcommit
 *
 * Purpose:	Save a transient datatype to a file and turn the type handle
 *		into a named, immutable type.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Robb Matzke
 *              Monday, June  1, 1998
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Tcommit(hid_t loc_id, const char *name, hid_t type_id)
{
    H5G_loc_t	loc;
    H5G_loc_t	type_loc;
    H5F_t       *file;
    H5T_t	*type = NULL;
    hbool_t     uncommit = FALSE;          /* TRUE if H5T_commit needs to be undone */
    H5T_state_t old_state;                 /* The state of the datatype before H5T_commit. */
    herr_t      ret_value = SUCCEED;       /* Return value */

    FUNC_ENTER_API(H5Tcommit, FAIL)
    H5TRACE3("e","isi",loc_id,name,type_id);

    /* Check arguments */
    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")

    /* Find the insertion file */
    if(NULL == (file = H5G_insertion_file(&loc, name, H5AC_dxpl_id)))
	HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "unable to find insertion point")

    /* Record the type's state so that we can revert to it if linking fails */
    old_state = type->shared->state;

    /* Write the type to disk */
    if(H5T_commit(file, type, H5AC_dxpl_id, H5P_DATATYPE_CREATE_DEFAULT, H5P_DEFAULT) < 0)
	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")

    if(H5G_loc(type_id, &type_loc) < 0)
	HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to get committed datatype's location")

    /* Link the type into the group hierarchy */
    if( H5L_link(&loc, name, &type_loc, H5AC_dxpl_id, H5P_DEFAULT) < 0)
    {
        uncommit = TRUE;    /* Linking failed, and we need to undo H5T_commit. */
	HGOTO_ERROR(H5E_ATOM, H5E_CANTREGISTER, FAIL, "unable to create link to type")
    }

done:
    /* If the datatype was committed but couldn't be linked, we need to return it to the state it was in
     * before it was committed. */
    if(TRUE == uncommit)
    {
	if(type->shared->state == H5T_STATE_OPEN && H5F_addr_defined(type->oloc.addr)) {
            /* Remove the datatype from the list of opened objects in the file */
            if(H5FO_top_decr(type->oloc.file, type->oloc.addr) < 0)
                HDONE_ERROR(H5E_DATASET, H5E_CANTRELEASE, FAIL, "can't decrement count for object")
            if(H5FO_delete(type->oloc.file, H5AC_dxpl_id, type->oloc.addr) < 0)
                HDONE_ERROR(H5E_DATASET, H5E_CANTRELEASE, FAIL, "can't remove dataset from list of open objects")
	    if(H5O_close(&(type->oloc)) < 0)
                HDONE_ERROR(H5E_DATATYPE, H5E_CLOSEERROR, FAIL, "unable to release object header")
            if(H5O_delete(file, H5AC_dxpl_id, type->oloc.addr) < 0)
                HDONE_ERROR(H5E_DATATYPE, H5E_CANTDELETE, FAIL, "unable to delete object header")
            /* Mark datatype as being back in memory */
            if(H5T_set_loc(type, file, H5T_LOC_MEMORY))
                HDONE_ERROR(H5E_DATATYPE, H5E_CANTDELETE, FAIL, "unable to return datatype to memory")
	    type->oloc.addr = HADDR_UNDEF;
            type->shared->state = old_state;
	} /* end if */    }
    FUNC_LEAVE_API(ret_value)
} /* end H5Tcommit() */

#ifdef H5_GROUP_REVISION

/*-------------------------------------------------------------------------
 * Function:	H5Tcommit_expand
 *
 * Purpose:	Save a transient datatype to a file and turn the type handle
 *		into a "named", immutable type.
 *
 *              The resulting ID should be linked into the file with
 *              H5Llink or it will be deleted when closed.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:  Peter Cao
 *              May 17, 2005
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Tcommit_expand(hid_t loc_id, hid_t type_id, hid_t tcpl_id, hid_t tapl_id)
{
    H5G_loc_t	loc;
    H5T_t	*type = NULL;
    herr_t      ret_value=SUCCEED;       /* Return value */

    FUNC_ENTER_API(H5Tcommit_expand, FAIL)
    H5TRACE4("e","iiii",loc_id,type_id,tcpl_id,tapl_id);

    /* Check arguments */
    if(H5G_loc (loc_id, &loc) < 0)
	HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
    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)
        tcpl_id = H5P_DATATYPE_CREATE_DEFAULT;
    else
        if(TRUE != H5P_isa_class(tcpl_id, H5P_DATATYPE_CREATE))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not datatype create property list")

#ifdef LATER
    /* Get correct property list */
    if(H5P_DEFAULT == tapl_id)
        tapl_id = H5P_DATATYPE_ACCESS_DEFAULT;
    else
        if(TRUE != H5P_isa_class(tapl_id, H5P_DATATYPE_ACCESS))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not datatype access property list")
#endif /* LATER */

    /* Commit the type */
    if(H5T_commit(loc.oloc->file, 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() */
#endif /* H5_GROUP_REVISION */


/*-------------------------------------------------------------------------
 * Function:	H5T_commit
 *
 * Purpose:	Commit a type, giving it a name and causing it to become
 *		immutable.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Robb Matzke
 *              Monday, June  1, 1998
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5T_commit(H5F_t *file, 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 */
    H5G_loc_t   type_loc;               /* Dataset location */
    herr_t      ret_value = SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI_NOINIT(H5T_commit)

    HDassert(file);
    HDassert(type);
    HDassert(tcpl_id != H5P_DEFAULT);
#ifdef LATER
    HDassert(tapl_id != H5P_DEFAULT);
#endif /* LATER */

    /*
     * Check arguments.  We cannot commit an immutable type because H5Tclose()
     * 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")

    /* Check for a "sensible" datatype to store on disk */
    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)
        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->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)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a property list")

    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->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, TRUE) < 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
     * after committed to disk, change its size back as in memory. */
    if(H5T_set_loc(type, NULL, H5T_LOC_MEMORY)<0)
        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->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->oloc.addr) < 0)
                HDONE_ERROR(H5E_DATATYPE, H5E_CANTDELETE, FAIL, "unable to delete object header")
	    type->oloc.addr = HADDR_UNDEF;
	} /* end if */
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
} /* H5T_commit() */


/*-------------------------------------------------------------------------
 * Function:	H5Tcommitted
 *
 * Purpose:	Determines if a datatype is committed or not.
 *
 * Return:	Success:	TRUE if committed, FALSE otherwise.
 *
 *		Failure:	Negative
 *
 * Programmer:	Robb Matzke
 *              Thursday, June  4, 1998
 *
 *-------------------------------------------------------------------------
 */
htri_t
H5Tcommitted(hid_t type_id)
{
    H5T_t	*type = NULL;
    htri_t      ret_value;       /* Return value */

    FUNC_ENTER_API(H5Tcommitted, FAIL)
    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")

    /* Set return value */
    ret_value = H5T_committed(type);

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Tcommitted() */


/*-------------------------------------------------------------------------
 * Function:	H5T_committed
 *
 * Purpose:	Determines if a datatype is committed or not.
 *
 * Return:	Success:	TRUE if committed, FALSE otherwise.
 *
 * Programmer:	Quincey Koziol
 *              Wednesday, September 24, 2003
 *
 *-------------------------------------------------------------------------
 */
htri_t
H5T_committed(const H5T_t *type)
{
    /* Use no-init for efficiency */
    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5T_committed)

    HDassert(type);

    FUNC_LEAVE_NOAPI(H5T_STATE_OPEN == type->shared->state || H5T_STATE_NAMED == type->shared->state)
} /* end H5T_committed() */


/*-------------------------------------------------------------------------
 * Function:	H5T_link
 *
 * Purpose:	Adjust the link count for an object header by adding
 *		ADJUST to the link count.
 *
 * Return:	Success:	New link count
 *
 *		Failure:	Negative
 *
 * Programmer:	Quincey Koziol
 *              Friday, September 26, 2003
 *
 *-------------------------------------------------------------------------
 */
int
H5T_link(const H5T_t *type, int adjust, hid_t dxpl_id)
{
    int ret_value;      /* Return value */

    /* Use no-init for efficiency */
    FUNC_ENTER_NOAPI(H5T_link,FAIL)

    HDassert(type);

    /* Adjust the link count on the named datatype */
    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, FALSE) < 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")

#if defined(H5_USING_PURIFY) || !defined(NDEBUG)
        /* Clear object location */
        if(H5O_loc_reset(&(dt->oloc)) < 0)
            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, NULL, "unable to reset location")

        /* Clear path name */
        if(H5G_name_reset(&(dt->path)) < 0)
            HGOTO_ERROR(H5E_DATATYPE, H5E_CANTOPENOBJ, NULL, "unable to reset path")
#endif /* H5_USING_PURIFY */

        /* Shallow copy (take ownership) of the object location object */
        if(H5O_loc_copy(&(dt->oloc), loc->oloc, H5_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, H5_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, H5_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, H5_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() */