path: root/src/H5Gtraverse.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * 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://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
 * access to either file, you may request a copy from help@hdfgroup.org.     *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*-------------------------------------------------------------------------
 *
 * Created:		H5Gtraverse.c
 *			Sep 13 2005
 *			Quincey Koziol <koziol@ncsa.uiuc.edu>
 *
 * Purpose:		Functions for traversing group hierarchy
 *
 *-------------------------------------------------------------------------
 */

/****************/
/* Module Setup */
/****************/

#define H5G_PACKAGE		/*suppress error about including H5Gpkg	  */


/***********/
/* Headers */
/***********/
#include "H5private.h"		/* Generic Functions			*/
#include "H5Dprivate.h"         /* Datasets                             */
#include "H5Eprivate.h"		/* Error handling		  	*/
#include "H5Fprivate.h"		/* File access				*/
#include "H5Gpkg.h"		/* Groups		  		*/
#include "H5HLprivate.h"	/* Local Heaps				*/
#include "H5Iprivate.h"		/* IDs					*/
#include "H5Lprivate.h"		/* Links				*/
#include "H5MMprivate.h"	/* Memory management			*/
#include "H5Ppublic.h"		/* Property Lists			*/
#include "H5WBprivate.h"        /* Wrapped Buffers                      */
#include "H5VLnative.h" 	/* Native Plugin                        */
#include "H5VLprivate.h"	/* VOL          		  	*/

/****************/
/* Local Macros */
/****************/


/******************/
/* Local Typedefs */
/******************/

/* User data for path traversal routine */
typedef struct {
    /* down */
    hbool_t chk_exists;         /* Flag to indicate we are checking if object exists */

    /* up */
    H5G_loc_t *obj_loc;         /* Object location */
    hbool_t exists;             /* Indicate if object exists */
} H5G_trav_slink_t;


/********************/
/* Package Typedefs */
/********************/


/********************/
/* Local Prototypes */
/********************/
static herr_t H5G_traverse_slink_cb(H5G_loc_t *grp_loc, const char *name,
    const H5O_link_t *lnk, H5G_loc_t *obj_loc, void *_udata/*in,out*/,
    H5G_own_loc_t *own_loc/*out*/);
static herr_t H5G_traverse_ud(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
    H5G_loc_t *obj_loc/*in,out*/, unsigned target, size_t *nlinks/*in,out*/,
    hbool_t *obj_exists, hid_t lapl_id, hid_t dxpl_id);
static herr_t H5G_traverse_slink(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
    H5G_loc_t *obj_loc/*in,out*/, unsigned target, size_t *nlinks/*in,out*/,
    hbool_t *obj_exists, hid_t lapl_id, hid_t dxpl_id);
static herr_t H5G_traverse_real(const H5G_loc_t *loc, const char *name,
    unsigned target, size_t *nlinks, H5G_traverse_t op, void *op_data,
    hid_t lapl_id, hid_t dxpl_id);


/*********************/
/* Package Variables */
/*********************/


/*****************************/
/* Library Private Variables */
/*****************************/


/*******************/
/* Local Variables */
/*******************/



/*-------------------------------------------------------------------------
 * Function:	H5G_traverse_slink_cb
 *
 * Purpose:	Callback for soft link traversal.  This routine sets the
 *              correct information for the object location.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *              Tuesday, September 13, 2005
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5G_traverse_slink_cb(H5G_loc_t UNUSED *grp_loc, const char UNUSED *name,
    const H5O_link_t UNUSED *lnk, H5G_loc_t *obj_loc, void *_udata/*in,out*/,
    H5G_own_loc_t *own_loc/*out*/)
{
    H5G_trav_slink_t *udata = (H5G_trav_slink_t *)_udata;   /* User data passed in */
    herr_t ret_value = SUCCEED;         /* Return value */

    FUNC_ENTER_NOAPI_NOINIT

    /* Check for dangling soft link */
    if(obj_loc == NULL) {
        if(udata->chk_exists)
            udata->exists = FALSE;
        else
            HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "component not found")
    } /* end if */
    else {
        /* Copy new location information for resolved object */
        H5O_loc_copy(udata->obj_loc->oloc, obj_loc->oloc, H5_COPY_DEEP);

        /* Indicate that the object exists */
        udata->exists = TRUE;
    } /* end else */

done:
    /* Indicate that this callback didn't take ownership of the group *
     * location for the object */
    *own_loc = H5G_OWN_NONE;

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5G_traverse_slink_cb() */


/*-------------------------------------------------------------------------
 * Function:	H5G_traverse_link_ud
 *
 * Purpose:	Callback for user-defined link traversal.  Sets up a
 *              location ID and passes it to the user traversal callback.
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *              Tuesday, September 13, 2005
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5G_traverse_ud(const H5G_loc_t *grp_loc/*in,out*/, const H5O_link_t *lnk,
    H5G_loc_t *obj_loc/*in,out*/, unsigned target, size_t *nlinks/*in,out*/,
    hbool_t *obj_exists, hid_t _lapl_id, hid_t dxpl_id)
{
    const H5L_class_t   *link_class;       /* User-defined link class */
    hid_t               cb_return = -1;         /* The ID the user-defined callback returned */
    H5G_loc_t           grp_loc_copy;
    H5G_name_t          grp_path_copy;
    H5O_loc_t           grp_oloc_copy;
    H5G_loc_t           new_loc;                /* Group location for newly opened external object */
    H5G_t              *grp;
    hid_t               lapl_id = (-1);         /* LAPL local to this routine */
    H5P_genplist_t     *lapl;                   /* LAPL with nlinks set */
    hid_t               cur_grp = (-1);
    herr_t              ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_NOAPI_NOINIT

    /* Sanity check */
    HDassert(grp_loc);
    HDassert(lnk);
    HDassert(lnk->type >= H5L_TYPE_UD_MIN);
    HDassert(obj_loc);
    HDassert(nlinks);
    HDassert(_lapl_id >= 0);

    /* Get the link class for this type of link. */
    if(NULL == (link_class = H5L_find_class(lnk->type)))
        HGOTO_ERROR(H5E_SYM, H5E_NOTREGISTERED, FAIL, "unable to get UD link class")

    /* Set up location for user-defined callback.  Use a copy of our current
     * grp_loc. */
    grp_loc_copy.path = &grp_path_copy;
    grp_loc_copy.oloc = &grp_oloc_copy;
    H5G_loc_reset(&grp_loc_copy);
    if(H5G__loc_copy(&grp_loc_copy, grp_loc, H5_COPY_DEEP) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTCOPY, FAIL, "unable to copy object location")

    /* Create a group ID to pass to the user-defined callback */
    if(NULL == (grp = H5G_open(&grp_loc_copy, dxpl_id)))
        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to open group")
    if((cur_grp = H5I_register(H5I_GROUP, grp, FALSE)) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTREGISTER, FAIL, "unable to register group")
    if(H5VL_native_register_aux(cur_grp) < 0)
        HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "can't attach native vol info to ID")

    /* Check for generic default property list and use link access default if so */
    if(_lapl_id == H5P_DEFAULT) {
        HDassert(H5P_LINK_ACCESS_DEFAULT != -1);
        if(NULL == (lapl = (H5P_genplist_t *)H5I_object(H5P_LINK_ACCESS_DEFAULT)))
            HGOTO_ERROR(H5E_SYM, H5E_BADATOM, FAIL, "unable to get default property list")
    } /* end if */
    else {
        /* Get the underlying property list passed in */
        if(NULL == (lapl = (H5P_genplist_t *)H5I_object(_lapl_id)))
            HGOTO_ERROR(H5E_SYM, H5E_BADATOM, FAIL, "unable to get property list from ID")
    } /* end else */

    /* Copy the property list passed in */
    if((lapl_id = H5P_copy_plist(lapl, FALSE)) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTCOPY, FAIL, "unable to copy property list")

    /* Get the underlying property list copy */
    if(NULL == (lapl = (H5P_genplist_t *)H5I_object(lapl_id)))
        HGOTO_ERROR(H5E_SYM, H5E_BADATOM, FAIL, "unable to get property list from ID")

    /* Record number of soft links left to traverse in the property list. */
    if(H5P_set(lapl, H5L_ACS_NLINKS_NAME, nlinks) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTSET, FAIL, "can't set nlink info")

    /* User-defined callback function */
    cb_return = (link_class->trav_func)(lnk->name, cur_grp, lnk->u.ud.udata, lnk->u.ud.size, lapl_id);

    /* Check for failing to locate the object */
    if(cb_return < 0) {
        /* Check if we just needed to know if the object exists */
        if(target & H5G_TARGET_EXISTS) {
            /* Clear any errors from the stack */
            H5E_clear_stack(NULL);

            /* Indicate that the object doesn't exist */
            *obj_exists = FALSE;

            /* Get out now */
            HGOTO_DONE(SUCCEED);
        } /* end if */
        /* else, we really needed to open the object */
        else
            HGOTO_ERROR(H5E_SYM, H5E_BADATOM, FAIL, "traversal callback returned invalid ID")
    } /* end if */

    /* Get the object location information from the ID the user callback returned */
    if(H5G_loc(cb_return, &new_loc) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_BADVALUE, FAIL, "unable to get object location from ID")

    /* Release any previous location information for the object */
    H5G_loc_free(obj_loc);

    /* Copy new object's location information */
    H5G__loc_copy(obj_loc, &new_loc, H5_COPY_DEEP);

    /* Hold the file open until we free this object header (otherwise the
     * object location will be invalidated when the file closes).
     */
    if(H5O_loc_hold_file(obj_loc->oloc) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to hold file open")

    /* We have a copy of the location and we're holding the file open.
     * Close the open ID the user passed back.
     */
    if(H5I_dec_ref(cb_return) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to close atom from UD callback")
    cb_return = (-1);

done:
    /* Close location given to callback. */
    if(cur_grp > 0 && H5I_dec_ref(cur_grp) < 0)
        HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to close atom for current location")

    if(ret_value < 0 && cb_return > 0 && H5I_dec_ref(cb_return) < 0)
        HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to close atom from UD callback")

    /* Close the LAPL, if we copied one */
    if(lapl_id > 0 && H5I_dec_ref(lapl_id) < 0)
        HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to close copied link access property list")

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5G_traverse_ud() */


/*-------------------------------------------------------------------------
 * Function:	H5G_traverse_slink
 *
 * Purpose:	Traverses symbolic link.  The link head appears in the group
 *		whose entry is GRP_LOC and the link tail entry is OBJ_LOC.
 *
 * Return:	Success:	Non-negative, OBJ_LOC will contain information
 *				about the object to which the link points
 *
 *		Failure:	Negative
 *
 * Programmer:	Robb Matzke
 *              Friday, April 10, 1998
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5G_traverse_slink(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
    H5G_loc_t *obj_loc/*in,out*/, unsigned target, size_t *nlinks/*in,out*/,
    hbool_t *obj_exists, hid_t lapl_id, hid_t dxpl_id)
{
    H5G_trav_slink_t      udata;                  /* User data to pass to link traversal callback */
    H5G_name_t          tmp_obj_path;           /* Temporary copy of object's path */
    hbool_t             tmp_obj_path_set = FALSE;       /* Flag to indicate that tmp object path is initialized */
    H5O_loc_t           tmp_grp_oloc;           /* Temporary copy of group entry */
    H5G_name_t          tmp_grp_path;           /* Temporary copy of group's path */
    H5G_loc_t           tmp_grp_loc;            /* Temporary copy of group's location */
    hbool_t             tmp_grp_loc_set = FALSE;       /* Flag to indicate that tmp group location is initialized */
    herr_t              ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_NOAPI_NOINIT

    /* Sanity check */
    HDassert(grp_loc);
    HDassert(lnk);
    HDassert(lnk->type == H5L_TYPE_SOFT);
    HDassert(nlinks);

    /* Set up temporary location */
    tmp_grp_loc.oloc = &tmp_grp_oloc;
    tmp_grp_loc.path = &tmp_grp_path;

    /* Portably initialize the temporary objects */
    H5G_loc_reset(&tmp_grp_loc);
    H5G_name_reset(&tmp_obj_path);

    /* Clone the group location, so we can track the names properly */
    /* ("tracking the names properly" means to ignore the effects of the
     *  link traversal on the object's & group's paths - QAK)
     */
    H5G__loc_copy(&tmp_grp_loc, grp_loc, H5_COPY_DEEP);
    tmp_grp_loc_set = TRUE;

    /* Hold the object's group hier. path to restore later */
    /* (Part of "tracking the names properly") */
    H5G_name_copy(&tmp_obj_path, obj_loc->path, H5_COPY_SHALLOW);
    tmp_obj_path_set = TRUE;

    /* Set up user data for traversal callback */
    udata.chk_exists = (target & H5G_TARGET_EXISTS) ? TRUE : FALSE;
    udata.exists = FALSE;
    udata.obj_loc = obj_loc;

    /* Traverse the link */
    if(H5G_traverse_real(&tmp_grp_loc, lnk->u.soft.name, target, nlinks, H5G_traverse_slink_cb, &udata, lapl_id, dxpl_id) < 0)
	HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "unable to follow symbolic link")

    /* Pass back information about whether the object exists */
    *obj_exists = udata.exists;

done:
    /* Restore object's group hier. path */
    if(tmp_obj_path_set) {
        H5G_name_free(obj_loc->path);
        H5G_name_copy(obj_loc->path, &tmp_obj_path, H5_COPY_SHALLOW);
    } /* end if */

    /* Release cloned copy of group location */
    if(tmp_grp_loc_set)
        H5G_loc_free(&tmp_grp_loc);

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5G_traverse_slink() */


/*-------------------------------------------------------------------------
 * Function:	H5G__traverse_special
 *
 * Purpose:	Handle traversing special link situations
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *		koziol@hdfgroup.org
 *		Nov 20 2006
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5G__traverse_special(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
    unsigned target, size_t *nlinks, hbool_t last_comp,
    H5G_loc_t *obj_loc, hbool_t *obj_exists, hid_t lapl_id, hid_t dxpl_id)
{
    herr_t ret_value = SUCCEED;         /* Return value */

    FUNC_ENTER_PACKAGE

    /* Sanity check */
    HDassert(grp_loc);
    HDassert(lnk);
    HDassert(obj_loc);
    HDassert(nlinks);

    /*
     * If we found a symbolic link then we should follow it.  But if this
     * is the last component of the name and the H5G_TARGET_SLINK bit of
     * TARGET is set then we don't follow it.
     */
    if(H5L_TYPE_SOFT == lnk->type &&
            (0 == (target & H5G_TARGET_SLINK) || !last_comp)) {
        if((*nlinks)-- <= 0)
            HGOTO_ERROR(H5E_LINK, H5E_NLINKS, FAIL, "too many links")
        if(H5G_traverse_slink(grp_loc, lnk, obj_loc, (target & H5G_TARGET_EXISTS), nlinks, obj_exists, lapl_id, dxpl_id) < 0)
            HGOTO_ERROR(H5E_LINK, H5E_TRAVERSE, FAIL, "symbolic link traversal failed")
    } /* end if */

    /*
     * If we found a user-defined link then we should follow it.  But if this
     * is the last component of the name and the H5G_TARGET_UDLINK bit of
     * TARGET is set then we don't follow it.
     */
    if(lnk->type >= H5L_TYPE_UD_MIN &&
            (0 == (target & H5G_TARGET_UDLINK) || !last_comp) ) {
        if((*nlinks)-- <= 0)
            HGOTO_ERROR(H5E_LINK, H5E_NLINKS, FAIL, "too many links")
        if(H5G_traverse_ud(grp_loc, lnk, obj_loc, (target & H5G_TARGET_EXISTS), nlinks, obj_exists, lapl_id, dxpl_id) < 0)
            HGOTO_ERROR(H5E_LINK, H5E_TRAVERSE, FAIL, "user-defined link traversal failed")
    } /* end if */

    /*
     * Resolve mount points to the mounted group.  Do not do this step if
     * the H5G_TARGET_MOUNT bit of TARGET is set and this is the last
     * component of the name.
     *
     * (If this link is a hard link, try to perform mount point traversal)
     *
     * (Note that the soft and external link traversal above can change
     *  the status of the object (into a hard link), so don't use an 'else'
     *  statement here. -QAK)
     */
    if(H5F_addr_defined(obj_loc->oloc->addr) &&
            (0 == (target & H5G_TARGET_MOUNT) || !last_comp)) {
        if(H5F_traverse_mount(obj_loc->oloc/*in,out*/) < 0)
            HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "mount point traversal failed")
    } /* end if */

    /* If the grp_loc is the only thing holding an external file open
     * and obj_loc is in the same file, obj_loc should also hold the
     * file open so that closing the grp_loc doesn't close the file.
     */
    if(grp_loc->oloc->holding_file && grp_loc->oloc->file == obj_loc->oloc->file)
        if(H5O_loc_hold_file(obj_loc->oloc) < 0)
            HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to hold file open")

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5G__traverse_special() */


/*-------------------------------------------------------------------------
 * Function:	H5G_traverse_real
 *
 * Purpose:	Internal version of path traversal routine
 *
 * Return:	Success:	Non-negative if name can be fully resolved.
 *
 *		Failure:	Negative if the name could not be fully
 *				resolved.
 *
 * Programmer:	Robb Matzke
 *		matzke@llnl.gov
 *		Aug 11 1997
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5G_traverse_real(const H5G_loc_t *_loc, const char *name, unsigned target,
    size_t *nlinks, H5G_traverse_t op, void *op_data, hid_t lapl_id, hid_t dxpl_id)
{
    H5G_loc_t           loc;            /* Location of start object     */
    H5O_loc_t           grp_oloc;	/* Object loc. for current group */
    H5G_name_t		grp_path;	/* Path for current group	*/
    H5G_loc_t           grp_loc;        /* Location of group            */
    H5O_loc_t		obj_oloc;	/* Object found			*/
    H5G_name_t		obj_path;	/* Path for object found	*/
    H5G_loc_t           obj_loc;        /* Location of object           */
    size_t		nchars;		/* component name length	*/
    H5O_link_t          lnk;            /* Link information for object  */
    hbool_t link_valid = FALSE;         /* Flag to indicate that the link information is valid */
    hbool_t obj_loc_valid = FALSE;      /* Flag to indicate that the object location is valid */
    H5G_own_loc_t own_loc = H5G_OWN_NONE; /* Enum to indicate whether callback took ownership of locations*/
    hbool_t group_copy = FALSE;         /* Flag to indicate that the group entry is copied */
    char                comp_buf[1024];     /* Temporary buffer for path components */
    char                *comp;          /* Pointer to buffer for path components */
    H5WB_t              *wb = NULL;     /* Wrapped buffer for temporary buffer */
    hbool_t last_comp = FALSE;          /* Flag to indicate that a component is the last component in the name */
    herr_t              ret_value = SUCCEED;       /* Return value */

    FUNC_ENTER_NOAPI_NOINIT

    /* Check parameters */
    HDassert(_loc);
    HDassert(name);
    HDassert(nlinks);
    HDassert(op);

    /*
     * Where does the searching start?  For absolute names it starts at the
     * root of the file; for relative names it starts at CWG.
     */
    /* Check if we need to get the root group's entry */
    if('/' == *name) {
        H5G_t *root_grp;         /* Temporary pointer to root group of file */

        /* Look up root group for starting location */
        root_grp = H5G_rootof(_loc->oloc->file);
        HDassert(root_grp);

        /* Set the location entry to the root group's info */
        loc.oloc = &(root_grp->oloc);
        loc.path = &(root_grp->path);
    } /* end if */
    else {
        loc.oloc = _loc->oloc;
        loc.path = _loc->path;
    } /* end else */

    /* Set up group & object locations */
    grp_loc.oloc = &grp_oloc;
    grp_loc.path = &grp_path;
    obj_loc.oloc = &obj_oloc;
    obj_loc.path = &obj_path;

#if defined(H5_USING_MEMCHECKER) || !defined(NDEBUG)
    /* Clear group location */
    if(H5G_loc_reset(&grp_loc) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to reset location")
#endif /* H5_USING_MEMCHECKER */

    /* Deep copy of the starting location to group location */
    if(H5G__loc_copy(&grp_loc, &loc, H5_COPY_DEEP) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to copy location")
    group_copy = TRUE;

    /* Clear object location */
    if(H5G_loc_reset(&obj_loc) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to reset location")

    /* Wrap the local buffer for serialized header info */
    if(NULL == (wb = H5WB_wrap(comp_buf, sizeof(comp_buf))))
        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "can't wrap buffer")

    /* Get a pointer to a buffer that's large enough  */
    if(NULL == (comp = (char *)H5WB_actual(wb, (HDstrlen(name) + 1))))
        HGOTO_ERROR(H5E_SYM, H5E_NOSPACE, FAIL, "can't get actual buffer")

    /* Traverse the path */
    while((name = H5G__component(name, &nchars)) && *name) {
        const char *s;                  /* Temporary string pointer */
        htri_t lookup_status;           /* Status from object lookup */
        hbool_t obj_exists;             /* Whether the object exists */

	/*
	 * Copy the component name into a null-terminated buffer so
	 * we can pass it down to the other symbol table functions.
	 */
	HDmemcpy(comp, name, nchars);
	comp[nchars] = '\0';

	/*
	 * The special name `.' is a no-op.
	 */
	if('.' == comp[0] && !comp[1]) {
	    name += nchars;
	    continue;
	} /* end if */

        /* Check if this is the last component of the name */
        if(!((s = H5G__component(name + nchars, NULL)) && *s))
            last_comp = TRUE;

        /* If there's valid information in the link, reset it */
        if(link_valid) {
            H5O_msg_reset(H5O_LINK_ID, &lnk);
            link_valid = FALSE;
        } /* end if */

        /* Get information for object in current group */
        if((lookup_status = H5G__obj_lookup(grp_loc.oloc, comp, &lnk/*out*/, dxpl_id)) < 0)
            HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "can't look up component")
        obj_exists = FALSE;

        /* If the lookup was OK, build object location and traverse special links, etc. */
        if(lookup_status) {
            /* Sanity check link and indicate it's valid */
            HDassert(lnk.type >= H5L_TYPE_HARD);
            HDassert(!HDstrcmp(comp, lnk.name));
            link_valid = TRUE;

            /* Build object location from the link */
            if(H5G__link_to_loc(&grp_loc, &lnk, &obj_loc) < 0)
                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "cannot initialize object location")
            obj_loc_valid = TRUE;

            /* Assume object exists */
            obj_exists = TRUE;

            /* Perform any special traversals that the link needs */
            /* (soft links, user-defined links, file mounting, etc.) */
            if(H5G__traverse_special(&grp_loc, &lnk, target, nlinks, last_comp, &obj_loc, &obj_exists, lapl_id, dxpl_id) < 0)
                HGOTO_ERROR(H5E_LINK, H5E_TRAVERSE, FAIL, "special link traversal failed")
        } /* end if */

        /* Check for last component in name provided */
        if(last_comp) {
            H5O_link_t         *cb_lnk;    /* Pointer to link info for callback */
            H5G_loc_t          *cb_loc;    /* Pointer to object location for callback */

            /* Set callback parameters appropriately, based on link being found */
            if(lookup_status) {
                cb_lnk = &lnk;
                if(obj_exists)
                    cb_loc = &obj_loc;
                else
                    cb_loc = NULL;
            } /* end if */
            else {
                HDassert(!obj_loc_valid);
                cb_lnk = NULL;
                cb_loc = NULL;
            } /* end else */

            /* Call 'operator' routine */
            if((op)(&grp_loc, comp, cb_lnk, cb_loc, op_data, &own_loc) < 0)
                HGOTO_ERROR(H5E_SYM, H5E_CALLBACK, FAIL, "traversal operator failed")

            HGOTO_DONE(SUCCEED)
        } /* end if */

        /* Handle lookup failures now */
        if(!lookup_status) {
            /* If an intermediate group doesn't exist & flag is set, create the group */
            if(target & H5G_CRT_INTMD_GROUP) {
                const H5O_ginfo_t def_ginfo = H5G_CRT_GROUP_INFO_DEF;   /* Default group info settings */
                const H5O_linfo_t def_linfo = H5G_CRT_LINK_INFO_DEF;    /* Default link info settings */
                const H5O_pline_t def_pline = H5O_CRT_PIPELINE_DEF;     /* Default filter pipeline settings */
                H5O_ginfo_t	par_ginfo;	/* Group info settings for parent group */
                H5O_linfo_t	par_linfo;	/* Link info settings for parent group */
                H5O_pline_t	par_pline;	/* Filter pipeline settings for parent group */
                H5O_linfo_t	tmp_linfo;	/* Temporary link info settings */
                htri_t          exists;         /* Whether a group or link info message exists */
                const H5O_ginfo_t *ginfo;	/* Group info settings for new group */
                const H5O_linfo_t *linfo;	/* Link info settings for new group */
                const H5O_pline_t *pline;	/* Filter pipeline settings for new group */
                H5G_obj_create_t gcrt_info;     /* Group creation info */

                /* Check for the parent group having a group info message */
                /* (OK if not found) */
                if((exists = H5O_msg_exists(grp_loc.oloc, H5O_GINFO_ID, dxpl_id)) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "unable to read object header")
                if(exists) {
                    /* Get the group info for parent group */
                    if(NULL == H5O_msg_read(grp_loc.oloc, H5O_GINFO_ID, &par_ginfo, dxpl_id))
                        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "group info message not present")

                    /* Use parent group info settings */
                    ginfo = &par_ginfo;
                } /* end if */
                else
                    /* Use default group info settings */
                    ginfo = &def_ginfo;

                /* Check for the parent group having a link info message */
                /* (OK if not found) */
                /* Get the link info for parent group */
                if((exists = H5G__obj_get_linfo(grp_loc.oloc, &par_linfo, dxpl_id)) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "unable to read object header")
                if(exists) {
                    /* Only keep the creation order information from the parent
                     *  group's link info
                     */
                    HDmemcpy(&tmp_linfo, &def_linfo, sizeof(H5O_linfo_t));
                    tmp_linfo.track_corder = par_linfo.track_corder;
                    tmp_linfo.index_corder = par_linfo.index_corder;
                    linfo = &tmp_linfo;
                } /* end if */
                else
                    /* Use default link info settings */
                    linfo = &def_linfo;

                /* Check for the parent group having a filter pipeline message */
                /* (OK if not found) */
                if((exists = H5O_msg_exists(grp_loc.oloc, H5O_PLINE_ID, dxpl_id)) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "unable to read object header")
                if(exists) {
                    /* Get the filter pipeline for parent group */
                    if(NULL == H5O_msg_read(grp_loc.oloc, H5O_PLINE_ID, &par_pline, dxpl_id))
                        HGOTO_ERROR(H5E_SYM, H5E_CANTGET, FAIL, "filter pipeline message not present")

                    /* Use parent filter pipeline settings */
                    pline = &par_pline;
                } /* end if */
                else
                    /* Use default filter pipeline settings */
                    pline = &def_pline;

                /* Create the intermediate group */
/* XXX: Should we allow user to control the group creation params here? -QAK */
                gcrt_info.gcpl_id = H5P_GROUP_CREATE_DEFAULT;
                gcrt_info.cache_type = H5G_NOTHING_CACHED;
                HDmemset(&gcrt_info.cache, 0, sizeof(gcrt_info.cache));
                if(H5G__obj_create_real(grp_oloc.file, dxpl_id, ginfo, linfo, pline, &gcrt_info, obj_loc.oloc/*out*/) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "unable to create group entry")

                /* Insert new group into current group's symbol table */
                if(H5G__loc_insert(&grp_loc, comp, &obj_loc, H5O_TYPE_GROUP, &gcrt_info, dxpl_id) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTINSERT, FAIL, "unable to insert intermediate group")

                /* Decrement refcount on intermediate group's object header in memory */
                if(H5O_dec_rc_by_loc(obj_loc.oloc, dxpl_id) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTDEC, FAIL, "unable to decrement refcount on newly created object")

                /* Close new group */
                if(H5O_close(obj_loc.oloc) < 0)
                    HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "unable to close")

                /* If the parent group was holding the file open, the
                 * newly-created group should, as well.
                 */
                if(grp_loc.oloc->holding_file)
                    if(H5O_loc_hold_file(obj_loc.oloc) < 0)
                        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to hold file open")

                /* Reset any non-default object header messages */
                if(ginfo != &def_ginfo)
                    /* (Casting away const OK - QAK) */
                    if(H5O_msg_reset(H5O_GINFO_ID, (void *)ginfo) < 0)
                        HGOTO_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to reset group info message")
                if(linfo != &def_linfo)
                    /* (Casting away const OK - QAK) */
                    if(H5O_msg_reset(H5O_LINFO_ID, (void *)linfo) < 0)
                        HGOTO_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to reset link info message")
                if(pline != &def_pline)
                    /* (Casting away const OK - QAK) */
                    if(H5O_msg_reset(H5O_PLINE_ID, (void *)pline) < 0)
                        HGOTO_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to reset I/O pipeline message")
            } /* end if */
            else
                HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "component not found")
        } /* end if */

	/*
	 * Advance to the next component of the path.
	 */

        /* Transfer "ownership" of the object's information to the group object */
        H5G_loc_free(&grp_loc);
        H5G__loc_copy(&grp_loc, &obj_loc, H5_COPY_SHALLOW);
        H5G_loc_reset(&obj_loc);
        obj_loc_valid = FALSE;

	/* Advance to next component in string */
	name += nchars;
    } /* end while */

    /* Call 'operator' routine */
    /* If we've fallen through to here, the name must be something like just '.'
     * and we should issue the callback on that. -QAK
     * Since we don't have a group location or a link to the object we pass in
     * NULL.
     */
    HDassert(group_copy);
    if((op)(NULL, ".", NULL, &grp_loc, op_data, &own_loc) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_CANTNEXT, FAIL, "traversal operator failed")

    /* If the callback took ownership of the object location, it actually has
     * ownership of grp_loc.  It shouldn't have tried to take ownership of
     * the "group location", which was NULL. */
     HDassert(!(own_loc & H5G_OWN_GRP_LOC));
     if(own_loc & H5G_OWN_OBJ_LOC)
         own_loc |= H5G_OWN_GRP_LOC;

done:
    /* If there's been an error, the callback doesn't really get ownership of
     * any location and we should close them both */
    if(ret_value < 0)
        own_loc = H5G_OWN_NONE;

    /* Free all open locations.  This also closes any open external files. */
    if(obj_loc_valid && !(own_loc & H5G_OWN_OBJ_LOC))
        H5G_loc_free(&obj_loc);
    if(group_copy && !(own_loc & H5G_OWN_GRP_LOC))
        H5G_loc_free(&grp_loc);

    /* If there's valid information in the link, reset it */
    if(link_valid)
        if(H5O_msg_reset(H5O_LINK_ID, &lnk) < 0)
            HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to reset link message")

    /* Release temporary component buffer */
    if(wb && H5WB_unwrap(wb) < 0)
        HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "can't release wrapped buffer")

   FUNC_LEAVE_NOAPI(ret_value)
} /* end H5G_traverse_real() */


/*-------------------------------------------------------------------------
 * Function:	H5G_traverse
 *
 * Purpose:	Traverse a path from a location & perform an operation when
 *              the last component of the name is reached.
 *
 * Return:	Success:	Non-negative if path can be fully traversed.
 *		Failure:	Negative if the path could not be fully
 *				traversed.
 *
 * Programmer:	Quincey Koziol
 *		koziol@ncsa.uiuc.edu
 *		Sep 13 2005
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5G_traverse(const H5G_loc_t *loc, const char *name, unsigned target, H5G_traverse_t op,
    void *op_data, hid_t lapl_id, hid_t dxpl_id)
{
    size_t	    nlinks;                 /* Link countdown value */
    H5P_genplist_t *lapl;                   /* Property list with value for nlinks */
    herr_t          ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    /* Check args */
    if(!name || !*name)
        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "no name given")
    if(!loc)
        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "no starting location")
    if(!op)
        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "no operation provided")
    HDassert(lapl_id >= 0);

    /* Set nlinks value from property list, if it exists */
    if(lapl_id == H5P_DEFAULT)
        nlinks = H5L_NUM_LINKS;
    else {
        if(NULL == (lapl = (H5P_genplist_t *)H5I_object(lapl_id)))
            HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
        if(H5P_get(lapl, H5L_ACS_NLINKS_NAME, &nlinks) < 0)
            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get number of links")
    } /* end else */
    
    /* Set up invalid tag. This is a precautionary step only. Setting an invalid
       tag here will ensure that no metadata accessed while doing the traversal
       is given an improper tag, unless another one is specifically set up 
       first. This will ensure we're not accidentally tagging something we 
       shouldn't be during the traversal. Note that for best tagging assertion 
       coverage, setting H5C_DO_TAGGING_SANITY_CHECKS is advised. */
    H5_BEGIN_TAG(dxpl_id, H5AC__INVALID_TAG, FAIL);

    /* Go perform "real" traversal */
    if(H5G_traverse_real(loc, name, target, &nlinks, op, op_data, lapl_id, dxpl_id) < 0)
        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "internal path traversal failed")

    /* Reset tag after traversal */
    H5_END_TAG(FAIL);

done:
   FUNC_LEAVE_NOAPI(ret_value)
} /* end H5G_traverse() */