[svn-r12954] Description:

    Initial refactoring to prepare for H5Oopen_by_idx() API support.

Tested on:
    Linux/32 2.4 (chicago)
    Linux/64 2.4 (chicago2)

8 files changed, 418 insertions, 104 deletions

diff --git a/src/H5Glink.c b/src/H5Glink.c
index b0966d7..e984a91 100644
--- a/src/H5Glink.c
+++ b/src/H5Glink.c
@@ -415,6 +415,54 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5G_link_to_loc
+ *
+ * Purpose:	Build group location from group and link object 
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Monday, November 20 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5G_link_to_loc(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
+    H5G_loc_t *obj_loc)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI(H5G_link_to_loc, FAIL)
+
+    /* Sanity check */
+    HDassert(grp_loc);
+    HDassert(lnk);
+    HDassert(obj_loc);
+
+    /*
+     * Build location from the link
+     */
+
+    /* Check for unknown library-internal link */
+    if(lnk->type > H5L_TYPE_BUILTIN_MAX && lnk->type < H5L_TYPE_UD_MIN)
+        HGOTO_ERROR(H5E_SYM, H5E_UNSUPPORTED, FAIL, "unknown link type")
+
+    /* Build object's group hier. location */
+    if(H5G_name_set(grp_loc->path, obj_loc->path, lnk->name) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "cannot set name")
+
+    /* Set the object location, if it's a hard link set the address also */
+    obj_loc->oloc->file = grp_loc->oloc->file;
+    obj_loc->oloc->holding_file = FALSE;
+    if(lnk->type == H5L_TYPE_HARD)
+        obj_loc->oloc->addr = lnk->u.hard.addr;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5G_link_to_loc() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5G_link_copy_file
  *
  * Purpose:     Copy a link and the object it points to from one file to
diff --git a/src/H5Gloc.c b/src/H5Gloc.c
index 3a94a79..ca488cf 100644
--- a/src/H5Gloc.c
+++ b/src/H5Gloc.c
@@ -22,10 +22,17 @@
  *
  *-------------------------------------------------------------------------
  */
+
+/****************/
+/* Module Setup */
+/****************/
+
 #define H5G_PACKAGE		/*suppress error about including H5Gpkg	  */
 
 
-/* Packages needed by this file... */
+/***********/
+/* Headers */
+/***********/
 #include "H5private.h"		/* Generic Functions			*/
 #include "H5Aprivate.h"		/* Attributes				*/
 #include "H5Dprivate.h"		/* Datasets				*/
@@ -33,21 +40,61 @@
 #include "H5Gpkg.h"		/* Groups		  		*/
 #include "H5Iprivate.h"		/* IDs			  		*/
 
-/* Private typedefs */
+/****************/
+/* Local Macros */
+/****************/
+
+
+/******************/
+/* Local Typedefs */
+/******************/
 
 /* User data for looking up an object in a group */
 typedef struct {
+    /* upward */
     H5G_loc_t  *loc;            /* Group location to set */
-} H5G_loc_ud1_t;
+} H5G_loc_fnd_t;
 
-/* Private macros */
+/* User data for looking up an object in a group by index */
+typedef struct {
+    /* downward */
+    hid_t dxpl_id;              /* DXPL to use for operation */
+    H5L_index_t idx_type;       /* Index to use */
+    H5_iter_order_t order;      /* Iteration order within index */
+    hsize_t n;                  /* Offset within index */
+
+    /* upward */
+    H5G_loc_t  *loc;            /* Group location to set */
+} H5G_loc_fbi_t;
 
-/* Local variables */
 
-/* PRIVATE PROTOTYPES */
+/********************/
+/* Local Prototypes */
+/********************/
+
+/* Group traversal callbacks */
 static herr_t H5G_loc_find_cb(H5G_loc_t *grp_loc, const char *name,
     const H5O_link_t *lnk, H5G_loc_t *obj_loc, void *_udata,
     H5G_own_loc_t *own_loc/*out*/);
+static herr_t H5G_loc_find_by_idx_cb(H5G_loc_t *grp_loc, const char *name,
+    const H5O_link_t *lnk, H5G_loc_t *obj_loc, void *_udata,
+    H5G_own_loc_t *own_loc/*out*/);
+
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+
+/*******************/
+/* Local Variables */
+/*******************/
+
 
 
 /*-------------------------------------------------------------------------
@@ -184,7 +231,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5G_loc_copy(H5G_loc_t *dst, H5G_loc_t *src, H5_copy_depth_t depth)
+H5G_loc_copy(H5G_loc_t *dst, const H5G_loc_t *src, H5_copy_depth_t depth)
 {
     herr_t      ret_value = SUCCEED;       /* Return value */
 
@@ -261,10 +308,6 @@ H5G_loc_free(H5G_loc_t *loc)
     HDassert(loc);
 
     /* Reset components of the location */
-#ifdef NOT_YET
-    if(H5G_ent_free(loc->ent) < 0)
-        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to free entry")
-#endif /* NOT_YET */
     if(H5G_name_free(loc->path) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "unable to free path")
     if(H5O_loc_free(loc->oloc) < 0)
@@ -291,8 +334,8 @@ static herr_t
 H5G_loc_find_cb(H5G_loc_t UNUSED *grp_loc/*in*/, 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_loc_ud1_t *udata = (H5G_loc_ud1_t *)_udata;   /* User data passed in */
-    herr_t ret_value = SUCCEED;              /* Return value */
+    H5G_loc_fnd_t *udata = (H5G_loc_fnd_t *)_udata;   /* User data passed in */
+    herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT(H5G_loc_find_cb)
 
@@ -328,8 +371,8 @@ herr_t
 H5G_loc_find(H5G_loc_t *loc, const char *name, H5G_loc_t *obj_loc/*out*/,
     hid_t lapl_id, hid_t dxpl_id)
 {
-    H5G_loc_ud1_t udata;                /* User data for traversal callback */
-    herr_t      ret_value = SUCCEED;    /* Return value */
+    H5G_loc_fnd_t udata;                /* User data for traversal callback */
+    herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(H5G_loc_find, FAIL)
 
@@ -351,6 +394,99 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5G_loc_find_by_idx_cb
+ *
+ * Purpose:	Callback for retrieving object location for an object in a group
+ *              according to the order within an index
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Monday, November 20, 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5G_loc_find_by_idx_cb(H5G_loc_t UNUSED *grp_loc/*in*/, 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_loc_fbi_t *udata = (H5G_loc_fbi_t *)_udata;   /* User data passed in */
+    H5O_link_t fnd_lnk;                 /* Link within group */
+    hbool_t lnk_copied = FALSE;         /* Whether the link was copied */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT(H5G_loc_find_by_idx_cb)
+
+    /* Check if the name in this group resolved to a valid link */
+    if(obj_loc == NULL)
+        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "group doesn't exist")
+
+    /* Query link */
+    if(H5G_obj_lookup_by_idx(obj_loc->oloc, udata->idx_type, udata->order,
+                udata->n, &fnd_lnk, udata->dxpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "link not found")
+    lnk_copied = TRUE;
+
+    /* Build the object location for the link */
+
+done:
+    /* Reset the link information, if we have a copy */
+    if(lnk_copied)
+        H5O_reset(H5O_LINK_ID, &fnd_lnk);
+
+    /* 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_loc_find_by_idx_cb() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5G_loc_find_by_idx
+ *
+ * Purpose:	Find a symbol from a location, according to the order in an index
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *		Monday, November 20, 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5G_loc_find_by_idx(H5G_loc_t *loc, const char *group_name, H5L_index_t idx_type,
+    H5_iter_order_t order, hsize_t n, H5G_loc_t *obj_loc/*out*/, hid_t lapl_id,
+    hid_t dxpl_id)
+{
+    H5G_loc_fbi_t udata;                /* User data for traversal callback */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI(H5G_loc_find_by_idx, FAIL)
+
+    /* Check args. */
+    HDassert(loc);
+    HDassert(group_name && *group_name);
+    HDassert(obj_loc);
+
+    /* Set up user data for locating object */
+    udata.dxpl_id = dxpl_id;
+    udata.idx_type = idx_type;
+    udata.order = order;
+    udata.n = n;
+    udata.loc = obj_loc;
+
+    /* Traverse group hierarchy to locate object */
+    if(H5G_traverse(loc, group_name, H5G_TARGET_NORMAL, H5G_loc_find_by_idx_cb, &udata, lapl_id, dxpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "can't find object")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5G_loc_find_by_idx() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5G_loc_insert
  *
  * Purpose:	Insert an object at a location
diff --git a/src/H5Gpkg.h b/src/H5Gpkg.h
index b240fb0..411a8e7 100644
--- a/src/H5Gpkg.h
+++ b/src/H5Gpkg.h
@@ -434,6 +434,8 @@ H5_DLL herr_t H5G_ent_to_link(H5F_t *f, hid_t dxpl_id, H5O_link_t *lnk,
 H5_DLL herr_t H5G_ent_to_info(H5F_t *f, hid_t dxpl_id, H5L_info_t *info,
     haddr_t lheap_addr, const H5G_entry_t *ent);
 H5_DLL herr_t H5G_link_to_info(const H5O_link_t *lnk, H5L_info_t *linfo);
+H5_DLL herr_t H5G_link_to_loc(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
+    H5G_loc_t *obj_loc);
 H5_DLL herr_t H5G_link_copy_file(H5F_t *dst_file, hid_t dxpl_id,
     const H5O_link_t *_src_lnk, const H5O_loc_t *src_oloc, H5O_link_t *dst_lnk,
     H5O_copy_t *cpy_info);
@@ -529,7 +531,7 @@ H5_DLL H5RS_str_t *H5G_build_fullpath_refstr_str(H5RS_str_t *path_r, const char
 /*
  * These functions operate on group "locations"
  */
-H5_DLL herr_t H5G_loc_copy(H5G_loc_t *dst, H5G_loc_t *src, H5_copy_depth_t depth);
+H5_DLL herr_t H5G_loc_copy(H5G_loc_t *dst, const H5G_loc_t *src, H5_copy_depth_t depth);
 H5_DLL herr_t H5G_loc_insert(H5G_loc_t *grp_loc, const char *name,
     H5G_loc_t *obj_loc, hid_t dxpl_id);
 
diff --git a/src/H5Gprivate.h b/src/H5Gprivate.h
index 69a448a..786b6a6 100644
--- a/src/H5Gprivate.h
+++ b/src/H5Gprivate.h
@@ -193,6 +193,9 @@ H5_DLL ssize_t H5G_get_refobj_name(hid_t fid, hid_t dxpl_id,
 H5_DLL herr_t H5G_loc(hid_t loc_id, H5G_loc_t *loc);
 H5_DLL herr_t H5G_loc_find(H5G_loc_t *loc, const char *name,
     H5G_loc_t *obj_loc/*out*/, hid_t lapl_id, hid_t dxpl_id);
+H5_DLL herr_t H5G_loc_find_by_idx(H5G_loc_t *loc, const char *group_name,
+    H5L_index_t idx_type, H5_iter_order_t order, hsize_t n,
+    H5G_loc_t *obj_loc/*out*/, hid_t lapl_id, hid_t dxpl_id);
 H5_DLL herr_t H5G_loc_reset(H5G_loc_t *loc);
 H5_DLL herr_t H5G_loc_free(H5G_loc_t *loc);
 
diff --git a/src/H5Gtraverse.c b/src/H5Gtraverse.c
index 4c92bc4..3cb66cc 100644
--- a/src/H5Gtraverse.c
+++ b/src/H5Gtraverse.c
@@ -52,13 +52,13 @@ static char *H5G_comp_g = NULL;                 /*component buffer      */
 static size_t H5G_comp_alloc_g = 0;             /*sizeof component buffer */
 
 /* PRIVATE PROTOTYPES */
-static herr_t H5G_traverse_link_cb(H5G_loc_t *grp_loc/*in*/, const char *name,
+static herr_t H5G_traverse_link_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(H5G_loc_t *grp_loc/*in,out*/, H5O_link_t *lnk,
+static herr_t H5G_traverse_ud(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
     H5G_loc_t *obj_loc/*in,out*/, size_t *nlinks/*in,out*/, hid_t lapl_id,
     hid_t dxpl_id);
-static herr_t H5G_traverse_slink(H5G_loc_t *grp_loc/*in,out*/, H5O_link_t *lnk,
+static herr_t H5G_traverse_slink(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
     H5G_loc_t *obj_loc/*in,out*/, size_t *nlinks/*in,out*/, hid_t lapl_id,
     hid_t dxpl_id);
 static herr_t H5G_traverse_mount(H5G_loc_t *loc/*in,out*/);
@@ -147,7 +147,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5G_traverse_ud(H5G_loc_t *grp_loc/*in,out*/, H5O_link_t *lnk,
+H5G_traverse_ud(const H5G_loc_t *grp_loc/*in,out*/, const H5O_link_t *lnk,
     H5G_loc_t *obj_loc/*in,out*/, size_t *nlinks/*in,out*/, hid_t _lapl_id,
     hid_t dxpl_id)
 {
@@ -291,9 +291,7 @@ done:
  *		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 and
- *				GRP_LOC will contain the information about
- *				the group in which the link tail appears.
+ *				about the object to which the link points
  *
  *		Failure:	Negative
  *
@@ -303,7 +301,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5G_traverse_slink(H5G_loc_t *grp_loc/*in,out*/, H5O_link_t *lnk,
+H5G_traverse_slink(const H5G_loc_t *grp_loc, const H5O_link_t *lnk,
     H5G_loc_t *obj_loc/*in,out*/, size_t *nlinks/*in,out*/, hid_t lapl_id,
     hid_t dxpl_id)
 {
@@ -435,6 +433,90 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * 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
+ *
+ *-------------------------------------------------------------------------
+ */
+static 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, hid_t lapl_id, hid_t dxpl_id)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT(H5G_traverse_special)
+
+    /* 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, nlinks, 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, nlinks, 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(H5G_traverse_mount(obj_loc/*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_OHDR, H5E_LINKCOUNT, 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
@@ -564,75 +646,22 @@ H5G_traverse_real(const H5G_loc_t *_loc, const char *name, unsigned target,
         /* (Defer issuing error for bad lookup until later) */
         lookup_status = H5G_obj_lookup(grp_loc.oloc, H5G_comp_g, &lnk/*out*/, dxpl_id);
 
-        /* If the lookup was OK, try traversing soft links and mount points, if allowed */
+        /* If the lookup was OK, build object location and traverse special links, etc. */
         if(lookup_status >= 0) {
-            /* Indicate that the link info is valid */
+            /* Sanity check link and indicate it's valid */
             HDassert(lnk.type >= H5L_TYPE_HARD);
-            if(lnk.type >H5L_TYPE_BUILTIN_MAX && lnk.type < H5L_TYPE_UD_MIN)
-                HGOTO_ERROR(H5E_SYM, H5E_UNSUPPORTED, FAIL, "unknown link type")
+            HDassert(!HDstrcmp(H5G_comp_g, lnk.name));
             link_valid = TRUE;
 
-            /* Build object's group hier. location */
-            if(H5G_name_set(grp_loc.path, obj_loc.path, H5G_comp_g) < 0)
-                HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "cannot set name")
-
-            /* Set the object location, if it's a hard link set the address also */
-            obj_loc.oloc->file = grp_loc.oloc->file;
-            obj_loc.oloc->holding_file = FALSE;
-            if(lnk.type == H5L_TYPE_HARD)
-                obj_loc.oloc->addr = lnk.u.hard.addr;
+            /* 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;
 
-            /*
-             * 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/*in,out*/, &lnk/*in*/, &obj_loc, nlinks, 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/*in,out*/, &lnk/*in*/, &obj_loc, nlinks, 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(H5G_traverse_mount(&obj_loc/*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_OHDR, H5E_LINKCOUNT, FAIL, "unable to hold file open")
+            /* 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, 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 */
diff --git a/src/H5L.c b/src/H5L.c
index d6a9fa7..6ef6338 100644
--- a/src/H5L.c
+++ b/src/H5L.c
@@ -1935,7 +1935,7 @@ H5L_get_val_by_idx_cb(H5G_loc_t UNUSED *grp_loc/*in*/, const char UNUSED *name,
     H5G_own_loc_t *own_loc/*out*/)
 {
     H5L_trav_gvbi_t *udata = (H5L_trav_gvbi_t *)_udata;   /* User data passed in */
-    H5O_link_t grp_lnk;                 /* Link within group */
+    H5O_link_t fnd_lnk;                 /* Link within group */
     hbool_t lnk_copied = FALSE;         /* Whether the link was copied */
     herr_t ret_value = SUCCEED;         /* Return value */
 
@@ -1947,18 +1947,18 @@ H5L_get_val_by_idx_cb(H5G_loc_t UNUSED *grp_loc/*in*/, const char UNUSED *name,
 
     /* Query link */
     if(H5G_obj_lookup_by_idx(obj_loc->oloc, udata->idx_type, udata->order,
-                udata->n, &grp_lnk, udata->dxpl_id) < 0)
+                udata->n, &fnd_lnk, udata->dxpl_id) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "link not found")
     lnk_copied = TRUE;
 
     /* Retrieve the value for the link */
-    if(H5L_get_val_real(&grp_lnk, udata->buf, udata->size) < 0)
+    if(H5L_get_val_real(&fnd_lnk, udata->buf, udata->size) < 0)
         HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "can't retrieve link value")
 
 done:
     /* Reset the link information, if we have a copy */
     if(lnk_copied)
-        H5O_reset(H5O_LINK_ID, &grp_lnk);
+        H5O_reset(H5O_LINK_ID, &fnd_lnk);
 
     /* Indicate that this callback didn't take ownership of the group *
      * location for the object */
@@ -2610,7 +2610,7 @@ H5L_get_info_by_idx_cb(H5G_loc_t UNUSED *grp_loc/*in*/, const char UNUSED *name,
     H5G_own_loc_t *own_loc/*out*/)
 {
     H5L_trav_gibi_t *udata = (H5L_trav_gibi_t *)_udata;   /* User data passed in */
-    H5O_link_t grp_lnk;                 /* Link within group */
+    H5O_link_t fnd_lnk;                 /* Link within group */
     hbool_t lnk_copied = FALSE;         /* Whether the link was copied */
     herr_t ret_value = SUCCEED;         /* Return value */
 
@@ -2622,18 +2622,18 @@ H5L_get_info_by_idx_cb(H5G_loc_t UNUSED *grp_loc/*in*/, const char UNUSED *name,
 
     /* Query link */
     if(H5G_obj_lookup_by_idx(obj_loc->oloc, udata->idx_type, udata->order,
-                udata->n, &grp_lnk, udata->dxpl_id) < 0)
+                udata->n, &fnd_lnk, udata->dxpl_id) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "link not found")
     lnk_copied = TRUE;
 
     /* Get information from the link */
-    if(H5G_link_to_info(&grp_lnk, udata->linfo) < 0)
+    if(H5G_link_to_info(&fnd_lnk, udata->linfo) < 0)
         HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "can't get link info")
 
 done:
     /* Reset the link information, if we have a copy */
     if(lnk_copied)
-        H5O_reset(H5O_LINK_ID, &grp_lnk);
+        H5O_reset(H5O_LINK_ID, &fnd_lnk);
 
     /* Indicate that this callback didn't take ownership of the group *
      * location for the object */
diff --git a/src/H5O.c b/src/H5O.c
index b1b373a..ff18111 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -268,6 +268,7 @@ H5Oopen(hid_t loc_id, const char *name, hid_t lapl_id)
         HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "group not found")
     loc_found = TRUE;
 
+    /* Open the object */
     if((ret_value = H5O_open_by_loc(&obj_loc, H5AC_dxpl_id)) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to open object")
 
@@ -282,6 +283,81 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5Oopen_by_idx
+ *
+ * Purpose:	Opens an object within an HDF5 file, according to the offset
+ *              within an index.
+ *
+ *              This function opens an object in the same way that H5Gopen,
+ *              H5Topen, and H5Dopen do. However, H5Oopen doesn't require
+ *              the type of object to be known beforehand. This can be
+ *              useful in user-defined links, for instance, when only a
+ *              path is known.
+ *
+ *              The opened object should be closed again with H5Oclose
+ *              or H5Gclose, H5Tclose, or H5Dclose.
+ *
+ * Return:	Success:	An open object identifier
+ *		Failure:	Negative
+ *
+ * Programmer:	Quincey Koziol
+ *		November 20 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+hid_t
+H5Oopen_by_idx(hid_t loc_id, const char *group_name, H5L_index_t idx_type,
+    H5_iter_order_t order, hsize_t n, hid_t lapl_id)
+{
+    H5G_loc_t	loc;
+    H5G_loc_t   obj_loc;                /* Location used to open group */
+    H5G_name_t  obj_path;            	/* Opened object group hier. path */
+    H5O_loc_t   obj_oloc;            	/* Opened object object location */
+    hbool_t     loc_found = FALSE;      /* Entry at 'name' found */
+    hid_t       ret_value = FAIL;
+
+    FUNC_ENTER_API(H5Oopen_by_idx, FAIL)
+
+    /* Check args */
+    if(H5G_loc(loc_id, &loc) < 0)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
+    if(!group_name || !*group_name)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name specified")
+    if(idx_type <= H5L_INDEX_UNKNOWN || idx_type >= H5L_INDEX_N)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index type specified")
+    if(order <= H5_ITER_UNKNOWN || order >= H5_ITER_N)
+	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid iteration order specified")
+    if(H5P_DEFAULT == lapl_id)
+        lapl_id = H5P_LINK_ACCESS_DEFAULT;
+    else
+        if(TRUE != H5P_isa_class(lapl_id, H5P_LINK_ACCESS))
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not link access property list ID")
+
+    /* Set up opened group location to fill in */
+    obj_loc.oloc = &obj_oloc;
+    obj_loc.path = &obj_path;
+    H5G_loc_reset(&obj_loc);
+
+    /* Find the object's location, according to the order in the index */
+    if(H5G_loc_find_by_idx(&loc, group_name, idx_type, order, n, &obj_loc/*out*/, lapl_id, H5AC_dxpl_id) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_NOTFOUND, FAIL, "group not found")
+    loc_found = TRUE;
+
+    /* Open the object */
+    if((ret_value = H5O_open_by_loc(&obj_loc, H5AC_dxpl_id)) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to open object")
+
+done:
+    if(ret_value < 0)
+        if(loc_found)
+            if(H5G_loc_free(&obj_loc) < 0)
+                HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "can't free location")
+
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Oopen_by_idx() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5Oopen_by_addr
  *
  * Purpose:	Warning! This function is EXTREMELY DANGEROUS!
@@ -332,7 +408,7 @@ H5Oopen_by_addr(hid_t loc_id, haddr_t addr)
     /* Check args */
     if(H5G_loc(loc_id, &loc) < 0)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a location")
-    if(addr == 0)
+    if(!H5F_addr_defined(addr))
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no address supplied")
 
     /* Set up opened group location to fill in */
@@ -341,18 +417,17 @@ H5Oopen_by_addr(hid_t loc_id, haddr_t addr)
     H5G_loc_reset(&obj_loc);
     obj_loc.oloc->addr = addr;
     obj_loc.oloc->file = loc.oloc->file;
-    H5G_name_reset(obj_loc.path);
+    H5G_name_reset(obj_loc.path);       /* objects opened through this routine don't have a path name */
 
+    /* Open the object */
     if((ret_value = H5O_open_by_loc(&obj_loc, H5AC_dxpl_id)) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_CANTOPENOBJ, FAIL, "unable to open object")
 
 done:
-    if(ret_value < 0) {
-        if(loc_found) {
+    if(ret_value < 0)
+        if(loc_found)
             if(H5G_loc_free(&obj_loc) < 0)
                 HDONE_ERROR(H5E_SYM, H5E_CANTRELEASE, FAIL, "can't free location")
-        }
-    } /* end if */
 
     FUNC_LEAVE_API(ret_value)
 } /* end H5Oopen_by_addr() */
diff --git a/src/H5Opublic.h b/src/H5Opublic.h
index 9576ff1..258f701 100644
--- a/src/H5Opublic.h
+++ b/src/H5Opublic.h
@@ -29,8 +29,13 @@
 #define _H5Opublic_H
 
 /* Public headers needed by this file */
-#include "H5public.h"
-#include "H5Ipublic.h"
+#include "H5public.h"		/* Generic Functions			*/
+#include "H5Ipublic.h"		/* IDs			  		*/
+#include "H5Lpublic.h"		/* Links		  		*/
+
+/*****************/
+/* Public Macros */
+/*****************/
 
 /* Flags for object copy (H5Ocopy) */
 #define H5O_COPY_SHALLOW_HIERARCHY_FLAG (0x0001u)   /* Copy only immediate members */
@@ -57,6 +62,10 @@
 #define H5O_MESG_ALL_FLAG      (H5O_MESG_SDSPACE_FLAG | H5O_MESG_DTYPE_FLAG | H5O_MESG_FILL_FLAG | H5O_MESG_PLINE_FLAG | H5O_MESG_ATTR_FLAG)
 
 
+/*******************/
+/* Public Typedefs */
+/*******************/
+
 typedef struct H5O_stat_t {
     hsize_t size;               /* Total size of object header in file */
     hsize_t free;               /* Free space within object header */
@@ -64,12 +73,23 @@ typedef struct H5O_stat_t {
     unsigned nchunks;           /* Number of object header chunks */
 } H5O_stat_t;
 
+
+/********************/
+/* Public Variables */
+/********************/
+
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/*********************/
+/* Public Prototypes */
+/*********************/
 H5_DLL hid_t H5Oopen(hid_t loc_id, const char *name, hid_t lapl_id);
 H5_DLL hid_t H5Oopen_by_addr(hid_t loc_id, haddr_t addr);
+H5_DLL hid_t H5Oopen_by_idx(hid_t loc_id, const char *group_name,
+    H5L_index_t idx_type, H5_iter_order_t order, hsize_t n, hid_t lapl_id);
 H5_DLL herr_t H5Oincr_refcount(hid_t object_id);
 H5_DLL herr_t H5Odecr_refcount(hid_t object_id);
 H5_DLL herr_t H5Ocopy(hid_t src_loc_id, const char *src_name, hid_t dst_loc_id,
@@ -79,4 +99,5 @@ H5_DLL herr_t H5Oclose(hid_t object_id);
 #ifdef __cplusplus
 }
 #endif
-#endif
+#endif /* _H5Opublic_H */
+