[svn-r15886] Purpose: Close bug 1332

Description: Improved external link traversal of h5dump.  h5dump will now
    properly avoid all cycles, even those spanning multiple files.  Improvement
    to the output of committed datatypes.  Committed datatypes are now checked
    for uniqueness (like other objects).  Tests added for these cases.

Tested: kagiso, linew, smirom (h5committest)

3 files changed, 357 insertions, 72 deletions

diff --git a/tools/h5dump/h5dump.c b/tools/h5dump/h5dump.c
index 8ace682..979c2ff 100644
--- a/tools/h5dump/h5dump.c
+++ b/tools/h5dump/h5dump.c
@@ -55,9 +55,24 @@ const char  *progname = "h5dump";
 #define H5_SZIP_MSB_OPTION_MASK         16
 #define H5_SZIP_RAW_OPTION_MASK         128
 
+/* List of table structures.  There is one table structure for each file */
+typedef struct h5dump_table_list_t {
+    size_t      nalloc;
+    size_t      nused;
+    struct {
+        unsigned long   fileno;         /* File number that these tables refer to */
+        hid_t           oid;            /* ID of an object in this file, held open so fileno is consistent */
+        table_t         *group_table;   /* Table of groups */
+        table_t         *dset_table;    /* Table of datasets */
+        table_t         *type_table;    /* Table of datatypes */
+    } *tables;
+} h5dump_table_list_t;
+
 int                 d_status = EXIT_SUCCESS;
 static int          unamedtype = 0;     /* shared datatype with no name */
+static h5dump_table_list_t table_list = {0, 0, NULL};
 static table_t      *group_table = NULL, *dset_table = NULL, *type_table = NULL;
+static hbool_t      hit_elink = FALSE;  /* whether we have traversed an external link */
 static size_t       prefix_len = 1024;
 static char         *prefix;
 static const char   *driver = NULL;      /* The driver to open the file with. */
@@ -106,7 +121,7 @@ static void     init_prefix(char **prfx, size_t prfx_len);
 static void     add_prefix(char **prfx, size_t *prfx_len, const char *name);
 /* callback function used by H5Literate() */
 static herr_t   dump_all_cb(hid_t group, const char *name, const H5L_info_t *linfo, void *op_data);
-static int      dump_extlink(const char *filename, const char *targname);
+static int      dump_extlink(hid_t group, const char *linkname, const char *objname);
 
 
 static h5tool_format_t         dataformat = {
@@ -359,7 +374,7 @@ static char            *xml_escape_the_name(const char *);
 
 /* a structure for handling the order command-line parameters come in */
 struct handler_t {
-    void (*func)(hid_t, const char *, void *, int);
+    void (*func)(hid_t, const char *, void *, int, const char *);
     char *obj;
     struct subset_t *subset_info;
 };
@@ -690,6 +705,126 @@ usage(const char *prog)
     fprintf(stdout, "\n");
 }
 
+
+/*-------------------------------------------------------------------------
+ * Function: table_list_add
+ *
+ * Purpose: Add a new set of tables 
+ *
+ * Return: index of added table on success, -1 on failure
+ *
+ * Programmer: Neil Fortner, nfortne2@hdfgroup.org
+ *             Adapted from trav_addr_add in h5trav.c by Quincey Koziol
+ *
+ * Date: October 13, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+static ssize_t
+table_list_add(hid_t oid, unsigned long file_no)
+{
+    size_t      idx;         /* Index of table to use */
+    find_objs_t info;
+    void        *tmp_ptr;
+
+    /* Allocate space if necessary */
+    if(table_list.nused == table_list.nalloc) {
+        table_list.nalloc = MAX(1, table_list.nalloc * 2);
+        if(NULL == (tmp_ptr = HDrealloc(table_list.tables, table_list.nalloc * sizeof(table_list.tables[0]))))
+            return -1;
+        table_list.tables = tmp_ptr;
+    } /* end if */
+
+    /* Append it */
+    idx = table_list.nused++;
+    table_list.tables[idx].fileno = file_no;
+    table_list.tables[idx].oid = oid;
+    if(H5Iinc_ref(oid) < 0) {
+        table_list.nused--;
+        return -1;
+    }
+    if(init_objs(oid, &info, &table_list.tables[idx].group_table,
+        &table_list.tables[idx].dset_table, &table_list.tables[idx].type_table) < 0) {
+        H5Idec_ref(oid);
+        table_list.nused--;
+        return -1;
+    }
+
+#ifdef H5DUMP_DEBUG
+    dump_tables(&info);
+#endif /* H5DUMP_DEBUG */
+
+    return((ssize_t) idx);
+} /* end table_list_add() */
+
+
+/*-------------------------------------------------------------------------
+ * Function: table_list_visited
+ *
+ * Purpose: Check if a table already exists for the specified fileno
+ *
+ * Return: The index of the matching table, or -1 if no matches found
+ *
+ * Programmer: Neil Fortner, nfortne2@hdfgroup.org
+ *             Adapted from trav_addr_visited in h5trav.c by Quincey Koziol
+ *
+ * Date: October 13, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+static ssize_t
+table_list_visited(unsigned long file_no)
+{
+    size_t u;           /* Local index variable */
+
+    /* Look for table */
+    for(u = 0; u < table_list.nused; u++)
+        /* Check for fileno value already in array */
+        if(table_list.tables[u].fileno == file_no)
+            return((ssize_t) u);
+
+    /* Didn't find table */
+    return(-1);
+} /* end table_list_visited() */
+
+
+/*-------------------------------------------------------------------------
+ * Function: table_list_free
+ *
+ * Purpose: Frees the table list
+ *
+ * Return: void
+ *
+ * Programmer: Neil Fortner, nfortne2@hdfgroup.org
+ *
+ * Date: October 13, 2008
+ *
+ *-------------------------------------------------------------------------
+ */
+static void
+table_list_free(void)
+{
+    size_t u;           /* Local index variable */
+
+    /* Iterate over tables */
+    for(u = 0; u < table_list.nused; u++) {
+        /* Release object id */
+        if(H5Idec_ref(table_list.tables[u].oid) < 0)
+            d_status = EXIT_FAILURE;
+
+        /* Free each table */
+        free_table(table_list.tables[u].group_table);
+        free_table(table_list.tables[u].dset_table);
+        free_table(table_list.tables[u].type_table);
+    }
+
+    /* Free the table list */
+    HDfree(table_list.tables);
+    table_list.tables = NULL;
+    table_list.nalloc = table_list.nused = 0;
+} /* end table_list_free() */
+
+
 /*-------------------------------------------------------------------------
  * Function:    print_datatype
  *
@@ -1443,7 +1578,7 @@ dump_all_cb(hid_t group, const char *name, const H5L_info_t *linfo, void UNUSED
 
             case H5O_TYPE_DATASET:
                 if((obj = H5Dopen2(group, name, H5P_DEFAULT)) >= 0) {
-                    if(oinfo.rc > 1) {
+                    if(oinfo.rc > 1 || hit_elink) {
                         obj_t  *found_obj;    /* Found object */
 
                         found_obj = search_obj(dset_table, oinfo.addr);
@@ -1479,6 +1614,7 @@ dump_all_cb(hid_t group, const char *name, const H5L_info_t *linfo, void UNUSED
                                 char *t_obj_path = xml_escape_the_name(obj_path);
                                 char *t_prefix = xml_escape_the_name(HDstrcmp(prefix,"") ? prefix : "/");
                                 char *t_name = xml_escape_the_name(name);
+                                char *t_objname = xml_escape_the_name(found_obj->objname);
                                 char dsetxid[100];
                                 char parentxid[100];
                                 char pointerxid[100];
@@ -1501,13 +1637,14 @@ dump_all_cb(hid_t group, const char *name, const H5L_info_t *linfo, void UNUSED
                                 xml_name_to_XID(found_obj->objname, pointerxid, sizeof(pointerxid), 1);
                                 printf("<%sDatasetPtr OBJ-XID=\"%s\" H5Path=\"%s\"/>\n",
                                         xmlnsprefix,
-                                        pointerxid,t_obj_path);
+                                        pointerxid,t_objname);
                                 indentation(indent);
                                 printf("</%sDataset>\n", xmlnsprefix);
 
                                 HDfree(t_name);
                                 HDfree(t_obj_path);
                                 HDfree(t_prefix);
+                                HDfree(t_objname);
                             }
 
                             H5Dclose(obj);
@@ -1672,7 +1809,7 @@ dump_all_cb(hid_t group, const char *name, const H5L_info_t *linfo, void UNUSED
 
 
                             /* dump the external link */
-                            dump_extlink(filename,targname);
+                            dump_extlink(group, name, targname);
 
 
                         } /* end if */
@@ -1786,7 +1923,7 @@ done:
 static void
 dump_named_datatype(hid_t tid, const char *name)
 {
-
+    H5O_info_t  oinfo;
     unsigned  attr_crt_order_flags;
     hid_t     tcpl_id;  /* datatype creation property list ID */
 
@@ -1814,13 +1951,33 @@ dump_named_datatype(hid_t tid, const char *name)
     printf("%s \"%s\" %s", dump_header_format->datatypebegin, name,
             dump_header_format->datatypeblockbegin);
 
-    if(H5Tget_class(tid) == H5T_COMPOUND)
-        print_datatype(tid, 1);
-    else {
-        indentation(indent + COL);
-        print_datatype(tid, 1);
+    H5Oget_info(tid, &oinfo);
+
+    /* Must check for uniqueness of all objects if we've traversed an elink,
+     * otherwise only check if the reference count > 1.
+     */
+    if(oinfo.rc > 1 || hit_elink) {
+        obj_t  *found_obj;    /* Found object */
+
+        found_obj = search_obj(type_table, oinfo.addr);
+
+        if (found_obj == NULL) {
+            error_msg(progname, "internal error (file %s:line %d)\n",
+                __FILE__, __LINE__);
+            d_status = EXIT_FAILURE;
+            goto done;
+        }
+        else if (found_obj->displayed) {
+            printf("%s \"%s\"\n", HARDLINK, found_obj->objname);
+            goto done;
+        }
+        else
+            found_obj->displayed = TRUE;
+    } /* end if */
+
+    print_datatype(tid, 1);
+    if(H5Tget_class(tid) != H5T_COMPOUND)
         printf(";\n");
-    } /* end else */
 
     /* print attributes */
     indent += COL;
@@ -1834,6 +1991,8 @@ dump_named_datatype(hid_t tid, const char *name)
         H5Aiterate2(tid, H5_INDEX_NAME, sort_order, NULL, dump_attr_cb, NULL);
 
     indent -= COL;
+
+done:
     end_obj(dump_header_format->datatypeend,
             dump_header_format->datatypeblockend);
 }
@@ -1921,7 +2080,10 @@ dump_group(hid_t gid, const char *name)
 
     H5Oget_info(gid, &oinfo);
 
-    if(oinfo.rc > 1) {
+    /* Must check for uniqueness of all objects if we've traversed an elink,
+     * otherwise only check if the reference count > 1.
+     */
+    if(oinfo.rc > 1 || hit_elink) {
         obj_t  *found_obj;    /* Found object */
 
         found_obj = search_obj(group_table, oinfo.addr);
@@ -3149,7 +3311,7 @@ set_sort_order(const char *form)
  *-------------------------------------------------------------------------
  */
 static void
-handle_attributes(hid_t fid, const char *attr, void UNUSED * data, int pe)
+handle_attributes(hid_t fid, const char *attr, void UNUSED * data, int UNUSED pe, const char UNUSED *display_name)
 {
     dump_selected_attr(fid, attr);
 }
@@ -3301,20 +3463,21 @@ parse_subset_params(char *dset)
  *-------------------------------------------------------------------------
  */
 static void
-handle_datasets(hid_t fid, const char *dset, void *data, int pe)
+handle_datasets(hid_t fid, const char *dset, void *data, int pe, const char *display_name)
 {
     H5O_info_t       oinfo;
     hid_t            dsetid;
     struct subset_t *sset = (struct subset_t *)data;
+    const char      *real_name = display_name ? display_name : dset;
 
     if((dsetid = H5Dopen2(fid, dset, H5P_DEFAULT)) < 0)
     {
         if (pe)
         {
-            begin_obj(dump_header_format->datasetbegin, dset,
+            begin_obj(dump_header_format->datasetbegin, real_name,
                 dump_header_format->datasetblockbegin);
             indentation(COL);
-            error_msg(progname, "unable to open dataset \"%s\"\n", dset);
+            error_msg(progname, "unable to open dataset \"%s\"\n", real_name);
             end_obj(dump_header_format->datasetend,
                 dump_header_format->datasetblockend);
             d_status = EXIT_FAILURE;
@@ -3407,14 +3570,15 @@ handle_datasets(hid_t fid, const char *dset, void *data, int pe)
     }
 
     H5Oget_info(dsetid, &oinfo);
-    if(oinfo.rc > 1) {
+    if(oinfo.rc > 1 || hit_elink) {
         obj_t  *found_obj;    /* Found object */
 
         found_obj = search_obj(dset_table, oinfo.addr);
 
         if(found_obj) {
             if (found_obj->displayed) {
-                begin_obj(dump_header_format->datasetbegin, dset,
+                indentation(indent);
+                begin_obj(dump_header_format->datasetbegin, real_name,
                           dump_header_format->datasetblockbegin);
                 indentation(indent + COL);
                 printf("%s \"%s\"\n", HARDLINK, found_obj->objname);
@@ -3423,14 +3587,14 @@ handle_datasets(hid_t fid, const char *dset, void *data, int pe)
                         dump_header_format->datasetblockend);
             } else {
                 found_obj->displayed = TRUE;
-                dump_dataset(dsetid, dset, sset);
+                dump_dataset(dsetid, real_name, sset);
             }
         }
         else
             d_status = EXIT_FAILURE;
     }
     else
-        dump_dataset(dsetid, dset, sset);
+        dump_dataset(dsetid, real_name, sset);
 
     if(H5Dclose(dsetid) < 0)
         d_status = EXIT_FAILURE;
@@ -3459,18 +3623,19 @@ handle_datasets(hid_t fid, const char *dset, void *data, int pe)
  *-------------------------------------------------------------------------
  */
 static void
-handle_groups(hid_t fid, const char *group, void UNUSED * data, int pe)
+handle_groups(hid_t fid, const char *group, void UNUSED * data, int pe, const char * display_name)
 {
-    hid_t      gid;
+    hid_t       gid;
+    const char  *real_name = display_name ? display_name : group;
 
 
     if((gid = H5Gopen2(fid, group, H5P_DEFAULT)) < 0)
     {
         if ( pe )
         {
-            begin_obj(dump_header_format->groupbegin, group, dump_header_format->groupblockbegin);
+            begin_obj(dump_header_format->groupbegin, real_name, dump_header_format->groupblockbegin);
             indentation(COL);
-            error_msg(progname, "unable to open group \"%s\"\n", group);
+            error_msg(progname, "unable to open group \"%s\"\n", real_name);
             end_obj(dump_header_format->groupend, dump_header_format->groupblockend);
             d_status = EXIT_FAILURE;
         }
@@ -3488,7 +3653,7 @@ handle_groups(hid_t fid, const char *group, void UNUSED * data, int pe)
 
         HDstrcpy(prefix, group);
 
-        dump_group(gid, group);
+        dump_group(gid, real_name);
 
         if(H5Gclose(gid) < 0)
             d_status = EXIT_FAILURE;
@@ -3510,7 +3675,7 @@ handle_groups(hid_t fid, const char *group, void UNUSED * data, int pe)
  *-------------------------------------------------------------------------
  */
 static void
-handle_links(hid_t fid, const char *links, void UNUSED * data, int pe)
+handle_links(hid_t fid, const char *links, void UNUSED * data, int UNUSED pe, const char UNUSED *display_name)
 {
     H5L_info_t linfo;
 
@@ -3602,9 +3767,10 @@ handle_links(hid_t fid, const char *links, void UNUSED * data, int pe)
  *-------------------------------------------------------------------------
  */
 static void
-handle_datatypes(hid_t fid, const char *type, void UNUSED * data, int pe)
+handle_datatypes(hid_t fid, const char *type, void UNUSED * data, int pe, const char *display_name)
 {
     hid_t       type_id;
+    const char  *real_name = display_name ? display_name : type;
 
     if((type_id = H5Topen2(fid, type, H5P_DEFAULT)) < 0)
     {
@@ -3619,7 +3785,7 @@ handle_datatypes(hid_t fid, const char *type, void UNUSED * data, int pe)
                 /* unamed datatype */
                 sprintf(name, "/#"H5_PRINTF_HADDR_FMT, type_table->objs[idx].objno);
 
-                if(!HDstrcmp(name, type))
+                if(!HDstrcmp(name, real_name))
                     break;
             } /* end if */
 
@@ -3631,10 +3797,10 @@ handle_datatypes(hid_t fid, const char *type, void UNUSED * data, int pe)
             if ( pe )
             {
                 /* unknown type */
-                begin_obj(dump_header_format->datatypebegin, type,
+                begin_obj(dump_header_format->datatypebegin, real_name,
                     dump_header_format->datatypeblockbegin);
                 indentation(COL);
-                error_msg(progname, "unable to open datatype \"%s\"\n", type);
+                error_msg(progname, "unable to open datatype \"%s\"\n", real_name);
                 end_obj(dump_header_format->datatypeend,
                     dump_header_format->datatypeblockend);
                 d_status = EXIT_FAILURE;
@@ -3645,14 +3811,14 @@ handle_datatypes(hid_t fid, const char *type, void UNUSED * data, int pe)
         {
             hid_t dsetid = H5Dopen2(fid, type_table->objs[idx].objname, H5P_DEFAULT);
             type_id = H5Dget_type(dsetid);
-            dump_named_datatype(type_id, type);
+            dump_named_datatype(type_id, real_name);
             H5Tclose(type_id);
             H5Dclose(dsetid);
         }
     }
     else
     {
-        dump_named_datatype(type_id, type);
+        dump_named_datatype(type_id, real_name);
 
         if(H5Tclose(type_id) < 0)
             d_status = EXIT_FAILURE;
@@ -4073,7 +4239,7 @@ main(int argc, const char *argv[])
     char               *fname = NULL;
     void               *edata;
     H5E_auto2_t         func;
-    find_objs_t         info;
+    H5O_info_t          oi;
     struct handler_t   *hand;
     int                 i;
     unsigned            u;
@@ -4162,12 +4328,22 @@ main(int argc, const char *argv[])
     }
 
 
-    /* find all shared objects */
-    if(init_objs(fid, &info, &group_table, &dset_table, &type_table) < 0) {
+    /* Get object info for root group */
+    if(H5Oget_info_by_name(fid, "/", &oi, H5P_DEFAULT) < 0) {
         error_msg(progname, "internal error (file %s:line %d)\n", __FILE__, __LINE__);
         d_status = EXIT_FAILURE;
         goto done;
     }
+        
+    /* Initialize object tables */
+    if(table_list_add(fid, oi.fileno) < 0) {
+        error_msg(progname, "internal error (file %s:line %d)\n", __FILE__, __LINE__);
+        d_status = EXIT_FAILURE;
+        goto done;
+    }
+    group_table = table_list.tables[0].group_table;
+    dset_table = table_list.tables[0].dset_table;
+    type_table = table_list.tables[0].type_table;
 
     /* does there exist unamed committed datatype */
     for (u = 0; u < type_table->nobjs; u++)
@@ -4176,10 +4352,6 @@ main(int argc, const char *argv[])
             break;
         } /* end if */
 
-#ifdef H5DUMP_DEBUG
-    dump_tables(&info);
-#endif /* H5DUMP_DEBUG */
-
     /* start to dump - display file header information */
     if (!doxml) {
         begin_obj(dump_header_format->filebegin, fname,
@@ -4257,7 +4429,7 @@ main(int argc, const char *argv[])
 
         for(i = 0; i < argc; i++)
             if(hand[i].func)
-                hand[i].func(fid, hand[i].obj, hand[i].subset_info, 1);
+                hand[i].func(fid, hand[i].obj, hand[i].subset_info, 1, NULL);
     }
 
     if (!doxml) {
@@ -4267,16 +4439,14 @@ main(int argc, const char *argv[])
     }
 
 done:
+    /* Free tables for objects */
+    table_list_free();
+
     if (H5Fclose(fid) < 0)
         d_status = EXIT_FAILURE;
 
     free_handler(hand, argc);
 
-    /* Free tables for objects */
-    free_table(group_table);
-    free_table(dset_table);
-    free_table(type_table);
-
     HDfree(prefix);
     HDfree(fname);
 
@@ -5435,20 +5605,49 @@ xml_dump_named_datatype(hid_t type, const char *name)
         "Parents=\"%s\" H5ParentPaths=\"%s\">\n",
         xmlnsprefix,
         name, dtxid,
-        parentxid,(HDstrcmp(prefix, "") ? t_prefix : "/"));
+        parentxid, HDstrcmp(prefix,"") ? t_prefix : "/");
     } else {
+        H5O_info_t  oinfo;          /* Object info */
+
         printf("<%sNamedDataType Name=\"%s\" OBJ-XID=\"%s\" "
         "H5Path=\"%s\" Parents=\"%s\" H5ParentPaths=\"%s\">\n",
         xmlnsprefix,
         t_name, dtxid,
         t_tmp, parentxid, (HDstrcmp(prefix, "") ? t_prefix : "/"));
+
+        /* Check uniqueness of named datatype */
+        H5Oget_info(type, &oinfo);
+        if(oinfo.rc > 1) {
+            obj_t       *found_obj;     /* Found object */
+
+            /* Group with more than one link to it... */
+            found_obj = search_obj(type_table, oinfo.addr);
+
+            if (found_obj == NULL) {
+                indentation(indent);
+                    error_msg(progname, "internal error (file %s:line %d)\n",
+                              __FILE__, __LINE__);
+                d_status = EXIT_FAILURE;
+                goto done;
+            } else if(found_obj->displayed) {
+                /* We have already printed this named datatype, print it as a
+                 * NamedDatatypePtr
+                 */
+                char pointerxid[100];
+                char *t_objname = xml_escape_the_name(found_obj->objname);
+
+                indentation(indent + COL);
+                xml_name_to_XID(found_obj->objname, pointerxid, sizeof(pointerxid), 1);
+                printf("<%sNamedDatatypePtr OBJ-XID=\"%s\" H5Path=\"%s\"/>\n",
+                        xmlnsprefix, pointerxid, t_objname);
+                indentation(indent);
+                printf("</%sNamedDataType>\n", xmlnsprefix);
+                HDfree(t_objname);
+                goto done;
+            } else
+                found_obj->displayed = TRUE;
+        }
     }
-    HDfree(dtxid);
-    HDfree(parentxid);
-    HDfree(t_tmp);
-    HDfree(t_prefix);
-    HDfree(t_name);
-    HDfree(tmp);
 
     indent += COL;
     indentation(indent);
@@ -5464,6 +5663,14 @@ xml_dump_named_datatype(hid_t type, const char *name)
     indent -= COL;
     indentation(indent);
     printf("</%sNamedDataType>\n",xmlnsprefix);
+
+done:
+    HDfree(dtxid);
+    HDfree(parentxid);
+    HDfree(t_tmp);
+    HDfree(t_prefix);
+    HDfree(t_name);
+    HDfree(tmp);
 }
 
 /*-------------------------------------------------------------------------
@@ -5581,7 +5788,7 @@ xml_dump_group(hid_t gid, const char *name)
 
                 indentation(indent + COL);
                 ptrstr = malloc(100);
-                t_objname = xml_escape_the_name(found_obj->objname);
+                t_objname = xml_escape_the_name(found_obj->objname);/* point to the NDT by name */
                 par_name = xml_escape_the_name(par);
                 xml_name_to_XID(found_obj->objname, ptrstr, 100, 1);
                 xml_name_to_XID(par, parentxid, 100, 1);
@@ -6704,32 +6911,87 @@ add_prefix(char **prfx, size_t *prfx_len, const char *name)
  *   basis, attempting to dump as a dataset, as a group and as a named datatype
  *   Error messages are supressed
  *
+ * Modifications:
+ *      Neil Fortner
+ *      13 October 2008
+ *      Function basically rewritten.  No longer directly opens the target file,
+ *      now initializes a new set of tables for the external file.  No longer
+ *      dumps on a trial and error basis, but errors are still suppressed.
+ *
  *-------------------------------------------------------------------------
  */
 
-static int dump_extlink(const char *filename, const char *targname)
+static int dump_extlink(hid_t group, const char *linkname, const char *objname)
 {
-    hid_t fid;
+    hid_t       oid;
+    H5O_info_t  oi;
+    table_t     *old_group_table = group_table;
+    table_t     *old_dset_table = dset_table;
+    table_t     *old_type_table = type_table;
+    hbool_t     old_hit_elink;
+    ssize_t     idx;
 
 
-    fid = h5tools_fopen(filename, H5F_ACC_RDONLY, H5P_DEFAULT, driver, NULL, 0);
+    /* Open target object */
+    if ((oid = H5Oopen(group, linkname, H5P_DEFAULT)) < 0)
+        goto fail;
 
-    if (fid < 0)
-    {
+    /* Get object info */
+    if (H5Oget_info(oid, &oi) < 0) {
+        H5Oclose(oid);
         goto fail;
     }
 
-    /* add some indentation to distinguish that these objects are external */
-    indent += 2*COL;
+    /* Check if we have visited this file already */
+    if ((idx = table_list_visited(oi.fileno)) < 0) {
+        /* We have not visited this file, build object tables */
+        if ((idx = table_list_add(oid, oi.fileno)) < 0) {
+            H5Oclose(oid);
+            goto fail;
+        }
+    }
 
-    handle_datasets(fid, targname, NULL, 0);
-    handle_groups(fid, targname, NULL, 0);
-    handle_datatypes(fid, targname, NULL, 0);
+    /* Do not recurse through an external link into the original file (idx=0) */
+    if (idx) {
+        /* Update table pointers */
+        group_table = table_list.tables[idx].group_table;
+        dset_table = table_list.tables[idx].dset_table;
+        type_table = table_list.tables[idx].type_table;
 
-    indent -= 2*COL;
+        /* We will now traverse the external link, set this global to indicate this */
+        old_hit_elink = hit_elink;
+        hit_elink = TRUE;
 
+        /* add some indentation to distinguish that these objects are external */
+        indent += 2*COL;
 
-    if (H5Fclose(fid) < 0)
+        /* Recurse into the external file */
+        switch (oi.type) {
+            case H5O_TYPE_GROUP:
+                handle_groups(group, linkname, NULL, 0, objname);
+                break;
+            case H5O_TYPE_DATASET:
+                handle_datasets(group, linkname, NULL, 0, objname);
+                break;
+            case H5O_TYPE_NAMED_DATATYPE:
+                handle_datatypes(group, linkname, NULL, 0, objname);
+                break;
+            default:
+                d_status = EXIT_FAILURE;
+        }
+
+        indent -= 2*COL;
+
+        /* Reset table pointers */
+        group_table = old_group_table;
+        dset_table = old_dset_table;
+        type_table = old_type_table;
+
+        /* Reset hit_elink */
+        hit_elink = old_hit_elink;
+    } /* end if */
+
+    if (H5Idec_ref(oid) < 0)
         d_status = EXIT_FAILURE;
 
 
diff --git a/tools/h5dump/h5dumpgentest.c b/tools/h5dump/h5dumpgentest.c
index bd3c4de..05efda8 100644
--- a/tools/h5dump/h5dumpgentest.c
+++ b/tools/h5dump/h5dumpgentest.c
@@ -90,6 +90,7 @@
 #define FILE60  "tfpformat.h5"
 #define FILE61  "textlinksrc.h5"
 #define FILE62  "textlinktar.h5"
+#define FILE63  "textlinkfar.h5"
 
 
 
@@ -225,6 +226,7 @@ typedef struct s1_t {
 #define F42_DSETNAME "Dataset"
 #define F42_TYPENAME "Datatype"
 #define F42_ATTRNAME "Attribute"
+#define F42_LINKNAME "Link_to_Datatype"
 
 /* "File 43" macros */
 /* Name of dataset to create in datafile                              */
@@ -4417,6 +4419,10 @@ static void gent_named_dtype_attr(void)
    ret = H5Tcommit2(fid, F42_TYPENAME, tid, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
    assert(ret >= 0);
 
+   /* Create a hard link to the datatype */
+   ret = H5Lcreate_hard(fid, F42_TYPENAME, fid, F42_LINKNAME, H5P_DEFAULT, H5P_DEFAULT);
+   assert(ret >= 0);
+
    /* Create a scalar dataspace used for all objects */
    sid = H5Screate(H5S_SCALAR);
    assert(sid > 0);
@@ -6179,27 +6185,28 @@ gent_fpformat(void)
 /*-------------------------------------------------------------------------
  * Function:    gent_extlinks
  *
- * Purpose:     Generate 2 files to be used in the external links test
- *   External links point from one HDF5 file to an object (Group, Dataset, or
- *    committed Datatype) in another file.
+ * Purpose:     Generate 3 files to be used in the external links test
+ *   External links point from one HDF5 file to an object (Group, Dataset,
+ *    or committed Datatype) in another file.  Try to create cycles.
  *
  *-------------------------------------------------------------------------
  */
 static void
 gent_extlinks(void)
 {
- hid_t    source_fid, target_fid, sid, did, gid, tid;
+ hid_t    source_fid, target_fid, far_fid, sid, did, gid, gid2, tid;
  hsize_t  dims[1]  = {6};
  int      buf[6]  = {1, 2, 3, 4, 5, 6};
 
  /* create two files, a source and a target */
  source_fid = H5Fcreate(FILE61, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
  target_fid = H5Fcreate(FILE62, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+ far_fid = H5Fcreate(FILE63, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
 
 
 /*-------------------------------------------------------------------------
- * create Groups, a Dataset, a committed Datatype, and external links in
- * the target
+ * create Groups, a Dataset, a committed Datatype, external links, and a
+ * cycle in the target
  *-------------------------------------------------------------------------
  */
 
@@ -6210,8 +6217,13 @@ gent_extlinks(void)
  H5Dwrite(did, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf);
  H5Lcreate_external(FILE61, "/", gid, "elink_t1", H5P_DEFAULT, H5P_DEFAULT);
  H5Lcreate_external(FILE61, "/ext_link4", gid, "elink_t2", H5P_DEFAULT, H5P_DEFAULT);
+
+ gid2 = H5Gcreate2(gid, "subgroup", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+ H5Lcreate_hard(target_fid, "/group", gid2, "link_to_group", H5P_DEFAULT, H5P_DEFAULT);
+
  H5Dclose(did);
  H5Sclose(sid);
+ H5Gclose(gid2);
  H5Gclose(gid);
 
 
@@ -6236,9 +6248,16 @@ gent_extlinks(void)
  H5Lcreate_external(FILE62, "group/elink_t2", source_fid, "ext_link4", H5P_DEFAULT, H5P_DEFAULT);
  H5Lcreate_external(FILE62, "empty_group", source_fid, "ext_link5", H5P_DEFAULT, H5P_DEFAULT);
 
+/*-------------------------------------------------------------------------
+ * create external link in the "far" file pointing to the source file
+ *-------------------------------------------------------------------------
+ */
+ H5Lcreate_external(FILE61, "/", far_fid, "src_file", H5P_DEFAULT, H5P_DEFAULT);
+
  /* close */
  H5Fclose(source_fid);
  H5Fclose(target_fid);
+ H5Fclose(far_fid);
 }
 
 
diff --git a/tools/h5dump/testh5dump.sh.in b/tools/h5dump/testh5dump.sh.in
index 034c456..c1458a1 100644
--- a/tools/h5dump/testh5dump.sh.in
+++ b/tools/h5dump/testh5dump.sh.in
@@ -499,6 +499,10 @@ TOOLTEST torderattr4.ddl -H --sort_by=creation_order --sort_order=descending tor
 # tests for floating point user defined printf format
 TOOLTEST tfpformat.ddl -m %.7f tfpformat.h5
 
+# tests for traversal of external links
+TOOLTEST textlinksrc.ddl textlinksrc.h5
+TOOLTEST textlinkfar.ddl textlinkfar.h5
+
 
 
 if test $nerrors -eq 0 ; then