[svn-r12528] Added User-Defined links to the library.

Users can create external links using H5L_create_external().  These links
point to an object in another HDF5 file.  Users can alter the behavior of
external links or create new kinds of links by registering callbacks
using the H5L interface.

Added tests, tools support, etc.

Also a number of other, minor changes have been made (some restructuring of
the H5L interface, for instance).

Additional documentation and examples are forthcoming.

44 files changed, 886 insertions, 504 deletions

diff --git a/tools/h5diff/h5diffgentest.c b/tools/h5diff/h5diffgentest.c
index 11459a4..1811b9d 100644
--- a/tools/h5diff/h5diffgentest.c
+++ b/tools/h5diff/h5diffgentest.c
@@ -42,6 +42,26 @@
 #define FILE8    "file8.h5"
 
 
+#define MY_LINKCLASS 187
+/* A UD link traversal function.  Shouldn't actually be called. */
+static hid_t UD_traverse(UNUSED const char * link_name, UNUSED hid_t cur_group,
+    UNUSED void * udata, UNUSED size_t udata_size, UNUSED hid_t lapl_id)
+{
+return -1;
+}
+const H5L_link_class_t UD_link_class[1] = {{
+    H5L_LINK_CLASS_T_VERS,    /* H5L_link_class_t version       */
+    MY_LINKCLASS,             /* Link type id number            */
+    "UD link class",          /* name for debugging             */
+    NULL,                     /* Creation callback              */
+    NULL,                     /* Move/rename callback           */
+    NULL,                     /* Copy callback                  */
+    UD_traverse,              /* The actual traversal function  */
+    NULL,                     /* Deletion callback              */
+    NULL                      /* Query callback                 */
+}};
+
+
 /*-------------------------------------------------------------------------
  * Function: write_attr
  *
@@ -2153,7 +2173,7 @@ int test_basic(const char *file1,
  * Function: test_basic
  *
  * Purpose: Compare different HDF5 types (H5G_obj_t):
- * H5G_DATASET, H5G_TYPE, H5G_GROUP, H5G_LINK
+ * H5G_DATASET, H5G_TYPE, H5G_GROUP, H5G_LINK, H5G_UDLINK
  *
  *-------------------------------------------------------------------------
  */
@@ -2222,8 +2242,16 @@ int test_types(const char *file1,
  *-------------------------------------------------------------------------
  */
 
- status = H5Glink(fid1, H5G_LINK_SOFT, "g1", "l1");
- status = H5Glink(fid1, H5G_LINK_SOFT, "g2", "l2");
+ status = H5Glink(fid1, H5L_LINK_SOFT, "g1", "l1");
+ status = H5Glink(fid1, H5L_LINK_SOFT, "g2", "l2");
+
+/*-------------------------------------------------------------------------
+ * H5G_UDLINK
+ *-------------------------------------------------------------------------
+ */
+ H5Lcreate_external("filename", "objname", fid1, "ext_link", H5P_DEFAULT, H5P_DEFAULT);
+ H5Lregister(UD_link_class);
+ H5Lcreate_ud(fid1, "ud_link", MY_LINKCLASS, NULL, 0, H5P_DEFAULT, H5P_DEFAULT);
 
 /*-------------------------------------------------------------------------
  * Close
diff --git a/tools/h5dump/h5dump.c b/tools/h5dump/h5dump.c
index 4bd388a..7a49950 100644
--- a/tools/h5dump/h5dump.c
+++ b/tools/h5dump/h5dump.c
@@ -271,6 +271,10 @@ static const h5dump_header_t standardformat = {
     "",				/*dataend */
     SOFTLINK,			/*softlinkbegin */
     "",				/*softlinkend */
+    EXTLINK,			/*extlinkbegin */
+    "",				/*extlinkend */
+    UDLINK,			/*udlinkbegin */
+    "",				/*udlinkend */
     SUBSET,			/*subsettingbegin */
     "",				/*subsettingend */
     START,			/*startbegin */
@@ -300,6 +304,10 @@ static const h5dump_header_t standardformat = {
     "}",			/*datablockend */
     "{",			/*softlinkblockbegin */
     "}",			/*softlinkblockend */
+    "{",			/*extlinkblockbegin */
+    "}",			/*extlinkblockend */
+    "{",			/*udlinkblockbegin */
+    "}",			/*udlinkblockend */
     "{",			/*strblockbegin */
     "}",			/*strblockend */
     "{",			/*enumblockbegin */
@@ -1398,6 +1406,7 @@ dump_all(hid_t group, const char *name, void * op_data)
     hid_t       obj;
     char       *obj_path = NULL;        /* Full path of object */
     H5G_stat_t  statbuf;
+    H5L_linkinfo_t linfo;              /* Link information */
     herr_t      ret = SUCCEED;
 
     /* Stat the object */
@@ -1407,6 +1416,12 @@ dump_all(hid_t group, const char *name, void * op_data)
         ret = FAIL;
         goto done;
     } /* end if */
+    if(H5Lget_linkinfo(group, name, &linfo, H5P_DEFAULT) < 0) {
+        error_msg(progname, "unable to get object information\n");
+        d_status = EXIT_FAILURE;
+        ret = FAIL;
+        goto done;
+    } /* end if */
 
     if (*(int *)op_data != H5G_UNKNOWN && statbuf.type != *(int *) op_data)
         goto done;
@@ -1433,7 +1448,7 @@ dump_all(hid_t group, const char *name, void * op_data)
                 indentation(indent + COL);
             }
 
-            if (H5Gget_linkval(group, name, statbuf.linklen, targbuf) < 0) {
+            if (H5Lget_linkval(group, name, statbuf.linklen, targbuf, H5P_DEFAULT) < 0) {
                 error_msg(progname, "unable to get link value\n");
                 d_status = EXIT_FAILURE;
                 ret = FAIL;
@@ -1516,7 +1531,128 @@ dump_all(hid_t group, const char *name, void * op_data)
             HDfree(targbuf);
             break;
         }
+        case H5G_UDLINK:
+        {
+            indentation(indent);
+            switch(linfo.linkclass)
+            {
+              case H5L_LINK_EXTERNAL:
+              {
+                char *targbuf;
+                char *filename;
+                char *targname;
+                targbuf = HDmalloc(statbuf.linklen);
+                HDassert(targbuf);
+                if (!doxml) {
+                    begin_obj(dump_header_format->extlinkbegin, name,
+                            dump_header_format->extlinkblockbegin);
+                }
+                if (H5Lget_linkval(group, name, statbuf.linklen, targbuf, H5P_DEFAULT) < 0) {
+                    error_msg(progname, "unable to get external link value\n");
+                    d_status = EXIT_FAILURE;
+                    ret = FAIL;
+                } else {
+                    if(H5Lunpack_elink_val(targbuf, &filename, &targname) < 0) {
+                      error_msg(progname, "unable to unpack external link value\n");
+                      d_status = EXIT_FAILURE;
+                      ret = FAIL;
+                    } else {
+                      if (!doxml) {
+                          indentation(indent + COL);
+                          printf("LINKCLASS %d\n", linfo.linkclass);
+                          indentation(indent + COL);
+                          printf("TARGETFILE \"%s\"\n", filename);
+                          indentation(indent + COL);
+                          printf("TARGETPATH \"%s\"\n", targname);
+                      }
+                      else /* XML */
+                      {
+                        char linkxid[100];
+                        char parentxid[100];
+                        char *t_name = xml_escape_the_name(name);
+                        char *t_prefix = xml_escape_the_name(HDstrcmp(prefix,"") ? prefix : "/");
+                        char *t_obj_path = xml_escape_the_name(obj_path);
+                        char *t_filename = xml_escape_the_name(filename);
+                        char *t_targname = xml_escape_the_name(targname);
+
+                        /* Create OBJ-XIDs for the parent and object */
+                        xml_name_to_XID(t_obj_path, linkxid, sizeof(linkxid), 1);
+                        xml_name_to_XID(prefix, parentxid, sizeof(parentxid), 1);
+
+                            printf("<%sExternalLink LinkName=\"%s\" "
+                                  "OBJ-XID=\"%s\" "
+                                  "H5SourcePath=\"%s\" "
+                                  "TargetFilename=\"%s\"  "
+                                  "TargetPath=\"%s\"  "
+                                  "Parents=\"%s\" H5ParentPaths=\"%s\" />\n",
+                                    xmlnsprefix,
+                                    t_name,         /* LinkName */
+                                    linkxid,        /* OBJ-XID */
+                                    t_obj_path,     /* H5SourcePath */
+                                    filename,       /* TargetFilename */
+                                    targname,       /* TargetPath*/
+                                    parentxid,      /* Parents */
+                                    t_prefix);      /* H5ParentPaths */
+                        HDfree(t_prefix);
+                        HDfree(t_name);
+                        HDfree(t_filename);
+                        HDfree(t_targname);
+                        HDfree(t_obj_path);
+                      }
+                    }
+                }
+                if (!doxml) {
+                    end_obj(dump_header_format->extlinkend,
+                            dump_header_format->extlinkblockend);
+                }
+                HDfree(targbuf);
+              }
+              break;
+              default:
+                  if (!doxml) {
+                      begin_obj(dump_header_format->udlinkbegin, name,
+                                dump_header_format->udlinkblockbegin);
+                      indentation(indent + COL);
+                  }
+                  if (!doxml) {
+                      printf("LINKCLASS %d\n", linfo.linkclass);
+                  }
+                  else /* XML */
+                  {
+                    char linkxid[100];
+                    char parentxid[100];
+                    char *t_name = xml_escape_the_name(name);
+                    char *t_prefix = xml_escape_the_name(HDstrcmp(prefix,"") ? prefix : "/");
+                    char *t_obj_path = xml_escape_the_name(obj_path);
+
+                    /* Create OBJ-XIDs for the parent and object */
+                    xml_name_to_XID(t_obj_path, linkxid, sizeof(linkxid), 1);
+                    xml_name_to_XID(prefix, parentxid, sizeof(parentxid), 1);
 
+                        printf("<%sUserDefined LinkName=\"%s\" "
+                               "OBJ-XID=\"%s\" "
+                               "H5SourcePath=\"%s\" "
+                               "LinkClass=\"%d\"  "
+                               "Parents=\"%s\" H5ParentPaths=\"%s\" />\n",
+                                xmlnsprefix,
+                                t_name,             /* LinkName */
+                                linkxid,            /* OBJ-XID */
+                                t_obj_path,         /* H5SourcePath */
+                                linfo.linkclass,    /* LinkClass */
+                                parentxid,          /* Parents */
+                                t_prefix);          /* H5ParentPaths */
+                    HDfree(t_prefix);
+                    HDfree(t_name);
+                    HDfree(t_obj_path);
+                  }
+                  if (!doxml) {
+                      indentation(indent);
+                      end_obj(dump_header_format->udlinkend,
+                              dump_header_format->udlinkblockend);
+                  }
+            }
+            break;
+          }
         case H5G_GROUP:
             if ((obj = H5Gopen(group, name)) < 0) {
                 error_msg(progname, "unable to dump group \"%s\"\n", name);
@@ -2003,7 +2139,7 @@ dump_data(hid_t obj_id, int obj_data, struct subset_t *sset, int display_ai)
 
     /* Print all the values. */
     if (obj_data == DATASET_DATA) {
-        hid_t       f_type = H5Dget_type(obj_id); 
+        hid_t       f_type = H5Dget_type(obj_id);
         char        string_prefix[64];
         h5tool_format_t    string_dataformat;
 
@@ -2683,7 +2819,7 @@ set_output_file(const char *fname, int is_bin)
   else
    rawdatastream = NULL;
  }
- 
+
  /* binary output */
  if (is_bin)
  {
@@ -2699,7 +2835,7 @@ set_output_file(const char *fname, int is_bin)
    return 0;
   }
  }
- 
+
  return -1;
 }
 
@@ -3044,7 +3180,7 @@ handle_groups(hid_t fid, char *group, void UNUSED * data)
 /*-------------------------------------------------------------------------
  * Function:    handle_links
  *
- * Purpose:     Handle the links from the command.
+ * Purpose:     Handle soft or UD links from the command.
  *
  * Return:      void
  *
@@ -3059,18 +3195,24 @@ static void
 handle_links(hid_t fid, char *links, void UNUSED * data)
 {
     H5G_stat_t  statbuf;
+    H5L_linkinfo_t linfo;
+    char * elink_file;
+    char * elink_path;
 
     if (H5Gget_objinfo(fid, links, FALSE, &statbuf) < 0) {
         error_msg(progname, "unable to get obj info from \"%s\"\n", links);
         d_status = EXIT_FAILURE;
-    } else if (statbuf.type == H5G_LINK) {
+    } else if (H5Lget_linkinfo(fid, links, &linfo, H5P_DEFAULT) < 0) {
+        error_msg(progname, "unable to get link info from \"%s\"\n", links);
+        d_status = EXIT_FAILURE;
+    } else if (statbuf.type == H5G_LINK) {    /* Soft link */
         char *buf = HDmalloc(statbuf.linklen);
 
         begin_obj(dump_header_format->softlinkbegin, links,
                   dump_header_format->softlinkblockbegin);
         indentation(COL);
 
-        if (H5Gget_linkval(fid, links, statbuf.linklen, buf) >= 0) {
+        if (H5Lget_linkval(fid, links, statbuf.linklen, buf, H5P_DEFAULT) >= 0) {
             printf("LINKTARGET \"%s\"\n", buf);
         } else {
             error_msg(progname, "h5dump error: unable to get link value for \"%s\"\n",
@@ -3080,7 +3222,45 @@ handle_links(hid_t fid, char *links, void UNUSED * data)
 
         end_obj(dump_header_format->softlinkend,
                 dump_header_format->softlinkblockend);
-
+        HDfree(buf);
+    } else if (statbuf.type == H5G_UDLINK) {    /* User-defined link */
+        char *buf = HDmalloc(statbuf.linklen);
+        begin_obj(dump_header_format->udlinkbegin, links,
+                  dump_header_format->udlinkblockbegin);
+        indentation(COL);
+        switch(linfo.linkclass) {
+          case H5L_LINK_EXTERNAL:
+              begin_obj(dump_header_format->extlinkbegin, links,
+                        dump_header_format->extlinkblockbegin);
+              if (H5Lget_linkval(fid, links, statbuf.linklen, buf, H5P_DEFAULT) >= 0) {
+                  if(H5Lunpack_elink_val(buf, &elink_file, &elink_path)>=0) {
+                      indentation(COL);
+                      printf("LINKCLASS %d\n", linfo.linkclass);
+                      indentation(COL);
+                      printf("TARGETFILE \"%s\"\n", elink_file);
+                      indentation(COL);
+                      printf("TARGETPATH \"%s\"\n", elink_path);
+                  } else {
+                      error_msg(progname, "h5dump error: unable to unpack external link value for \"%s\"\n",
+                                links);
+                      d_status = EXIT_FAILURE;
+                  }
+              } else {
+                  error_msg(progname, "h5dump error: unable to get external link value for \"%s\"\n",
+                            links);
+                  d_status = EXIT_FAILURE;
+              }
+              end_obj(dump_header_format->extlinkend,
+                dump_header_format->extlinkblockend);
+          break;
+          default:
+              begin_obj(dump_header_format->udlinkbegin, links,
+                        dump_header_format->udlinkblockbegin);
+              indentation(COL);
+              printf("LINKCLASS %d\n", linfo.linkclass);
+              end_obj(dump_header_format->udlinkend,
+                      dump_header_format->udlinkblockend);
+        }
         HDfree(buf);
     } else {
         error_msg(progname, "\"%s\" is not a link\n", links);
@@ -5054,7 +5234,8 @@ xml_dump_group(hid_t gid, const char *name)
                 H5Giterate(gid, ".", NULL, dump_all, (void *) &xtype);
                 xtype = H5G_LINK;
                 H5Giterate(gid, ".", NULL, dump_all, (void *) &xtype);
-
+                xtype = H5G_UDLINK;
+                H5Giterate(gid, ".", NULL, dump_all, (void *) &xtype);
             }
             free(t_name);
             free(grpxid);
@@ -5114,7 +5295,8 @@ xml_dump_group(hid_t gid, const char *name)
   	H5Giterate(gid, ".", NULL, dump_all, (void *) &xtype);
 	xtype = H5G_LINK;
 	H5Giterate(gid, ".", NULL, dump_all, (void *) &xtype);
-
+	xtype = H5G_UDLINK;
+	H5Giterate(gid, ".", NULL, dump_all, (void *) &xtype);
     }
 
     indent -= COL;
diff --git a/tools/h5dump/h5dump.h b/tools/h5dump/h5dump.h
index dbc5de9..08aa527 100644
--- a/tools/h5dump/h5dump.h
+++ b/tools/h5dump/h5dump.h
@@ -45,6 +45,8 @@
 #define S_SIMPLE        "SIMPLE"
 #define S_NULL          "NULL"
 #define SOFTLINK        "SOFTLINK"
+#define EXTLINK         "EXTERNAL_LINK"
+#define UDLINK          "USERDEFINED_LINK"
 #define STORAGELAYOUT   "STORAGELAYOUT"
 #define START           "START"
 #define STRIDE          "STRIDE"
@@ -91,6 +93,10 @@ typedef struct h5dump_header_t {
     const char *dataend;
     const char *softlinkbegin;
     const char *softlinkend;
+    const char *extlinkbegin;
+    const char *extlinkend;
+    const char *udlinkbegin;
+    const char *udlinkend;
     const char *subsettingbegin;
     const char *subsettingend;
     const char *startbegin;
@@ -120,6 +126,10 @@ typedef struct h5dump_header_t {
     const char *datablockend;
     const char *softlinkblockbegin;
     const char *softlinkblockend;
+    const char *extlinkblockbegin;
+    const char *extlinkblockend;
+    const char *udlinkblockbegin;
+    const char *udlinkblockend;
     const char *strblockbegin;
     const char *strblockend;
     const char *enumblockbegin;
diff --git a/tools/h5dump/h5dumpgentest.c b/tools/h5dump/h5dumpgentest.c
index 89652f2..3a5272a 100644
--- a/tools/h5dump/h5dumpgentest.c
+++ b/tools/h5dump/h5dumpgentest.c
@@ -79,7 +79,8 @@
 #define FILE50  "taindices.h5"
 #define FILE51  "tlonglinks.h5"
 #define FILE52  "tldouble.h5"
-
+#define FILE53  "textlink.h5"
+#define FILE54  "tudlink.h5"
 
 
 
@@ -120,6 +121,27 @@ const H5Z_class_t H5Z_MYFILTER[1] = {{
 }};
 
 
+/* A UD link traversal function.  Shouldn't actually be called. */
+static hid_t UD_traverse(UNUSED const char * link_name, UNUSED hid_t cur_group,
+     UNUSED void * udata, UNUSED size_t udata_size, UNUSED hid_t lapl_id)
+{
+return -1;
+}
+
+#define MY_LINKCLASS 187
+
+const H5L_link_class_t UD_link_class[1] = {{
+    H5L_LINK_CLASS_T_VERS,    /* H5L_link_class_t version       */
+    MY_LINKCLASS,             /* Link type id number            */
+    "UD link class",          /* name for debugging             */
+    NULL,                     /* Creation callback              */
+    NULL,                     /* Move/rename callback           */
+    NULL,                     /* Copy callback                  */
+    UD_traverse,              /* The actual traversal function  */
+    NULL,                     /* Deletion callback              */
+    NULL                      /* Query callback                 */
+}};
+
 
 #define LENSTR  50
 #define LENSTR2  11
@@ -403,8 +425,8 @@ static void gent_softlink(void)
 
     fid = H5Fcreate(FILE4, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
     root = H5Gopen (fid, "/");
-    H5Glink (root, H5G_LINK_SOFT, "somevalue", "slink1");
-    H5Glink (root, H5G_LINK_SOFT, "linkvalue", "slink2");
+    H5Glink (root, H5L_LINK_SOFT, "somevalue", "slink1");
+    H5Glink (root, H5L_LINK_SOFT, "linkvalue", "slink2");
 
     H5Gclose(root);
     H5Fclose(fid);
@@ -441,19 +463,48 @@ static void gent_hardlink(void)
     H5Dclose(dataset);
 
     group = H5Gcreate (fid, "/g1", 0);
-    H5Glink (group, H5G_LINK_HARD, "/dset1", "dset2");
+    H5Glink (group, H5L_LINK_HARD, "/dset1", "dset2");
     H5Gclose(group);
 
     group = H5Gcreate (fid, "/g2", 0);
-    H5Glink (group, H5G_LINK_HARD, "/dset1", "dset3");
+    H5Glink (group, H5L_LINK_HARD, "/dset1", "dset3");
     H5Gclose(group);
 
     group = H5Gopen(fid, "/g1");
-    H5Glink (group, H5G_LINK_HARD, "/g2", "g1.1");
+    H5Glink (group, H5L_LINK_HARD, "/g2", "g1.1");
     H5Gclose(group);
     H5Fclose(fid);
 }
 
+static void gent_extlink(void)
+{
+    hid_t fid;
+
+    /* This external link will dangle, but that's okay */
+    fid = H5Fcreate(FILE53, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+    H5Lcreate_external("filename", "objname", fid, "extlink1", H5P_DEFAULT, H5P_DEFAULT);
+    H5Lcreate_external("anotherfile", "anotherobj", fid, "extlink2", H5P_DEFAULT, H5P_DEFAULT);
+
+    H5Fclose(fid);
+}
+
+static void gent_udlink(void)
+{
+    hid_t fid;
+    char buf[4];
+
+    H5Lregister(UD_link_class);
+
+    /* This ud link will dangle, but that's okay */
+    fid = H5Fcreate(FILE54, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+    H5Lcreate_ud(fid, "udlink1", MY_LINKCLASS, NULL, 0, H5P_DEFAULT, H5P_DEFAULT);
+    strcpy(buf, "foo");
+    H5Lcreate_ud(fid, "udlink2", MY_LINKCLASS, buf, 4, H5P_DEFAULT, H5P_DEFAULT);
+
+    H5Fclose(fid);
+}
+
+
 /*
                /
      /     |       \     \
@@ -830,9 +881,9 @@ static void gent_compound_dt2(void) {       /* test compound data type */
 / : g1  g2  attr1  attr2
 g1 : g1.1  g1.2
 g1.1 : dset1.1.1(attr1, attr2)   dset1.1.2
-g1.2 : g1.2.1
+g1.2 : g1.2.1 extlink
 g1.2.1 : slink
-g2 : dset2.1  dset2.2
+g2 : dset2.1  dset2.2 udlink
 
 */
 
@@ -926,9 +977,12 @@ float dset2_1[10], dset2_2[3][5];
 
   H5Gclose(group);
 
+  /* external link */
+  H5Lcreate_external("somefile", "somepath", fid, "/g1/g1.2/extlink", H5P_DEFAULT, H5P_DEFAULT);
+
   /* soft link */
   group = H5Gopen (fid, "/g1/g1.2/g1.2.1");
-  H5Glink (group, H5G_LINK_SOFT, "somevalue", "slink");
+  H5Glink (group, H5L_LINK_SOFT, "somevalue", "slink");
   H5Gclose(group);
 
   group = H5Gopen (fid, "/g2");
@@ -956,6 +1010,10 @@ float dset2_1[10], dset2_2[3][5];
 
   H5Gclose(group);
 
+  /* user-defined link */
+  H5Lregister(UD_link_class);
+  H5Lcreate_ud(fid, "/g2/udlink", MY_LINKCLASS, NULL, 0, H5P_DEFAULT, H5P_DEFAULT);
+
   H5Fclose(fid);
 
 }
@@ -981,8 +1039,8 @@ hid_t fid, group;
   group = H5Gcreate (fid, "/g2", 0);
   H5Gclose(group);
 
-  H5Glink(fid, H5G_LINK_HARD, "/g2", "/g1/g1.1");
-  H5Glink(fid, H5G_LINK_HARD, "/g1", "/g2/g2.1");
+  H5Glink(fid, H5L_LINK_HARD, "/g2", "/g1/g1.1");
+  H5Glink(fid, H5L_LINK_HARD, "/g1", "/g2/g2.1");
 
   H5Fclose(fid);
 }
@@ -1001,10 +1059,10 @@ hid_t fid, group;
   H5Gclose(group);
 
   /* create path from object at /g1 to object at /g2 and name it g1.1 */
-  H5Glink (fid, H5G_LINK_HARD, "/g2", "/g1/g1.1");
+  H5Glink (fid, H5L_LINK_HARD, "/g2", "/g1/g1.1");
 
   /* create path from object at /g2 to object at /g1 and name it g2.1 */
-  H5Glink (fid, H5G_LINK_SOFT, "/g1", "/g2/g2.1");
+  H5Glink (fid, H5L_LINK_SOFT, "/g1", "/g2/g2.1");
 
   H5Fclose(fid);
 
@@ -1012,13 +1070,13 @@ hid_t fid, group;
 
 /*
                   /
-     |       |       |   \    \    \
-     g1     g2      g3   g4   g5    g6
-    / \      |       |    \     \    \
- g1.1 g1.2 slink2  link3 dset2 slink4 dset3
-  |    |    (g1)  (dset2)      (dset3)
- dset1 link1
-      (dset1)
+     |       |       |   \    \    \     \      \
+     g1     g2      g3   g4   g5    g6    g7     g8
+    / \      |       |    \     \    \      \      \
+ g1.1 g1.2 slink2  link3 dset2 slink4 dset3 slink5   elink
+  |    |    (g1)  (dset2)      (dset3)      (elink)  udlink
+ dset1 link1                                slink6
+      (dset1)                               (udlink)
 */
 
 static void gent_many(void) {
@@ -1043,6 +1101,7 @@ static void gent_many(void) {
     hsize_t dim[4];
     int idx[4] = {0,1,2,3};  /* normal indicies */
     const int perm[4] = {0,1,2,3};  /* the 0'th and the 3'rd indices are permuted */
+    herr_t ret;
 
   fid = H5Fcreate(FILE12, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
 
@@ -1150,11 +1209,11 @@ static void gent_many(void) {
   H5Gclose(group);
 
   group = H5Gcreate (fid, "/g1/g1.2", 0);
-  H5Glink (group, H5G_LINK_HARD, "/g1/g1.1/dset1", "link1");
+  H5Glink (group, H5L_LINK_HARD, "/g1/g1.1/dset1", "link1");
   H5Gclose(group);
 
   group = H5Gcreate (fid, "/g2", 0);
-  H5Glink (group, H5G_LINK_SOFT, "/g1", "slink2");
+  H5Glink (group, H5L_LINK_SOFT, "/g1", "slink2");
   H5Gclose(group);
 
   group = H5Gcreate (fid, "/g3", 0);
@@ -1178,7 +1237,7 @@ static void gent_many(void) {
   H5Gclose(group);
 
   group = H5Gopen(fid, "/g3");
-  H5Glink (group, H5G_LINK_HARD, "/g4/dset2", "link3");
+  H5Glink (group, H5L_LINK_HARD, "/g4/dset2", "link3");
   H5Gclose(group);
 
   group = H5Gcreate (fid, "/g5", 0);
@@ -1201,10 +1260,26 @@ static void gent_many(void) {
   H5Gclose(group);
 
   group = H5Gopen(fid, "/g5");
-  H5Glink (group, H5G_LINK_SOFT, "/g6/dset3", "slink4");
+  H5Glink (group, H5L_LINK_SOFT, "/g6/dset3", "slink4");
   H5Gclose(group);
   H5Pclose(create_plist);
 
+  group = H5Gcreate (fid, "/g7", 0);
+  H5Gclose(group);
+  group = H5Gcreate (fid, "/g8", 0);
+  H5Gclose(group);
+
+  /* Create dangling external and UD links */
+  H5Lcreate_external("somefile", "somepath", fid, "/g8/elink", H5P_DEFAULT, H5P_DEFAULT);
+  H5Lregister(UD_link_class);
+  H5Lcreate_ud(fid, "/g8/udlink", MY_LINKCLASS, NULL, 0, H5P_DEFAULT, H5P_DEFAULT);
+
+  /* Create links to external and UD links */
+  ret= H5Glink (fid, H5L_LINK_SOFT, "/g8/elink", "/g7/slink5");
+  HDassert(ret >= 0);
+  ret= H5Glink (fid, H5L_LINK_SOFT, "/g8/udlink", "/g7/slink6");
+  HDassert(ret >= 0);
+
   H5Fclose(fid);
 
 }
@@ -4927,42 +5002,48 @@ static void gent_fcontents(void)
 
  /* hard link to "dset" */
  gid1 = H5Gcreate (fid, "/g1", 0);
- H5Glink (gid1, H5G_LINK_HARD, "/dset", "dset1");
+ H5Glink (gid1, H5L_LINK_HARD, "/dset", "dset1");
  H5Gclose(gid1);
 
 
  /* hard link to "dset" */
  gid1 = H5Gcreate (fid, "/g2", 0);
- H5Glink (gid1, H5G_LINK_HARD, "/dset", "dset2");
+ H5Glink (gid1, H5L_LINK_HARD, "/dset", "dset2");
  H5Gclose(gid1);
 
 
  /* hard link to "g2" */
  gid1 = H5Gopen(fid, "/g1");
- H5Glink (gid1, H5G_LINK_HARD, "/g2", "g1.1");
+ H5Glink (gid1, H5L_LINK_HARD, "/g2", "g1.1");
  H5Gclose(gid1);
 
 
  /* hard link to "dset" */
- ret=H5Glink (fid, H5G_LINK_HARD, "/dset", "dset3");
+ ret=H5Glink (fid, H5L_LINK_HARD, "/dset", "dset3");
  assert(ret>=0);
 
 
  /* hard link to "dset" */
- ret=H5Glink (fid, H5G_LINK_HARD, "/dset", "dset4");
+ ret=H5Glink (fid, H5L_LINK_HARD, "/dset", "dset4");
  assert(ret>=0);
 
 
  /* soft link to itself */
- ret=H5Glink (fid, H5G_LINK_SOFT, "mylink", "mylink");
+ ret=H5Glink (fid, H5L_LINK_SOFT, "mylink", "mylink");
  assert(ret>=0);
 
 
  /* soft link to "dset" */
- ret=H5Glink (fid, H5G_LINK_SOFT, "/dset", "softlink");
+ ret=H5Glink (fid, H5L_LINK_SOFT, "/dset", "softlink");
  assert(ret>=0);
 
+ /* dangling external link */
+ ret=H5Lcreate_external("fname", "oname", fid, "extlink", H5P_DEFAULT, H5P_DEFAULT);
+ assert(ret>=0);
 
+ /* dangling udlink */
+ ret=H5Lcreate_ud(fid, "udlink", MY_LINKCLASS, NULL, 0, H5P_DEFAULT, H5P_DEFAULT);
+ assert(ret>=0);
 
 /*-------------------------------------------------------------------------
  * datatypes
@@ -5397,11 +5478,11 @@ static void gent_longlinks(void)
     objname[F51_MAX_NAME_LEN] = '\0';
 
     /* Create hard link to existing object */
-    assert(H5Glink2(fid, "grp1", H5G_LINK_HARD, fid, objname) >= 0);
+    assert(H5Lcreate_hard(fid, "grp1", fid, objname, H5P_DEFAULT) >= 0);
 
     /* Create soft link to existing object */
     objname[0] = 'b';
-    assert(H5Glink2(fid, "grp1", H5G_LINK_SOFT, fid, objname) >= 0);
+    assert(H5Lcreate_soft("grp1", fid, objname, H5P_DEFAULT) >= 0);
 
     /* Create group with long name in existing group */
     gid2=H5Gcreate(gid, objname, (size_t)0);
@@ -5444,7 +5525,7 @@ static int gent_ldouble(void)
  if ((tid = H5Tcopy(H5T_NATIVE_LDOUBLE))<0)
   goto error;
 
- if ((size = H5Tget_size(tid))<0)
+ if ((size = H5Tget_size(tid))==0)
   goto error;
 
  if ((did = H5Dcreate(fid, "dset", tid, sid, H5P_DEFAULT))<0)
@@ -5483,6 +5564,8 @@ int main(void)
     gent_softlink();
     gent_dataset();
     gent_hardlink();
+    gent_extlink();
+    gent_udlink();
     gent_compound_dt();
     gent_all();
     gent_loop();
diff --git a/tools/h5dump/testh5dump.sh.in b/tools/h5dump/testh5dump.sh.in
index 783634c..3f40976 100644
--- a/tools/h5dump/testh5dump.sh.in
+++ b/tools/h5dump/testh5dump.sh.in
@@ -125,10 +125,12 @@ TOOLTEST tattr-3.ddl --header -a /attr2 --attribute=/attr tattr.h5
 # test for displaying attributes in shared datatype (also in group and dataset)
 TOOLTEST tnamed_dtype_attr.ddl tnamed_dtype_attr.h5
 
-# test for displaying soft links
+# test for displaying soft links and user-defined links
 TOOLTEST tslink-1.ddl tslink.h5
+TOOLTEST tudlink-1.ddl tudlink.h5
 # test for displaying the selected link
 TOOLTEST tslink-2.ddl -l slink2 tslink.h5
+TOOLTEST tudlink-2.ddl -l udlink2 tudlink.h5
 
 # tests for hard links
 TOOLTEST thlink-1.ddl thlink.h5
diff --git a/tools/h5dump/testh5dumpxml.sh.in b/tools/h5dump/testh5dumpxml.sh.in
index 21db71a..490832e 100755
--- a/tools/h5dump/testh5dumpxml.sh.in
+++ b/tools/h5dump/testh5dumpxml.sh.in
@@ -118,6 +118,8 @@ TOOLTEST tcompound_complex.h5.xml --xml tcompound_complex.h5
 TOOLTEST tobjref.h5.xml --xml tobjref.h5
 TOOLTEST topaque.h5.xml --xml topaque.h5
 TOOLTEST tslink.h5.xml --xml tslink.h5
+TOOLTEST tudlink.h5.xml --xml tudlink.h5
+TOOLTEST textlink.h5.xml --xml textlink.h5
 TOOLTEST tstr.h5.xml --xml tstr.h5
 TOOLTEST tstr2.h5.xml --xml tstr2.h5
 TOOLTEST tref.h5.xml --xml tref.h5
diff --git a/tools/h5jam/h5jam.c b/tools/h5jam/h5jam.c
index 5e4d885..afa9ffa 100644
--- a/tools/h5jam/h5jam.c
+++ b/tools/h5jam/h5jam.c
@@ -15,7 +15,6 @@
 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/stat.h>
-
 #ifdef H5_HAVE_UNISTD_H
 #include <unistd.h>
 #endif
diff --git a/tools/h5jam/h5jamgentest.c b/tools/h5jam/h5jamgentest.c
index a3a99ca..dd80c29 100644
--- a/tools/h5jam/h5jamgentest.c
+++ b/tools/h5jam/h5jamgentest.c
@@ -65,6 +65,8 @@ char pattern[11] = "abcdefghij";
  */
 
 
+#define BUF_SIZE 1024
+
 #define LENSTR  50
 #define LENSTR2  11
 
@@ -118,158 +120,63 @@ typedef struct s1_t {
 /* VL string datatype name */
 #define VLSTR_TYPE      "vl_string_type"
 
+/* A UD link traversal function.  Shouldn't actually be called. */
+static hid_t UD_traverse(const char * link_name, hid_t cur_group, void * udata, size_t udata_size, hid_t lapl_id)
+{
+return -1;
+}
+#define MY_LINKCLASS 187
+const H5L_link_class_t UD_link_class[1] = {{
+    H5L_LINK_CLASS_T_VERS,    /* H5L_link_class_t version       */
+    MY_LINKCLASS,             /* Link type id number            */
+    "UD link class",          /* name for debugging             */
+    NULL,                     /* Creation callback              */
+    NULL,                     /* Move/rename callback           */
+    UD_traverse,              /* The actual traversal function  */
+    NULL,                     /* Deletion callback              */
+    NULL                      /* Query callback                 */
+}};
+
 
-/*
+
+/* gent_ub
+    with no ub, identical to gent_all from h5dumpgentest.c
+
+    FILENAME is the name of the file to create
+    UB_SIZE is the size the buffer should be
+    UB_FILL characters will be set to the PATTERN array,
+        the rest of the user block will be NULL.
 
 / : g1  g2  attr1  attr2
 g1 : g1.1  g1.2
 g1.1 : dset1.1.1(attr1, attr2)   dset1.1.2
-g1.2 : g1.2.1
+g1.2 : g1.2.1 extlink
 g1.2.1 : slink
-g2 : dset2.1  dset2.2
+g2 : dset2.1  dset2.2 udlink
 
 */
 
-
-static void gent_all(void) {
-hid_t fid, group, attr, dataset, space;
-hsize_t dims[2];
-int data[2][2], dset1[10][10], dset2[20];
-char buf[60];
-int i, j;
-float dset2_1[10], dset2_2[3][5];
-
-  fid = H5Fcreate(FILE7, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
-
-  /* create groups */
-  group = H5Gcreate (fid, "/g1", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g2", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g1/g1.1", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g1/g1.2", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g1/g1.2/g1.2.1", 0);
-  H5Gclose(group);
-
-  /* root attributes */
-  group = H5Gopen (fid, "/");
-
-  dims[0] = 10;
-  space = H5Screate_simple(1, dims, NULL);
-  attr = H5Acreate (group, "attr1", H5T_STD_I8BE, space, H5P_DEFAULT);
-  sprintf(buf, "abcdefghi");
-  H5Awrite(attr, H5T_NATIVE_SCHAR, buf);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  dims[0] = 2; dims[1] = 2;
-  space = H5Screate_simple(2, dims, NULL);
-  attr = H5Acreate (group, "attr2", H5T_STD_I32BE, space, H5P_DEFAULT);
-  data[0][0] = 0; data[0][1] = 1; data[1][0] = 2; data[1][1] = 3;
-  H5Awrite(attr, H5T_NATIVE_INT, data);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  H5Gclose(group);
-
-  group = H5Gopen (fid, "/g1/g1.1");
-
-  /* dset1.1.1 */
-  dims[0] = 10; dims[1] = 10;
-  space = H5Screate_simple(2, dims, NULL);
-  dataset = H5Dcreate(group, "dset1.1.1", H5T_STD_I32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 10; i++)
-       for (j = 0; j < 10; j++)
-            dset1[i][j] = j*i;
-  H5Dwrite(dataset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset1);
-  H5Sclose(space);
-
-  /* attributes of dset1.1.1 */
-  dims[0] = 27;
-  space = H5Screate_simple(1, dims, NULL);
-  attr = H5Acreate (dataset, "attr1", H5T_STD_I8BE, space, H5P_DEFAULT);
-  sprintf(buf, "1st attribute of dset1.1.1");
-  H5Awrite(attr, H5T_NATIVE_SCHAR, buf);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  dims[0] = 27;
-  space = H5Screate_simple(1, dims, NULL);
-  attr = H5Acreate (dataset, "attr2", H5T_STD_I8BE, space, H5P_DEFAULT);
-  sprintf(buf, "2nd attribute of dset1.1.1");
-  H5Awrite(attr, H5T_NATIVE_SCHAR, buf);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  H5Dclose(dataset);
-
-  /* dset1.1.2 */
-  dims[0] = 20;
-  space = H5Screate_simple(1, dims, NULL);
-  dataset = H5Dcreate(group, "dset1.1.2", H5T_STD_I32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 20; i++)
-       dset2[i] = i;
-  H5Dwrite(dataset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset2);
-  H5Sclose(space);
-  H5Dclose(dataset);
-
-  H5Gclose(group);
-
-  /* soft link */
-  group = H5Gopen (fid, "/g1/g1.2/g1.2.1");
-  H5Glink (group, H5G_LINK_SOFT, "somevalue", "slink");
-  H5Gclose(group);
-
-  group = H5Gopen (fid, "/g2");
-
-  /* dset2.1 */
-  dims[0] = 10;
-  space = H5Screate_simple(1, dims, NULL);
-  dataset = H5Dcreate(group, "dset2.1", H5T_IEEE_F32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 10; i++)
-       dset2_1[i] = (float)(i*0.1+1);
-  H5Dwrite(dataset, H5T_NATIVE_FLOAT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset2_1);
-  H5Sclose(space);
-  H5Dclose(dataset);
-
-  /* dset2.2 */
-  dims[0] = 3; dims[1] = 5;
-  space = H5Screate_simple(2, dims, NULL);
-  dataset = H5Dcreate(group, "dset2.2", H5T_IEEE_F32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 3; i++)
-       for (j = 0; j < 5; j++)
-            dset2_2[i][j] = (float)((i+1)*j*0.1);
-  H5Dwrite(dataset, H5T_NATIVE_FLOAT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset2_2);
-  H5Sclose(space);
-  H5Dclose(dataset);
-
-  H5Gclose(group);
-
-  H5Fclose(fid);
-
-}
-
-static void gent_withub(void) {
+static void gent_ub(const char * filename, int ub_size, int ub_fill) {
 hid_t fid, group, attr, dataset, space;
 hid_t create_plist;
 hsize_t dims[2];
 int data[2][2], dset1[10][10], dset2[20];
-char buf[512];
+char buf[BUF_SIZE];
 int i, j;
-unsigned u;
 float dset2_1[10], dset2_2[3][5];
 int fd;
 char *bp;
 
-  create_plist = H5Pcreate(H5P_FILE_CREATE);
-  H5Pset_userblock(create_plist,(hsize_t)512);
-  fid = H5Fcreate(FILE8, H5F_ACC_TRUNC, create_plist, H5P_DEFAULT);
+  if(ub_size > 0)
+  {
+      create_plist = H5Pcreate(H5P_FILE_CREATE);
+      H5Pset_userblock(create_plist,(hsize_t)ub_size);
+      fid = H5Fcreate(filename, H5F_ACC_TRUNC, create_plist, H5P_DEFAULT);
+  }
+  else
+  {
+      fid = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+  }
 
   /* create groups */
   group = H5Gcreate (fid, "/g1", 0);
@@ -351,153 +258,12 @@ char *bp;
 
   H5Gclose(group);
 
-  /* soft link */
-  group = H5Gopen (fid, "/g1/g1.2/g1.2.1");
-  H5Glink (group, H5G_LINK_SOFT, "somevalue", "slink");
-  H5Gclose(group);
-
-  group = H5Gopen (fid, "/g2");
-
-  /* dset2.1 */
-  dims[0] = 10;
-  space = H5Screate_simple(1, dims, NULL);
-  dataset = H5Dcreate(group, "dset2.1", H5T_IEEE_F32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 10; i++)
-       dset2_1[i] = (float)(i*0.1+1);
-  H5Dwrite(dataset, H5T_NATIVE_FLOAT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset2_1);
-  H5Sclose(space);
-  H5Dclose(dataset);
-
-  /* dset2.2 */
-  dims[0] = 3; dims[1] = 5;
-  space = H5Screate_simple(2, dims, NULL);
-  dataset = H5Dcreate(group, "dset2.2", H5T_IEEE_F32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 3; i++)
-       for (j = 0; j < 5; j++)
-            dset2_2[i][j] = (float)((i+1)*j*0.1);
-  H5Dwrite(dataset, H5T_NATIVE_FLOAT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset2_2);
-  H5Sclose(space);
-  H5Dclose(dataset);
-
-  H5Gclose(group);
-
-  H5Fclose(fid);
-
-
-	fd = HDopen(FILE8,O_RDWR, 0);
-	if (fd < 0) {
-		/* panic */
-	}
-	/* fill buf with pattern */
-	memset(buf,'\0',512);
-	bp = buf;
-	for (u = 0; u < strlen(pattern); u++) {
-		*bp++ = pattern[u%10];
-	}
-
-	HDwrite(fd,buf,512);
-
-	close(fd);
-}
-
-static void gent_withub513(void) {
-hid_t fid, group, attr, dataset, space;
-hid_t create_plist;
-hsize_t dims[2];
-int data[2][2], dset1[10][10], dset2[20];
-char buf[1023];
-int i, j;
-float dset2_1[10], dset2_2[3][5];
-int fd;
-char *bp;
-
-  create_plist = H5Pcreate(H5P_FILE_CREATE);
-  H5Pset_userblock(create_plist,(hsize_t)1024);
-  fid = H5Fcreate(FILE9, H5F_ACC_TRUNC, create_plist, H5P_DEFAULT);
-
-  /* create groups */
-  group = H5Gcreate (fid, "/g1", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g2", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g1/g1.1", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g1/g1.2", 0);
-  H5Gclose(group);
-
-  group = H5Gcreate (fid, "/g1/g1.2/g1.2.1", 0);
-  H5Gclose(group);
-
-  /* root attributes */
-  group = H5Gopen (fid, "/");
-
-  dims[0] = 10;
-  space = H5Screate_simple(1, dims, NULL);
-  attr = H5Acreate (group, "attr1", H5T_STD_I8BE, space, H5P_DEFAULT);
-  sprintf(buf, "abcdefghi");
-  H5Awrite(attr, H5T_NATIVE_SCHAR, buf);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  dims[0] = 2; dims[1] = 2;
-  space = H5Screate_simple(2, dims, NULL);
-  attr = H5Acreate (group, "attr2", H5T_STD_I32BE, space, H5P_DEFAULT);
-  data[0][0] = 0; data[0][1] = 1; data[1][0] = 2; data[1][1] = 3;
-  H5Awrite(attr, H5T_NATIVE_INT, data);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  H5Gclose(group);
-
-  group = H5Gopen (fid, "/g1/g1.1");
-
-  /* dset1.1.1 */
-  dims[0] = 10; dims[1] = 10;
-  space = H5Screate_simple(2, dims, NULL);
-  dataset = H5Dcreate(group, "dset1.1.1", H5T_STD_I32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 10; i++)
-       for (j = 0; j < 10; j++)
-            dset1[i][j] = j*i;
-  H5Dwrite(dataset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset1);
-  H5Sclose(space);
-
-  /* attributes of dset1.1.1 */
-  dims[0] = 27;
-  space = H5Screate_simple(1, dims, NULL);
-  attr = H5Acreate (dataset, "attr1", H5T_STD_I8BE, space, H5P_DEFAULT);
-  sprintf(buf, "1st attribute of dset1.1.1");
-  H5Awrite(attr, H5T_NATIVE_SCHAR, buf);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  dims[0] = 27;
-  space = H5Screate_simple(1, dims, NULL);
-  attr = H5Acreate (dataset, "attr2", H5T_STD_I8BE, space, H5P_DEFAULT);
-  sprintf(buf, "2nd attribute of dset1.1.1");
-  H5Awrite(attr, H5T_NATIVE_SCHAR, buf);
-  H5Sclose(space);
-  H5Aclose(attr);
-
-  H5Dclose(dataset);
-
-  /* dset1.1.2 */
-  dims[0] = 20;
-  space = H5Screate_simple(1, dims, NULL);
-  dataset = H5Dcreate(group, "dset1.1.2", H5T_STD_I32BE, space, H5P_DEFAULT);
-  for (i = 0; i < 20; i++)
-       dset2[i] = i;
-  H5Dwrite(dataset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset2);
-  H5Sclose(space);
-  H5Dclose(dataset);
-
-  H5Gclose(group);
+  /* external link */
+  H5Lcreate_external("somefile", "somepath", fid, "/g1/g1.2/extlink", H5P_DEFAULT, H5P_DEFAULT);
 
   /* soft link */
   group = H5Gopen (fid, "/g1/g1.2/g1.2.1");
-  H5Glink (group, H5G_LINK_SOFT, "somevalue", "slink");
+  H5Glink (group, H5L_LINK_SOFT, "somevalue", "slink");
   H5Gclose(group);
 
   group = H5Gopen (fid, "/g2");
@@ -525,23 +291,32 @@ char *bp;
 
   H5Gclose(group);
 
+  /* user-defined link */
+  H5Lregister(UD_link_class);
+  H5Lcreate_ud(fid, "/g2/udlink", MY_LINKCLASS, NULL, 0, H5P_DEFAULT, H5P_DEFAULT);
+
   H5Fclose(fid);
 
+  /* If a user block is being used, write to it here */
+  if(ub_size > 0)
+  {
+        HDassert(ub_size < BUF_SIZE);
 
-	fd = HDopen(FILE9,O_RDWR, 0);
+	fd = HDopen(filename,O_RDWR, 0);
 	if (fd < 0) {
 		/* panic */
 	}
 	/* fill buf with pattern */
-	memset(buf,'\0',1024);
+	memset(buf,'\0',ub_size);
 	bp = buf;
-	for (i = 0; i < 513; i++) {
+	for (i = 0; i < ub_fill; i++) {
 		*bp++ = pattern[i%10];
 	}
 
-	HDwrite(fd,buf,1024);
+	HDwrite(fd,buf,ub_size);
 
 	close(fd);
+  }
 }
 
 static void
@@ -636,9 +411,9 @@ create_binfile(UBBIN4,512);
 create_binfile(UBBIN5,513);
 
 */
-    gent_all();
-    gent_withub();
-    gent_withub513();
+    gent_ub(FILE7, 0, 0);
+    gent_ub(FILE8, 512, strlen(pattern));
+    gent_ub(FILE9, 1024, 513);
 
     return 0;
 }
diff --git a/tools/h5ls/h5ls.c b/tools/h5ls/h5ls.c
index d279ea3..9a51ce2 100644
--- a/tools/h5ls/h5ls.c
+++ b/tools/h5ls/h5ls.c
@@ -1710,7 +1710,7 @@ datatype_list2(hid_t type, const char UNUSED *name)
 
 
 /*-------------------------------------------------------------------------
- * Function: link_open
+ * Function: slink_open
  *
  * Purpose: This gets called to open a symbolic link.  Since symbolic
  *  links don't correspond to actual objects we simply print the
@@ -1729,11 +1729,11 @@ datatype_list2(hid_t type, const char UNUSED *name)
  *-------------------------------------------------------------------------
  */
 static hid_t
-link_open(hid_t location, const char *name)
+slink_open(hid_t location, const char *name)
 {
     char buf[64];
 
-    if (H5Gget_linkval (location, name, sizeof(buf), buf)<0) return -1;
+    if (H5Lget_linkval (location, name, sizeof(buf), buf, H5P_DEFAULT)<0) return -1;
     if (NULL==HDmemchr(buf, 0, sizeof(buf))) {
  strcpy(buf+sizeof(buf)-4, "...");
     }
@@ -1741,6 +1741,59 @@ link_open(hid_t location, const char *name)
 
     return 0;
 }
+/*-------------------------------------------------------------------------
+ * Function: udlink_open
+ *
+ * Purpose: This gets called to open a user-defined link.  Since these
+ *  links don't correspond to actual objects we simply print a message
+ *  and return failure.
+ *
+ * Return: Success: 0 - an invalid object but successful return
+ *    of this function.
+ *
+ *  Failure: -1
+ *
+ * Programmer: James Laird
+ *              Tuesday, June 6, 2006
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static hid_t
+udlink_open(hid_t location, const char *name)
+{
+    H5L_linkinfo_t linfo;
+    char * buf = NULL;
+    char * filename = NULL;
+    char * path = NULL;
+
+    if(H5Lget_linkinfo(location, name, &linfo, H5P_DEFAULT) < 0) return -1;
+
+    switch(linfo.linkclass)
+    {
+      /* For external links, try to display info for the object it points to */
+      case H5L_LINK_EXTERNAL:
+        if ((buf = HDmalloc(linfo.u.link_size))==NULL) goto error;
+        if (H5Lget_linkval (location, name, sizeof(buf), buf, H5P_DEFAULT)<0) goto error;
+
+        if(H5Lunpack_elink_val(buf, &filename, &path) < 0) goto error;
+        fputs("file: ", stdout);
+        fputs(filename, stdout);
+        fputs("    path: ", stdout);
+        fputs(path, stdout);
+        break;
+
+      default:
+        fputs("cannot follow UD links", stdout);
+    }
+    return 0;
+
+error:
+    if(buf)
+      HDfree(buf);
+    return -1;
+}
 
 
 /*-------------------------------------------------------------------------
@@ -1828,7 +1881,7 @@ list (hid_t group, const char *name, void *_iter)
 
     /* Show detailed information about the object, beginning with information
      * which is common to all objects. */
-    if (verbose_g>0 && H5G_LINK!=sb.type) {
+    if (verbose_g>0 && H5G_LINK!=sb.type && H5G_UDLINK!=sb.type) {
         if (sb.type>=0)
             H5Aiterate(obj, NULL, list_attr, NULL);
         printf("    %-10s %lu:"H5_PRINTF_HADDR_FMT"\n", "Location:", sb.fileno[0], objno);
@@ -2063,7 +2116,9 @@ main (int argc, const char *argv[])
       NULL, group_list2);
     DISPATCH(H5G_TYPE, "Type", H5Topen, H5Tclose,
       NULL, datatype_list2);
-    DISPATCH(H5G_LINK, "-> ", link_open, NULL,
+    DISPATCH(H5G_LINK, "-> ", slink_open, NULL,
+      NULL, NULL);
+    DISPATCH(H5G_UDLINK, "-> ", udlink_open, NULL,
       NULL, NULL);
 
 #if 0
diff --git a/tools/h5ls/testh5ls.sh b/tools/h5ls/testh5ls.sh
index 37581f7..c9aa901 100755
--- a/tools/h5ls/testh5ls.sh
+++ b/tools/h5ls/testh5ls.sh
@@ -118,6 +118,10 @@ TOOLTEST tdset-1.ls -w80 -r -d tdset.h5
 # test for displaying soft links
 TOOLTEST tslink-1.ls -w80 -r tslink.h5
 
+# test for displaying external and user-defined links
+TOOLTEST textlink-1.ls -w80 -r textlink.h5
+TOOLTEST tudlink-1.ls -w80 -r tudlink.h5
+
 # tests for hard links
 TOOLTEST thlink-1.ls -w80 thlink.h5
 
diff --git a/tools/h5repack/h5repack_copy.c b/tools/h5repack/h5repack_copy.c
index dee6c3f..e59b6d0 100644
--- a/tools/h5repack/h5repack_copy.c
+++ b/tools/h5repack/h5repack_copy.c
@@ -264,17 +264,17 @@ int do_copy_objects(hid_t fidin,
                     trav_table_t *travt,
                     pack_opt_t *options) /* repack options */
 {
- hid_t     grp_in;       /* group ID */
- hid_t     grp_out;      /* group ID */
- hid_t     dset_in;      /* read dataset ID */
- hid_t     dset_out;     /* write dataset ID */
- hid_t     type_in;      /* named type ID */
- hid_t     type_out;     /* named type ID */
- hid_t     dcpl_id;      /* dataset creation property list ID */
- hid_t     dcpl_out;     /* dataset creation property list ID */
- hid_t     space_id;     /* space ID */
- hid_t     ftype_id;     /* file data type ID */
- hid_t     mtype_id;     /* memory data type ID */
+ hid_t     grp_in=-1;       /* group ID */
+ hid_t     grp_out=-1;      /* group ID */
+ hid_t     dset_in=-1;      /* read dataset ID */
+ hid_t     dset_out=-1;     /* write dataset ID */
+ hid_t     type_in=-1;      /* named type ID */
+ hid_t     type_out=-1;     /* named type ID */
+ hid_t     dcpl_id=-1;      /* dataset creation property list ID */
+ hid_t     dcpl_out=-1;     /* dataset creation property list ID */
+ hid_t     space_id=-1;     /* space ID */
+ hid_t     ftype_id=-1;     /* file data type ID */
+ hid_t     mtype_id=-1;     /* memory data type ID */
  size_t    msize;        /* memory size of memory type */
  void      *buf=NULL;    /* data buffer */
  hsize_t   nelmts;       /* number of elements in dataset */
@@ -561,30 +561,18 @@ int do_copy_objects(hid_t fidin,
 
 /*-------------------------------------------------------------------------
  * H5G_LINK
+ * H5G_UDLINK
+ *
+ * Only handles external links; H5Lcopy will fail for other UD link types
+ * since we don't have creation or copy callbacks for them.
  *-------------------------------------------------------------------------
  */
 
   case H5G_LINK:
+  case H5G_UDLINK:
    {
-    H5G_stat_t  statbuf;
-    char        *targbuf=NULL;
-
-    if (H5Gget_objinfo(fidin,travt->objs[i].name,FALSE,&statbuf)<0)
-     goto error;
-
-    targbuf = malloc(statbuf.linklen);
-
-    if (H5Gget_linkval(fidin,travt->objs[i].name,statbuf.linklen,targbuf)<0)
-     goto error;
-
-    if (H5Glink(fidout,
-     H5G_LINK_SOFT,
-     targbuf,        /* current name of object */
-     travt->objs[i].name   /* new name of object */
-     )<0)
-     goto error;
-
-    free(targbuf);
+    if(H5Lcopy(fidin, travt->objs[i].name,fidout, travt->objs[i].name, H5P_DEFAULT, H5P_DEFAULT) < 0)
+        goto error;
 
     if (options->verbose)
      printf(FORMAT_OBJ,"link",travt->objs[i].name );
@@ -592,6 +580,14 @@ int do_copy_objects(hid_t fidin,
    }
    break;
 
+/*-------------------------------------------------------------------------
+ *-------------------------------------------------------------------------
+ */
+  {
+
+  }
+  break;
+
   default:
    goto error;
   }
diff --git a/tools/h5repack/h5repack_list.c b/tools/h5repack/h5repack_list.c
index 05156d4..5622811 100644
--- a/tools/h5repack/h5repack_list.c
+++ b/tools/h5repack/h5repack_list.c
@@ -198,6 +198,9 @@ void print_objlist(const char *filename,
   case H5G_LINK:
    printf(" %-10s %s\n", "link", info[i].name );
    break;
+  case H5G_UDLINK:
+   printf(" %-10s %s\n", "User defined link", info[i].name );
+   break;
   default:
    printf(" %-10s %s\n", "User defined object", info[i].name );
    break;
diff --git a/tools/h5repack/h5repack_refs.c b/tools/h5repack/h5repack_refs.c
index 6e3156b..4884e04 100644
--- a/tools/h5repack/h5repack_refs.c
+++ b/tools/h5repack/h5repack_refs.c
@@ -93,7 +93,7 @@ int do_copy_refobjs(hid_t fidin,
     for ( j=0; j<travt->objs[i].nlinks; j++)
     {
       H5Glink(fidout,
-      H5G_LINK_HARD,
+      H5L_LINK_HARD,
       travt->objs[i].name,
       travt->objs[i].links[j].new_name);
     }
@@ -339,7 +339,7 @@ int do_copy_refobjs(hid_t fidin,
    {
     for ( j=0; j<travt->objs[i].nlinks; j++){
      H5Glink(fidout,
-      H5G_LINK_HARD,
+      H5L_LINK_HARD,
       travt->objs[i].name,
       travt->objs[i].links[j].new_name);
     }
@@ -384,10 +384,12 @@ int do_copy_refobjs(hid_t fidin,
 
   /*-------------------------------------------------------------------------
    * H5G_LINK
+   * H5G_UDLINK
    *-------------------------------------------------------------------------
    */
 
   case H5G_LINK:
+  case H5G_UDLINK:
 
    /*nothing to do */
    break;
diff --git a/tools/h5repack/testh5repack_dset.c b/tools/h5repack/testh5repack_dset.c
index c345028..ca0f0ca 100644
--- a/tools/h5repack/testh5repack_dset.c
+++ b/tools/h5repack/testh5repack_dset.c
@@ -128,7 +128,7 @@ void write_dset_in(hid_t loc_id,
 
 
  /* create hard link */
- status = H5Glink(loc_id, H5G_LINK_HARD, "string", "string_link");
+ status = H5Glink(loc_id, H5L_LINK_HARD, "string", "string_link");
 
 /*-------------------------------------------------------------------------
  * H5T_BITFIELD
diff --git a/tools/h5repack/testh5repack_main.c b/tools/h5repack/testh5repack_main.c
index 58a7c2a..5299cd4 100644
--- a/tools/h5repack/testh5repack_main.c
+++ b/tools/h5repack/testh5repack_main.c
@@ -1170,7 +1170,6 @@ if (szip_can_encode) {
  SKIPPED();
 #endif
 
-
 /*-------------------------------------------------------------------------
  * end
  *-------------------------------------------------------------------------
diff --git a/tools/h5repack/testh5repack_make.c b/tools/h5repack/testh5repack_make.c
index 43b68b1..a74d466 100644
--- a/tools/h5repack/testh5repack_make.c
+++ b/tools/h5repack/testh5repack_make.c
@@ -259,7 +259,14 @@ int make_all_objects(hid_t loc_id)
  *-------------------------------------------------------------------------
  */
 
- H5Glink(loc_id, H5G_LINK_SOFT, "dset", "link");
+ H5Glink(loc_id, H5L_LINK_SOFT, "dset", "link");
+
+/*-------------------------------------------------------------------------
+ * H5G_UDLINK
+ *-------------------------------------------------------------------------
+ */
+ /* Create an external link. Other UD links are not supported by h5repack */
+ H5Lcreate_external("file", "path", loc_id, "ext_link", H5P_DEFAULT, H5P_DEFAULT);
 
 /*-------------------------------------------------------------------------
  * write a series of datasetes
@@ -350,11 +357,11 @@ int make_hlinks(hid_t loc_id)
 
  if (write_dset(loc_id,2,dims,"dset",H5T_NATIVE_INT,buf)<0)
   return -1;
- if (H5Glink(loc_id, H5G_LINK_HARD, "dset", "link1 to dset")<0)
+ if (H5Glink(loc_id, H5L_LINK_HARD, "dset", "link1 to dset")<0)
   return -1;
- if (H5Glink(loc_id, H5G_LINK_HARD, "dset", "link2 to dset")<0)
+ if (H5Glink(loc_id, H5L_LINK_HARD, "dset", "link2 to dset")<0)
   return -1;
- if (H5Glink(loc_id, H5G_LINK_HARD, "dset", "link3 to dset")<0)
+ if (H5Glink(loc_id, H5L_LINK_HARD, "dset", "link3 to dset")<0)
   return -1;
 
 
@@ -370,9 +377,9 @@ int make_hlinks(hid_t loc_id)
  if ((group3_id = H5Gcreate(group2_id,"g3",0))<0)
   return -1;
 
- if (H5Glink2(loc_id, "g1", H5G_LINK_HARD, group2_id, "link1 to g1")<0)
+ if (H5Glink2(loc_id, "g1", H5L_LINK_HARD, group2_id, "link1 to g1")<0)
   return -1;
- if (H5Glink2(group1_id, "g2", H5G_LINK_HARD, group3_id, "link1 to g2")<0)
+ if (H5Glink2(group1_id, "g2", H5L_LINK_HARD, group3_id, "link1 to g2")<0)
   return -1;
 
  H5Gclose(group1_id);
diff --git a/tools/lib/h5diff.c b/tools/lib/h5diff.c
index e8c546e..4fed814 100644
--- a/tools/lib/h5diff.c
+++ b/tools/lib/h5diff.c
@@ -870,6 +870,7 @@ hsize_t diff_compare (hid_t file1_id,
  *  H5G_DATASET  Object is a dataset
  *  H5G_TYPE     Object is a named data type
  *  H5G_LINK     Object is a symbolic link
+ *  H5G_UDLINK   Object is a user-defined link
  *
  * Return: Number of differences found
  *
@@ -1067,6 +1068,90 @@ hsize_t diff (hid_t file1_id,
   }
   break;
 
+ /*-------------------------------------------------------------------------
+  * H5G_UDLINK
+  *-------------------------------------------------------------------------
+  */
+ case H5G_UDLINK:
+  {
+   char *buf1 = NULL;
+   char *buf2 = NULL;
+   H5L_linkinfo_t li1;
+   H5L_linkinfo_t li2;
+
+   if (H5Lget_linkinfo (file1_id, path1, &li1, H5P_DEFAULT) < 0)
+    goto out;
+   if (H5Lget_linkinfo (file1_id, path1, &li2, H5P_DEFAULT) < 0)
+    goto out;
+
+   /* Only external links will have a query function registered */
+   if(li1.linkclass == H5L_LINK_EXTERNAL && li2.linkclass == H5L_LINK_EXTERNAL)
+   {
+      buf1 = HDmalloc (li1.u.link_size);
+      buf2 = HDmalloc (li2.u.link_size);
+
+      if (H5Lget_linkval (file1_id, path1, li1.u.link_size, buf1, H5P_DEFAULT) < 0)
+      {
+        HDfree (buf1); HDfree (buf2);
+        goto out;
+      }
+      if (H5Lget_linkval (file2_id, path2, li2.u.link_size, buf2, H5P_DEFAULT) < 0)
+      {
+        HDfree (buf1); HDfree (buf2);
+        goto out;
+      }
+
+      /* If the buffers are the same size, compare them */
+      if(li1.u.link_size == li2.u.link_size)
+      {
+        if (H5Lget_linkval (file1_id, path1, li1.u.link_size, buf1, H5P_DEFAULT) < 0)
+        {
+          HDfree (buf1); HDfree (buf2);
+          goto out;
+        }
+        if (H5Lget_linkval (file2_id, path2, li2.u.link_size, buf2, H5P_DEFAULT) < 0)
+        {
+          HDfree (buf1); HDfree (buf2);
+          goto out;
+        }
+        ret = HDmemcmp (buf1, buf2, li1.u.link_size);
+      }
+      else
+        ret = 1;
+
+      /* if "buf1" != "buf2" then the links are "different" */
+      nfound = (ret != 0) ? 1 : 0;
+
+      if (print_objname (options, nfound))
+        parallel_print("External Link:        <%s> and <%s>\n", path1, path2);
+   }
+   else
+   {
+      /* If one or both of these links isn't an external link, we can only
+       * compare information from H5Lget_linkinfo since we don't have a query
+       * function registered for them. */
+
+      /* If the link classes or the buffer length are not the
+       * same, the links are "different"
+       */
+      if((li1.linkclass != li2.linkclass) || (li1.u.link_size != li2.u.link_size))
+        nfound = 1;
+      else
+        nfound = 0;
+
+      if (print_objname (options, nfound))
+        parallel_print("User-defined Link:        <%s> and <%s>\n", path1, path2);
+   }
+
+   /* always print the number of differences found in verbose mode */
+   if (options->m_verbose)
+    print_found(nfound);
+
+   HDfree (buf1);
+   HDfree (buf2);
+  }
+  break;
+
  default:
   nfound = 0;
   if (options->m_verbose)
diff --git a/tools/lib/h5diff_util.c b/tools/lib/h5diff_util.c
index c2c0659..4997c0c 100644
--- a/tools/lib/h5diff_util.c
+++ b/tools/lib/h5diff_util.c
@@ -269,6 +269,8 @@ get_type(int type)
   return("H5G_TYPE");
  case H5G_LINK:
   return("H5G_LINK");
+ case H5G_UDLINK:
+  return("H5G_UDLINK");
  default:
   return("user defined type");
  }
diff --git a/tools/lib/h5tools.c b/tools/lib/h5tools.c
index a4ccf63..cb62c71 100644
--- a/tools/lib/h5tools.c
+++ b/tools/lib/h5tools.c
@@ -594,12 +594,12 @@ h5tools_dump_simple_data(FILE *stream, const h5tool_format_t *info, hid_t contai
      /* Setup */
      memset(&buffer, 0, sizeof(h5tools_str_t));
      size = H5Tget_size(type);
-     
+
      if (info->line_ncols > 0)
       ncols = info->line_ncols;
-     
+
      h5tools_simple_prefix(stream, info, ctx, (hsize_t)0, 0);
-     
+
      for (i = 0; i < nelmts; i++, ctx->cur_elmt++, elmt_counter++) {
         /* Render the element */
         h5tools_str_reset(&buffer);
@@ -1340,7 +1340,7 @@ void init_acc_pos(h5tools_context_t *ctx, hsize_t *dims)
  *
  *-------------------------------------------------------------------------
  */
-static 
+static
 int do_bin_output(FILE *stream, hsize_t nelmts, hid_t tid, void *_mem)
 {
  unsigned char *mem  = (unsigned char*)_mem;
@@ -1349,7 +1349,7 @@ int do_bin_output(FILE *stream, hsize_t nelmts, hid_t tid, void *_mem)
 
  size = H5Tget_size(tid);
 
- for (i = 0; i < nelmts; i++) 
+ for (i = 0; i < nelmts; i++)
  {
   if (render_bin_output(stream,tid,mem + i * size)<0)
   {
@@ -1357,7 +1357,7 @@ int do_bin_output(FILE *stream, hsize_t nelmts, hid_t tid, void *_mem)
    return FAIL;
   }
  }
- 
+
  return SUCCEED;
 }
 
@@ -1377,7 +1377,7 @@ int do_bin_output(FILE *stream, hsize_t nelmts, hid_t tid, void *_mem)
  *
  *-------------------------------------------------------------------------
  */
-static 
+static
 int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 {
 #if 0
@@ -1407,88 +1407,88 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
   sprintf(fmt_ullong, "%%%su", H5_PRINTF_LL_WIDTH);
  }
 #endif
- 
+
  size = H5Tget_size(tid);
- 
- if (H5Tequal(tid, H5T_NATIVE_FLOAT)) 
+
+ if (H5Tequal(tid, H5T_NATIVE_FLOAT))
  {
   memcpy(&tempfloat, mem, sizeof(float));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%g ", tempfloat);
 #else
-  if (1 != fwrite(&tempfloat, size, 1, stream)) 
+  if (1 != fwrite(&tempfloat, size, 1, stream))
    return FAIL;
 #endif
- } 
- else if (H5Tequal(tid, H5T_NATIVE_DOUBLE)) 
+ }
+ else if (H5Tequal(tid, H5T_NATIVE_DOUBLE))
  {
   memcpy(&tempdouble, mem, sizeof(double));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%g ", tempdouble);
 #else
-  if (1 != fwrite(&tempdouble, size, 1, stream)) 
+  if (1 != fwrite(&tempdouble, size, 1, stream))
    return FAIL;
 #endif
- } 
+ }
 #if H5_SIZEOF_LONG_DOUBLE !=0
- else if (H5Tequal(tid, H5T_NATIVE_LDOUBLE)) 
+ else if (H5Tequal(tid, H5T_NATIVE_LDOUBLE))
  {
   memcpy(&templdouble, mem, sizeof(long double));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%Lf ", templdouble);
 #else
-  if (1 != fwrite(&templdouble, size, 1, stream)) 
+  if (1 != fwrite(&templdouble, size, 1, stream))
    return FAIL;
 #endif
  }
 #endif
- else if (H5T_STRING == H5Tget_class(tid)) 
+ else if (H5T_STRING == H5Tget_class(tid))
  {
   unsigned int i;
   H5T_str_t    pad;
   char        *s;
-  
+
   pad = H5Tget_strpad(tid);
-  
-  if(H5Tis_variable_str(tid)) 
+
+  if(H5Tis_variable_str(tid))
   {
    s = *(char**)mem;
    if(s!=NULL)
     size = HDstrlen(s);
   }
-  else 
+  else
   {
    s = mem;
    size = H5Tget_size(tid);
   }
-  for (i=0; i<size && (s[i] || pad!=H5T_STR_NULLTERM); i++) 
+  for (i=0; i<size && (s[i] || pad!=H5T_STR_NULLTERM); i++)
   {
    memcpy(&tempuchar, &s[i], sizeof(unsigned char));
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "%d", tempuchar);
 #else
-   if (1 != fwrite(&tempuchar, size, 1, stream)) 
+   if (1 != fwrite(&tempuchar, size, 1, stream))
     return FAIL;
 #endif
   } /* i */
  }
- else if (H5Tequal(tid, H5T_NATIVE_INT)) 
+ else if (H5Tequal(tid, H5T_NATIVE_INT))
  {
   memcpy(&tempint, mem, sizeof(int));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%d ", tempint);
 #else
-  if (1 != fwrite(&tempint, size, 1, stream)) 
+  if (1 != fwrite(&tempint, size, 1, stream))
    return FAIL;
 #endif
  }
- else if (H5Tequal(tid, H5T_NATIVE_UINT)) 
+ else if (H5Tequal(tid, H5T_NATIVE_UINT))
  {
   memcpy(&tempuint, mem, sizeof(unsigned int));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%u ", tempuint);
 #else
-  if (1 != fwrite(&tempuint, size, 1, stream)) 
+  if (1 != fwrite(&tempuint, size, 1, stream))
    return FAIL;
 #endif
  }
@@ -1498,17 +1498,17 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%d ", tempschar);
 #else
-  if (1 != fwrite(&tempschar, size, 1, stream)) 
+  if (1 != fwrite(&tempschar, size, 1, stream))
    return FAIL;
 #endif
- } 
+ }
  else if (H5Tequal(tid, H5T_NATIVE_UCHAR))
  {
   memcpy(&tempuchar, mem, sizeof(unsigned char));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%u ", tempuchar);
 #else
-  if (1 != fwrite(&tempuchar, size, 1, stream)) 
+  if (1 != fwrite(&tempuchar, size, 1, stream))
    return FAIL;
 #endif
  }
@@ -1518,7 +1518,7 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%d ", tempshort);
 #else
-  if (1 != fwrite(&tempshort, size, 1, stream)) 
+  if (1 != fwrite(&tempshort, size, 1, stream))
    return FAIL;
 #endif
  }
@@ -1528,7 +1528,7 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%u ", tempushort);
 #else
-  if (1 != fwrite(&tempushort, size, 1, stream)) 
+  if (1 != fwrite(&tempushort, size, 1, stream))
    return FAIL;
 #endif
  }
@@ -1538,27 +1538,27 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%ld ", templong);
 #else
-  if (1 != fwrite(&templong, size, 1, stream)) 
+  if (1 != fwrite(&templong, size, 1, stream))
    return FAIL;
 #endif
- } 
+ }
  else if (H5Tequal(tid, H5T_NATIVE_ULONG))
  {
   memcpy(&tempulong, mem, sizeof(unsigned long));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, "%lu ", tempulong);
 #else
-  if (1 != fwrite(&tempulong, size, 1, stream)) 
+  if (1 != fwrite(&tempulong, size, 1, stream))
    return FAIL;
 #endif
- } 
+ }
  else if (H5Tequal(tid, H5T_NATIVE_LLONG))
  {
   memcpy(&templlong, mem, sizeof(long_long));
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, fmt_llong, templlong);
 #else
-  if (1 != fwrite(&templlong, size, 1, stream)) 
+  if (1 != fwrite(&templlong, size, 1, stream))
    return FAIL;
 #endif
  }
@@ -1568,29 +1568,29 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
   fprintf(stream, fmt_ullong, tempullong);
 #else
-  if (1 != fwrite(&tempullong, size, 1, stream)) 
+  if (1 != fwrite(&tempullong, size, 1, stream))
    return FAIL;
 #endif
  }
- else if (H5Tequal(tid, H5T_NATIVE_HSSIZE)) 
+ else if (H5Tequal(tid, H5T_NATIVE_HSSIZE))
  {
-  if (sizeof(hssize_t) == sizeof(int)) 
+  if (sizeof(hssize_t) == sizeof(int))
   {
    memcpy(&tempint, mem, sizeof(int));
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "%d ", tempint);
 #else
-   if (1 != fwrite(&tempint, size, 1, stream)) 
+   if (1 != fwrite(&tempint, size, 1, stream))
     return FAIL;
 #endif
   }
-  else if (sizeof(hssize_t) == sizeof(long)) 
+  else if (sizeof(hssize_t) == sizeof(long))
   {
    memcpy(&templong, mem, sizeof(long));
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "%ld ", templong);
 #else
-   if (1 != fwrite(&templong, size, 1, stream)) 
+   if (1 != fwrite(&templong, size, 1, stream))
     return FAIL;
 #endif
   }
@@ -1600,30 +1600,30 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, fmt_llong, templlong);
 #else
-   if (1 != fwrite(&templlong, size, 1, stream)) 
+   if (1 != fwrite(&templlong, size, 1, stream))
     return FAIL;
 #endif
   }
- } 
- else if (H5Tequal(tid, H5T_NATIVE_HSIZE)) 
+ }
+ else if (H5Tequal(tid, H5T_NATIVE_HSIZE))
  {
-  if (sizeof(hsize_t) == sizeof(int)) 
+  if (sizeof(hsize_t) == sizeof(int))
   {
    memcpy(&tempuint, mem, sizeof(unsigned int));
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "%u ", tempuint);
 #else
-   if (1 != fwrite(&tempuint, size, 1, stream)) 
+   if (1 != fwrite(&tempuint, size, 1, stream))
     return FAIL;
 #endif
   }
-  else if (sizeof(hsize_t) == sizeof(long)) 
+  else if (sizeof(hsize_t) == sizeof(long))
   {
    memcpy(&tempulong, mem, sizeof(unsigned long));
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "%lu ", tempulong);
 #else
-   if (1 != fwrite(&tempulong, size, 1, stream)) 
+   if (1 != fwrite(&tempulong, size, 1, stream))
     return FAIL;
 #endif
   }
@@ -1633,57 +1633,57 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, fmt_ullong, tempullong);
 #else
-   if (1 != fwrite(&tempullong, size, 1, stream)) 
+   if (1 != fwrite(&tempullong, size, 1, stream))
     return FAIL;
 #endif
   }
  }
- else if (H5Tget_class(tid) == H5T_COMPOUND) 
+ else if (H5Tget_class(tid) == H5T_COMPOUND)
  {
   unsigned j;
   hid_t    memb;
   unsigned nmembs;
   size_t   offset;
-  
+
   nmembs = H5Tget_nmembers(tid);
-  
-  for (j = 0; j < nmembs; j++) 
+
+  for (j = 0; j < nmembs; j++)
   {
    offset = H5Tget_member_offset(tid, j);
    memb   = H5Tget_member_type(tid, j);
-   
+
    if (render_bin_output(stream,memb,mem + offset)<0)
     return FAIL;
-   
+
    H5Tclose(memb);
   }
  }
- else if (H5Tget_class(tid) == H5T_ENUM) 
+ else if (H5Tget_class(tid) == H5T_ENUM)
  {
   unsigned int i;
-  if (1==size) 
+  if (1==size)
   {
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "0x%02x", mem[0]);
 #else
-   if (1 != fwrite(&mem[0], size, 1, stream)) 
+   if (1 != fwrite(&mem[0], size, 1, stream))
     return FAIL;
 #endif
-  } 
-  else 
+  }
+  else
   {
    for (i = 0; i < size; i++)
    {
 #ifdef DEBUG_H5DUMP_BIN
     fprintf(stream, "%s%02x", i?":":"", mem[i]);
 #else
-    if (1 != fwrite(&mem[i], sizeof(char), 1, stream)) 
+    if (1 != fwrite(&mem[i], sizeof(char), 1, stream))
      return FAIL;
 #endif
    } /*i*/
   }/*else 1 */
  }
- else if (H5Tget_class(tid) == H5T_ARRAY) 
+ else if (H5Tget_class(tid) == H5T_ARRAY)
  {
   int     k, ndims;
   hsize_t i, dims[H5S_MAX_RANK], temp_nelmts, nelmts;
@@ -1703,63 +1703,63 @@ int render_bin_output(FILE *stream, hid_t tid, void *_mem)
    temp_nelmts *= dims[k];
    nelmts = (size_t)temp_nelmts;
   }
-   
+
   /* dump the array element */
-  for (i = 0; i < nelmts; i++) 
+  for (i = 0; i < nelmts; i++)
   {
    if (render_bin_output(stream,memb,mem + i * size)<0)
     return FAIL;
   }
-  
+
   H5Tclose(memb);
  }
- else if (H5Tget_class(tid) == H5T_VLEN) 
+ else if (H5Tget_class(tid) == H5T_VLEN)
  {
   unsigned int i;
   hsize_t nelmts;
   hid_t   memb;
-  
+
   /* get the VL sequences's base datatype for each element */
   memb = H5Tget_super(tid);
   size = H5Tget_size(memb);
- 
+
   /* Get the number of sequence elements */
   nelmts = ((hvl_t *)mem)->len;
-  
-  for (i = 0; i < nelmts; i++) 
+
+  for (i = 0; i < nelmts; i++)
   {
    /* dump the array element */
    if (render_bin_output(stream,memb,((char *)(((hvl_t *)mem)->p)) + i * size)<0)
     return FAIL;
-  } 
+  }
   H5Tclose(memb);
  }
- else 
+ else
  {
   size_t i;
-  if (1==size) 
+  if (1==size)
   {
 #ifdef DEBUG_H5DUMP_BIN
    fprintf(stream, "0x%02x", mem[0]);
 #else
-   if (1 != fwrite(&mem[0], size, 1, stream)) 
+   if (1 != fwrite(&mem[0], size, 1, stream))
     return FAIL;
 #endif
-  } 
-  else 
+  }
+  else
   {
    for (i = 0; i < size; i++)
    {
 #ifdef DEBUG_H5DUMP_BIN
     fprintf(stream, "%s%02x", i?":":"", mem[i]);
 #else
-    if (1 != fwrite(&mem[i], sizeof(char), 1, stream)) 
+    if (1 != fwrite(&mem[i], sizeof(char), 1, stream))
      return FAIL;
 #endif
    } /*i*/
   }/*else 1 */
  }
-  
+
 
  return SUCCEED;
 }
diff --git a/tools/lib/h5tools_ref.c b/tools/lib/h5tools_ref.c
index f49cb07..5d6cfae 100644
--- a/tools/lib/h5tools_ref.c
+++ b/tools/lib/h5tools_ref.c
@@ -171,6 +171,12 @@ ref_path_table_lookup(const char *thepath)
         if(H5Gget_objinfo(thefile, thepath, TRUE, &sb)<0)
             /*  fatal error ? */
             return HADDR_UNDEF;
+    } else if(sb.type == H5G_UDLINK)
+    {
+        /* UD links can't be followed, so they always "dangle" like
+         * soft links.
+         */
+        return HADDR_UNDEF;
     } /* end if */
     objno = (haddr_t)sb.objno[0] | ((haddr_t)sb.objno[1] << (8 * sizeof(long)));
 
diff --git a/tools/lib/h5trav.c b/tools/lib/h5trav.c
index f5c6e91..2ff927c 100644
--- a/tools/lib/h5trav.c
+++ b/tools/lib/h5trav.c
@@ -462,7 +462,7 @@ static int traverse( hid_t loc_id,
    */
 
   case H5G_LINK:
-   {
+  {
     /* increment */
     inserted_objs++;
 
@@ -489,9 +489,60 @@ static int traverse( hid_t loc_id,
 
    break;
 
+  /*-------------------------------------------------------------------------
+   * H5G_UDLINK
+   *-------------------------------------------------------------------------
+   */
+
+  case H5G_UDLINK:
+  {
+    H5L_linkinfo_t linkbuf;
+
+    /* increment */
+    inserted_objs++;
+
+    /* add object to table */
+    trav_table_add(HADDR_UNDEF, path, H5G_UDLINK, table );
+
+    /* Get type of link */
+    H5E_BEGIN_TRY {
+
+    /* get link class info */
+    H5Lget_linkinfo( loc_id, path, &linkbuf, H5P_DEFAULT);
+    } H5E_END_TRY;
+
+    if(linkbuf.linkclass == H5L_LINK_EXTERNAL)
+    {
+      if (statbuf.linklen>0)
+      {
+      char *targbuf;
+      char *objname;
+
+      targbuf = HDmalloc(statbuf.linklen);
+      assert(targbuf);
+      H5Gget_linkval(loc_id,path,statbuf.linklen,targbuf);
+      H5Lunpack_elink_val(targbuf, NULL, &objname);
+      if (print)
+        printf(" %-10s %s -> %s %s\n", "ext link", path, targbuf, objname);
+      free(targbuf);
+      }
+      else
+      {
+      if (print)
+        printf(" %-10s %s ->\n", "udlink", path);
+      }
+    }
+    else  /* Unknown user-defined type */
+    {
+      if (print)
+        printf(" %-10s %s ->\n", "UD link type", path);
+    }
+  }
+  break;
+
 
   default:
-    HDfprintf(stderr, "traverse: Unknown object!\n");
+    HDfprintf(stderr, "traverse: Unknown object %d!\n", type); /* JAMES */
     return (-1);
    break;
 
@@ -548,6 +599,9 @@ void h5trav_printinfo(int nobjs, trav_info_t *travi)
   case H5G_LINK:
    printf(" %-10s %s\n", "link", travi[i].name );
    break;
+  case H5G_UDLINK:
+   printf(" %-10s %s\n", "User defined link", travi[i].name );
+   break;
   default:
    printf(" %-10s %s\n", "User defined object", travi[i].name );
    break;
diff --git a/tools/misc/h5stat.c b/tools/misc/h5stat.c
index 4855e68..5d0f23b 100644
--- a/tools/misc/h5stat.c
+++ b/tools/misc/h5stat.c
@@ -608,7 +608,8 @@ printf("walk: fullname = %s\n", fullname);
                 break;
 
             case H5G_LINK:
-                /* Gather statistics about this type of object */
+            case H5G_UDLINK:
+                /* Gather statistics about links and UD links */
                 iter->uniq_links++;
                 break;
 
diff --git a/tools/testfiles/file3.h5 b/tools/testfiles/file3.h5
index 4750ce9..a9eff83 100644
--- a/tools/testfiles/file3.h5
+++ b/tools/testfiles/file3.h5
diff --git a/tools/testfiles/tall-1.ddl b/tools/testfiles/tall-1.ddl
index 2fd5494..6069293 100644
--- a/tools/testfiles/tall-1.ddl
+++ b/tools/testfiles/tall-1.ddl
@@ -64,6 +64,11 @@ GROUP "/" {
          }
       }
       GROUP "g1.2" {
+         EXTERNAL_LINK "extlink" {
+            LINKCLASS 64
+            TARGETFILE "somefile"
+            TARGETPATH "somepath"
+}
          GROUP "g1.2.1" {
             SOFTLINK "slink" {
                LINKTARGET "somevalue"
@@ -88,6 +93,9 @@ GROUP "/" {
          (2,0): 0, 0.3, 0.6, 0.9, 1.2
          }
       }
+      USERDEFINED_LINK "udlink" {
+         LINKCLASS 187
+      }
    }
 }
 }
diff --git a/tools/testfiles/tall-2.ls b/tools/testfiles/tall-2.ls
index e1b0bcf..5513214 100644
--- a/tools/testfiles/tall-2.ls
+++ b/tools/testfiles/tall-2.ls
@@ -15,6 +15,7 @@
     Data:
         (0) 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19
 /g1/g1.2                 Group
+/g1/g1.2/extlink         -> file: somefile    path: somepath
 /g1/g1.2/g1.2.1          Group
 /g1/g1.2/g1.2.1/slink    -> somevalue
 /g2                      Group
@@ -25,3 +26,4 @@
     Data:
         (0,0) 0, 0.1, 0.2, 0.3, 0.4, 0, 0.2, 0.4, 0.6, 0.8, 0, 0.3, 0.6, 0.9,
         (2,4) 1.2
+/g2/udlink               -> cannot follow UD links
diff --git a/tools/testfiles/tall-2A.ddl b/tools/testfiles/tall-2A.ddl
index 604c307..b16feb8 100644
--- a/tools/testfiles/tall-2A.ddl
+++ b/tools/testfiles/tall-2A.ddl
@@ -48,6 +48,11 @@ GROUP "/" {
          }
       }
       GROUP "g1.2" {
+         EXTERNAL_LINK "extlink" {
+            LINKCLASS 64
+            TARGETFILE "somefile"
+            TARGETPATH "somepath"
+}
          GROUP "g1.2.1" {
             SOFTLINK "slink" {
                LINKTARGET "somevalue"
@@ -64,6 +69,9 @@ GROUP "/" {
          DATATYPE  H5T_IEEE_F32BE
          DATASPACE  SIMPLE { ( 3, 5 ) / ( 3, 5 ) }
       }
+      USERDEFINED_LINK "udlink" {
+         LINKCLASS 187
+      }
    }
 }
 }
diff --git a/tools/testfiles/tall-2A.h5.xml b/tools/testfiles/tall-2A.h5.xml
index e83f0b3..586afb5 100644
--- a/tools/testfiles/tall-2A.h5.xml
+++ b/tools/testfiles/tall-2A.h5.xml
@@ -3,7 +3,7 @@ Expected output for 'h5dump --xml -A tall.h5'
 #############################
 <?xml version="1.0" encoding="UTF-8"?>
 <hdf5:HDF5-File xmlns:hdf5="http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hdf.ncsa.uiuc.edu/DTDs/HDF5File http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File.xsd">
-<hdf5:RootGroup OBJ-XID="xid_928" H5Path="/">
+<hdf5:RootGroup OBJ-XID="xid_96" H5Path="/">
    <hdf5:Attribute Name="attr1">
       <hdf5:Dataspace>
          <hdf5:SimpleDataspace Ndims="1">
@@ -40,9 +40,9 @@ Expected output for 'h5dump --xml -A tall.h5'
          </hdf5:DataFromFile>
       </hdf5:Data>
    </hdf5:Attribute>
-   <hdf5:Group Name="g1" OBJ-XID="xid_1576" H5Path="/g1" Parents="xid_928" H5ParentPaths="/" >
-      <hdf5:Group Name="g1.1" OBJ-XID="xid_3200" H5Path="/g1/g1.1" Parents="xid_1576" H5ParentPaths="/g1" >
-         <hdf5:Dataset Name="dset1.1.1" OBJ-XID="xid_5200" H5Path= "/g1/g1.1/dset1.1.1" Parents="xid_3200" H5ParentPaths="/g1/g1.1">
+   <hdf5:Group Name="g1" OBJ-XID="xid_792" H5Path="/g1" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Group Name="g1.1" OBJ-XID="xid_2512" H5Path="/g1/g1.1" Parents="xid_792" H5ParentPaths="/g1" >
+         <hdf5:Dataset Name="dset1.1.1" OBJ-XID="xid_5432" H5Path= "/g1/g1.1/dset1.1.1" Parents="xid_2512" H5ParentPaths="/g1/g1.1">
             <hdf5:StorageLayout>
                <hdf5:ContiguousLayout/>
             </hdf5:StorageLayout>
@@ -102,7 +102,7 @@ Expected output for 'h5dump --xml -A tall.h5'
                <hdf5:NoData/>
             </hdf5:Data>
          </hdf5:Dataset>
-         <hdf5:Dataset Name="dset1.1.2" OBJ-XID="xid_5800" H5Path= "/g1/g1.1/dset1.1.2" Parents="xid_3200" H5ParentPaths="/g1/g1.1">
+         <hdf5:Dataset Name="dset1.1.2" OBJ-XID="xid_8272" H5Path= "/g1/g1.1/dset1.1.2" Parents="xid_2512" H5ParentPaths="/g1/g1.1">
             <hdf5:StorageLayout>
                <hdf5:ContiguousLayout/>
             </hdf5:StorageLayout>
@@ -126,14 +126,15 @@ Expected output for 'h5dump --xml -A tall.h5'
             </hdf5:Data>
          </hdf5:Dataset>
       </hdf5:Group>
-      <hdf5:Group Name="g1.2" OBJ-XID="xid_4176" H5Path="/g1/g1.2" Parents="xid_1576" H5ParentPaths="/g1" >
-         <hdf5:Group Name="g1.2.1" OBJ-XID="xid_4824" H5Path="/g1/g1.2/g1.2.1" Parents="xid_4176" H5ParentPaths="/g1/g1.2" >
-            <hdf5:SoftLink LinkName="slink" OBJ-XID="xid_18446744073709551614" H5SourcePath="/g1/g1.2/g1.2.1/slink" TargetPath="somevalue"  Parents="xid_4824" H5ParentPaths="/g1/g1.2/g1.2.1" />
+      <hdf5:Group Name="g1.2" OBJ-XID="xid_3536" H5Path="/g1/g1.2" Parents="xid_792" H5ParentPaths="/g1" >
+         <hdf5:Group Name="g1.2.1" OBJ-XID="xid_4232" H5Path="/g1/g1.2/g1.2.1" Parents="xid_3536" H5ParentPaths="/g1/g1.2" >
+            <hdf5:SoftLink LinkName="slink" OBJ-XID="xid_18446744073709551614" H5SourcePath="/g1/g1.2/g1.2.1/slink" TargetPath="somevalue"  Parents="xid_4232" H5ParentPaths="/g1/g1.2/g1.2.1" />
          </hdf5:Group>
+         <hdf5:ExternalLink LinkName="extlink" OBJ-XID="xid_18446744073709551613" H5SourcePath="/g1/g1.2/extlink" TargetFilename="somefile"  TargetPath="somepath"  Parents="xid_3536" H5ParentPaths="/g1/g1.2" />
       </hdf5:Group>
    </hdf5:Group>
-   <hdf5:Group Name="g2" OBJ-XID="xid_2552" H5Path="/g2" Parents="xid_928" H5ParentPaths="/" >
-      <hdf5:Dataset Name="dset2.1" OBJ-XID="xid_8520" H5Path= "/g2/dset2.1" Parents="xid_2552" H5ParentPaths="/g2">
+   <hdf5:Group Name="g2" OBJ-XID="xid_1816" H5Path="/g2" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Dataset Name="dset2.1" OBJ-XID="xid_8872" H5Path= "/g2/dset2.1" Parents="xid_1816" H5ParentPaths="/g2">
          <hdf5:StorageLayout>
             <hdf5:ContiguousLayout/>
          </hdf5:StorageLayout>
@@ -156,7 +157,7 @@ Expected output for 'h5dump --xml -A tall.h5'
             <hdf5:NoData/>
          </hdf5:Data>
       </hdf5:Dataset>
-      <hdf5:Dataset Name="dset2.2" OBJ-XID="xid_9120" H5Path= "/g2/dset2.2" Parents="xid_2552" H5ParentPaths="/g2">
+      <hdf5:Dataset Name="dset2.2" OBJ-XID="xid_9472" H5Path= "/g2/dset2.2" Parents="xid_1816" H5ParentPaths="/g2">
          <hdf5:StorageLayout>
             <hdf5:ContiguousLayout/>
          </hdf5:StorageLayout>
@@ -180,6 +181,7 @@ Expected output for 'h5dump --xml -A tall.h5'
             <hdf5:NoData/>
          </hdf5:Data>
       </hdf5:Dataset>
+      <hdf5:UserDefined LinkName="udlink" OBJ-XID="xid_18446744073709551612" H5SourcePath="/g2/udlink" LinkClass="187"  Parents="xid_1816" H5ParentPaths="/g2" />
    </hdf5:Group>
 </hdf5:RootGroup>
 </hdf5:HDF5-File>
diff --git a/tools/testfiles/tall-2B.ddl b/tools/testfiles/tall-2B.ddl
index 4969987..002156e 100644
--- a/tools/testfiles/tall-2B.ddl
+++ b/tools/testfiles/tall-2B.ddl
@@ -44,6 +44,11 @@ GROUP "/" {
          }
       }
       GROUP "g1.2" {
+         EXTERNAL_LINK "extlink" {
+            LINKCLASS 64
+            TARGETFILE "somefile"
+            TARGETPATH "somepath"
+}
          GROUP "g1.2.1" {
             SOFTLINK "slink" {
                LINKTARGET "somevalue"
@@ -60,6 +65,9 @@ GROUP "/" {
          DATATYPE  H5T_IEEE_F32BE
          DATASPACE  SIMPLE { ( 3, 5 ) / ( 3, 5 ) }
       }
+      USERDEFINED_LINK "udlink" {
+         LINKCLASS 187
+      }
    }
 }
 }
diff --git a/tools/testfiles/tall.h5 b/tools/testfiles/tall.h5
index 2bc4993..0ed5ed2 100644
--- a/tools/testfiles/tall.h5
+++ b/tools/testfiles/tall.h5
diff --git a/tools/testfiles/tall.h5.xml b/tools/testfiles/tall.h5.xml
index 22e6f51..ce740fe 100644
--- a/tools/testfiles/tall.h5.xml
+++ b/tools/testfiles/tall.h5.xml
@@ -3,7 +3,7 @@ Expected output for 'h5dump --xml tall.h5'
 #############################
 <?xml version="1.0" encoding="UTF-8"?>
 <hdf5:HDF5-File xmlns:hdf5="http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hdf.ncsa.uiuc.edu/DTDs/HDF5File http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File.xsd">
-<hdf5:RootGroup OBJ-XID="xid_928" H5Path="/">
+<hdf5:RootGroup OBJ-XID="xid_96" H5Path="/">
    <hdf5:Attribute Name="attr1">
       <hdf5:Dataspace>
          <hdf5:SimpleDataspace Ndims="1">
@@ -40,9 +40,9 @@ Expected output for 'h5dump --xml tall.h5'
          </hdf5:DataFromFile>
       </hdf5:Data>
    </hdf5:Attribute>
-   <hdf5:Group Name="g1" OBJ-XID="xid_1576" H5Path="/g1" Parents="xid_928" H5ParentPaths="/" >
-      <hdf5:Group Name="g1.1" OBJ-XID="xid_3200" H5Path="/g1/g1.1" Parents="xid_1576" H5ParentPaths="/g1" >
-         <hdf5:Dataset Name="dset1.1.1" OBJ-XID="xid_5200" H5Path= "/g1/g1.1/dset1.1.1" Parents="xid_3200" H5ParentPaths="/g1/g1.1">
+   <hdf5:Group Name="g1" OBJ-XID="xid_792" H5Path="/g1" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Group Name="g1.1" OBJ-XID="xid_2512" H5Path="/g1/g1.1" Parents="xid_792" H5ParentPaths="/g1" >
+         <hdf5:Dataset Name="dset1.1.1" OBJ-XID="xid_5432" H5Path= "/g1/g1.1/dset1.1.1" Parents="xid_2512" H5ParentPaths="/g1/g1.1">
             <hdf5:StorageLayout>
                <hdf5:ContiguousLayout/>
             </hdf5:StorageLayout>
@@ -113,7 +113,7 @@ Expected output for 'h5dump --xml tall.h5'
                </hdf5:DataFromFile>
             </hdf5:Data>
          </hdf5:Dataset>
-         <hdf5:Dataset Name="dset1.1.2" OBJ-XID="xid_5800" H5Path= "/g1/g1.1/dset1.1.2" Parents="xid_3200" H5ParentPaths="/g1/g1.1">
+         <hdf5:Dataset Name="dset1.1.2" OBJ-XID="xid_8272" H5Path= "/g1/g1.1/dset1.1.2" Parents="xid_2512" H5ParentPaths="/g1/g1.1">
             <hdf5:StorageLayout>
                <hdf5:ContiguousLayout/>
             </hdf5:StorageLayout>
@@ -139,14 +139,15 @@ Expected output for 'h5dump --xml tall.h5'
             </hdf5:Data>
          </hdf5:Dataset>
       </hdf5:Group>
-      <hdf5:Group Name="g1.2" OBJ-XID="xid_4176" H5Path="/g1/g1.2" Parents="xid_1576" H5ParentPaths="/g1" >
-         <hdf5:Group Name="g1.2.1" OBJ-XID="xid_4824" H5Path="/g1/g1.2/g1.2.1" Parents="xid_4176" H5ParentPaths="/g1/g1.2" >
-            <hdf5:SoftLink LinkName="slink" OBJ-XID="xid_18446744073709551614" H5SourcePath="/g1/g1.2/g1.2.1/slink" TargetPath="somevalue"  Parents="xid_4824" H5ParentPaths="/g1/g1.2/g1.2.1" />
+      <hdf5:Group Name="g1.2" OBJ-XID="xid_3536" H5Path="/g1/g1.2" Parents="xid_792" H5ParentPaths="/g1" >
+         <hdf5:Group Name="g1.2.1" OBJ-XID="xid_4232" H5Path="/g1/g1.2/g1.2.1" Parents="xid_3536" H5ParentPaths="/g1/g1.2" >
+            <hdf5:SoftLink LinkName="slink" OBJ-XID="xid_18446744073709551614" H5SourcePath="/g1/g1.2/g1.2.1/slink" TargetPath="somevalue"  Parents="xid_4232" H5ParentPaths="/g1/g1.2/g1.2.1" />
          </hdf5:Group>
+         <hdf5:ExternalLink LinkName="extlink" OBJ-XID="xid_18446744073709551613" H5SourcePath="/g1/g1.2/extlink" TargetFilename="somefile"  TargetPath="somepath"  Parents="xid_3536" H5ParentPaths="/g1/g1.2" />
       </hdf5:Group>
    </hdf5:Group>
-   <hdf5:Group Name="g2" OBJ-XID="xid_2552" H5Path="/g2" Parents="xid_928" H5ParentPaths="/" >
-      <hdf5:Dataset Name="dset2.1" OBJ-XID="xid_8520" H5Path= "/g2/dset2.1" Parents="xid_2552" H5ParentPaths="/g2">
+   <hdf5:Group Name="g2" OBJ-XID="xid_1816" H5Path="/g2" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Dataset Name="dset2.1" OBJ-XID="xid_8872" H5Path= "/g2/dset2.1" Parents="xid_1816" H5ParentPaths="/g2">
          <hdf5:StorageLayout>
             <hdf5:ContiguousLayout/>
          </hdf5:StorageLayout>
@@ -171,7 +172,7 @@ Expected output for 'h5dump --xml tall.h5'
             </hdf5:DataFromFile>
          </hdf5:Data>
       </hdf5:Dataset>
-      <hdf5:Dataset Name="dset2.2" OBJ-XID="xid_9120" H5Path= "/g2/dset2.2" Parents="xid_2552" H5ParentPaths="/g2">
+      <hdf5:Dataset Name="dset2.2" OBJ-XID="xid_9472" H5Path= "/g2/dset2.2" Parents="xid_1816" H5ParentPaths="/g2">
          <hdf5:StorageLayout>
             <hdf5:ContiguousLayout/>
          </hdf5:StorageLayout>
@@ -199,6 +200,7 @@ Expected output for 'h5dump --xml tall.h5'
             </hdf5:DataFromFile>
          </hdf5:Data>
       </hdf5:Dataset>
+      <hdf5:UserDefined LinkName="udlink" OBJ-XID="xid_18446744073709551612" H5SourcePath="/g2/udlink" LinkClass="187"  Parents="xid_1816" H5ParentPaths="/g2" />
    </hdf5:Group>
 </hdf5:RootGroup>
 </hdf5:HDF5-File>
diff --git a/tools/testfiles/tcontents.ddl b/tools/testfiles/tcontents.ddl
index 43afb9d..935ff8c 100644
--- a/tools/testfiles/tcontents.ddl
+++ b/tools/testfiles/tcontents.ddl
@@ -3,11 +3,12 @@ Expected output for 'h5dump -n tfcontents1.h5'
 #############################
 HDF5 "tfcontents1.h5" {
 FILE_CONTENTS {
- datatype   /#5696
+ datatype   /#6056
  dataset    /dset
  dataset    /dset3 -> /dset
  dataset    /dset4 -> /dset
  dataset    /dsetmytype2
+ ext link   /extlink -> fname oname
  group      /g1
  dataset    /g1/dset1 -> /dset
  group      /g1/g1.1
@@ -16,5 +17,6 @@ FILE_CONTENTS {
  link       /mylink -> mylink
  datatype   /mytype
  link       /softlink -> /dset
+ UD link type /udlink ->
  }
 }
diff --git a/tools/testfiles/textlink.h5 b/tools/testfiles/textlink.h5
new file mode 100644
index 0000000..a851011
--- /dev/null
+++ b/tools/testfiles/textlink.h5
diff --git a/tools/testfiles/textlink.h5.xml b/tools/testfiles/textlink.h5.xml
new file mode 100644
index 0000000..fe6f68a
--- /dev/null
+++ b/tools/testfiles/textlink.h5.xml
@@ -0,0 +1,10 @@
+#############################
+Expected output for 'h5dump --xml textlink.h5'
+#############################
+<?xml version="1.0" encoding="UTF-8"?>
+<hdf5:HDF5-File xmlns:hdf5="http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hdf.ncsa.uiuc.edu/DTDs/HDF5File http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File.xsd">
+<hdf5:RootGroup OBJ-XID="xid_96" H5Path="/">
+   <hdf5:ExternalLink LinkName="extlink1" OBJ-XID="xid_18446744073709551614" H5SourcePath="/extlink1" TargetFilename="filename"  TargetPath="objname"  Parents="xid_96" H5ParentPaths="/" />
+   <hdf5:ExternalLink LinkName="extlink2" OBJ-XID="xid_18446744073709551613" H5SourcePath="/extlink2" TargetFilename="anotherfile"  TargetPath="anotherobj"  Parents="xid_96" H5ParentPaths="/" />
+</hdf5:RootGroup>
+</hdf5:HDF5-File>
diff --git a/tools/testfiles/tfcontents1.h5 b/tools/testfiles/tfcontents1.h5
index a7cf2d3..8b043fb 100644
--- a/tools/testfiles/tfcontents1.h5
+++ b/tools/testfiles/tfcontents1.h5
diff --git a/tools/testfiles/tfcontents2.h5 b/tools/testfiles/tfcontents2.h5
index 216a885..1df0779 100644
--- a/tools/testfiles/tfcontents2.h5
+++ b/tools/testfiles/tfcontents2.h5
diff --git a/tools/testfiles/tmany.h5 b/tools/testfiles/tmany.h5
index 271f13a..0422f93 100644
--- a/tools/testfiles/tmany.h5
+++ b/tools/testfiles/tmany.h5
diff --git a/tools/testfiles/tmany.h5.xml b/tools/testfiles/tmany.h5.xml
index 60ccb08..1f7fa70 100644
--- a/tools/testfiles/tmany.h5.xml
+++ b/tools/testfiles/tmany.h5.xml
@@ -3,10 +3,10 @@ Expected output for 'h5dump --xml tmany.h5'
 #############################
 <?xml version="1.0" encoding="UTF-8"?>
 <hdf5:HDF5-File xmlns:hdf5="http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hdf.ncsa.uiuc.edu/DTDs/HDF5File http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File.xsd">
-<hdf5:RootGroup OBJ-XID="xid_696" H5Path="/">
-   <hdf5:Group Name="g1" OBJ-XID="xid_1344" H5Path="/g1" Parents="xid_696" H5ParentPaths="/" >
-      <hdf5:Group Name="g1.1" OBJ-XID="xid_2320" H5Path="/g1/g1.1" Parents="xid_1344" H5ParentPaths="/g1" >
-         <hdf5:Dataset Name="dset1" OBJ-XID="xid_2696" H5Path= "/g1/g1.1/dset1" Parents="xid_2320" H5ParentPaths="/g1/g1.1">
+<hdf5:RootGroup OBJ-XID="xid_96" H5Path="/">
+   <hdf5:Group Name="g1" OBJ-XID="xid_792" H5Path="/g1" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Group Name="g1.1" OBJ-XID="xid_1816" H5Path="/g1/g1.1" Parents="xid_792" H5ParentPaths="/g1" >
+         <hdf5:Dataset Name="dset1" OBJ-XID="xid_2840" H5Path= "/g1/g1.1/dset1" Parents="xid_1816" H5ParentPaths="/g1/g1.1">
             <hdf5:StorageLayout>
                <hdf5:ChunkedLayout Ndims="1">
                   <hdf5:ChunkDimension DimSize="2" />
@@ -265,17 +265,17 @@ Expected output for 'h5dump --xml tmany.h5'
             </hdf5:Data>
          </hdf5:Dataset>
       </hdf5:Group>
-      <hdf5:Group Name="g1.2" OBJ-XID="xid_5832" H5Path="/g1/g1.2" Parents="xid_1344" H5ParentPaths="/g1" >
-         <hdf5:Dataset Name="link1" OBJ-XID="xid_2696-1" H5Path="/g1/g1.2/link1" Parents="xid_5832" H5ParentPaths="/g1/g1.2">
-            <hdf5:DatasetPtr OBJ-XID="xid_2696" H5Path="/g1/g1.2/link1"/>
+      <hdf5:Group Name="g1.2" OBJ-XID="xid_6040" H5Path="/g1/g1.2" Parents="xid_792" H5ParentPaths="/g1" >
+         <hdf5:Dataset Name="link1" OBJ-XID="xid_2840-1" H5Path="/g1/g1.2/link1" Parents="xid_6040" H5ParentPaths="/g1/g1.2">
+            <hdf5:DatasetPtr OBJ-XID="xid_2840" H5Path="/g1/g1.2/link1"/>
          </hdf5:Dataset>
       </hdf5:Group>
    </hdf5:Group>
-   <hdf5:Group Name="g2" OBJ-XID="xid_6808" H5Path="/g2" Parents="xid_696" H5ParentPaths="/" >
-      <hdf5:SoftLink LinkName="slink2" OBJ-XID="xid_1344" H5SourcePath="/g2/slink2" TargetPath="/g1" TargetObj="xid_1344" Parents="xid_6808" H5ParentPaths="/g2" />
+   <hdf5:Group Name="g2" OBJ-XID="xid_6520" H5Path="/g2" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:SoftLink LinkName="slink2" OBJ-XID="xid_792" H5SourcePath="/g2/slink2" TargetPath="/g1" TargetObj="xid_792" Parents="xid_6520" H5ParentPaths="/g2" />
    </hdf5:Group>
-   <hdf5:Group Name="g3" OBJ-XID="xid_7784" H5Path="/g3" Parents="xid_696" H5ParentPaths="/" >
-      <hdf5:Dataset Name="link3" OBJ-XID="xid_8480" H5Path= "/g3/link3" Parents="xid_7784" H5ParentPaths="/g3">
+   <hdf5:Group Name="g3" OBJ-XID="xid_10160" H5Path="/g3" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Dataset Name="link3" OBJ-XID="xid_11552" H5Path= "/g3/link3" Parents="xid_10160" H5ParentPaths="/g3">
          <hdf5:StorageLayout>
             <hdf5:ContiguousLayout/>
          </hdf5:StorageLayout>
@@ -311,16 +311,16 @@ Expected output for 'h5dump --xml tmany.h5'
          </hdf5:Data>
       </hdf5:Dataset>
    </hdf5:Group>
-   <hdf5:Group Name="g4" OBJ-XID="xid_8432" H5Path="/g4" Parents="xid_696" H5ParentPaths="/" >
-      <hdf5:Dataset Name="dset2" OBJ-XID="xid_8480-2" H5Path="/g4/dset2" Parents="xid_8432" H5ParentPaths="/g4">
-         <hdf5:DatasetPtr OBJ-XID="xid_8480" H5Path="/g4/dset2"/>
+   <hdf5:Group Name="g4" OBJ-XID="xid_10856" H5Path="/g4" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Dataset Name="dset2" OBJ-XID="xid_11552-2" H5Path="/g4/dset2" Parents="xid_10856" H5ParentPaths="/g4">
+         <hdf5:DatasetPtr OBJ-XID="xid_11552" H5Path="/g4/dset2"/>
       </hdf5:Dataset>
    </hdf5:Group>
-   <hdf5:Group Name="g5" OBJ-XID="xid_10248" H5Path="/g5" Parents="xid_696" H5ParentPaths="/" >
-      <hdf5:SoftLink LinkName="slink4" OBJ-XID="xid_10944" H5SourcePath="/g5/slink4" TargetPath="/g6/dset3" TargetObj="xid_10944" Parents="xid_10248" H5ParentPaths="/g5" />
+   <hdf5:Group Name="g5" OBJ-XID="xid_8512" H5Path="/g5" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:SoftLink LinkName="slink4" OBJ-XID="xid_15872" H5SourcePath="/g5/slink4" TargetPath="/g6/dset3" TargetObj="xid_15872" Parents="xid_8512" H5ParentPaths="/g5" />
    </hdf5:Group>
-   <hdf5:Group Name="g6" OBJ-XID="xid_10896" H5Path="/g6" Parents="xid_696" H5ParentPaths="/" >
-      <hdf5:Dataset Name="dset3" OBJ-XID="xid_10944" H5Path= "/g6/dset3" Parents="xid_10896" H5ParentPaths="/g6">
+   <hdf5:Group Name="g6" OBJ-XID="xid_8560" H5Path="/g6" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:Dataset Name="dset3" OBJ-XID="xid_15872" H5Path= "/g6/dset3" Parents="xid_8560" H5ParentPaths="/g6">
          <hdf5:StorageLayout>
             <hdf5:ContiguousLayout/>
          </hdf5:StorageLayout>
@@ -356,5 +356,13 @@ Expected output for 'h5dump --xml tmany.h5'
          </hdf5:Data>
       </hdf5:Dataset>
    </hdf5:Group>
+   <hdf5:Group Name="g7" OBJ-XID="xid_12688" H5Path="/g7" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:SoftLink LinkName="slink5" OBJ-XID="xid_18446744073709551614" H5SourcePath="/g7/slink5" TargetPath="/g8/elink"  Parents="xid_12688" H5ParentPaths="/g7" />
+      <hdf5:SoftLink LinkName="slink6" OBJ-XID="xid_18446744073709551613" H5SourcePath="/g7/slink6" TargetPath="/g8/udlink"  Parents="xid_12688" H5ParentPaths="/g7" />
+   </hdf5:Group>
+   <hdf5:Group Name="g8" OBJ-XID="xid_720" H5Path="/g8" Parents="xid_96" H5ParentPaths="/" >
+      <hdf5:ExternalLink LinkName="elink" OBJ-XID="xid_18446744073709551612" H5SourcePath="/g8/elink" TargetFilename="somefile"  TargetPath="somepath"  Parents="xid_720" H5ParentPaths="/g8" />
+      <hdf5:UserDefined LinkName="udlink" OBJ-XID="xid_18446744073709551611" H5SourcePath="/g8/udlink" LinkClass="187"  Parents="xid_720" H5ParentPaths="/g8" />
+   </hdf5:Group>
 </hdf5:RootGroup>
 </hdf5:HDF5-File>
diff --git a/tools/testfiles/tudlink-1.ddl b/tools/testfiles/tudlink-1.ddl
new file mode 100644
index 0000000..5f76c40
--- /dev/null
+++ b/tools/testfiles/tudlink-1.ddl
@@ -0,0 +1,13 @@
+#############################
+Expected output for 'h5dump tudlink.h5'
+#############################
+HDF5 "tudlink.h5" {
+GROUP "/" {
+   USERDEFINED_LINK "udlink1" {
+      LINKCLASS 187
+   }
+   USERDEFINED_LINK "udlink2" {
+      LINKCLASS 187
+   }
+}
+}
diff --git a/tools/testfiles/tudlink-1.ls b/tools/testfiles/tudlink-1.ls
new file mode 100644
index 0000000..e83fce7
--- /dev/null
+++ b/tools/testfiles/tudlink-1.ls
@@ -0,0 +1,5 @@
+#############################
+ output for 'h5ls -w80 -r tudlink.h5'
+#############################
+/udlink1                 -> cannot follow UD links
+/udlink2                 -> cannot follow UD links
diff --git a/tools/testfiles/tudlink-2.ddl b/tools/testfiles/tudlink-2.ddl
new file mode 100644
index 0000000..9ae3a54
--- /dev/null
+++ b/tools/testfiles/tudlink-2.ddl
@@ -0,0 +1,9 @@
+#############################
+Expected output for 'h5dump -l udlink2 tudlink.h5'
+#############################
+HDF5 "tudlink.h5" {
+USERDEFINED_LINK "udlink2" {
+   USERDEFINED_LINK "udlink2" {
+   LINKCLASS 187
+}
+}
diff --git a/tools/testfiles/tudlink.h5 b/tools/testfiles/tudlink.h5
new file mode 100644
index 0000000..3b10447
--- /dev/null
+++ b/tools/testfiles/tudlink.h5
diff --git a/tools/testfiles/tudlink.h5.xml b/tools/testfiles/tudlink.h5.xml
new file mode 100644
index 0000000..aa5fb6c
--- /dev/null
+++ b/tools/testfiles/tudlink.h5.xml
@@ -0,0 +1,10 @@
+#############################
+Expected output for 'h5dump --xml tudlink.h5'
+#############################
+<?xml version="1.0" encoding="UTF-8"?>
+<hdf5:HDF5-File xmlns:hdf5="http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hdf.ncsa.uiuc.edu/DTDs/HDF5File http://hdf.ncsa.uiuc.edu/DTDs/HDF5-File.xsd">
+<hdf5:RootGroup OBJ-XID="xid_96" H5Path="/">
+   <hdf5:UserDefined LinkName="udlink1" OBJ-XID="xid_18446744073709551614" H5SourcePath="/udlink1" LinkClass="187"  Parents="xid_96" H5ParentPaths="/" />
+   <hdf5:UserDefined LinkName="udlink2" OBJ-XID="xid_18446744073709551613" H5SourcePath="/udlink2" LinkClass="187"  Parents="xid_96" H5ParentPaths="/" />
+</hdf5:RootGroup>
+</hdf5:HDF5-File>
diff --git a/tools/testfiles/twithub.h5 b/tools/testfiles/twithub.h5
index 105319f..2176034 100644
--- a/tools/testfiles/twithub.h5
+++ b/tools/testfiles/twithub.h5
diff --git a/tools/testfiles/twithub513.h5 b/tools/testfiles/twithub513.h5
index 8b6a2e2..fbb872a 100644
--- a/tools/testfiles/twithub513.h5
+++ b/tools/testfiles/twithub513.h5