Add info_to_str and str_to_info "management" callbacks for serializing and

deserializing a connector's info object.

12 files changed, 295 insertions, 53 deletions

diff --git a/examples/h5_vol_external_log_native.c b/examples/h5_vol_external_log_native.c
index 0d48b73..19eaa5e 100644
--- a/examples/h5_vol_external_log_native.c
+++ b/examples/h5_vol_external_log_native.c
@@ -53,6 +53,8 @@ static const H5VL_class_t H5VL_log_g = {
     NULL,                                       /* info copy    */
     NULL,                                       /* info compare */
     NULL,                                       /* info free    */
+    NULL,                                       /* info to str  */
+    NULL,                                       /* str to info  */
     NULL,                                       /* get_object   */
     NULL,                                       /* get_wrap_ctx */
     NULL,                                       /* free_wrap_ctx */
diff --git a/src/H5PLint.c b/src/H5PLint.c
index 166b300..bbe71fe 100644
--- a/src/H5PLint.c
+++ b/src/H5PLint.c
@@ -30,7 +30,6 @@
 #include "H5Eprivate.h"     /* Error handling               */
 #include "H5MMprivate.h"    /* Memory management            */
 #include "H5PLpkg.h"        /* Plugin                       */
-#include "H5VLprivate.h"    /* Virtual Object Layer         */
 #include "H5Zprivate.h"     /* Filter pipeline              */
 
 
@@ -236,7 +235,7 @@ done:
  *-------------------------------------------------------------------------
  */
 const void *
-H5PL_load(H5PL_type_t type, H5PL_key_t key)
+H5PL_load(H5PL_type_t type, const H5PL_key_t *key)
 {
     H5PL_search_params_t    search_params;          /* Plugin search parameters     */
     hbool_t                 found = FALSE;          /* Whether the plugin was found */
@@ -263,7 +262,7 @@ H5PL_load(H5PL_type_t type, H5PL_key_t key)
 
     /* Set up the search parameters */
     search_params.type = type;
-    search_params.key.id = key.id;
+    search_params.key.id = key->id;
 
     /* Search in the table of already loaded plugin libraries */
     if(H5PL__find_plugin_in_cache(&search_params, &found, &plugin_info) < 0)
@@ -308,7 +307,8 @@ done:
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wpedantic"
 herr_t
-H5PL__open(const char *path, H5PL_type_t type, H5PL_key_t key, hbool_t *success, const void **plugin_info)
+H5PL__open(const char *path, H5PL_type_t type, const H5PL_key_t *key,
+    hbool_t *success, const void **plugin_info)
 {
     H5PL_HANDLE             handle = NULL;
     H5PL_get_plugin_info_t  get_plugin_info = NULL;
@@ -350,29 +350,44 @@ H5PL__open(const char *path, H5PL_type_t type, H5PL_key_t key, hbool_t *success,
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get filter info from plugin")
 
             /* If the filter IDs match, we're done. Set the output parameters. */
-            if (filter_info->id == key.id) {
+            if (filter_info->id == key->id) {
                 *plugin_info = (const void *)filter_info;
                 *success = TRUE;
             }
 
             break;
         }
+
         case H5PL_TYPE_VOL:
         {
-            const H5VL_class_t *cls = NULL;
+            const H5VL_class_t *cls;
 
             /* Get the plugin info */
-            if (NULL == (cls = (const H5VL_class_t *)(*get_plugin_info)()))
+            if(NULL == (cls = (const H5VL_class_t *)(*get_plugin_info)()))
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "can't get VOL driver info from plugin")
 
-            /* If the plugin names match, we're done. Set the output parameters. */
-            if (cls->name && !HDstrcmp(cls->name, key.name)) {
-                *plugin_info = (const void *)cls;
-                *success = TRUE;
-            }
+            /* Which kind of key are we looking for? */
+            if(key->vol.kind == H5VL_GET_CONNECTOR_BY_NAME) {
+                /* If the plugin names match, we're done. Set the output parameters. */
+                if(cls->name && !HDstrcmp(cls->name, key->vol.u.name)) {
+                    *plugin_info = (const void *)cls;
+                    *success = TRUE;
+                } /* end if */
+            } /* end if */
+            else {
+                /* Sanity check */
+                HDassert(key->vol.kind == H5VL_GET_CONNECTOR_BY_VALUE);
+
+                /* If the plugin values match, we're done. Set the output parameters. */
+                if(cls->value == key->vol.u.value) {
+                    *plugin_info = (const void *)cls;
+                    *success = TRUE;
+                } /* end if */
+            } /* end else */
 
             break;
         }
+
         case H5PL_TYPE_ERROR:
         case H5PL_TYPE_NONE:
         default:
diff --git a/src/H5PLpath.c b/src/H5PLpath.c
index 972f1d0..460f19d 100644
--- a/src/H5PLpath.c
+++ b/src/H5PLpath.c
@@ -689,7 +689,7 @@ H5PL__find_plugin_in_path(const H5PL_search_params_t *search_params, hbool_t *fo
                 continue;
 
             /* attempt to open the dynamic library as a filter library */
-            if (H5PL__open(path, search_params->type, search_params->key, found, plugin_info) < 0)
+            if (H5PL__open(path, search_params->type, &(search_params->key), found, plugin_info) < 0)
                 HGOTO_ERROR(H5E_PLUGIN, H5E_CANTGET, FAIL, "search in directory failed")
             if (*found)
                 HGOTO_DONE(SUCCEED)
diff --git a/src/H5PLpkg.h b/src/H5PLpkg.h
index dfaa4af..d60da82 100644
--- a/src/H5PLpkg.h
+++ b/src/H5PLpkg.h
@@ -134,13 +134,15 @@ H5_DLL herr_t H5PL__get_plugin_control_mask(unsigned int *mask /*out*/);
 H5_DLL herr_t H5PL__set_plugin_control_mask(unsigned int mask);
 
 /* Plugin search and manipulation */
-H5_DLL herr_t H5PL__open(const char *libname, H5PL_type_t type, H5PL_key_t key, hbool_t *success /*out*/, const void **plugin_info /*out*/);
+H5_DLL herr_t H5PL__open(const char *libname, H5PL_type_t type, const H5PL_key_t *key,
+    hbool_t *success /*out*/, const void **plugin_info /*out*/);
 H5_DLL herr_t H5PL__close(H5PL_HANDLE handle);
 
 /* Plugin cache calls */
 H5_DLL herr_t H5PL__create_plugin_cache(void);
 H5_DLL herr_t H5PL__close_plugin_cache(hbool_t *already_closed /*out*/);
-H5_DLL herr_t H5PL__add_plugin(H5PL_type_t type, H5PL_key_t key, H5PL_HANDLE handle);
+H5_DLL herr_t H5PL__add_plugin(H5PL_type_t type, const H5PL_key_t *key,
+    H5PL_HANDLE handle);
 H5_DLL herr_t H5PL__find_plugin_in_cache(const H5PL_search_params_t *search_params, hbool_t *found /*out*/, const void **plugin_info /*out*/);
 
 /* Plugin search path calls */
diff --git a/src/H5PLplugin_cache.c b/src/H5PLplugin_cache.c
index e905ac2..7fe676d 100644
--- a/src/H5PLplugin_cache.c
+++ b/src/H5PLplugin_cache.c
@@ -216,7 +216,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5PL__add_plugin(H5PL_type_t type, H5PL_key_t key, H5PL_HANDLE handle)
+H5PL__add_plugin(H5PL_type_t type, const H5PL_key_t *key, H5PL_HANDLE handle)
 {
     herr_t      ret_value = SUCCEED;
 
@@ -229,7 +229,7 @@ H5PL__add_plugin(H5PL_type_t type, H5PL_key_t key, H5PL_HANDLE handle)
 
     /* Store the plugin info and bump the # of plugins */
     H5PL_cache_g[H5PL_num_plugins_g].type       = type;
-    H5PL_cache_g[H5PL_num_plugins_g].key        = key;
+    H5PL_cache_g[H5PL_num_plugins_g].key        = *key;
     H5PL_cache_g[H5PL_num_plugins_g].handle     = handle;
 
     H5PL_num_plugins_g++;
diff --git a/src/H5PLprivate.h b/src/H5PLprivate.h
index 2af1b70..5ce9b87 100644
--- a/src/H5PLprivate.h
+++ b/src/H5PLprivate.h
@@ -21,7 +21,8 @@
 #include "H5PLpublic.h"
 
 /* Private headers needed by this file */
-#include "H5private.h"          /* Generic Functions                    */
+#include "H5private.h"      /* Generic Functions            */
+#include "H5VLprivate.h"    /* Virtual Object Layer         */
 
 
 /**************************/
@@ -35,8 +36,14 @@
 
 /* The key that will be used to find the plugin */
 typedef union H5PL_key_t {
-    int         id;         /* filters      */
-    const char *name;       /* VOL drivers  */
+    int         id;         /* I/O filters */
+    struct {
+        H5VL_get_connector_kind_t kind; /* Kind of VOL lookup to do */
+        union {
+            H5VL_class_value_t value;   /* VOL connector value */
+            const char *name;           /* VOL connector name */
+        } u;
+    } vol;
 } H5PL_key_t;
 
 
@@ -50,7 +57,7 @@ typedef union H5PL_key_t {
 /***************************************/
 
 /* Internal API routines */
-H5_DLL const void *H5PL_load(H5PL_type_t plugin_type, H5PL_key_t key);
+H5_DLL const void *H5PL_load(H5PL_type_t plugin_type, const H5PL_key_t *key);
 
 #endif /* _H5PLprivate_H */
 
diff --git a/src/H5VL.c b/src/H5VL.c
index 0a835a2..5eeb201 100644
--- a/src/H5VL.c
+++ b/src/H5VL.c
@@ -41,38 +41,51 @@
 /* Local Macros */
 /****************/
 
+
 /******************/
 /* Local Typedefs */
 /******************/
 
 /* Information needed for iterating over the registered VOL connector hid_t IDs.
- * The name of the new VOL connector that is being registered is stored in the
- * name field and the found_id field is initialized to H5I_INVALID_HID (-1).
- * If we find a VOL connector with the same name, we set the found_id field to
- * the existing ID for return to the function.
+ * The name or value of the new VOL connector that is being registered is
+ * stored in the name (or value) field and the found_id field is initialized to
+ * H5I_INVALID_HID (-1).  If we find a VOL connector with the same name / value,
+ * we set the found_id field to the existing ID for return to the function.
  */
 typedef struct {
-    const char *name;           /* The name of the VOL connector to check */
-    hid_t found_id;             /* The library ID if we found a match */
+    /* IN */
+    H5VL_get_connector_kind_t kind;     /* Which kind of connector search to make */
+    union {
+        const char *name;               /* The name of the VOL connector to check */
+        H5VL_class_value_t value;       /* The value of the VOL connector to check */
+    } u;
+
+    /* OUT */
+    hid_t found_id;                     /* The connector ID, if we found a match */
 } H5VL_get_connector_ud_t;
 
+
 /********************/
 /* Local Prototypes */
 /********************/
 static int H5VL__get_connector_cb(void *obj, hid_t id, void *_op_data);
 
+
 /*********************/
 /* Package Variables */
 /*********************/
 
+
 /*****************************/
 /* Library Private Variables */
 /*****************************/
 
+
 /*******************/
 /* Local Variables */
 /*******************/
 
+
 
 /*-------------------------------------------------------------------------
  * Function:    H5VL__get_connector_cb
@@ -95,10 +108,19 @@ H5VL__get_connector_cb(void *obj, hid_t id, void *_op_data)
 
     FUNC_ENTER_STATIC_NOERR
 
-    if (0 == HDstrcmp(cls->name, op_data->name)) {
-        op_data->found_id = id;
-        ret_value = H5_ITER_STOP;
+    if(H5VL_GET_CONNECTOR_BY_NAME == op_data->kind) {
+        if(0 == HDstrcmp(cls->name, op_data->u.name)) {
+            op_data->found_id = id;
+            ret_value = H5_ITER_STOP;
+        } /* end if */
     } /* end if */
+    else {
+        HDassert(H5VL_GET_CONNECTOR_BY_VALUE == op_data->kind);
+        if(cls->value == op_data->u.value) {
+            op_data->found_id = id;
+            ret_value = H5_ITER_STOP;
+        } /* end if */
+    } /* end else */
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL__get_connector_cb() */
@@ -139,8 +161,9 @@ H5VLregister_connector(const H5VL_class_t *cls, hid_t vipl_id)
     if (cls->get_wrap_ctx && !cls->free_wrap_ctx)
         HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID, "VOL connector must provide free callback for object wrapping contexts when a get callback is provided")
 
+    op_data.kind = H5VL_GET_CONNECTOR_BY_NAME;
+    op_data.u.name = cls->name;
     op_data.found_id = H5I_INVALID_HID;
-    op_data.name = cls->name;
 
     /* check if connector is already registered */
     if (H5I_iterate(H5I_VOL, H5VL__get_connector_cb, &op_data, TRUE) < 0)
@@ -192,16 +215,17 @@ H5VLregister_connector_by_name(const char *name, hid_t vipl_id)
     if (0 == HDstrlen(name))
         HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, H5I_INVALID_HID, "zero-length VOL connector name is disallowed")
 
+    op_data.kind = H5VL_GET_CONNECTOR_BY_NAME;
+    op_data.u.name = name;
     op_data.found_id = H5I_INVALID_HID;
-    op_data.name = name;
 
     /* Check if connector is already registered */
-    if (H5I_iterate(H5I_VOL, H5VL__get_connector_cb, &op_data, TRUE) < 0)
+    if(H5I_iterate(H5I_VOL, H5VL__get_connector_cb, &op_data, TRUE) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_BADITER, H5I_INVALID_HID, "can't iterate over VOL ids")
 
     /* If connector alread registered, increment ref count on ID and return ID */
-    if (op_data.found_id != H5I_INVALID_HID) {
-        if (H5I_inc_ref(op_data.found_id, TRUE) < 0)
+    if(op_data.found_id != H5I_INVALID_HID) {
+        if(H5I_inc_ref(op_data.found_id, TRUE) < 0)
             HGOTO_ERROR(H5E_VOL, H5E_CANTINC, H5I_INVALID_HID, "unable to increment ref count on VOL connector")
         ret_value = op_data.found_id;
     } /* end if */
@@ -210,12 +234,13 @@ H5VLregister_connector_by_name(const char *name, hid_t vipl_id)
         const H5VL_class_t *cls;
 
         /* Try loading the connector */
-        key.name = name;
-        if (NULL == (cls = (const H5VL_class_t *)H5PL_load(H5PL_TYPE_VOL, key)))
+        key.vol.kind = H5VL_GET_CONNECTOR_BY_NAME;
+        key.vol.u.name = name;
+        if(NULL == (cls = (const H5VL_class_t *)H5PL_load(H5PL_TYPE_VOL, &key)))
             HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, H5I_INVALID_HID, "unable to load VOL connector")
 
         /* Register the connector we loaded */
-        if ((ret_value = H5VL_register_connector(cls, TRUE, vipl_id)) < 0)
+        if((ret_value = H5VL_register_connector(cls, TRUE, vipl_id)) < 0)
             HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID, "unable to register VOL connector ID")
     } /* end else */
 
@@ -225,6 +250,66 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VLregister_connector_by_value
+ *
+ * Purpose:     Registers a new VOL connector as a member of the virtual object
+ *              layer class.
+ *
+ * Return:      Success:    A VOL connector ID which is good until the
+ *                          library is closed or the connector is
+ *                          unregistered.
+ *
+ *              Failure:    H5I_INVALID_HID
+ *
+ *-------------------------------------------------------------------------
+ */
+hid_t
+H5VLregister_connector_by_value(H5VL_class_value_t value, hid_t vipl_id)
+{
+    H5VL_get_connector_ud_t op_data;       /* Callback info for connector search */
+    hid_t ret_value = H5I_INVALID_HID;
+
+    FUNC_ENTER_API(H5I_INVALID_HID)
+
+    /* Check arguments */
+    if(value < 0)
+        HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, H5I_INVALID_HID, "negative VOL connector value is disallowed")
+
+    op_data.kind = H5VL_GET_CONNECTOR_BY_VALUE;
+    op_data.u.value = value;
+    op_data.found_id = H5I_INVALID_HID;
+
+    /* Check if connector is already registered */
+    if(H5I_iterate(H5I_VOL, H5VL__get_connector_cb, &op_data, TRUE) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_BADITER, H5I_INVALID_HID, "can't iterate over VOL ids")
+
+    /* If connector alread registered, increment ref count on ID and return ID */
+    if(op_data.found_id != H5I_INVALID_HID) {
+        if(H5I_inc_ref(op_data.found_id, TRUE) < 0)
+            HGOTO_ERROR(H5E_VOL, H5E_CANTINC, H5I_INVALID_HID, "unable to increment ref count on VOL connector")
+        ret_value = op_data.found_id;
+    } /* end if */
+    else {
+        H5PL_key_t key;
+        const H5VL_class_t *cls;
+
+        /* Try loading the connector */
+        key.vol.kind = H5VL_GET_CONNECTOR_BY_NAME;
+        key.vol.u.value = value;
+        if(NULL == (cls = (const H5VL_class_t *)H5PL_load(H5PL_TYPE_VOL, &key)))
+            HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, H5I_INVALID_HID, "unable to load VOL connector")
+
+        /* Register the connector we loaded */
+        if((ret_value = H5VL_register_connector(cls, TRUE, vipl_id)) < 0)
+            HGOTO_ERROR(H5E_VOL, H5E_CANTREGISTER, H5I_INVALID_HID, "unable to register VOL connector ID")
+    } /* end else */
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5VLregister_connector_by_value() */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5VLis_connector_registered
  *
  * Purpose:     Tests whether a VOL class has been registered or not
@@ -246,8 +331,9 @@ H5VLis_connector_registered(const char *name)
     FUNC_ENTER_API(FAIL)
     H5TRACE1("t", "*s", name);
 
+    op_data.kind = H5VL_GET_CONNECTOR_BY_NAME;
+    op_data.u.name = name;
     op_data.found_id = H5I_INVALID_HID;
-    op_data.name = name;
 
     /* Check arguments */
     if (H5I_iterate(H5I_VOL, H5VL__get_connector_cb, &op_data, TRUE) < 0)
@@ -280,8 +366,9 @@ H5VLget_connector_id(const char *name)
     FUNC_ENTER_API(H5I_INVALID_HID)
     H5TRACE1("i", "*s", name);
 
-    op_data.found_id    = H5I_INVALID_HID;
-    op_data.name        = name;
+    op_data.kind = H5VL_GET_CONNECTOR_BY_NAME;
+    op_data.u.name = name;
+    op_data.found_id = H5I_INVALID_HID;
 
     /* Check arguments */
     if (H5I_iterate(H5I_VOL, H5VL__get_connector_cb, &op_data, TRUE) < 0)
diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index e921dea..7b67964 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -291,6 +291,37 @@ done:
 } /* H5VLget_cap_flags */
 
 
+/*---------------------------------------------------------------------------
+ * Function:    H5VLget_value
+ *
+ * Purpose:     Retrieves the 'value' for a connector
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *---------------------------------------------------------------------------
+ */
+herr_t
+H5VLget_value(hid_t connector_id, H5VL_class_value_t *value)
+{
+    H5VL_class_t *cls;                  /* VOL connector's class struct */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API_NOINIT
+
+    /* Check args */
+    if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(connector_id, H5I_VOL)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
+
+    /* Retrieve connector value */
+    if(value)
+        *value = cls->value;
+
+done:
+    FUNC_LEAVE_API_NOINIT(ret_value)
+} /* H5VLget_value */
+
+
 /*-------------------------------------------------------------------------
  * Function:    H5VL_copy_connector_info
  *
@@ -523,6 +554,88 @@ done:
 
 
 /*---------------------------------------------------------------------------
+ * Function:    H5VLconnector_info_to_str
+ *
+ * Purpose:     Serialize a connector's info into a string
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *---------------------------------------------------------------------------
+ */
+herr_t
+H5VLconnector_info_to_str(const void *info, hid_t connector_id, char **str)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API_NOINIT
+
+    /* Only serialize info object, if it's non-NULL */
+    if(info) {
+        H5VL_class_t *cls;                  /* VOL connector's class struct */
+
+        /* Check args and get class pointer */
+        if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(connector_id, H5I_VOL)))
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
+
+        /* Allow the connector to serialize info */
+        if(cls->info_to_str) {
+            if((cls->info_to_str)(info, str) < 0)
+                HGOTO_ERROR(H5E_VOL, H5E_CANTSERIALIZE, FAIL, "can't serialize connector info")
+        } /* end if */
+        else
+            *str = NULL;
+    } /* end if */
+    else
+        *str = NULL;
+
+done:
+    FUNC_LEAVE_API_NOINIT(ret_value)
+} /* H5VLconnector_info_to_str() */
+
+
+/*---------------------------------------------------------------------------
+ * Function:    H5VLconnector_str_to_info
+ *
+ * Purpose:     Deserialize a string into a connector's info
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *---------------------------------------------------------------------------
+ */
+herr_t
+H5VLconnector_str_to_info(const char *str, hid_t connector_id, void **info)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API_NOINIT
+
+    /* Only deserialize string, if it's non-NULL */
+    if(str) {
+        H5VL_class_t *cls;                  /* VOL connector's class struct */
+
+        /* Check args and get class pointer */
+        if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(connector_id, H5I_VOL)))
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
+
+        /* Allow the connector to deserialize info */
+        if(cls->str_to_info) {
+            if((cls->str_to_info)(str, info) < 0)
+                HGOTO_ERROR(H5E_VOL, H5E_CANTUNSERIALIZE, FAIL, "can't deserialize connector info")
+        } /* end if */
+        else
+            *info = NULL;
+    } /* end if */
+    else
+        *info = NULL;
+
+done:
+    FUNC_LEAVE_API_NOINIT(ret_value)
+} /* H5VLconnector_str_to_info() */
+
+
+/*---------------------------------------------------------------------------
  * Function:    H5VLget_object
  *
  * Purpose:     Retrieves an underlying object.
@@ -658,7 +771,7 @@ H5VL_free_wrap_ctx(const H5VL_class_t *connector, void *wrap_ctx)
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5VL_free_connector_info() */
+} /* end H5VL_free_wrap_ctx() */
 
 
 /*---------------------------------------------------------------------------
diff --git a/src/H5VLnative.c b/src/H5VLnative.c
index e506af4..71f4276 100644
--- a/src/H5VLnative.c
+++ b/src/H5VLnative.c
@@ -130,6 +130,8 @@ static H5VL_class_t H5VL_native_cls_g = {
     NULL,                                           /* info copy    */
     NULL,                                           /* info compare */
     NULL,                                           /* info free    */
+    NULL,                                           /* info to str  */
+    NULL,                                           /* str to info  */
     NULL,                                           /* get_object   */
     NULL,                                           /* get_wrap_ctx */
     NULL,                                           /* free_wrap_ctx */
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index 6b69d93..97e9119 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -45,10 +45,18 @@ typedef struct H5VL_connector_prop_t {
     const void         *connector_info; /* VOL connector info, for open callbacks               */
 } H5VL_connector_prop_t;
 
+/* Which kind of VOL connector field to use for searching */
+typedef enum H5VL_get_connector_kind_t {
+    H5VL_GET_CONNECTOR_BY_NAME,         /* Name field is set */
+    H5VL_GET_CONNECTOR_BY_VALUE         /* Value field is set */
+} H5VL_get_connector_kind_t;
+
+
 /*****************************/
 /* Library Private Variables */
 /*****************************/
 
+
 /******************************/
 /* Library Private Prototypes */
 /******************************/
diff --git a/src/H5VLpublic.h b/src/H5VLpublic.h
index 26e841d..9fe5bcd 100644
--- a/src/H5VLpublic.h
+++ b/src/H5VLpublic.h
@@ -382,13 +382,15 @@ typedef struct H5VL_class_t {
     herr_t  (*initialize)(hid_t vipl_id);           /* Connector initialization callback            */
     herr_t  (*terminate)(void);                     /* Connector termination callback               */
     size_t  info_size;                              /* size of the vol info                         */
-    void *  (*info_copy)(const void *info);         /* callback to create a copy of the vol info    */
-    int     (*info_cmp)(const void *info1, const void *info2); /* callback to compare vol info      */
-    herr_t  (*info_free)(void *info);               /* callback to release the vol info copy        */
-    void *  (*get_object)(const void *obj);         /* callback to retrieve underlying object       */
-    herr_t  (*get_wrap_ctx)(const void *obj, void **wrap_ctx); /* callback to retrieve the object wrapping context for the connector */
-    herr_t  (*free_wrap_ctx)(void *wrap_ctx);       /* callback to release the object wrapping context for the connector */
-    void*   (*wrap_object)(void *obj, void *wrap_ctx); /* callback to wrap an object */
+    void *  (*info_copy)(const void *info);         /* Callback to create a copy of the vol info    */
+    int     (*info_cmp)(const void *info1, const void *info2); /* Callback to compare vol info      */
+    herr_t  (*info_free)(void *info);               /* Callback to release the vol info copy        */
+    herr_t  (*info_to_str)(const void *info, char **str); /* Callback to serialize connector's info into a string */
+    herr_t  (*str_to_info)(const char *str, void **info); /* Callback to deserialize a string into connector's info */
+    void *  (*get_object)(const void *obj);         /* Callback to retrieve underlying object       */
+    herr_t  (*get_wrap_ctx)(const void *obj, void **wrap_ctx); /* Callback to retrieve the object wrapping context for the connector */
+    herr_t  (*free_wrap_ctx)(void *wrap_ctx);       /* Callback to release the object wrapping context for the connector */
+    void*   (*wrap_object)(void *obj, void *wrap_ctx); /* Callback to wrap an object */
 
     /* Data Model */
     H5VL_attr_class_t          attr_cls;            /* attribute class callbacks    */
@@ -422,6 +424,7 @@ extern "C" {
 /* VOL Connector Functionality */
 H5_DLL hid_t H5VLregister_connector(const H5VL_class_t *cls, hid_t vipl_id);
 H5_DLL hid_t H5VLregister_connector_by_name(const char *connector_name, hid_t vipl_id);
+H5_DLL hid_t H5VLregister_connector_by_value(H5VL_class_value_t connector_value, hid_t vipl_id);
 H5_DLL htri_t H5VLis_connector_registered(const char *name);
 H5_DLL hid_t H5VLget_connector_id(const char *name);
 H5_DLL ssize_t H5VLget_connector_name(hid_t id, char *name/*out*/, size_t size);
@@ -442,10 +445,13 @@ H5_DLL herr_t H5VLcmp_connector_cls(int *cmp, hid_t connector_id1, hid_t connect
 H5_DLL herr_t H5VLinitialize(hid_t connector_id, hid_t vipl_id);
 H5_DLL herr_t H5VLterminate(hid_t connector_id);
 H5_DLL herr_t H5VLget_cap_flags(hid_t connector_id, unsigned *cap_flags);
+H5_DLL herr_t H5VLget_value(hid_t connector_id, H5VL_class_value_t *conn_value);
 H5_DLL herr_t H5VLcopy_connector_info(hid_t connector_id, void **dst_vol_info, void *src_vol_info);
 H5_DLL herr_t H5VLcmp_connector_info(int *cmp, hid_t connector_id, const void *info1,
     const void *info2);
 H5_DLL herr_t H5VLfree_connector_info(hid_t connector_id, void *vol_info);
+H5_DLL herr_t H5VLconnector_info_to_str(const void *info, hid_t connector_id, char **str);
+H5_DLL herr_t H5VLconnector_str_to_info(const char *str, hid_t connector_id, void **info);
 H5_DLL void *H5VLget_object(void *obj, hid_t connector_id);
 H5_DLL herr_t H5VLget_wrap_ctx(void *obj, hid_t connector_id, void **wrap_ctx);
 H5_DLL herr_t H5VLfree_wrap_ctx(void *wrap_ctx, hid_t connector_id);
diff --git a/src/H5Z.c b/src/H5Z.c
index aeb7602..f41588f 100644
--- a/src/H5Z.c
+++ b/src/H5Z.c
@@ -697,11 +697,11 @@ H5Z_filter_avail(H5Z_filter_t id)
             HGOTO_DONE(TRUE)
 
     key.id = (int)id;
-    if (NULL != (filter_info = (const H5Z_class2_t *)H5PL_load(H5PL_TYPE_FILTER, key))) {
-        if (H5Z_register(filter_info) < 0)
+    if(NULL != (filter_info = (const H5Z_class2_t *)H5PL_load(H5PL_TYPE_FILTER, &key))) {
+        if(H5Z_register(filter_info) < 0)
             HGOTO_ERROR(H5E_PLINE, H5E_CANTINIT, FAIL, "unable to register loaded filter")
         HGOTO_DONE(TRUE)
-    }
+    } /* end if */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -1289,7 +1289,7 @@ H5Z_pipeline(const H5O_pline_t *pline, unsigned flags,
 
                 /* Try loading the filter */
                 key.id = (int)(pline->filter[idx].id);
-                if(NULL != (filter_info = (const H5Z_class2_t *)H5PL_load(H5PL_TYPE_FILTER, key))) {
+                if(NULL != (filter_info = (const H5Z_class2_t *)H5PL_load(H5PL_TYPE_FILTER, &key))) {
                     /* Register the filter we loaded */
                     if(H5Z_register(filter_info) < 0)
                         HGOTO_ERROR(H5E_PLINE, H5E_CANTINIT, FAIL, "unable to register filter")