Bring async branch to develop (#166)

* Add H5Fwait, H5Dwait, and other changes for async vol connector

* Revert temporary testing changes

* Add H5Fwait to header file

* Add H5VLreset_lib_state() routine.

* Correct VOL wrap context when retrieving library state for file open & create.

* Manage the API context's VOL connector state as part of the library state.

* Set the 'VOL connector property valid' flag when restoring the library state.

* Don't push new API context on stack when retrieving "current" one.

* Check for NULL VOL wrap context before decrementing refcount on it, when
freeing the API context state.

* Manage recount of underlying connector for VOL wrap context.

* Add H5TSmutex_acquire() and H5TSmutex_release() routines to acquire and
release the global lock on the HDF5 library.

* Update library with new functions related to library global lock

* Add asynchronous token API

* Add new lightweight FUNC_ENTER / LEAVE macros for helping to structure the
threadsafety (H5TS*) routines.

* Sync w/develop

* Initial event set code framework.

* Elaborate on the H5ES routines, starting to add API routines.

Update the "close ID" callbacks to allow asynchronous request tokens to be
passed in from an asynchronous close API call.

Refactor current asynchronous API routines (H5Fopen/H5Fclose and
H5Dread/H5Dread) to use event sets instead of directly working with request
tokens from the application.

Clean up a few other minor warnings & code style issues.

* Implement H5EScreate, H5ESget_count, and H5ESclose.

It should be possible to write a simple application that creates an event
set and uses it with H5Fopen_async, H5Dread_async, H5Dwrite_async, and
H5Fclose_async, then calls H5ESclose (which waits for all async events to
complete).

* Add source file for event set test.

* Refactor sync & async API routines to call common routine.

Move dataset API read / write routines to src/H5D.c, along with all the other
API routines.

Progress on "fake" async VOL connector, for testing.

* Modify async implementation to wrap async requests in a H5VL_object_t
struct so the VOL layer can find the connector when accessing the
request at a later point.

* Free the requests is H5ESclose.  Remove comments implying that request
wait, notify, and cancel callbacks should free the request.

* Fix bug in error handling in H5Fclose.

* Fix bugs in async file routines.  Rename H5VL_create_object_generic to
H5VL_create_object.

* Add explicit async version of H5Fcreate.

* Add more _async routines

* Correct typo for return value from H5Awrite changes

* Add H5EStest and H5ESwait routines

* Updated with API tracing info

* Fix NULL pointer dereference in H5ES__wait

* Add H5is_library_terminating() routine, so that VOL connectors can detect
when the library is shutting down.

* Fix typo

* Remove event from event set's linked list

* Move block of code so that vol_obj is valid

* Avoid setting properties in the DXPL when reseting the library state (and in
the test code).

* Refactor argument tracing to implement new capability for tracing arguments
of non-API routines, with the H5ARG_TRACE macro.   This macro is updated
automatically with the bin/trace script that runs as part of the autogen.sh
process.   Major changes were in src/H5trace.c and bin/trace, with the other
changes being cleanups to the argument lists, to improve their presentation
in the tracing output.

Also - added the "managed string" routines, which can dynamically allocate
strings, appending printf-formatted output to the string efficiently.

* Release memory for managed strings

* Fix printf() formats.

* More printf() format fixes.

* Add H5Eappend_stack routine and regression tests

* Clean up a few missed merge conflicts and update the error stacks.

* Remove unnecessary fork() operations and ten second sleep().

* Restore commented out attribute out, to better enable tracking down the previous failure

* Allow multiple H5ARG_TRACE macros within a routine to be updated

* Switch to using "new" H5ES_insert (which takes the arguments for the caller routine) for all event set operations.  Renames H5ES_insert_new to H5ES_insert and removes the previous H5ES_insert.

* Merge "managed" string routines into "ref-counted" strings, and refactor code to use them.

* Add missing file.

* Add caller's name and arguments to event, for error reporting

* Refactor event set setup for "API common" internal routines

* Checkin async API routines for H5A* and H5G* modules as listed in ID-283.
Fix couple h5dump expected output files due to the changes.

* Add some of the error query routines needed for event sets.

* Refactor to make async setup / teardown and "common" routines cleaner

* (1) Add async APIs to H5L, H5F, and H5D modules
(2) Fix errors in previous checkins of async APIs in H5A and H5G modules
(3) h5dump expected output changes

* Enhance event info, for better error handling

* Change name of temporary vol_obj variable, to help reduce coding errors

* Fix oversight with vol_obj pointer

* Minor code cleanup

* Add missing \'valid\' flag for VOL wrapper context, when restoring the library\'s state

* Run source formatter

* Change H5TSmutex lock and release to include a lock count

* Update error reporting ideas

* Minor updates to improve sanity checking for retrieving / restoring library state

* Updated with feedback from h5py team members

* Refactor internal event set list and event handling, add implementation for H5ESget_err_info

* Change the VOL request subclass callbacks that switch from using "H5ES_status_t" to "H5VL_request_status_t", and also add a H5VL_request_status_t* parameter to the 'cancel' callback in the request subclass.  Also more code quality cleanups to add iterator callbacks to internal event set routines.

* Update API tracing for new H5VL_request_status_t typedef

* Finish converting internal event set operations to use list iterator callbacks, instead of directly accessing the list structure

* Add H5VL_REQUEST_GET_ERR_STACK operation to request subclass, for retrieving a copy of the error stack for a failed asynchronous operation

* Remove 'canceled' event status from Java constants

* Be safer about releasing resources when inserting a newly opened/created object or file into an event set

* Remove H5EStest, add H5ES_WAIT_NONE for 0 timeout, and revise parameters to H5ESwait, to make it more "aggregate".

* Remove H5ES_STATUS_CANCELED from Java wrappers also

* (a) Add async APIs for H5O module as listed in jira issue ID-283.
(b) Remove verification of name parameter in async related routines for H55A and H5L modules
    because it is checked in H5VL_setup* routine.
(c) Modify h5dump expected output due to the async changes.

* Corrections based on PR feedback.

* Further changes to make based on PR feedback.

* Fix missed merge marker, and reformatted line

* Clean up some warnings

* Correct level of indirection

* Relocate prototype (and doxygen info) for H5Aclose

* Change non-static function declarations to be static

* Ensure that H5TSpublic.h header gets installed (#129)

* Add 'wrapper' versions of async calls, to allow language wrappers and layers on top of HDF5 to pass in their application information.

* Switch H5Aexists\*_async and H5Lexists\*_async to use flag to return status, instead of return value.  Make the corresponding changes through most of the v1 and v2 B-tree code.  Clean up warnings in H5public.h and cmpd_dtransform.c.

* Add H5Iregister_future routine and tests.

* Correct return value for H5Lexists_async

* Add H5_DLL macro to public H5ES API routines

* Update supported -> flags parameter for introspect_query callback

* Remove my email address.  Update passthrough VOL connector ID.

* Fix comment for post_open_api_common

* Remove unused non-blocking VOL connector

* Minor cleanup in async branch in preparation for merge to develop

* Update CMake and the Autotools to use the new pass-through VOL ID

* Fix for SWMR daily test failures (#160)

The H5I_register_using_existing_id() call did not initialize the future
ID callbacks, causing the library to segfault when it tried to
resolve those function pointers.

* Added selective async APIs (#150)

* Added selective async APIs

Description:
    Added the following APIs:
        H5Ropen_attr_async
        H5Ropen_object_async
        H5Ropen_region_async

        H5Mcreate_async
        H5Mopen_async
        H5Mput_async
        H5Mget_async
        H5Mclose_async

        H5Tcommit_async
        H5Topen_async
        H5Tcopy_async
        H5Tclose_async
    - Updated an expected output file to include a new internal function
      in the error stack for the failure case.

* Updated async APIs per reviews, including removing async version of
H5Tcopy.

* Removed statements that were added by mistake in the previous commit.

* Fix compile issues in H5M and warnings elsewhere

* Reformat code

* Brings VOL_LIST changes from develop. (#163)

Co-authored-by: Houjun Tang <htang4@lbl.gov>
Co-authored-by: Neil Fortner <nfortne2@hdfgroup.org>
Co-authored-by: vchoi <vchoi@jelly.ad.hdfgroup.org>
Co-authored-by: vchoi-hdfgroup <55293060+vchoi-hdfgroup@users.noreply.github.com>
Co-authored-by: jhendersonHDF <jhenderson@hdfgroup.org>
Co-authored-by: Dana Robinson <derobins@hdfgroup.org>
Co-authored-by: Dana Robinson <43805+derobins@users.noreply.github.com>
Co-authored-by: bmribler <39579120+bmribler@users.noreply.github.com>

1 files changed, 595 insertions, 201 deletions

diff --git a/src/H5L.c b/src/H5L.c
index fbf5b1f..44fdeff 100644
--- a/src/H5L.c
+++ b/src/H5L.c
@@ -25,6 +25,7 @@
 #include "H5CXprivate.h"        /* API Contexts                             */
 #include "H5Dprivate.h"         /* Datasets                                 */
 #include "H5Eprivate.h"         /* Error handling                           */
+#include "H5ESprivate.h"        /* Event Sets                               */
 #include "H5Fprivate.h"         /* File access                              */
 #include "H5Gprivate.h"         /* Groups                                   */
 #include "H5Iprivate.h"         /* IDs                                      */
@@ -82,7 +83,7 @@ typedef struct {
     char *sep; /* Pointer to next separator in the string */
 
     /* Up */
-    hbool_t exists; /* Whether the link exists or not */
+    hbool_t *exists; /* Whether the link exists or not */
 } H5L_trav_le_t;
 
 /* User data for path traversal routine for getting link value */
@@ -129,6 +130,22 @@ static herr_t H5L__get_info_by_idx_cb(H5G_loc_t *grp_loc /*in*/, const char *nam
 static herr_t H5L__get_name_by_idx_cb(H5G_loc_t *grp_loc /*in*/, const char *name, const H5O_link_t *lnk,
                                       H5G_loc_t *obj_loc, void *_udata /*in,out*/,
                                       H5G_own_loc_t *own_loc /*out*/);
+static herr_t H5L__create_soft_api_common(const char *link_target, hid_t link_loc_id, const char *link_name,
+                                          hid_t lcpl_id, hid_t lapl_id, void **token_ptr,
+                                          H5VL_object_t **_vol_obj_ptr);
+static herr_t H5L__create_hard_api_common(hid_t cur_loc_id, const char *cur_name, hid_t new_loc_id,
+                                          const char *new_name, hid_t lcpl_id, hid_t lapl_id,
+                                          void **token_ptr, H5VL_object_t **_vol_obj_ptr);
+static herr_t H5L__delete_api_common(hid_t loc_id, const char *name, hid_t lapl_id, void **token_ptr,
+                                     H5VL_object_t **_vol_obj_ptr);
+static herr_t H5L__delete_by_idx_api_common(hid_t loc_id, const char *group_name, H5_index_t idx_type,
+                                            H5_iter_order_t order, hsize_t n, hid_t lapl_id, void **token_ptr,
+                                            H5VL_object_t **_vol_obj_ptr);
+static herr_t H5L__exists_api_common(hid_t loc_id, const char *name, hbool_t *exists, hid_t lapl_id,
+                                     void **token_ptr, H5VL_object_t **_vol_obj_ptr);
+static herr_t H5L__iterate_api_common(hid_t group_id, H5_index_t idx_type, H5_iter_order_t order,
+                                      hsize_t *idx_p, H5L_iterate2_t op, void *op_data, void **token_ptr,
+                                      H5VL_object_t **_vol_obj_ptr);
 
 /*********************/
 /* Package Variables */
@@ -422,33 +439,25 @@ done:
 } /* end H5Lcopy() */
 
 /*-------------------------------------------------------------------------
- * Function:    H5Lcreate_soft
+ * Function:    H5L__create_soft_api_common
  *
- * Purpose:     Creates a soft link from LINK_NAME to LINK_TARGET.
- *
- *              LINK_TARGET can be anything and is interpreted at lookup
- *              time relative to the group which contains the final component
- *              of LINK_NAME.  For instance, if LINK_TARGET is `./foo' and
- *              LINK_NAME is `./x/y/bar' and a request is made for `./x/y/bar'
- *              then the actual object looked up is `./x/y/./foo'.
+ * Purpose:     This is the common function for creating a soft link
  *
  * Return:      Non-negative on success/Negative on failure
  *
- * Programmer:  Robb Matzke
- *              Monday, April  6, 1998
- *
  *-------------------------------------------------------------------------
  */
-herr_t
-H5Lcreate_soft(const char *link_target, hid_t link_loc_id, const char *link_name, hid_t lcpl_id,
-               hid_t lapl_id)
+static herr_t
+H5L__create_soft_api_common(const char *link_target, hid_t link_loc_id, const char *link_name, hid_t lcpl_id,
+                            hid_t lapl_id, void **token_ptr, H5VL_object_t **_vol_obj_ptr)
 {
-    H5VL_object_t *   vol_obj = NULL; /* object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
+    H5VL_object_t **vol_obj_ptr =
+        (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
+    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
+    herr_t            ret_value = SUCCEED;            /* Return value */
 
-    FUNC_ENTER_API(FAIL)
-    H5TRACE5("e", "*si*sii", link_target, link_loc_id, link_name, lcpl_id, lapl_id);
+    FUNC_ENTER_STATIC
 
     /* Check arguments */
     if (link_loc_id == H5L_SAME_LOC)
@@ -457,10 +466,6 @@ H5Lcreate_soft(const char *link_target, hid_t link_loc_id, const char *link_name
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "link_target parameter cannot be NULL")
     if (!*link_target)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "link_target parameter cannot be an empty string")
-    if (!link_name)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "link_name parameter cannot be NULL")
-    if (!*link_name)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "link_name parameter cannot be an empty string")
     if (lcpl_id != H5P_DEFAULT && (TRUE != H5P_isa_class(lcpl_id, H5P_LINK_CREATE)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a link creation property list")
 
@@ -471,37 +476,31 @@ H5Lcreate_soft(const char *link_target, hid_t link_loc_id, const char *link_name
     /* Set the LCPL for the API context */
     H5CX_set_lcpl(lcpl_id);
 
-    /* Verify access property list and set up collective metadata if appropriate */
-    if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, link_loc_id, TRUE) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set access property list info")
-
-    /* Set location fields */
-    loc_params.type                         = H5VL_OBJECT_BY_NAME;
-    loc_params.loc_data.loc_by_name.name    = link_name;
-    loc_params.loc_data.loc_by_name.lapl_id = lapl_id;
-    loc_params.obj_type                     = H5I_get_type(link_loc_id);
-
-    /* get the location object */
-    if (NULL == (vol_obj = (H5VL_object_t *)H5VL_vol_object(link_loc_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
+    /* link_name is verified in H5VL_setup_name_args() */
+    /* Set up object access arguments */
+    if (H5VL_setup_name_args(link_loc_id, link_name, H5P_CLS_LACC, TRUE, lapl_id, vol_obj_ptr, &loc_params) <
+        0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set object access arguments")
 
     /* Create the link */
-    if (H5VL_link_create(H5VL_LINK_CREATE_SOFT, vol_obj, &loc_params, lcpl_id, lapl_id,
-                         H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, link_target) < 0)
+    if (H5VL_link_create(H5VL_LINK_CREATE_SOFT, *vol_obj_ptr, &loc_params, lcpl_id, lapl_id,
+                         H5P_DATASET_XFER_DEFAULT, token_ptr, link_target) < 0)
         HGOTO_ERROR(H5E_LINK, H5E_CANTCREATE, FAIL, "unable to create soft link")
 
 done:
-    FUNC_LEAVE_API(ret_value)
-} /* end H5Lcreate_soft() */
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5L__create_soft_api_common() */
 
 /*-------------------------------------------------------------------------
- * Function:    H5Lcreate_hard
+ * Function:    H5Lcreate_soft
  *
- * Purpose:     Creates a hard link from NEW_NAME to CUR_NAME.
+ * Purpose:     Creates a soft link from LINK_NAME to LINK_TARGET.
  *
- *              CUR_NAME must name an existing object.  CUR_NAME and
- *              NEW_NAME are interpreted relative to CUR_LOC_ID and
- *              NEW_LOC_ID, which are either file IDs or group IDs.
+ *              LINK_TARGET can be anything and is interpreted at lookup
+ *              time relative to the group which contains the final component
+ *              of LINK_NAME.  For instance, if LINK_TARGET is `./foo' and
+ *              LINK_NAME is `./x/y/bar' and a request is made for `./x/y/bar'
+ *              then the actual object looked up is `./x/y/./foo'.
  *
  * Return:      Non-negative on success/Negative on failure
  *
@@ -511,18 +510,88 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5Lcreate_hard(hid_t cur_loc_id, const char *cur_name, hid_t new_loc_id, const char *new_name, hid_t lcpl_id,
+H5Lcreate_soft(const char *link_target, hid_t link_loc_id, const char *link_name, hid_t lcpl_id,
                hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj1 = NULL; /* Object of cur_loc_id */
-    H5VL_object_t *   vol_obj2 = NULL; /* Object of new_loc_id */
-    H5VL_object_t     tmp_vol_obj;     /* Temporary object */
-    H5VL_loc_params_t loc_params1;
-    H5VL_loc_params_t loc_params2;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    herr_t ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
-    H5TRACE6("e", "i*si*sii", cur_loc_id, cur_name, new_loc_id, new_name, lcpl_id, lapl_id);
+    H5TRACE5("e", "*si*sii", link_target, link_loc_id, link_name, lcpl_id, lapl_id);
+
+    /* Creates a soft link synchronously */
+    if (H5L__create_soft_api_common(link_target, link_loc_id, link_name, lcpl_id, lapl_id, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTCREATE, FAIL, "unable to synchronously create soft link")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Lcreate_soft() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Lcreate_soft_async
+ *
+ * Purpose:     Asynchronous version of H5Lcreate_soft
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Lcreate_soft_async(const char *app_file, const char *app_func, unsigned app_line, const char *link_target,
+                     hid_t link_loc_id, const char *link_name, hid_t lcpl_id, hid_t lapl_id, hid_t es_id)
+{
+    H5VL_object_t *vol_obj   = NULL;            /* Object for loc_id */
+    void *         token     = NULL;            /* Request token for async operation        */
+    void **        token_ptr = H5_REQUEST_NULL; /* Pointer to request token for async operation        */
+    herr_t         ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE9("e", "*s*sIu*si*siii", app_file, app_func, app_line, link_target, link_loc_id, link_name,
+             lcpl_id, lapl_id, es_id);
+
+    /* Set up request token pointer for asynchronous operation */
+    if (H5ES_NONE != es_id)
+        token_ptr = &token; /* Point at token for VOL connector to set up */
+
+    /* Creates a soft link asynchronously */
+    if (H5L__create_soft_api_common(link_target, link_loc_id, link_name, lcpl_id, lapl_id, token_ptr,
+                                    &vol_obj) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTCREATE, FAIL, "unable to asynchronously create soft link")
+
+    /* If a token was created, add the token to the event set */
+    if (NULL != token)
+        if (H5ES_insert(es_id, vol_obj->connector, token,
+                        H5ARG_TRACE9(FUNC, "*s*sIu*si*siii", app_file, app_func, app_line, link_target,
+                                     link_loc_id, link_name, lcpl_id, lapl_id, es_id)) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTINSERT, FAIL, "can't insert token into event set")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Lcreate_soft_async() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5L__create_hard_api_common
+ *
+ * Purpose:     This is the common function for creating a hard link
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5L__create_hard_api_common(hid_t cur_loc_id, const char *cur_name, hid_t new_loc_id, const char *new_name,
+                            hid_t lcpl_id, hid_t lapl_id, void **token_ptr, H5VL_object_t **_vol_obj_ptr)
+{
+    H5VL_object_t * vol_obj1 = NULL;                /* Object of cur_loc_id */
+    H5VL_object_t * vol_obj2 = NULL;                /* Object of new_loc_id */
+    H5VL_object_t   tmp_vol_obj;                    /* Temporary object */
+    H5VL_object_t * tmp_vol_obj_ptr = &tmp_vol_obj; /* Ptr to temporary object */
+    H5VL_object_t **tmp_vol_obj_ptr_ptr =
+        (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj_ptr); /* Ptr to ptr to temporary object */
+    H5VL_loc_params_t loc_params1;         /* Location parameters for cur_loc_id object access */
+    H5VL_loc_params_t loc_params2;         /* Location parameters for new_loc_id object access */
+    herr_t            ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_STATIC
 
     /* Check arguments */
     if (cur_loc_id == H5L_SAME_LOC && new_loc_id == H5L_SAME_LOC)
@@ -576,20 +645,97 @@ H5Lcreate_hard(hid_t cur_loc_id, const char *cur_name, hid_t new_loc_id, const c
                         "Objects are accessed through different VOL connectors and can't be linked")
 
     /* Construct a temporary VOL object */
-    tmp_vol_obj.data      = (vol_obj2 ? (vol_obj2->data) : NULL);
-    tmp_vol_obj.connector = (vol_obj1 != NULL ? vol_obj1->connector : vol_obj2->connector);
+    (*tmp_vol_obj_ptr_ptr)->data      = (vol_obj2 ? (vol_obj2->data) : NULL);
+    (*tmp_vol_obj_ptr_ptr)->connector = (vol_obj1 != NULL ? vol_obj1->connector : vol_obj2->connector);
 
     /* Create the link */
-    if (H5VL_link_create(H5VL_LINK_CREATE_HARD, &tmp_vol_obj, &loc_params2, lcpl_id, lapl_id,
-                         H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, (vol_obj1 ? vol_obj1->data : NULL),
+    if (H5VL_link_create(H5VL_LINK_CREATE_HARD, *tmp_vol_obj_ptr_ptr, &loc_params2, lcpl_id, lapl_id,
+                         H5P_DATASET_XFER_DEFAULT, token_ptr, (vol_obj1 ? vol_obj1->data : NULL),
                          &loc_params1) < 0)
         HGOTO_ERROR(H5E_LINK, H5E_CANTCREATE, FAIL, "unable to create hard link")
 
 done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5L__create_hard_api_common() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Lcreate_hard
+ *
+ * Purpose:     Creates a hard link from NEW_NAME to CUR_NAME.
+ *
+ *              CUR_NAME must name an existing object.  CUR_NAME and
+ *              NEW_NAME are interpreted relative to CUR_LOC_ID and
+ *              NEW_LOC_ID, which are either file IDs or group IDs.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Programmer:  Robb Matzke
+ *              Monday, April  6, 1998
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Lcreate_hard(hid_t cur_loc_id, const char *cur_name, hid_t new_loc_id, const char *new_name, hid_t lcpl_id,
+               hid_t lapl_id)
+{
+    herr_t ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE6("e", "i*si*sii", cur_loc_id, cur_name, new_loc_id, new_name, lcpl_id, lapl_id);
+
+    /* Creates a hard link synchronously */
+    if (H5L__create_hard_api_common(cur_loc_id, cur_name, new_loc_id, new_name, lcpl_id, lapl_id, NULL,
+                                    NULL) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTCREATE, FAIL, "unable to synchronously create hard link")
+
+done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Lcreate_hard() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5Lcreate_hard_async
+ *
+ * Purpose:     Asynchronous version of H5Lcreate_hard
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Lcreate_hard_async(const char *app_file, const char *app_func, unsigned app_line, hid_t cur_loc_id,
+                     const char *cur_name, hid_t new_loc_id, const char *new_name, hid_t lcpl_id,
+                     hid_t lapl_id, hid_t es_id)
+{
+    H5VL_object_t *vol_obj   = NULL;            /* Object for loc_id */
+    void *         token     = NULL;            /* Request token for async operation        */
+    void **        token_ptr = H5_REQUEST_NULL; /* Pointer to request token for async operation        */
+    herr_t         ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE10("e", "*s*sIui*si*siii", app_file, app_func, app_line, cur_loc_id, cur_name, new_loc_id,
+              new_name, lcpl_id, lapl_id, es_id);
+
+    /* Set up request token pointer for asynchronous operation */
+    if (H5ES_NONE != es_id)
+        token_ptr = &token; /* Point at token for VOL connector to set up */
+
+    /* Creates a hard link asynchronously */
+    if (H5L__create_hard_api_common(cur_loc_id, cur_name, new_loc_id, new_name, lcpl_id, lapl_id, token_ptr,
+                                    &vol_obj) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTCREATE, FAIL, "unable to asynchronously create hard link")
+
+    /* If a token was created, add the token to the event set */
+    if (NULL != token)
+        if (H5ES_insert(es_id, vol_obj->connector, token,
+                        H5ARG_TRACE10(FUNC, "*s*sIui*si*siii", app_file, app_func, app_line, cur_loc_id,
+                                      cur_name, new_loc_id, new_name, lcpl_id, lapl_id, es_id)) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTINSERT, FAIL, "can't insert token into event set")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Lcreate_hard_async() */
+
+/*-------------------------------------------------------------------------
  * Function:    H5Lcreate_external
  *
  * Purpose:     Creates an external link from LINK_NAME to OBJ_NAME.
@@ -759,6 +905,43 @@ done:
 } /* end H5Lcreate_ud() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5L__delete_api_common
+ *
+ * Purpose:     This is the common function for deleting a link
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5L__delete_api_common(hid_t loc_id, const char *name, hid_t lapl_id, void **token_ptr,
+                       H5VL_object_t **_vol_obj_ptr)
+{
+    H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
+    H5VL_object_t **vol_obj_ptr =
+        (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
+    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
+    herr_t            ret_value = SUCCEED;            /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check arguments */
+    /* name is verified in H5VL_setup_name_args() */
+
+    /* Set up object access arguments */
+    if (H5VL_setup_name_args(loc_id, name, H5P_CLS_LACC, TRUE, lapl_id, vol_obj_ptr, &loc_params) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set object access arguments")
+
+    /* Unlink */
+    if (H5VL_link_specific(*vol_obj_ptr, &loc_params, H5VL_LINK_DELETE, H5P_DATASET_XFER_DEFAULT, token_ptr) <
+        0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to delete link")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5L__delete_api_common() */
+
+/*-------------------------------------------------------------------------
  * Function:    H5Ldelete
  *
  * Purpose:     Removes the specified NAME from the group graph and
@@ -778,39 +961,103 @@ done:
 herr_t
 H5Ldelete(hid_t loc_id, const char *name, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj = NULL; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    herr_t ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE3("e", "i*si", loc_id, name, lapl_id);
 
-    /* Check arguments */
-    if (!name || !*name)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name")
+    /* Delete a link synchronously */
+    if (H5L__delete_api_common(loc_id, name, lapl_id, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to synchronously delete link")
 
-    /* Verify access property list and set up collective metadata if appropriate */
-    if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, loc_id, TRUE) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set access property list info")
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Ldelete() */
 
-    /* Fill in the location struct fields */
-    loc_params.type                         = H5VL_OBJECT_BY_NAME;
-    loc_params.obj_type                     = H5I_get_type(loc_id);
-    loc_params.loc_data.loc_by_name.name    = name;
-    loc_params.loc_data.loc_by_name.lapl_id = lapl_id;
+/*-------------------------------------------------------------------------
+ * Function:    H5Ldelete_async
+ *
+ * Purpose:     Asynchronous version of H5Ldelete
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Ldelete_async(const char *app_file, const char *app_func, unsigned app_line, hid_t loc_id, const char *name,
+                hid_t lapl_id, hid_t es_id)
+{
+    H5VL_object_t *vol_obj   = NULL;            /* Object for loc_id */
+    void *         token     = NULL;            /* Request token for async operation        */
+    void **        token_ptr = H5_REQUEST_NULL; /* Pointer to request token for async operation        */
+    herr_t         ret_value = SUCCEED;         /* Return value */
 
-    /* get the location object */
-    if (NULL == (vol_obj = (H5VL_object_t *)H5I_object(loc_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
+    FUNC_ENTER_API(FAIL)
+    H5TRACE7("e", "*s*sIui*sii", app_file, app_func, app_line, loc_id, name, lapl_id, es_id);
 
-    /* Unlink */
-    if (H5VL_link_specific(vol_obj, &loc_params, H5VL_LINK_DELETE, H5P_DATASET_XFER_DEFAULT,
-                           H5_REQUEST_NULL) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to delete link")
+    /* Set up request token pointer for asynchronous operation */
+    if (H5ES_NONE != es_id)
+        token_ptr = &token; /* Point at token for VOL connector to set up */
+
+    /* Delete a link asynchronously */
+    if (H5L__delete_api_common(loc_id, name, lapl_id, token_ptr, &vol_obj) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to asynchronously delete link")
+
+    /* If a token was created, add the token to the event set */
+    if (NULL != token)
+        if (H5ES_insert(es_id, vol_obj->connector, token,
+                        H5ARG_TRACE7(FUNC, "*s*sIui*sii", app_file, app_func, app_line, loc_id, name, lapl_id,
+                                     es_id)) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTINSERT, FAIL, "can't insert token into event set")
 
 done:
     FUNC_LEAVE_API(ret_value)
-} /* end H5Ldelete() */
+} /* H5Ldelete_async() */
+
+/*-------------------------------------------------------------------------
+ * Function:    H5L__delete_by_idx_api_common
+ *
+ * Purpose:     This is the common function for deleting a link
+ *		        according to the order within an index.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5L__delete_by_idx_api_common(hid_t loc_id, const char *group_name, H5_index_t idx_type,
+                              H5_iter_order_t order, hsize_t n, hid_t lapl_id, void **token_ptr,
+                              H5VL_object_t **_vol_obj_ptr)
+{
+    H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
+    H5VL_object_t **vol_obj_ptr =
+        (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
+    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
+    herr_t            ret_value = SUCCEED;            /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check arguments */
+    if (!group_name || !*group_name)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name specified")
+    if (idx_type <= H5_INDEX_UNKNOWN || idx_type >= H5_INDEX_N)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index type specified")
+    if (order <= H5_ITER_UNKNOWN || order >= H5_ITER_N)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid iteration order specified")
+
+    /* Set up object access arguments */
+    if (H5VL_setup_idx_args(loc_id, group_name, idx_type, order, n, H5P_CLS_LACC, TRUE, lapl_id, vol_obj_ptr,
+                            &loc_params) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set object access arguments")
+
+    /* Delete the link */
+    if (H5VL_link_specific(*vol_obj_ptr, &loc_params, H5VL_LINK_DELETE, H5P_DATASET_XFER_DEFAULT, token_ptr) <
+        0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to delete link")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5L__delete_by_idx_api_common() */
 
 /*-------------------------------------------------------------------------
  * Function:	H5Ldelete_by_idx
@@ -835,45 +1082,61 @@ herr_t
 H5Ldelete_by_idx(hid_t loc_id, const char *group_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n,
                  hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj = NULL; /* object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    herr_t ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE6("e", "i*sIiIohi", loc_id, group_name, idx_type, order, n, lapl_id);
 
-    /* Check arguments */
-    if (!group_name || !*group_name)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no name specified")
-    if (idx_type <= H5_INDEX_UNKNOWN || idx_type >= H5_INDEX_N)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index type specified")
-    if (order <= H5_ITER_UNKNOWN || order >= H5_ITER_N)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid iteration order specified")
+    /* Delete a link synchronously */
+    if (H5L__delete_by_idx_api_common(loc_id, group_name, idx_type, order, n, lapl_id, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to synchronously delete link")
 
-    /* Verify access property list and set up collective metadata if appropriate */
-    if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, loc_id, TRUE) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set access property list info")
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Ldelete_by_idx() */
 
-    loc_params.type                         = H5VL_OBJECT_BY_IDX;
-    loc_params.loc_data.loc_by_idx.name     = group_name;
-    loc_params.loc_data.loc_by_idx.idx_type = idx_type;
-    loc_params.loc_data.loc_by_idx.order    = order;
-    loc_params.loc_data.loc_by_idx.n        = n;
-    loc_params.loc_data.loc_by_idx.lapl_id  = lapl_id;
-    loc_params.obj_type                     = H5I_get_type(loc_id);
+/*-------------------------------------------------------------------------
+ * Function:    H5Ldelete_by_idx_async
+ *
+ * Purpose:     Asynchronous version of H5Ldelete_by_idx
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Ldelete_by_idx_async(const char *app_file, const char *app_func, unsigned app_line, hid_t loc_id,
+                       const char *group_name, H5_index_t idx_type, H5_iter_order_t order, hsize_t n,
+                       hid_t lapl_id, hid_t es_id)
+{
+    H5VL_object_t *vol_obj   = NULL;            /* Object for loc_id */
+    void *         token     = NULL;            /* Request token for async operation        */
+    void **        token_ptr = H5_REQUEST_NULL; /* Pointer to request token for async operation        */
+    herr_t         ret_value = SUCCEED;         /* Return value */
 
-    /* Get the location object */
-    if (NULL == (vol_obj = (H5VL_object_t *)H5I_object(loc_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
+    FUNC_ENTER_API(FAIL)
+    H5TRACE10("e", "*s*sIui*sIiIohii", app_file, app_func, app_line, loc_id, group_name, idx_type, order, n,
+              lapl_id, es_id);
 
-    /* Delete the link */
-    if (H5VL_link_specific(vol_obj, &loc_params, H5VL_LINK_DELETE, H5P_DATASET_XFER_DEFAULT,
-                           H5_REQUEST_NULL) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to delete link")
+    /* Set up request token pointer for asynchronous operation */
+    if (H5ES_NONE != es_id)
+        token_ptr = &token; /* Point at token for VOL connector to set up */
+
+    /* Delete a link asynchronously */
+    if (H5L__delete_by_idx_api_common(loc_id, group_name, idx_type, order, n, lapl_id, token_ptr, &vol_obj) <
+        0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTDELETE, FAIL, "unable to asynchronously delete link")
+
+    /* If a token was created, add the token to the event set */
+    if (NULL != token)
+        if (H5ES_insert(es_id, vol_obj->connector, token,
+                        H5ARG_TRACE10(FUNC, "*s*sIui*sIiIohii", app_file, app_func, app_line, loc_id,
+                                      group_name, idx_type, order, n, lapl_id, es_id)) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTINSERT, FAIL, "can't insert token into event set")
 
 done:
     FUNC_LEAVE_API(ret_value)
-} /* end H5Ldelete_by_idx() */
+} /* H5Ldelete_by_idx_async() */
 
 /*-------------------------------------------------------------------------
  * Function:	H5Lget_val
@@ -992,6 +1255,45 @@ done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Lget_val_by_idx() */
 
+/*--------------------------------------------------------------------------
+ *  NAME
+ *      H5L__exists_api_common
+ *  PURPOSE
+ *      Common helper routine for sync/async check if an attribute exists
+ *  RETURNS
+ *      Non-negative on success/Negative on failure
+ *
+ *--------------------------------------------------------------------------*/
+static herr_t
+H5L__exists_api_common(hid_t loc_id, const char *name, hbool_t *exists, hid_t lapl_id, void **token_ptr,
+                       H5VL_object_t **_vol_obj_ptr)
+{
+    H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
+    H5VL_object_t **vol_obj_ptr =
+        (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
+    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
+    herr_t            ret_value = SUCCEED;            /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check arguments */
+    /* name is verified in H5VL_setup_name_args() */
+    if (NULL == exists)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid pointer for link existence")
+
+    /* Set up object access arguments */
+    if (H5VL_setup_name_args(loc_id, name, H5P_CLS_LACC, FALSE, lapl_id, vol_obj_ptr, &loc_params) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set object access arguments")
+
+    /* Check for the existence of the link */
+    if (H5VL_link_specific(*vol_obj_ptr, &loc_params, H5VL_LINK_EXISTS, H5P_DATASET_XFER_DEFAULT, token_ptr,
+                           exists) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "unable to get link info")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5L__exists_api_common() */
+
 /*-------------------------------------------------------------------------
  * Function:    H5Lexists
  *
@@ -1007,41 +1309,62 @@ done:
 htri_t
 H5Lexists(hid_t loc_id, const char *name, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj = NULL; /* object of loc_id */
-    H5VL_loc_params_t loc_params;
-    htri_t            ret_value = FAIL; /* Return value */
+    hbool_t exists;           /* Flag to indicate if link exists */
+    htri_t  ret_value = FAIL; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE3("t", "i*si", loc_id, name, lapl_id);
 
-    /* Check arguments */
-    if (!name)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "name parameter cannot be NULL")
-    if (!*name)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "name parameter cannot be an empty string")
+    /* Synchronously check if a link exists */
+    exists = FALSE;
+    if (H5L__exists_api_common(loc_id, name, &exists, lapl_id, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "unable to synchronously check link existence")
 
-    /* Verify access property list and set up collective metadata if appropriate */
-    if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, loc_id, FALSE) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set access property list info")
+    /* Set return value */
+    ret_value = (htri_t)exists;
 
-    /* Set location struct fields */
-    loc_params.type                         = H5VL_OBJECT_BY_NAME;
-    loc_params.obj_type                     = H5I_get_type(loc_id);
-    loc_params.loc_data.loc_by_name.name    = name;
-    loc_params.loc_data.loc_by_name.lapl_id = lapl_id;
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Lexists() */
 
-    /* Get the location object */
-    if (NULL == (vol_obj = (H5VL_object_t *)H5I_object(loc_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
+/*--------------------------------------------------------------------------
+ * Function:    H5Lexists_async
+ *
+ * Purpose:     Asynchronous version of H5Lexists
+ *
+ * Return:      Success:    TRUE/FALSE/FAIL
+ *
+ *--------------------------------------------------------------------------*/
+herr_t
+H5Lexists_async(const char *app_file, const char *app_func, unsigned app_line, hid_t loc_id, const char *name,
+                hbool_t *exists, hid_t lapl_id, hid_t es_id)
+{
+    H5VL_object_t *vol_obj   = NULL;            /* Object for loc_id */
+    void *         token     = NULL;            /* Request token for async operation        */
+    void **        token_ptr = H5_REQUEST_NULL; /* Pointer to request token for async operation        */
+    herr_t         ret_value = SUCCEED;         /* Return value */
 
-    /* Check for the existence of the link */
-    if (H5VL_link_specific(vol_obj, &loc_params, H5VL_LINK_EXISTS, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL,
-                           &ret_value) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "unable to get link info")
+    FUNC_ENTER_API(FAIL)
+    H5TRACE8("e", "*s*sIui*s*bii", app_file, app_func, app_line, loc_id, name, exists, lapl_id, es_id);
+
+    /* Set up request token pointer for asynchronous operation */
+    if (H5ES_NONE != es_id)
+        token_ptr = &token; /* Point at token for VOL connector to set up */
+
+    /* Asynchronously check if a link exists */
+    if (H5L__exists_api_common(loc_id, name, exists, lapl_id, token_ptr, &vol_obj) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "unable to asynchronously check link existence")
+
+    /* If a token was created, add the token to the event set */
+    if (NULL != token)
+        if (H5ES_insert(es_id, vol_obj->connector, token,
+                        H5ARG_TRACE8(FUNC, "*s*sIui*s*bii", app_file, app_func, app_line, loc_id, name,
+                                     exists, lapl_id, es_id)) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTINSERT, FAIL, "can't insert token into event set")
 
 done:
     FUNC_LEAVE_API(ret_value)
-} /* end H5Lexists() */
+} /* H5Lexists_async() */
 
 /*-------------------------------------------------------------------------
  * Function:    H5Lget_info2
@@ -1349,6 +1672,53 @@ done:
 } /* end H5Lget_name_by_idx() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5L__iterate_api_common
+ *
+ * Purpose:     This is the common function for iterating over links
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5L__iterate_api_common(hid_t group_id, H5_index_t idx_type, H5_iter_order_t order, hsize_t *idx_p,
+                        H5L_iterate2_t op, void *op_data, void **token_ptr, H5VL_object_t **_vol_obj_ptr)
+{
+    H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
+    H5VL_object_t **vol_obj_ptr =
+        (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
+    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
+    H5I_type_t        id_type;                        /* Type of ID */
+    herr_t            ret_value = H5_ITER_CONT;       /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check arguments */
+    id_type = H5I_get_type(group_id);
+    if (!(H5I_GROUP == id_type || H5I_FILE == id_type))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid argument")
+    if (idx_type <= H5_INDEX_UNKNOWN || idx_type >= H5_INDEX_N)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index type specified")
+    if (order <= H5_ITER_UNKNOWN || order >= H5_ITER_N)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid iteration order specified")
+    if (!op)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no operator specified")
+
+    /* Set up object access arguments */
+    if (H5VL_setup_self_args(group_id, vol_obj_ptr, &loc_params) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_CANTSET, FAIL, "can't set object access arguments")
+
+    /* Iterate over the links */
+    if ((ret_value = H5VL_link_specific(*vol_obj_ptr, &loc_params, H5VL_LINK_ITER, H5P_DATASET_XFER_DEFAULT,
+                                        token_ptr, (unsigned)FALSE, (int)idx_type, (int)order, idx_p, op,
+                                        op_data)) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_BADITER, FAIL, "link iteration failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5L__iterate_api_common() */
+
+/*-------------------------------------------------------------------------
  * Function:    H5Literate2
  *
  * Purpose:     Iterates over links in a group, with user callback routine,
@@ -1370,42 +1740,68 @@ herr_t
 H5Literate2(hid_t group_id, H5_index_t idx_type, H5_iter_order_t order, hsize_t *idx_p, H5L_iterate2_t op,
             void *op_data)
 {
-    H5VL_object_t *   vol_obj = NULL; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    H5I_type_t        id_type;   /* Type of ID */
-    herr_t            ret_value; /* Return value */
+    herr_t ret_value; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE6("e", "iIiIo*hLI*x", group_id, idx_type, order, idx_p, op, op_data);
 
-    /* Check arguments */
-    id_type = H5I_get_type(group_id);
-    if (!(H5I_GROUP == id_type || H5I_FILE == id_type))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid argument")
-    if (idx_type <= H5_INDEX_UNKNOWN || idx_type >= H5_INDEX_N)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid index type specified")
-    if (order <= H5_ITER_UNKNOWN || order >= H5_ITER_N)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid iteration order specified")
-    if (!op)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no operator specified")
+    /* Iterate over links synchronously */
+    if ((ret_value = H5L__iterate_api_common(group_id, idx_type, order, idx_p, op, op_data, NULL, NULL)) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_BADITER, FAIL, "asynchronous link iteration failed")
 
-    /* Get the location object */
-    if (NULL == (vol_obj = (H5VL_object_t *)H5I_object(group_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Literate2() */
 
-    /* Set location struct fields */
-    loc_params.type     = H5VL_OBJECT_BY_SELF;
-    loc_params.obj_type = H5I_get_type(group_id);
+/*-------------------------------------------------------------------------
+ * Function:    H5Literate_async
+ *
+ * Purpose:     Asynchronous version of H5Literate2
+ *
+ * Return:      Success:    The return value of the first operator that
+ *                          returns non-zero, or zero if all members were
+ *                          processed with no operator returning non-zero.
+ *
+ *              Failure:    Negative if something goes wrong within the
+ *                          library, or the negative value returned by one
+ *                          of the operators.
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Literate_async(const char *app_file, const char *app_func, unsigned app_line, hid_t group_id,
+                 H5_index_t idx_type, H5_iter_order_t order, hsize_t *idx_p, H5L_iterate2_t op, void *op_data,
+                 hid_t es_id)
+{
+    H5VL_object_t *vol_obj   = NULL;            /* Object for loc_id */
+    void *         token     = NULL;            /* Request token for async operation        */
+    void **        token_ptr = H5_REQUEST_NULL; /* Pointer to request token for async operation        */
+    herr_t         ret_value;                   /* Return value */
 
-    /* Iterate over the links */
-    if ((ret_value = H5VL_link_specific(vol_obj, &loc_params, H5VL_LINK_ITER, H5P_DATASET_XFER_DEFAULT,
-                                        H5_REQUEST_NULL, (unsigned)FALSE, (int)idx_type, (int)order, idx_p,
-                                        op, op_data)) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_BADITER, FAIL, "link iteration failed")
+    FUNC_ENTER_API(FAIL)
+    H5TRACE10("e", "*s*sIuiIiIo*hLI*xi", app_file, app_func, app_line, group_id, idx_type, order, idx_p, op,
+              op_data, es_id);
+
+    /* Set up request token pointer for asynchronous operation */
+    if (H5ES_NONE != es_id)
+        token_ptr = &token; /* Point at token for VOL connector to set up */
+
+    /* Iterate over links asynchronously */
+    if ((ret_value =
+             H5L__iterate_api_common(group_id, idx_type, order, idx_p, op, op_data, token_ptr, &vol_obj)) < 0)
+        HGOTO_ERROR(H5E_LINK, H5E_BADITER, FAIL, "asynchronous link iteration failed")
+
+    /* If a token was created, add the token to the event set */
+    if (NULL != token)
+        if (H5ES_insert(es_id, vol_obj->connector, token,
+                        H5ARG_TRACE10(FUNC, "*s*sIuiIiIo*hLI*xi", app_file, app_func, app_line, group_id,
+                                      idx_type, order, idx_p, op, op_data, es_id)) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTINSERT, FAIL, "can't insert token into event set")
 
 done:
     FUNC_LEAVE_API(ret_value)
-} /* end H5Literate2() */
+} /* H5Literate_async() */
 
 /*-------------------------------------------------------------------------
  * Function:    H5Literate_by_name2
@@ -3094,7 +3490,7 @@ H5L__exists_final_cb(H5G_loc_t H5_ATTR_UNUSED *grp_loc /*in*/, const char H5_ATT
     FUNC_ENTER_STATIC_NOERR
 
     /* Check if the name in this group resolved to a valid link */
-    udata->exists = (hbool_t)(lnk != NULL);
+    *udata->exists = (hbool_t)(lnk != NULL);
 
     /* Indicate that this callback didn't take ownership of the group *
      * location for the object */
@@ -3149,10 +3545,10 @@ H5L__exists_inter_cb(H5G_loc_t H5_ATTR_UNUSED *grp_loc /*in*/, const char H5_ATT
                 HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "can't determine if link exists")
         } /* end if */
         else
-            udata->exists = TRUE;
+            *udata->exists = TRUE;
     } /* end if */
     else
-        udata->exists = FALSE;
+        *udata->exists = FALSE;
 
     /* Indicate that this callback didn't take ownership of the group *
      * location for the object */
@@ -3177,20 +3573,21 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-htri_t
-H5L_exists_tolerant(const H5G_loc_t *loc, const char *name)
+herr_t
+H5L_exists_tolerant(const H5G_loc_t *loc, const char *name, hbool_t *exists)
 {
-    H5L_trav_le_t  udata;            /* User data for traversal */
-    H5G_traverse_t cb_func;          /* Callback function for tranversal */
-    char *         name_copy = NULL; /* Duplicate of name */
-    char *         name_trav;        /* Name to traverse */
-    htri_t         ret_value = FAIL; /* Return value */
+    H5L_trav_le_t  udata;               /* User data for traversal */
+    H5G_traverse_t cb_func;             /* Callback function for tranversal */
+    char *         name_copy = NULL;    /* Duplicate of name */
+    char *         name_trav;           /* Name to traverse */
+    herr_t         ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
     /* Sanity checks */
     HDassert(loc);
     HDassert(name);
+    HDassert(exists);
 
     /* Copy the name and skip leading '/'s */
     name_trav = name_copy = H5MM_strdup(name);
@@ -3199,27 +3596,25 @@ H5L_exists_tolerant(const H5G_loc_t *loc, const char *name)
 
     /* A path of "/" will always exist in a file */
     if ('\0' == *name_trav)
-        HGOTO_DONE(TRUE)
-
-    /* Set up user data & correct callback */
-    udata.exists = FALSE;
-    if (NULL == (udata.sep = HDstrchr(name_trav, '/')))
-        cb_func = H5L__exists_final_cb;
+        *exists = TRUE;
     else {
-        /* Chew through adjacent separators, if present */
-        do {
-            *udata.sep = '\0';
-            udata.sep++;
-        } while ('/' == *udata.sep);
-        cb_func = H5L__exists_inter_cb;
-    } /* end else */
-
-    /* Traverse the group hierarchy to locate the link to check */
-    if (H5G_traverse(loc, name_trav, H5G_TARGET_SLINK | H5G_TARGET_UDLINK, cb_func, &udata) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "can't determine if link exists")
+        /* Set up user data & correct callback */
+        udata.exists = exists;
+        if (NULL == (udata.sep = HDstrchr(name_trav, '/')))
+            cb_func = H5L__exists_final_cb;
+        else {
+            /* Chew through adjacent separators, if present */
+            do {
+                *udata.sep = '\0';
+                udata.sep++;
+            } while ('/' == *udata.sep);
+            cb_func = H5L__exists_inter_cb;
+        } /* end else */
 
-    /* Set return value */
-    ret_value = (htri_t)udata.exists;
+        /* Traverse the group hierarchy to locate the link to check */
+        if (H5G_traverse(loc, name_trav, H5G_TARGET_SLINK | H5G_TARGET_UDLINK, cb_func, &udata) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_CANTGET, FAIL, "can't determine if link exists")
+    }
 
 done:
     /* Release duplicated string */
@@ -3236,36 +3631,35 @@ done:
  * Note:	Same as H5L_exists_tolerant, except that missing links are reported
  *		as failures
  *
- * Return:	Non-negative (TRUE/FALSE) on success/Negative on failure
+ * Return:	Non-negative on success, with *exists set/Negative on failure
  *
  * Programmer:	Quincey Koziol
  *              Friday, March 16 2007
  *
  *-------------------------------------------------------------------------
  */
-htri_t
-H5L__exists(const H5G_loc_t *loc, const char *name)
+herr_t
+H5L__exists(const H5G_loc_t *loc, const char *name, hbool_t *exists)
 {
-    H5L_trav_le_t udata;            /* User data for traversal */
-    htri_t        ret_value = FAIL; /* Return value */
+    H5L_trav_le_t udata;               /* User data for traversal */
+    herr_t        ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_PACKAGE
 
     /* Sanity checks */
     HDassert(loc);
     HDassert(name);
+    HDassert(exists);
 
     /* A path of "/" will always exist in a file */
     if (0 == HDstrcmp(name, "/"))
-        HGOTO_DONE(TRUE)
-
-    /* Traverse the group hierarchy to locate the object to get info about */
-    udata.exists = FALSE;
-    if (H5G_traverse(loc, name, H5G_TARGET_SLINK | H5G_TARGET_UDLINK, H5L__exists_final_cb, &udata) < 0)
-        HGOTO_ERROR(H5E_LINK, H5E_EXISTS, FAIL, "path doesn't exist")
-
-    /* Set return value */
-    ret_value = (htri_t)udata.exists;
+        *exists = TRUE;
+    else {
+        /* Traverse the group hierarchy to locate the object to get info about */
+        udata.exists = exists;
+        if (H5G_traverse(loc, name, H5G_TARGET_SLINK | H5G_TARGET_UDLINK, H5L__exists_final_cb, &udata) < 0)
+            HGOTO_ERROR(H5E_LINK, H5E_EXISTS, FAIL, "link doesn't exist")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)