/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the COPYING file, which can be found at the root of the source code       *
 * distribution tree, or in https://www.hdfgroup.org/licenses.               *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#include "H5private.h"
#include "h5tools.h"
#include "h5tools_utils.h"
#include "h5diff.h"
#include "ph5diff.h"

#ifdef H5_HAVE_PARALLEL
static diff_err_t handle_worker_request(char *worker_tasks, int *n_busy_tasks, diff_opt_t *opts,
                                        hsize_t *n_diffs);
static diff_err_t dispatch_diff_to_worker(struct diff_mpi_args *args, char *worker_tasks, int *n_busy_tasks);
#endif

/*-------------------------------------------------------------------------
 * Function: print_objname
 *
 * Purpose:  check if object name is to be printed, only when:
 *             1) verbose mode
 *             2) when diff was found (normal mode)
 *-------------------------------------------------------------------------
 */
H5_ATTR_PURE int
print_objname(diff_opt_t *opts, hsize_t nfound)
{
    return ((opts->mode_verbose || nfound) && !opts->mode_quiet) ? 1 : 0;
}

/*-------------------------------------------------------------------------
 * Function: do_print_objname
 *
 * Purpose:  print object name
 *-------------------------------------------------------------------------
 */
void
do_print_objname(const char *OBJ, const char *path1, const char *path2, diff_opt_t *opts)
{
    /* if verbose level is higher than 0, put space line before
     * displaying any object or symbolic links. This improves
     * readability of the output.
     */
    if (opts->mode_verbose_level >= 1)
        parallel_print("\n");
    parallel_print("%-7s: <%s> and <%s>\n", OBJ, path1, path2);
}

/*-------------------------------------------------------------------------
 * Function: do_print_attrname
 *
 * Purpose:  print attribute name
 *-------------------------------------------------------------------------
 */
void
do_print_attrname(const char *attr, const char *path1, const char *path2)
{
    parallel_print("%-7s: <%s> and <%s>\n", attr, path1, path2);
}

/*-------------------------------------------------------------------------
 * Function: print_warn
 *
 * Purpose:  check print warning condition.
 * Return:
 *           1 if verbose mode
 *           0 if not verbos mode
 *-------------------------------------------------------------------------
 */
static int
print_warn(diff_opt_t *opts)
{
    return ((opts->mode_verbose)) ? 1 : 0;
}

#ifdef H5_HAVE_PARALLEL
/*-------------------------------------------------------------------------
 * Function: phdiff_dismiss_workers
 *
 * Purpose:  tell all workers to end.
 *
 * Return:   none
 *-------------------------------------------------------------------------
 */
void
phdiff_dismiss_workers(void)
{
    int i;
    for (i = 1; i < g_nTasks; i++)
        MPI_Send(NULL, 0, MPI_BYTE, i, MPI_TAG_END, MPI_COMM_WORLD);
}
#endif

/*-------------------------------------------------------------------------
 * Function: is_valid_options
 *
 * Purpose:  check if options are valid
 *
 * Return:
 *           1 : Valid
 *           0 : Not valid
 *------------------------------------------------------------------------*/
static int
is_valid_options(diff_opt_t *opts)
{
    int ret_value = 1; /* init to valid */

    /*-----------------------------------------------
     * no -q(quiet) with -v (verbose) or -r (report) */
    if (opts->mode_quiet && (opts->mode_verbose || opts->mode_report)) {
        parallel_print("Error: -q (quiet mode) cannot be added to verbose or report modes\n");
        opts->err_stat = H5DIFF_ERR;
        H5TOOLS_GOTO_DONE(0);
    }

    /* -------------------------------------------------------
     * only allow --no-dangling-links along with --follow-symlinks */
    if (opts->no_dangle_links && !opts->follow_links) {
        parallel_print("Error: --no-dangling-links must be used along with --follow-symlinks option.\n");
        opts->err_stat = H5DIFF_ERR;
        H5TOOLS_GOTO_DONE(0);
    }

done:
    return ret_value;
}

/*-------------------------------------------------------------------------
 * Function: is_exclude_path
 *
 * Purpose:  check if 'paths' are part of exclude path list
 *
 * Return:
 *           1 - excluded path
 *           0 - not excluded path
 *------------------------------------------------------------------------*/
static int
is_exclude_path(char *path, h5trav_type_t type, diff_opt_t *opts)
{
    struct exclude_path_list *exclude_path_ptr;
    int                       ret_cmp;
    int                       ret_value = 0;

    /* check if exclude path option is given */
    if (!opts->exclude_path)
        H5TOOLS_GOTO_DONE(0);

    /* assign to local exclude list pointer */
    exclude_path_ptr = opts->exclude;

    /* search objects in exclude list */
    while (NULL != exclude_path_ptr) {
        /* if exclude path is in group, exclude its members as well */
        if (exclude_path_ptr->obj_type == H5TRAV_TYPE_GROUP) {
            ret_cmp = strncmp(exclude_path_ptr->obj_path, path, strlen(exclude_path_ptr->obj_path));
            if (ret_cmp == 0) { /* found matching members */
                size_t len_grp;

                /* check if given path belong to an excluding group, if so
                 * exclude it as well.
                 * This verifies if “/grp1/dset1” is only under “/grp1”, but
                 * not under “/grp1xxx/” group.
                 */
                len_grp = strlen(exclude_path_ptr->obj_path);
                if (path[len_grp] == '/') {
                    /* belong to excluded group! */
                    ret_value = 1;
                    break; /* while */
                }
            }
        }
        /* exclude target is not group, just exclude the object */
        else {
            ret_cmp = strcmp(exclude_path_ptr->obj_path, path);
            if (ret_cmp == 0) { /* found matching object */
                /* excluded non-group object */
                ret_value = 1;
                /* remember the type of this matching object.
                 * if it's group, it can be used for excluding its member
                 * objects in this while() loop */
                exclude_path_ptr->obj_type = type;
                break; /* while */
            }
        }
        exclude_path_ptr = exclude_path_ptr->next;
    }

done:
    return ret_value;
}

/*-------------------------------------------------------------------------
 * Function: is_exclude_attr
 *
 * Purpose:  check if 'paths' are part of exclude path list
 *
 * Return:
 *           1 - excluded path
 *           0 - not excluded path
 *------------------------------------------------------------------------*/
static int
is_exclude_attr(const char *path, h5trav_type_t type, diff_opt_t *opts)
{
    struct exclude_path_list *exclude_ptr;
    int                       ret_cmp;
    int                       ret_value = 0;

    /* check if exclude attr option is given */
    if (!opts->exclude_attr_path)
        H5TOOLS_GOTO_DONE(0);

    /* assign to local exclude list pointer */
    exclude_ptr = opts->exclude_attr;

    /* search objects in exclude list */
    while (NULL != exclude_ptr) {
        /* if exclude path is in group, exclude its members as well */
        if (exclude_ptr->obj_type == H5TRAV_TYPE_GROUP) {
            ret_cmp = strncmp(exclude_ptr->obj_path, path, strlen(exclude_ptr->obj_path));
            if (ret_cmp == 0) { /* found matching members */
                size_t len_grp;

                /* check if given path belong to an excluding group, if so
                 * exclude it as well.
                 * This verifies if “/grp1/dset1” is only under “/grp1”, but
                 * not under “/grp1xxx/” group.
                 */
                len_grp = strlen(exclude_ptr->obj_path);
                if (path[len_grp] == '/') {
                    /* belong to excluded group! */
                    ret_value = 1;
                    break; /* while */
                }
            }
        }
        /* exclude target is not group, just exclude the object */
        else {
            ret_cmp = strcmp(exclude_ptr->obj_path, path);
            if (ret_cmp == 0) { /* found matching object */
                /* excluded non-group object */
                ret_value = 1;
                /* remember the type of this matching object.
                 * if it's group, it can be used for excluding its member
                 * objects in this while() loop */
                exclude_ptr->obj_type = type;
                break; /* while */
            }
        }
        exclude_ptr = exclude_ptr->next;
    }

done:
    return ret_value;
}

/*-------------------------------------------------------------------------
 * Function: free_exclude_path_list
 *
 * Purpose:  free exclude object list from diff options
 *------------------------------------------------------------------------*/
static void
free_exclude_path_list(diff_opt_t *opts)
{
    struct exclude_path_list *curr = opts->exclude;
    struct exclude_path_list *next;

    while (NULL != curr) {
        next = curr->next;
        free(curr);
        curr = next;
    }
}

/*-------------------------------------------------------------------------
 * Function: free_exclude_attr_list
 *
 * Purpose:  free exclude object attribute list from diff options
 *------------------------------------------------------------------------*/
static void
free_exclude_attr_list(diff_opt_t *opts)
{
    struct exclude_path_list *curr = opts->exclude_attr;
    struct exclude_path_list *next;

    while (NULL != curr) {
        next = curr->next;
        free(curr);
        curr = next;
    }
}

/*-------------------------------------------------------------------------
 * Function: build_match_list
 *
 * Purpose:  get list of matching path_name from info1 and info2
 *
 * Note:
 *           Find common objects; the algorithm used for this search is the
 *           cosequential match algorithm and is described in
 *           Folk, Michael; Zoellick, Bill. (1992). File Structures. Addison-Wesley.
 *           Moved out from diff_match() to make code more flexible.
 *
 * Parameter:
 *           table_out [OUT] : return the list
 *------------------------------------------------------------------------*/
static void
build_match_list(const char *objname1, trav_info_t *info1, const char *objname2, trav_info_t *info2,
                 trav_table_t **table_out, diff_opt_t *opts)
{
    size_t        curr1 = 0;
    size_t        curr2 = 0;
    unsigned      infile[2];
    char         *path1_lp = NULL;
    char         *path2_lp = NULL;
    h5trav_type_t type1_l;
    h5trav_type_t type2_l;
    size_t        path1_offset = 0;
    size_t        path2_offset = 0;
    int           cmp;
    trav_table_t *table = NULL;
    size_t        idx;

    H5TOOLS_START_DEBUG(" - errstat:%d", opts->err_stat);
    /* init */
    trav_table_init(info1->fid, &table);
    if (table == NULL) {
        H5TOOLS_INFO("Cannot create traverse table");
        H5TOOLS_GOTO_DONE_NO_RET();
    }

    /*
     * This is necessary for the case that given objects are group and
     * have different names (ex: obj1 is /grp1 and obj2 is /grp5).
     * All the objects belong to given groups are the candidates.
     * So prepare to compare paths without the group names.
     */
    H5TOOLS_DEBUG("objname1 = %s objname2 = %s ", objname1, objname2);

    /* if obj1 is not root */
    if (strcmp(objname1, "/") != 0)
        path1_offset = strlen(objname1);
    /* if obj2 is not root */
    if (strcmp(objname2, "/") != 0)
        path2_offset = strlen(objname2);

    /*--------------------------------------------------
     * build the list
     */
    while (curr1 < info1->nused && curr2 < info2->nused) {
        path1_lp = (info1->paths[curr1].path) + path1_offset;
        path2_lp = (info2->paths[curr2].path) + path2_offset;
        type1_l  = info1->paths[curr1].type;
        type2_l  = info2->paths[curr2].type;

        /* criteria is string compare */
        cmp = strcmp(path1_lp, path2_lp);
        if (cmp == 0) {
            if (!is_exclude_path(path1_lp, type1_l, opts)) {
                infile[0] = 1;
                infile[1] = 1;
                trav_table_addflags(infile, path1_lp, info1->paths[curr1].type, table);
                /* if the two point to the same target object,
                 * mark that in table */
                if (info1->paths[curr1].fileno == info2->paths[curr2].fileno) {
                    int token_cmp;

                    if (H5Otoken_cmp(info1->fid, &info1->paths[curr1].obj_token,
                                     &info2->paths[curr2].obj_token, &token_cmp) < 0) {
                        H5TOOLS_INFO("Failed to compare object tokens");
                        opts->err_stat = H5DIFF_ERR;
                        H5TOOLS_GOTO_DONE_NO_RET();
                    }

                    if (!token_cmp) {
                        idx                             = table->nobjs - 1;
                        table->objs[idx].is_same_trgobj = 1;
                    }
                }
            }
            curr1++;
            curr2++;
        } /* end if */
        else if (cmp < 0) {
            if (!is_exclude_path(path1_lp, type1_l, opts)) {
                infile[0] = 1;
                infile[1] = 0;
                trav_table_addflags(infile, path1_lp, info1->paths[curr1].type, table);
            }
            curr1++;
        } /* end else-if */
        else {
            if (!is_exclude_path(path2_lp, type2_l, opts)) {
                infile[0] = 0;
                infile[1] = 1;
                trav_table_addflags(infile, path2_lp, info2->paths[curr2].type, table);
            }
            curr2++;
        } /* end else */
    }     /* end while */

    /* list1 did not end */
    infile[0] = 1;
    infile[1] = 0;
    while (curr1 < info1->nused) {
        path1_lp = (info1->paths[curr1].path) + path1_offset;
        type1_l  = info1->paths[curr1].type;

        if (!is_exclude_path(path1_lp, type1_l, opts)) {
            trav_table_addflags(infile, path1_lp, info1->paths[curr1].type, table);
        }
        curr1++;
    } /* end while */

    /* list2 did not end */
    infile[0] = 0;
    infile[1] = 1;
    while (curr2 < info2->nused) {
        path2_lp = (info2->paths[curr2].path) + path2_offset;
        type2_l  = info2->paths[curr2].type;

        if (!is_exclude_path(path2_lp, type2_l, opts)) {
            trav_table_addflags(infile, path2_lp, info2->paths[curr2].type, table);
        }
        curr2++;
    } /* end while */

    free_exclude_path_list(opts);

done:
    *table_out = table;

    H5TOOLS_ENDDEBUG(" ");
}

/*-------------------------------------------------------------------------
 * Function: trav_grp_objs
 *
 * Purpose:  Call back function from h5trav_visit().
 *------------------------------------------------------------------------*/
static herr_t
trav_grp_objs(const char *path, const H5O_info2_t *oinfo, const char *already_visited, void *udata)
{
    trav_info_visit_obj(path, oinfo, already_visited, udata);

    return 0;
}

/*-------------------------------------------------------------------------
 * Function: trav_grp_symlinks
 *
 * Purpose:  Call back function from h5trav_visit().
 *           Track and extra checkings while visiting all symbolic-links.
 *------------------------------------------------------------------------*/
static herr_t
trav_grp_symlinks(const char *path, const H5L_info2_t *linfo, void *udata)
{
    trav_info_t       *tinfo = (trav_info_t *)udata;
    diff_opt_t        *opts  = (diff_opt_t *)tinfo->opts;
    h5tool_link_info_t lnk_info;
    const char        *ext_fname;
    const char        *ext_path;
    herr_t             ret_value = SUCCEED;

    H5TOOLS_START_DEBUG(" ");
    /* init linkinfo struct */
    memset(&lnk_info, 0, sizeof(h5tool_link_info_t));

    if (!opts->follow_links) {
        trav_info_visit_lnk(path, linfo, tinfo);
        H5TOOLS_GOTO_DONE(SUCCEED);
    }

    switch (linfo->type) {
        case H5L_TYPE_SOFT:
            if ((ret_value = H5tools_get_symlink_info(tinfo->fid, path, &lnk_info, opts->follow_links)) < 0) {
                H5TOOLS_GOTO_DONE(FAIL);
            }
            else if (ret_value == 0) {
                /* no dangling link option given and detect dangling link */
                tinfo->symlink_visited.dangle_link = true;
                trav_info_visit_lnk(path, linfo, tinfo);
                if (opts->no_dangle_links)
                    opts->err_stat = H5DIFF_ERR; /* make dangling link is error */
                H5TOOLS_GOTO_DONE(SUCCEED);
            }

            /* check if already visit the target object */
            if (symlink_is_visited(&(tinfo->symlink_visited), linfo->type, NULL, lnk_info.trg_path))
                H5TOOLS_GOTO_DONE(SUCCEED);

            /* add this link as visited link */
            if (symlink_visit_add(&(tinfo->symlink_visited), linfo->type, NULL, lnk_info.trg_path) < 0)
                H5TOOLS_GOTO_DONE(SUCCEED);

            if (h5trav_visit(tinfo->fid, path, true, true, trav_grp_objs, trav_grp_symlinks, tinfo,
                             H5O_INFO_BASIC) < 0) {
                parallel_print("Error: Could not get file contents\n");
                opts->err_stat = H5DIFF_ERR;
                H5TOOLS_GOTO_ERROR(FAIL, "Error: Could not get file contents");
            }
            break;

        case H5L_TYPE_EXTERNAL:
            if ((ret_value = H5tools_get_symlink_info(tinfo->fid, path, &lnk_info, opts->follow_links)) < 0) {
                H5TOOLS_GOTO_DONE(FAIL);
            }
            else if (ret_value == 0) {
                /* no dangling link option given and detect dangling link */
                tinfo->symlink_visited.dangle_link = true;
                trav_info_visit_lnk(path, linfo, tinfo);
                if (opts->no_dangle_links)
                    opts->err_stat = H5DIFF_ERR; /* make dangling link is error */
                H5TOOLS_GOTO_DONE(SUCCEED);
            }

            if (H5Lunpack_elink_val(lnk_info.trg_path, linfo->u.val_size, NULL, &ext_fname, &ext_path) < 0)
                H5TOOLS_GOTO_DONE(SUCCEED);

            /* check if already visit the target object */
            if (symlink_is_visited(&(tinfo->symlink_visited), linfo->type, ext_fname, ext_path))
                H5TOOLS_GOTO_DONE(SUCCEED);

            /* add this link as visited link */
            if (symlink_visit_add(&(tinfo->symlink_visited), linfo->type, ext_fname, ext_path) < 0)
                H5TOOLS_GOTO_DONE(SUCCEED);

            if (h5trav_visit(tinfo->fid, path, true, true, trav_grp_objs, trav_grp_symlinks, tinfo,
                             H5O_INFO_BASIC) < 0) {
                parallel_print("Error: Could not get file contents\n");
                opts->err_stat = H5DIFF_ERR;
                H5TOOLS_GOTO_ERROR(FAIL, "Error: Could not get file contents\n");
            }
            break;

        case H5L_TYPE_HARD:
        case H5L_TYPE_MAX:
        case H5L_TYPE_ERROR:
        default:
            parallel_print("Error: Invalid link type\n");
            opts->err_stat = H5DIFF_ERR;
            H5TOOLS_GOTO_ERROR(FAIL, "Error: Invalid link type");
            break;
    } /* end of switch */

done:
    if (lnk_info.trg_path)
        free(lnk_info.trg_path);
    H5TOOLS_ENDDEBUG(" ");
    return ret_value;
}

/*-------------------------------------------------------------------------
 * Function: h5diff
 *
 * Purpose:  public function, can be called in an application program.
 *           return differences between 2 HDF5 files
 *
 * Return:   Number of differences found.
 *-------------------------------------------------------------------------
 */
hsize_t
h5diff(const char *fname1, const char *fname2, const char *objname1, const char *objname2, diff_opt_t *opts)
{
    hid_t   file1_id = H5I_INVALID_HID;
    hid_t   file2_id = H5I_INVALID_HID;
    hid_t   fapl1_id = H5P_DEFAULT;
    hid_t   fapl2_id = H5P_DEFAULT;
    char    filenames[2][MAX_FILENAME];
    hsize_t nfound        = 0;
    int     l_ret1        = -1;
    int     l_ret2        = -1;
    char   *obj1fullname  = NULL;
    char   *obj2fullname  = NULL;
    int     both_objs_grp = 0;
    /* init to group type */
    h5trav_type_t obj1type = H5TRAV_TYPE_GROUP;
    h5trav_type_t obj2type = H5TRAV_TYPE_GROUP;
    /* for single object */
    H5O_info2_t  oinfo1, oinfo2; /* object info */
    trav_info_t *info1_obj = NULL;
    trav_info_t *info2_obj = NULL;
    /* for group object */
    trav_info_t *info1_grp = NULL;
    trav_info_t *info2_grp = NULL;
    /* local pointer */
    trav_info_t *info1_lp = NULL;
    trav_info_t *info2_lp = NULL;
    /* link info from specified object */
    H5L_info2_t src_linfo1;
    H5L_info2_t src_linfo2;
    /* link info from member object */
    h5tool_link_info_t trg_linfo1;
    h5tool_link_info_t trg_linfo2;
    /* list for common objects */
    trav_table_t *match_list = NULL;
    diff_err_t    ret_value  = H5DIFF_NO_ERR;

    H5TOOLS_START_DEBUG(" ");
    /* init filenames */
    memset(filenames, 0, MAX_FILENAME * 2);
    /* init link info struct */
    memset(&trg_linfo1, 0, sizeof(h5tool_link_info_t));
    memset(&trg_linfo2, 0, sizeof(h5tool_link_info_t));

    /*-------------------------------------------------------------------------
     * check invalid combination of options
     *-----------------------------------------------------------------------*/
    if (!is_valid_options(opts))
        H5TOOLS_GOTO_DONE(0);

    opts->cmn_objs = 1;             /* eliminate warning */
    opts->err_stat = H5DIFF_NO_ERR; /* initialize error status */

    /*-------------------------------------------------------------------------
     * open the files first; if they are not valid, no point in continuing
     *-------------------------------------------------------------------------
     */
    /* open file 1 */
    if ((fapl1_id = h5tools_get_new_fapl(H5P_DEFAULT)) < 0) {
        parallel_print("h5diff: unable to create fapl for input file\n");
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to create input fapl\n");
    }

    /* Set non-default virtual file driver, if requested */
    if (opts->custom_vfd[0] && opts->vfd_info[0].u.name) {
        if (h5tools_set_fapl_vfd(fapl1_id, &(opts->vfd_info[0])) < 0) {
            parallel_print("h5diff: unable to set VFD on fapl for input file\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "failed to set VFD on FAPL\n");
        }
    }

    /* Set non-default VOL connector, if requested */
    if (opts->custom_vol[0]) {
        if (h5tools_set_fapl_vol(fapl1_id, &(opts->vol_info[0])) < 0) {
            parallel_print("h5diff: unable to set VOL on fapl for input file\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "failed to set VOL on FAPL\n");
        }
    }

    if (opts->page_cache > 0) {
        if (H5Pset_page_buffer_size(fapl1_id, opts->page_cache, 0, 0) < 0) {
            parallel_print("h5diff: unable to set page buffer cache size for fapl for input file\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to set page buffer cache size on FAPL\n");
        }
    }

    if ((file1_id = h5tools_fopen(fname1, H5F_ACC_RDONLY, fapl1_id,
                                  (opts->custom_vol[0] || opts->custom_vfd[0]), NULL, (size_t)0)) < 0) {
        parallel_print("h5diff: <%s>: unable to open file\n", fname1);
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "<%s>: unable to open file\n", fname1);
    }
    H5TOOLS_DEBUG("file1_id = %s", fname1);

    /* open file 2 */
    if ((fapl2_id = h5tools_get_new_fapl(H5P_DEFAULT)) < 0) {
        parallel_print("h5diff: unable to create fapl for output file\n");
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to create output fapl\n");
    }

    /* Set non-default virtual file driver, if requested */
    if (opts->custom_vfd[1] && opts->vfd_info[1].u.name) {
        if (h5tools_set_fapl_vfd(fapl2_id, &(opts->vfd_info[1])) < 0) {
            parallel_print("h5diff: unable to set VFD on fapl for output file\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "failed to set VFD on FAPL\n");
        }
    }

    /* Set non-default VOL connector, if requested */
    if (opts->custom_vol[1]) {
        if (h5tools_set_fapl_vol(fapl2_id, &(opts->vol_info[1])) < 0) {
            parallel_print("h5diff: unable to set VOL on fapl for output file\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "failed to set VOL on FAPL\n");
        }
    }

    if (opts->page_cache > 0) {
        if (H5Pset_page_buffer_size(fapl2_id, opts->page_cache, 0, 0) < 0) {
            parallel_print("h5diff: unable to set page buffer cache size for fapl for output file\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to set page buffer cache size for output fapl\n");
        }
    }

    if ((file2_id = h5tools_fopen(fname2, H5F_ACC_RDONLY, fapl2_id,
                                  (opts->custom_vol[1] || opts->custom_vfd[1]), NULL, (size_t)0)) < 0) {
        parallel_print("h5diff: <%s>: unable to open file\n", fname2);
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "<%s>: unable to open file\n", fname2);
    }
    H5TOOLS_DEBUG("file2_id = %s", fname2);

    /*-------------------------------------------------------------------------
     * Initialize the info structs
     *-------------------------------------------------------------------------
     */
    trav_info_init(fname1, file1_id, &info1_obj);
    trav_info_init(fname2, file2_id, &info2_obj);

    H5TOOLS_DEBUG("trav_info_init initialized");
    /* if any object is specified */
    if (objname1) {
        /* make the given object1 fullpath, start with "/"  */
        if (strncmp(objname1, "/", 1) != 0) {
#ifdef H5_HAVE_ASPRINTF
            /* Use the asprintf() routine, since it does what we're trying to do below */
            if (asprintf(&obj1fullname, "/%s", objname1) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "name buffer allocation failed");
#else  /* H5_HAVE_ASPRINTF */
            /* (malloc 2 more for "/" and end-of-line) */
            if ((obj1fullname = (char *)malloc(strlen(objname1) + 2)) == NULL)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "name buffer allocation failed");

            strcpy(obj1fullname, "/");
            strcat(obj1fullname, objname1);
#endif /* H5_HAVE_ASPRINTF */
        }
        else
            obj1fullname = strdup(objname1);
        H5TOOLS_DEBUG("obj1fullname = %s", obj1fullname);

        /* make the given object2 fullpath, start with "/" */
        if (strncmp(objname2, "/", 1) != 0) {
#ifdef H5_HAVE_ASPRINTF
            /* Use the asprintf() routine, since it does what we're trying to do below */
            if (asprintf(&obj2fullname, "/%s", objname2) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "name buffer allocation failed");
#else  /* H5_HAVE_ASPRINTF */
            /* (malloc 2 more for "/" and end-of-line) */
            if ((obj2fullname = (char *)malloc(strlen(objname2) + 2)) == NULL)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "name buffer allocation failed");
            strcpy(obj2fullname, "/");
            strcat(obj2fullname, objname2);
#endif /* H5_HAVE_ASPRINTF */
        }
        else
            obj2fullname = strdup(objname2);
        H5TOOLS_DEBUG("obj2fullname = %s", obj2fullname);

        /*----------------------------------------------------------
         * check if obj1 is root, group, single object or symlink
         */
        H5TOOLS_DEBUG("h5diff check if obj1=%s is root, group, single object or symlink", obj1fullname);
        if (!strcmp(obj1fullname, "/")) {
            obj1type = H5TRAV_TYPE_GROUP;
        }
        else {
            /* check if link itself exist */
            if (H5Lexists(file1_id, obj1fullname, H5P_DEFAULT) <= 0) {
                parallel_print("Object <%s> could not be found in <%s>\n", obj1fullname, fname1);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Error: Object could not be found");
            }
            /* get info from link */
            if (H5Lget_info2(file1_id, obj1fullname, &src_linfo1, H5P_DEFAULT) < 0) {
                parallel_print("Unable to get link info from <%s>\n", obj1fullname);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Lget_info failed");
            }

            info1_lp = info1_obj;

            /*
             * check the type of specified path for hard and symbolic links
             */
            if (src_linfo1.type == H5L_TYPE_HARD) {
                size_t idx;

                /* optional data pass */
                info1_obj->opts = (diff_opt_t *)opts;

                if (H5Oget_info_by_name3(file1_id, obj1fullname, &oinfo1, H5O_INFO_BASIC, H5P_DEFAULT) < 0) {
                    parallel_print("Error: Could not get file contents\n");
                    H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Error: Could not get file contents");
                }
                obj1type = (h5trav_type_t)oinfo1.type;
                trav_info_add(info1_obj, obj1fullname, obj1type);
                idx = info1_obj->nused - 1;
                memcpy(&info1_obj->paths[idx].obj_token, &oinfo1.token, sizeof(H5O_token_t));
                info1_obj->paths[idx].fileno = oinfo1.fileno;
            }
            else if (src_linfo1.type == H5L_TYPE_SOFT) {
                obj1type = H5TRAV_TYPE_LINK;
                trav_info_add(info1_obj, obj1fullname, obj1type);
            }
            else if (src_linfo1.type == H5L_TYPE_EXTERNAL) {
                obj1type = H5TRAV_TYPE_UDLINK;
                trav_info_add(info1_obj, obj1fullname, obj1type);
            }
        }

        /*----------------------------------------------------------
         * check if obj2 is root, group, single object or symlink
         */
        H5TOOLS_DEBUG("h5diff check if obj2=%s is root, group, single object or symlink", obj2fullname);
        if (!strcmp(obj2fullname, "/")) {
            obj2type = H5TRAV_TYPE_GROUP;
        }
        else {
            /* check if link itself exist */
            if (H5Lexists(file2_id, obj2fullname, H5P_DEFAULT) <= 0) {
                parallel_print("Object <%s> could not be found in <%s>\n", obj2fullname, fname2);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Error: Object could not be found");
            }
            /* get info from link */
            if (H5Lget_info2(file2_id, obj2fullname, &src_linfo2, H5P_DEFAULT) < 0) {
                parallel_print("Unable to get link info from <%s>\n", obj2fullname);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Lget_info failed");
            }

            info2_lp = info2_obj;

            /*
             * check the type of specified path for hard and symbolic links
             */
            if (src_linfo2.type == H5L_TYPE_HARD) {
                size_t idx;

                /* optional data pass */
                info2_obj->opts = (diff_opt_t *)opts;

                if (H5Oget_info_by_name3(file2_id, obj2fullname, &oinfo2, H5O_INFO_BASIC, H5P_DEFAULT) < 0) {
                    parallel_print("Error: Could not get file contents\n");
                    H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Error: Could not get file contents");
                }
                obj2type = (h5trav_type_t)oinfo2.type;
                trav_info_add(info2_obj, obj2fullname, obj2type);
                idx = info2_obj->nused - 1;
                memcpy(&info2_obj->paths[idx].obj_token, &oinfo2.token, sizeof(H5O_token_t));
                info2_obj->paths[idx].fileno = oinfo2.fileno;
            }
            else if (src_linfo2.type == H5L_TYPE_SOFT) {
                obj2type = H5TRAV_TYPE_LINK;
                trav_info_add(info2_obj, obj2fullname, obj2type);
            }
            else if (src_linfo2.type == H5L_TYPE_EXTERNAL) {
                obj2type = H5TRAV_TYPE_UDLINK;
                trav_info_add(info2_obj, obj2fullname, obj2type);
            }
        }
    }
    /* if no object specified */
    else {
        H5TOOLS_DEBUG("h5diff no object specified");
        /* set root group */
        obj1fullname = (char *)strdup("/");
        obj1type     = H5TRAV_TYPE_GROUP;
        obj2fullname = (char *)strdup("/");
        obj2type     = H5TRAV_TYPE_GROUP;
    }

    H5TOOLS_DEBUG("get any symbolic links info - errstat:%d", opts->err_stat);
    /* get any symbolic links info */
    l_ret1 = H5tools_get_symlink_info(file1_id, obj1fullname, &trg_linfo1, opts->follow_links);
    l_ret2 = H5tools_get_symlink_info(file2_id, obj2fullname, &trg_linfo2, opts->follow_links);

    /*---------------------------------------------
     * check for following symlinks
     */
    if (opts->follow_links) {
        /* pass how to handle printing warning to linkinfo option */
        if (print_warn(opts))
            trg_linfo1.opt.msg_mode = trg_linfo2.opt.msg_mode = 1;

        /*-------------------------------
         * check symbolic link (object1)
         */
        H5TOOLS_DEBUG("h5diff check symbolic link (object1)");
        /* dangling link */
        if (l_ret1 == 0) {
            H5TOOLS_DEBUG("h5diff ... dangling link");
            if (opts->no_dangle_links) {
                /* treat dangling link as error */
                if (opts->mode_verbose)
                    parallel_print("Warning: <%s> is a dangling link.\n", obj1fullname);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "treat dangling link as error");
            }
            else {
                if (opts->mode_verbose)
                    parallel_print("obj1 <%s> is a dangling link.\n", obj1fullname);
                if (l_ret1 != 0 || l_ret2 != 0) {
                    nfound++;
                    print_found(nfound);
                    H5TOOLS_GOTO_DONE(H5DIFF_NO_ERR);
                }
            }
        }
        else if (l_ret1 < 0) { /* fail */
            parallel_print("Object <%s> could not be found in <%s>\n", obj1fullname, fname1);
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Object could not be found");
        }
        else if (l_ret1 != 2) { /* symbolic link */
            obj1type = (h5trav_type_t)trg_linfo1.trg_type;
            H5TOOLS_DEBUG("h5diff ... ... trg_linfo1.trg_type == H5L_TYPE_HARD");
            if (info1_lp != NULL) {
                size_t idx = info1_lp->nused - 1;

                H5TOOLS_DEBUG("h5diff ... ... ... info1_obj not null");
                memcpy(&info1_lp->paths[idx].obj_token, &trg_linfo1.obj_token, sizeof(H5O_token_t));
                info1_lp->paths[idx].type   = (h5trav_type_t)trg_linfo1.trg_type;
                info1_lp->paths[idx].fileno = trg_linfo1.fileno;
            }
            H5TOOLS_DEBUG("h5diff check symbolic link (object1) finished");
        }

        /*-------------------------------
         * check symbolic link (object2)
         */
        H5TOOLS_DEBUG("h5diff check symbolic link (object2)");
        /* dangling link */
        if (l_ret2 == 0) {
            H5TOOLS_DEBUG("h5diff ... dangling link");
            if (opts->no_dangle_links) {
                /* treat dangling link as error */
                if (opts->mode_verbose)
                    parallel_print("Warning: <%s> is a dangling link.\n", obj2fullname);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "treat dangling link as error");
            }
            else {
                if (opts->mode_verbose)
                    parallel_print("obj2 <%s> is a dangling link.\n", obj2fullname);
                if (l_ret1 != 0 || l_ret2 != 0) {
                    nfound++;
                    print_found(nfound);
                    H5TOOLS_GOTO_DONE(H5DIFF_NO_ERR);
                }
            }
        }
        else if (l_ret2 < 0) { /* fail */
            parallel_print("Object <%s> could not be found in <%s>\n", obj2fullname, fname2);
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Object could not be found");
        }
        else if (l_ret2 != 2) { /* symbolic link */
            obj2type = (h5trav_type_t)trg_linfo2.trg_type;
            if (info2_lp != NULL) {
                size_t idx = info2_lp->nused - 1;

                H5TOOLS_DEBUG("h5diff ... ... ... info2_obj not null");
                memcpy(&info2_lp->paths[idx].obj_token, &trg_linfo2.obj_token, sizeof(H5O_token_t));
                info2_lp->paths[idx].type   = (h5trav_type_t)trg_linfo2.trg_type;
                info2_lp->paths[idx].fileno = trg_linfo2.fileno;
            }
            H5TOOLS_DEBUG("h5diff check symbolic link (object1) finished");
        }
    } /* end of if follow symlinks */

    /*
     * If verbose options is not used, don't need to traverse through the list
     * of objects in the group to display objects information,
     * So use h5tools_is_obj_same() to improve performance by skipping
     * comparing details of same objects.
     */

    if (!(opts->mode_verbose || opts->mode_report)) {
        H5TOOLS_DEBUG("h5diff NOT (opts->mode_verbose || opts->mode_report)");
        /* if no danglink links */
        if (l_ret1 > 0 && l_ret2 > 0)
            if (h5tools_is_obj_same(file1_id, obj1fullname, file2_id, obj2fullname) != 0)
                H5TOOLS_GOTO_DONE(H5DIFF_NO_ERR);
    }

    both_objs_grp = (obj1type == H5TRAV_TYPE_GROUP && obj2type == H5TRAV_TYPE_GROUP);
    if (both_objs_grp) {
        H5TOOLS_DEBUG("h5diff both_objs_grp true");
        /*
         * traverse group1
         */
        trav_info_init(fname1, file1_id, &info1_grp);
        /* optional data pass */
        info1_grp->opts = (diff_opt_t *)opts;

        if (h5trav_visit(file1_id, obj1fullname, true, true, trav_grp_objs, trav_grp_symlinks, info1_grp,
                         H5O_INFO_BASIC) < 0) {
            parallel_print("Error: Could not get file contents\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Could not get file contents");
        }
        info1_lp = info1_grp;

        /*
         * traverse group2
         */
        trav_info_init(fname2, file2_id, &info2_grp);
        /* optional data pass */
        info2_grp->opts = (diff_opt_t *)opts;

        if (h5trav_visit(file2_id, obj2fullname, true, true, trav_grp_objs, trav_grp_symlinks, info2_grp,
                         H5O_INFO_BASIC) < 0) {
            parallel_print("Error: Could not get file contents\n");
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "Could not get file contents");
        } /* end if */
        info2_lp = info2_grp;
    }
    H5TOOLS_DEBUG("groups traversed - errstat:%d", opts->err_stat);

    H5TOOLS_DEBUG("build_match_list next - errstat:%d", opts->err_stat);
    /* process the objects */
    build_match_list(obj1fullname, info1_lp, obj2fullname, info2_lp, &match_list, opts);
    H5TOOLS_DEBUG("build_match_list finished - errstat:%d", opts->err_stat);
    if (both_objs_grp) {
        /*------------------------------------------------------
         * print the list
         */
        if (opts->mode_verbose) {
            unsigned u;

            if (opts->mode_verbose_level > 2) {
                parallel_print("file1: %s\n", fname1);
                parallel_print("file2: %s\n", fname2);
            }

            parallel_print("\n");
            /* if given objects is group under root */
            if (strcmp(obj1fullname, "/") != 0 || strcmp(obj2fullname, "/") != 0)
                parallel_print("group1   group2\n");
            else
                parallel_print("file1     file2\n");
            parallel_print("---------------------------------------\n");
            for (u = 0; u < match_list->nobjs; u++) {
                int c1, c2;
                c1 = (match_list->objs[u].flags[0]) ? 'x' : ' ';
                c2 = (match_list->objs[u].flags[1]) ? 'x' : ' ';
                parallel_print("%5c %6c    %-15s\n", c1, c2, match_list->objs[u].name);
            } /* end for */
            parallel_print("\n");
        } /* end if */
    }

#ifdef H5_HAVE_PARALLEL
    if (g_Parallel) {
        if ((strlen(fname1) > MAX_FILENAME - 1) || (strlen(fname2) > MAX_FILENAME - 1)) {
            fprintf(stderr, "The parallel diff only supports path names up to %d characters\n",
                    MAX_FILENAME - 1);
            MPI_Abort(MPI_COMM_WORLD, 0);
        } /* end if */

        strcpy(filenames[0], fname1);
        strcpy(filenames[1], fname2);

        /* Alert the worker tasks that there's going to be work. */
        for (int i = 1; i < g_nTasks; i++)
            MPI_Send(filenames, (MAX_FILENAME * 2), MPI_CHAR, i, MPI_TAG_PARALLEL, MPI_COMM_WORLD);
    } /* end if */
#endif

    H5TOOLS_DEBUG("diff_match next - errstat:%d", opts->err_stat);
    nfound = diff_match(file1_id, obj1fullname, info1_lp, file2_id, obj2fullname, info2_lp, match_list, opts);
    H5TOOLS_DEBUG("diff_match nfound: %d - errstat:%d", nfound, opts->err_stat);

done:
    opts->err_stat = opts->err_stat | ret_value;

#ifdef H5_HAVE_PARALLEL
    if (g_Parallel)
        /* All done at this point, let tasks know that they won't be needed */
        phdiff_dismiss_workers();
#endif
    /* free buffers in trav_info structures */
    if (info1_obj)
        trav_info_free(info1_obj);
    if (info2_obj)
        trav_info_free(info2_obj);

    if (info1_grp)
        trav_info_free(info1_grp);
    if (info2_grp)
        trav_info_free(info2_grp);

    /* free buffers */
    if (obj1fullname)
        free(obj1fullname);
    if (obj2fullname)
        free(obj2fullname);

    /* free link info buffer */
    if (trg_linfo1.trg_path)
        free(trg_linfo1.trg_path);
    if (trg_linfo2.trg_path)
        free(trg_linfo2.trg_path);

    /* close */
    H5E_BEGIN_TRY
    {
        H5Fclose(file1_id);
        H5Fclose(file2_id);
        if (fapl1_id != H5P_DEFAULT)
            H5Pclose(fapl1_id);
        if (fapl2_id != H5P_DEFAULT)
            H5Pclose(fapl2_id);
    }
    H5E_END_TRY

    H5TOOLS_ENDDEBUG(" - errstat:%d", opts->err_stat);

    return nfound;
}

/*-------------------------------------------------------------------------
 * Function: diff_match
 *
 * Purpose:  Compare common objects in given groups according to table structure.
 *           The table structure has flags which can be used to find common objects
 *           and will be compared.
 *           Common object means same name (absolute path) objects in both location.
 *
 * Return:   Number of differences found
 *
 *-------------------------------------------------------------------------
 */
hsize_t
diff_match(hid_t file1_id, const char *grp1, trav_info_t *info1, hid_t file2_id, const char *grp2,
           trav_info_t *info2, trav_table_t *table, diff_opt_t *opts)
{
    hsize_t     nfound = 0;
    unsigned    i;
    const char *grp1_path     = "";
    const char *grp2_path     = "";
    char       *obj1_fullpath = NULL;
    char       *obj2_fullpath = NULL;
    diff_args_t argdata;
    size_t      idx1 = 0;
    size_t      idx2 = 0;
#ifdef H5_HAVE_PARALLEL
    char *workerTasks = NULL;
    int   busyTasks   = 0;
#endif
    diff_err_t ret_value = opts->err_stat;

    H5TOOLS_START_DEBUG(" - errstat:%d", opts->err_stat);

#ifdef H5_HAVE_PARALLEL
    if (g_Parallel) {
        if (NULL == (workerTasks = malloc((size_t)(g_nTasks - 1) * sizeof(char))))
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "unable to allocate worker tasks array");

        /*set all tasks as free */
        memset(workerTasks, 1, (size_t)(g_nTasks - 1) * sizeof(char));
    }
#endif

    /*
     * if not root, prepare object name to be pre-appended to group path to
     * make full path
     */
    if (strcmp(grp1, "/") != 0)
        grp1_path = grp1;
    if (strcmp(grp2, "/") != 0)
        grp2_path = grp2;

    /*-------------------------------------------------------------------------
     * regarding the return value of h5diff (0, no difference in files, 1 difference )
     * 1) the number of objects in file1 must be the same as in file2
     * 2) the graph must match, i.e same names (absolute path)
     * 3) objects with the same name must be of the same type
     *-------------------------------------------------------------------------
     */

    H5TOOLS_DEBUG("exclude_path opts->contents:%d", opts->contents);
    /* not valid compare used when --exclude-path option is used */
    if (!opts->exclude_path) {
        /* number of different objects */
        if (info1->nused != info2->nused) {
            opts->contents = 0;
        }
        H5TOOLS_DEBUG("opts->exclude_path opts->contents:%d", opts->contents);
    }

    /* objects in one file and not the other */
    for (i = 0; i < table->nobjs; i++) {
        if (table->objs[i].flags[0] != table->objs[i].flags[1]) {
            opts->contents = 0;
            break;
        }
        H5TOOLS_DEBUG("table->nobjs[%d] opts->contents:%d", i, opts->contents);
    }

    /*-------------------------------------------------------------------------
     * do the diff for common objects
     *-------------------------------------------------------------------------
     */
    for (i = 0; i < table->nobjs; i++) {
        H5TOOLS_DEBUG("diff for common objects[%d] - errstat:%d", i, opts->err_stat);

        /* Check if object is present in both files first before diffing */
        if (!(table->objs[i].flags[0] && table->objs[i].flags[1]))
            continue;

            /* Make full paths for objects */
#ifdef H5_HAVE_ASPRINTF
        /* Use the asprintf() routine, since it does what we're trying to do below */
        if (asprintf(&obj1_fullpath, "%s%s", grp1_path, table->objs[i].name) < 0)
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "name buffer allocation failed");
        if (asprintf(&obj2_fullpath, "%s%s", grp2_path, table->objs[i].name) < 0)
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "name buffer allocation failed");
#else
        if (NULL == (obj1_fullpath = malloc(strlen(grp1_path) + strlen(table->objs[i].name) + 1)))
            H5TOOLS_ERROR(H5DIFF_ERR, "name buffer allocation failed");
        else {
            strcpy(obj1_fullpath, grp1_path);
            strcat(obj1_fullpath, table->objs[i].name);
        }
        if (NULL == (obj2_fullpath = malloc(strlen(grp2_path) + strlen(table->objs[i].name) + 1)))
            H5TOOLS_ERROR(H5DIFF_ERR, "name buffer allocation failed");
        else {
            strcpy(obj2_fullpath, grp2_path);
            strcat(obj2_fullpath, table->objs[i].name);
        }
#endif

        H5TOOLS_DEBUG("diff_match path1 - %s", obj1_fullpath);
        H5TOOLS_DEBUG("diff_match path2 - %s", obj2_fullpath);

        /* get index to figure out type of the object in file1 */
        while (info1->paths[idx1].path && (strcmp(obj1_fullpath, info1->paths[idx1].path) != 0))
            idx1++;
        /* get index to figure out type of the object in file2 */
        while (info2->paths[idx2].path && (strcmp(obj2_fullpath, info2->paths[idx2].path) != 0))
            idx2++;

        /* Set argdata to pass other args into diff() */
        argdata.type[0]        = info1->paths[idx1].type;
        argdata.type[1]        = info2->paths[idx2].type;
        argdata.is_same_trgobj = table->objs[i].is_same_trgobj;

        opts->cmn_objs = 1;

        H5TOOLS_DEBUG("diff paths - errstat:%d", opts->err_stat);

        if (!g_Parallel)
            nfound += diff(file1_id, obj1_fullpath, file2_id, obj2_fullpath, opts, &argdata);
#ifdef H5_HAVE_PARALLEL
        else {
            struct diff_mpi_args args;

            /* Dispatch diff requests to as many worker tasks as possible before
             * handling incoming requests from worker tasks.
             */

            /* Check length of object names before handling and dispatching work */
            if (strlen(obj1_fullpath) > 255 || strlen(obj2_fullpath) > 255)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR,
                                   "parallel h5diff only supports object names up to 255 characters");

            /* If no worker tasks are available, handle requests until one is */
            if (busyTasks == g_nTasks - 1)
                if (H5DIFF_ERR == handle_worker_request(workerTasks, &busyTasks, opts, &nfound))
                    H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't handle parallel worker task request");

            /* Set up args to pass to worker task. */
            strcpy(args.name1, obj1_fullpath);
            strcpy(args.name2, obj2_fullpath);
            args.opts    = *opts;
            args.argdata = argdata;

            /* Dispatch diff request for this object to a worker task */
            if (H5DIFF_ERR == dispatch_diff_to_worker(&args, workerTasks, &busyTasks))
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't dispatch diff command to worker task");
        }
#endif

        if (obj1_fullpath) {
            free(obj1_fullpath);
            obj1_fullpath = NULL;
        }
        if (obj2_fullpath) {
            free(obj2_fullpath);
            obj2_fullpath = NULL;
        }
    }
    H5TOOLS_DEBUG("done with for loop - errstat:%d", opts->err_stat);

#ifdef H5_HAVE_PARALLEL
    if (g_Parallel) {
        /* Make sure all worker tasks are done */
        while (busyTasks > 0) {
            if (H5DIFF_ERR == handle_worker_request(workerTasks, &busyTasks, opts, &nfound))
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't handle parallel worker task request");
        }
    }
#endif /* H5_HAVE_PARALLEL */

done:
    free(obj1_fullpath);
    free(obj2_fullpath);

#ifdef H5_HAVE_PARALLEL
    free(workerTasks);
#endif

    opts->err_stat = opts->err_stat | ret_value;

    free_exclude_attr_list(opts);

    /* free table */
    if (table)
        trav_table_free(table);

    H5TOOLS_ENDDEBUG(" diffs=%d - errstat:%d", nfound, opts->err_stat);

    return nfound;
}

/*-------------------------------------------------------------------------
 * Function: diff
 *
 * Purpose:  switch between types and choose the diff function
 *           TYPE is either
 *               H5G_GROUP         Object is a group
 *               H5G_DATASET       Object is a dataset
 *               H5G_TYPE          Object is a named data type
 *               H5G_LINK          Object is a symbolic link
 *
 * Return:   Number of differences found
 *-------------------------------------------------------------------------
 */
hsize_t
diff(hid_t file1_id, const char *path1, hid_t file2_id, const char *path2, diff_opt_t *opts,
     diff_args_t *argdata)
{
    int           status          = -1;
    hid_t         dset1_id        = H5I_INVALID_HID;
    hid_t         dset2_id        = H5I_INVALID_HID;
    hid_t         type1_id        = H5I_INVALID_HID;
    hid_t         type2_id        = H5I_INVALID_HID;
    hid_t         grp1_id         = H5I_INVALID_HID;
    hid_t         grp2_id         = H5I_INVALID_HID;
    bool          is_dangle_link1 = false;
    bool          is_dangle_link2 = false;
    bool          is_hard_link    = false;
    hsize_t       nfound          = 0;
    h5trav_type_t object_type;
    diff_err_t    ret_value = opts->err_stat;

    /* to get link info */
    h5tool_link_info_t linkinfo1;
    h5tool_link_info_t linkinfo2;

    H5TOOLS_START_DEBUG(" - errstat:%d", opts->err_stat);

    /*init link info struct */
    memset(&linkinfo1, 0, sizeof(h5tool_link_info_t));
    memset(&linkinfo2, 0, sizeof(h5tool_link_info_t));

    /* pass how to handle printing warnings to linkinfo option */
    if (print_warn(opts))
        linkinfo1.opt.msg_mode = linkinfo2.opt.msg_mode = 1;

    /* for symbolic links, take care follow symlink and no dangling link
     * options */
    if (argdata->type[0] == H5TRAV_TYPE_LINK || argdata->type[0] == H5TRAV_TYPE_UDLINK ||
        argdata->type[1] == H5TRAV_TYPE_LINK || argdata->type[1] == H5TRAV_TYPE_UDLINK) {
        /*
         * check dangling links for path1 and path2
         */

        H5TOOLS_DEBUG("diff links");
        /* target object1 - get type and name */
        if ((status = H5tools_get_symlink_info(file1_id, path1, &linkinfo1, opts->follow_links)) < 0)
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5tools_get_symlink_info failed");

        /* dangling link */
        if (status == 0) {
            if (opts->no_dangle_links) {
                /* dangling link is error */
                if (opts->mode_verbose)
                    parallel_print("Warning: <%s> is a dangling link.\n", path1);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "dangling link is error");
            }
            else
                is_dangle_link1 = true;
        }

        /* target object2 - get type and name */
        if ((status = H5tools_get_symlink_info(file2_id, path2, &linkinfo2, opts->follow_links)) < 0)
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5tools_get_symlink_info failed");
        /* dangling link */
        if (status == 0) {
            if (opts->no_dangle_links) {
                /* dangling link is error */
                if (opts->mode_verbose)
                    parallel_print("Warning: <%s> is a dangling link.\n", path2);
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "dangling link is error");
            }
            else
                is_dangle_link2 = true;
        }

        /* found dangling link */
        if (is_dangle_link1 || is_dangle_link2) {
            H5TOOLS_GOTO_DONE(H5DIFF_NO_ERR);
        }

        /* follow symbolic link option */
        if (opts->follow_links) {
            if (linkinfo1.linfo.type == H5L_TYPE_SOFT || linkinfo1.linfo.type == H5L_TYPE_EXTERNAL)
                argdata->type[0] = (h5trav_type_t)linkinfo1.trg_type;

            if (linkinfo2.linfo.type == H5L_TYPE_SOFT || linkinfo2.linfo.type == H5L_TYPE_EXTERNAL)
                argdata->type[1] = (h5trav_type_t)linkinfo2.trg_type;
        }
    }
    /* if objects are not the same type */
    if (argdata->type[0] != argdata->type[1]) {
        H5TOOLS_DEBUG("diff objects are not the same");
        if (opts->mode_verbose || opts->mode_list_not_cmp) {
            parallel_print("Not comparable: <%s> is of type %s and <%s> is of type %s\n", path1,
                           get_type(argdata->type[0]), path2, get_type(argdata->type[1]));
        }

        opts->not_cmp = 1;
        /* TODO: will need to update non-comparable is different
         * opts->contents = 0;
         */
        H5TOOLS_GOTO_DONE(H5DIFF_NO_ERR);
    }
    else /* now both object types are same */
        object_type = argdata->type[0];

    /*
     * If both points to the same target object, skip comparing details inside
     * of the objects to improve performance.
     * Always check for the hard links, otherwise if follow symlink option is
     * specified.
     *
     * Perform this to match the outputs as bypassing.
     */
    if (argdata->is_same_trgobj) {
        H5TOOLS_DEBUG("argdata->is_same_trgobj");
        is_hard_link = (object_type == H5TRAV_TYPE_DATASET || object_type == H5TRAV_TYPE_NAMED_DATATYPE ||
                        object_type == H5TRAV_TYPE_GROUP);
        if (opts->follow_links || is_hard_link) {
            /* print information is only verbose option is used */
            if (opts->mode_verbose || opts->mode_report) {
                switch (object_type) {
                    case H5TRAV_TYPE_DATASET:
                        do_print_objname("dataset", path1, path2, opts);
                        break;
                    case H5TRAV_TYPE_NAMED_DATATYPE:
                        do_print_objname("datatype", path1, path2, opts);
                        break;
                    case H5TRAV_TYPE_GROUP:
                        do_print_objname("group", path1, path2, opts);
                        break;
                    case H5TRAV_TYPE_LINK:
                        do_print_objname("link", path1, path2, opts);
                        break;
                    case H5TRAV_TYPE_UDLINK:
                        if (linkinfo1.linfo.type == H5L_TYPE_EXTERNAL &&
                            linkinfo2.linfo.type == H5L_TYPE_EXTERNAL)
                            do_print_objname("external link", path1, path2, opts);
                        else
                            do_print_objname("user defined link", path1, path2, opts);
                        break;
                    case H5TRAV_TYPE_UNKNOWN:
                    default:
                        parallel_print("Comparison not supported: <%s> and <%s> are of type %s\n", path1,
                                       path2, get_type(object_type));
                        opts->not_cmp = 1;
                        break;
                } /* switch(type)*/

                print_found(nfound);
            } /* if(opts->mode_verbose || opts->mode_report) */

            /* exact same, so comparison is done */
            H5TOOLS_GOTO_DONE(H5DIFF_NO_ERR);
        }
    }

    switch (object_type) {
            /*----------------------------------------------------------------------
             * H5TRAV_TYPE_DATASET
             *----------------------------------------------------------------------
             */
        case H5TRAV_TYPE_DATASET:
            H5TOOLS_DEBUG("diff object type H5TRAV_TYPE_DATASET - errstat:%d", opts->err_stat);
            if ((dset1_id = H5Dopen2(file1_id, path1, H5P_DEFAULT)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Dopen2 failed");
            if ((dset2_id = H5Dopen2(file2_id, path2, H5P_DEFAULT)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Dopen2 failed");
            H5TOOLS_DEBUG("paths: %s - %s", path1, path2);
            /* verbose (-v) and report (-r) mode */
            if (opts->mode_verbose || opts->mode_report) {
                do_print_objname("dataset", path1, path2, opts);
                H5TOOLS_DEBUG("call diff_dataset 1:%s  2:%s ", path1, path2);
                nfound = diff_dataset(file1_id, file2_id, path1, path2, opts);
                print_found(nfound);
            }
            /* quiet mode (-q), just count differences */
            else if (opts->mode_quiet) {
                nfound = diff_dataset(file1_id, file2_id, path1, path2, opts);
            }
            /* the rest (-c, none, ...) */
            else {
                nfound = diff_dataset(file1_id, file2_id, path1, path2, opts);
                /* print info if difference found  */
                if (nfound) {
                    do_print_objname("dataset", path1, path2, opts);
                    print_found(nfound);
                }
            }
            H5TOOLS_DEBUG("diff after dataset:%d - errstat:%d", nfound, opts->err_stat);

            /*---------------------------------------------------------
             * compare attributes
             * if condition refers to cases when the dataset is a
             * referenced object
             *---------------------------------------------------------
             */
            if (path1 && !is_exclude_attr(path1, object_type, opts)) {
                H5TOOLS_DEBUG("call diff_attr 1:%s  2:%s ", path1, path2);
                nfound += diff_attr(dset1_id, dset2_id, path1, path2, opts);
            }

            if (H5Dclose(dset1_id) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Dclose failed");
            if (H5Dclose(dset2_id) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Dclose failed");
            break;

            /*----------------------------------------------------------------------
             * H5TRAV_TYPE_NAMED_DATATYPE
             *----------------------------------------------------------------------
             */
        case H5TRAV_TYPE_NAMED_DATATYPE:
            H5TOOLS_DEBUG("H5TRAV_TYPE_NAMED_DATATYPE 1:%s  2:%s ", path1, path2);
            if ((type1_id = H5Topen2(file1_id, path1, H5P_DEFAULT)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Topen2 failed");
            if ((type2_id = H5Topen2(file2_id, path2, H5P_DEFAULT)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Topen2 failed");

            if ((status = H5Tequal(type1_id, type2_id)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Tequal failed");

            /* if H5Tequal is > 0 then the datatypes refer to the same datatype */
            nfound = (status > 0) ? 0 : 1;

            if (print_objname(opts, nfound))
                do_print_objname("datatype", path1, path2, opts);

            /* always print the number of differences found in verbose mode */
            if (opts->mode_verbose)
                print_found(nfound);

            /*-----------------------------------------------------------------
             * compare attributes
             * the if condition refers to cases when the dataset is a
             * referenced object
             *-----------------------------------------------------------------
             */
            if (path1 && !is_exclude_attr(path1, object_type, opts)) {
                H5TOOLS_DEBUG("call diff_attr 1:%s  2:%s ", path1, path2);
                nfound += diff_attr(type1_id, type2_id, path1, path2, opts);
            }

            if (H5Tclose(type1_id) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Tclose failed");
            if (H5Tclose(type2_id) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Tclose failed");
            break;

            /*----------------------------------------------------------------------
             * H5TRAV_TYPE_GROUP
             *----------------------------------------------------------------------
             */
        case H5TRAV_TYPE_GROUP:
            H5TOOLS_DEBUG("H5TRAV_TYPE_GROUP 1:%s  2:%s ", path1, path2);
            if (print_objname(opts, nfound))
                do_print_objname("group", path1, path2, opts);

            /* always print the number of differences found in verbose mode */
            if (opts->mode_verbose)
                print_found(nfound);

            if ((grp1_id = H5Gopen2(file1_id, path1, H5P_DEFAULT)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Gclose failed");
            if ((grp2_id = H5Gopen2(file2_id, path2, H5P_DEFAULT)) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Gclose failed");

            /*-----------------------------------------------------------------
             * compare attributes
             * the if condition refers to cases when the dataset is a
             * referenced object
             *-----------------------------------------------------------------
             */
            if (path1 && !is_exclude_attr(path1, object_type, opts)) {
                H5TOOLS_DEBUG("call diff_attr 1:%s  2:%s ", path1, path2);
                nfound += diff_attr(grp1_id, grp2_id, path1, path2, opts);
            }

            if (H5Gclose(grp1_id) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Gclose failed");
            if (H5Gclose(grp2_id) < 0)
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "H5Gclose failed");
            break;

            /*----------------------------------------------------------------------
             * H5TRAV_TYPE_LINK
             *----------------------------------------------------------------------
             */
        case H5TRAV_TYPE_LINK: {
            H5TOOLS_DEBUG("H5TRAV_TYPE_LINK 1:%s  2:%s ", path1, path2);
            status = strcmp(linkinfo1.trg_path, linkinfo2.trg_path);

            /* if the target link name is not same then the links are "different" */
            nfound = (status != 0) ? 1 : 0;

            if (print_objname(opts, nfound))
                do_print_objname("link", path1, path2, opts);

            /* always print the number of differences found in verbose mode */
            if (opts->mode_verbose)
                print_found(nfound);
        } break;

            /*----------------------------------------------------------------------
             * H5TRAV_TYPE_UDLINK
             *----------------------------------------------------------------------
             */
        case H5TRAV_TYPE_UDLINK: {
            H5TOOLS_DEBUG("H5TRAV_TYPE_UDLINK 1:%s  2:%s ", path1, path2);
            /* Only external links will have a query function registered */
            if (linkinfo1.linfo.type == H5L_TYPE_EXTERNAL && linkinfo2.linfo.type == H5L_TYPE_EXTERNAL) {
                /* If the buffers are the same size, compare them */
                if (linkinfo1.linfo.u.val_size == linkinfo2.linfo.u.val_size) {
                    status = memcmp(linkinfo1.trg_path, linkinfo2.trg_path, linkinfo1.linfo.u.val_size);
                }
                else
                    status = 1;

                /* if "linkinfo1.trg_path" != "linkinfo2.trg_path" then the links
                 * are "different" extlinkinfo#.path is combination string of
                 * file_name and obj_name
                 */
                nfound = (status != 0) ? 1 : 0;

                if (print_objname(opts, nfound))
                    do_print_objname("external link", path1, path2, opts);

            } /* end if */
            else {
                /* If one or both of these links isn't an external link, we can only
                 * compare information from H5Lget_info 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 ((linkinfo1.linfo.type != linkinfo2.linfo.type) ||
                    (linkinfo1.linfo.u.val_size != linkinfo2.linfo.u.val_size))
                    nfound = 1;
                else
                    nfound = 0;

                if (print_objname(opts, nfound))
                    do_print_objname("user defined link", path1, path2, opts);
            } /* end else */

            /* always print the number of differences found in verbose mode */
            if (opts->mode_verbose)
                print_found(nfound);
        } break;

        case H5TRAV_TYPE_UNKNOWN:
        default:
            if (opts->mode_verbose)
                parallel_print("Comparison not supported: <%s> and <%s> are of type %s\n", path1, path2,
                               get_type(object_type));
            opts->not_cmp = 1;
            break;
    }

done:
    opts->err_stat = opts->err_stat | ret_value;

    /*-----------------------------------
     * handle dangling link(s)
     */
    /* both path1 and path2 are dangling links */
    if (is_dangle_link1 && is_dangle_link2) {
        if (print_objname(opts, nfound)) {
            do_print_objname("dangling link", path1, path2, opts);
            print_found(nfound);
        }
    }
    /* path1 is dangling link */
    else if (is_dangle_link1) {
        if (opts->mode_verbose)
            parallel_print("obj1 <%s> is a dangling link.\n", path1);
        nfound++;
        if (print_objname(opts, nfound))
            print_found(nfound);
    }
    /* path2 is dangling link */
    else if (is_dangle_link2) {
        if (opts->mode_verbose)
            parallel_print("obj2 <%s> is a dangling link.\n", path2);
        nfound++;
        if (print_objname(opts, nfound))
            print_found(nfound);
    }

    /* free link info buffer */
    if (linkinfo1.trg_path)
        free(linkinfo1.trg_path);
    if (linkinfo2.trg_path)
        free(linkinfo2.trg_path);

    /* close */
    /* disable error reporting */
    H5E_BEGIN_TRY
    {
        H5Dclose(dset1_id);
        H5Dclose(dset2_id);
        H5Tclose(type1_id);
        H5Tclose(type2_id);
        H5Gclose(grp1_id);
        H5Gclose(grp2_id);
        /* enable error reporting */
    }
    H5E_END_TRY

    H5TOOLS_ENDDEBUG(": %d - errstat:%d", nfound, opts->err_stat);

    return nfound;
}

#ifdef H5_HAVE_PARALLEL
/*-------------------------------------------------------------------------
 * Function: handle_worker_request
 *
 * Purpose:  Handles MPI communication from a worker task. Returns when a
 *           worker task becomes free (either a MPI_TAG_DONE message is
 *           received from it or a MPI_TAG_TOK_RETURN message is received
 *           from it after processing a MPI_TAG_TOK_REQUEST message event).
 *
 * Return:   H5DIFF_NO_ERR on success/H5DIFF_ERR on failure
 *-------------------------------------------------------------------------
 */
static diff_err_t
handle_worker_request(char *worker_tasks, int *n_busy_tasks, diff_opt_t *opts, hsize_t *n_diffs)
{
    struct diffs_found ndiffs_found;
    MPI_Status         status;
    int                task_idx  = 0;
    int                source    = 0;
    diff_err_t         ret_value = H5DIFF_NO_ERR;

    /* Must have at least one busy worker task */
    assert(*n_busy_tasks > 0);

    if (MPI_SUCCESS != (MPI_Probe(MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status)))
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't check for message from worker task");
    source   = status.MPI_SOURCE;
    task_idx = source - 1;

    /* Currently, only MPI_TAG_DONE or MPI_TAG_TOK_REQUEST messages should be received
     * from worker tasks. MPI_TAG_TOK_REQUEST messages begin a sequence that is handled
     * "atomically" to simplify things and prevent the potential for interleaved output,
     * out-of-order or unreceived messages, etc.
     */
    if (status.MPI_TAG != MPI_TAG_DONE && status.MPI_TAG != MPI_TAG_TOK_REQUEST)
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "invalid MPI message tag received from worker task");

    if (status.MPI_TAG == MPI_TAG_DONE) {
        if (MPI_SUCCESS != (MPI_Recv(&ndiffs_found, sizeof(ndiffs_found), MPI_BYTE, source, MPI_TAG_DONE,
                                     MPI_COMM_WORLD, &status)))
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't receive 'done' message from worker");

        /* Update diff stats */
        opts->not_cmp = opts->not_cmp | ndiffs_found.not_cmp;
        (*n_diffs) += ndiffs_found.nfound;

        /* Mark worker task as free */
        worker_tasks[task_idx] = 1;
        (*n_busy_tasks)--;
    }
    else if (status.MPI_TAG == MPI_TAG_TOK_REQUEST) {
        char data[PRINT_DATA_MAX_SIZE + 1];
        int  incoming_output = 0;

        if (MPI_SUCCESS !=
            (MPI_Recv(NULL, 0, MPI_BYTE, source, MPI_TAG_TOK_REQUEST, MPI_COMM_WORLD, &status)))
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't receive print token request message");

        /* Give print token to worker task */
        if (MPI_SUCCESS != (MPI_Send(NULL, 0, MPI_BYTE, source, MPI_TAG_PRINT_TOK, MPI_COMM_WORLD)))
            H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't send print token to worker");

        /* Print incoming output until print token is returned */
        incoming_output = 1;
        do {
            if (MPI_SUCCESS != (MPI_Probe(source, MPI_ANY_TAG, MPI_COMM_WORLD, &status)))
                H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't check for message from worker task");

            if (status.MPI_TAG == MPI_TAG_PRINT_DATA) {
                memset(data, 0, PRINT_DATA_MAX_SIZE + 1);
                if (MPI_SUCCESS != (MPI_Recv(data, PRINT_DATA_MAX_SIZE, MPI_CHAR, source, MPI_TAG_PRINT_DATA,
                                             MPI_COMM_WORLD, &status)))
                    H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't receive output from worker task");

                parallel_print("%s", data);
            }
            else if (status.MPI_TAG == MPI_TAG_TOK_RETURN) {
                if (MPI_SUCCESS != (MPI_Recv(&ndiffs_found, sizeof(ndiffs_found), MPI_BYTE, source,
                                             MPI_TAG_TOK_RETURN, MPI_COMM_WORLD, &status)))
                    H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't receive print token message from worker");

                incoming_output = 0;
            }
        } while (incoming_output);

        /* Update diff stats */
        opts->not_cmp = opts->not_cmp | ndiffs_found.not_cmp;
        (*n_diffs) += ndiffs_found.nfound;

        /* Mark worker task as free */
        worker_tasks[task_idx] = 1;
        (*n_busy_tasks)--;
    }

done:
    return ret_value;
}

/*-------------------------------------------------------------------------
 * Function: dispatch_diff_to_worker
 *
 * Purpose:  Sends arguments to a worker task to allow it to start
 *           processing the differences between two objects.
 *
 * Return:   H5DIFF_NO_ERR on success/H5DIFF_ERR on failure
 *-------------------------------------------------------------------------
 */
static diff_err_t
dispatch_diff_to_worker(struct diff_mpi_args *args, char *worker_tasks, int *n_busy_tasks)
{
    int        target_task = -1;
    diff_err_t ret_value   = H5DIFF_NO_ERR;

    /* Must have a free worker task */
    assert(*n_busy_tasks < g_nTasks - 1);

    /* Check array of tasks to see which ones are free.
     * Manager task never does work, so workerTasks[0] is
     * really worker task 0, or MPI rank 1.
     */
    target_task = -1;
    for (int n = 1; n < g_nTasks; n++)
        if (worker_tasks[n - 1]) {
            target_task = n - 1;
            break;
        }

    /* We should always find a free worker here */
    if (target_task < 0)
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't find a free worker task to dispatch diff request to");

    /* Send diff arguments to worker */
    if (MPI_SUCCESS != (MPI_Send(args, sizeof(struct diff_mpi_args), MPI_BYTE, target_task + 1, MPI_TAG_ARGS,
                                 MPI_COMM_WORLD)))
        H5TOOLS_GOTO_ERROR(H5DIFF_ERR, "couldn't send diff arguments to worker task");

    /* Mark worker task as busy */
    worker_tasks[target_task] = 0;
    (*n_busy_tasks)++;

done:
    return ret_value;
}
#endif
