/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Copyright by The HDF Group. *
* Copyright by the Board of Trustees of the University of Illinois. *
* 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. *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/* This program demonstrates how to translate an external link created on
* a Windows machine into a format that a *nix machine can read.
* This is done by registering a new traversal function for external links.
*
* This example is designed to be run on Unix and will create an external
* link with a Windows-style path. Using the traversal function below,
* the example then successfully follows the external link.
*
* The external link will create a file called "u2w/u2w_target.h5".
* The example will fail if the directory u2w does not exist.
*/
#include "hdf5.h"
#include <stdlib.h>
#include <string.h>
/* "Windows to Unix" traversal function for external links
*
* Translates a filename stored in Unix format to Windows format by replacing
* forward slashes with backslashes.
* Makes no attempt to handle Windows drive names (e.g., "C:\"), spaces within
* file names, quotes, etc. These are left as an exercise for the user. :)
* Note that this may not be necessary on your system; many Windows systems can
* understand Unix paths.
*/
static hid_t
elink_unix2win_trav(const char *link_name, hid_t cur_group, const void *udata, size_t udata_size,
hid_t lapl_id, hid_t dxpl_id)
{
hid_t fid;
const char *file_name;
const char *obj_name;
char *new_fname = NULL; /* Buffer allocated to hold Unix file path */
ssize_t prefix_len; /* External link prefix length */
size_t fname_len;
size_t start_pos; /* Initial position in new_fname buffer */
size_t x; /* Counter variable */
hid_t ret_value = -1;
printf("Converting Unix path to Windows path.\n");
if (H5Lunpack_elink_val(udata, udata_size, NULL, &file_name, &obj_name) < 0)
goto error;
fname_len = strlen(file_name);
/* See if the external link prefix property is set */
if ((prefix_len = H5Pget_elink_prefix(lapl_id, NULL, 0)) < 0)
goto error;
/* If so, prepend it to the filename. We assume that the prefix
* is in the correct format for the current file system.
*/
if (prefix_len > 0) {
/* Allocate a buffer to hold the filename plus prefix */
new_fname = malloc(prefix_len + fname_len + 1);
/* Copy the prefix into the buffer */
if (H5Pget_elink_prefix(lapl_id, new_fname, (size_t)(prefix_len + 1)) < 0)
goto error;
start_pos = prefix_len;
}
else {
/* Allocate a buffer to hold just the filename */
new_fname = malloc(fname_len + 1);
start_pos = 0;
}
/* We should now copy file_name into new_fname starting at position pos.
* We'll convert '/' characters into '\' characters as we go.
*/
for (x = 0; file_name[x] != '\0'; x++) {
if (file_name[x] == '/')
new_fname[x + start_pos] = '\\';
else
new_fname[x + start_pos] = file_name[x];
}
new_fname[x + start_pos] = '\0';
/* Now open the file and object within it */
if ((fid = H5Fopen(new_fname, H5F_ACC_RDWR, H5P_DEFAULT)) < 0)
goto error;
ret_value = H5Oopen(fid, obj_name, lapl_id); /* If this fails, our return value will be negative. */
if (H5Fclose(fid) < 0)
goto error;
/* Free file name if it's been allocated */
if (new_fname)
free(new_fname);
return ret_value;
error:
/* Free file name if it's been allocated */
if (new_fname)
free(new_fname);
return -1;
}
const H5L_class_t elink_unix2win_class[1] = {{
H5L_LINK_CLASS_T_VERS, /* H5L_class_t version */
H5L_TYPE_EXTERNAL, /* Link type id number */
"unix2win external link", /* Link class name for debugging */
NULL, /* Creation callback */
NULL, /* Move callback */
NULL, /* Copy callback */
elink_unix2win_trav, /* The actual traversal function */
NULL, /* Deletion callback */
NULL /* Query callback */
}};
/* The example function.
* Creates a file named "unix2win.h5" with an external link pointing to
* the file "u2w/u2w_target.h5".
*
* Registers a new traversal function for external links and then
* follows the external link to open the target file.
*/
static int
unix2win_example(void)
{
hid_t fid = (-1); /* File ID */
hid_t gid = (-1); /* Group ID */
/* Create the target file. */
#ifdef H5_HAVE_WIN32_API
if ((fid = H5Fcreate("u2w\\u2w_target.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
goto error;
#else
if ((fid = H5Fcreate("u2w/u2w_target.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
goto error;
#endif
if (H5Fclose(fid) < 0)
goto error;
/* Create the source file with an external link in Windows format */
if ((fid = H5Fcreate("unix2win.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
goto error;
/* Create the external link */
if (H5Lcreate_external("u2w/../u2w/u2w_target.h5", "/", fid, "ext_link", H5P_DEFAULT, H5P_DEFAULT) < 0)
goto error;
/* If we are not on Windows, assume we are on a Unix-y filesystem and
* follow the external link normally.
* If we are on Windows, register the unix2win traversal function so
* that external links can be traversed.
*/
#ifdef H5_HAVE_WIN32_API
/* Register the elink_unix2win class defined above to replace default
* external links
*/
if (H5Lregister(elink_unix2win_class) < 0)
goto error;
#endif
/* Now follow the link */
if ((gid = H5Gopen2(fid, "ext_link", H5P_DEFAULT)) < 0)
goto error;
printf("Successfully followed external link.\n");
/* Close the group and the file */
if (H5Gclose(gid) < 0)
goto error;
if (H5Fclose(fid) < 0)
goto error;
return 0;
error:
printf("Error!\n");
H5E_BEGIN_TRY
{
H5Gclose(gid);
H5Fclose(fid);
}
H5E_END_TRY;
return -1;
}
/* Main function
*
* Invokes the example function.
*/
int
main(void)
{
int ret;
printf("Testing unix2win external links.\n");
ret = unix2win_example();
return ret;
}