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/**
* slibc — Yet another C library
* Copyright © 2015 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
/**
* Get the relative path of a file.
*
* This is a slibc extension.
*
* @param file The file.
* @param ref The file the result shall be relative to,
* `NULL` for the current working directory.
* If and only if this path ends with a slash,
* (or if it is `NULL`,) it will be treated as
* a directory in which a symbolic link, with
* the result as it target, can be located to
* point to `file`.
*
* @throws ENOMEM The process cannot allocate more memory.
*
* @since Always.
*/
char* relpath(const char* file, const char* ref) /* XXX may also fail as get_current_dir_name */
{
int saved_errno;
char* cwd = NULL;
char* absfile = NULL;
char* absref = NULL;
char* rc;
char* prc;
size_t ptr, p, n = 0;
if ((cwd = get_current_dir_name()) == NULL) goto fail;
if ((absfile = abspath(file, cwd)) == NULL) goto fail;
if (ref)
if ((absref = abspath(ref, cwd)) == NULL) goto fail;
if (absref == NULL)
{
p = strlen(cwd);
absref = malloc((p + 2) * sizeof(char));
if (absref == NULL)
goto fail;
memcpy(absref, cwd, p);
absref[p] = '/';
absref[p + 1] = '\0';
}
else
strrchr(absref, '/')[1] = '\0';
ptr = 0;
while (absfile[ptr] && (absfile[ptr] == absref[ptr]))
ptr++;
while (absfile[ptr] != '/')
ptr--;
ptr++;
for (p = ptr; absref[p]; p++)
if (absref[p] == '/')
n += 1;
rc = malloc((strlen(absfile + ptr) + 1 + 3 * n) * sizeof(char));
if (prc = rc, rc == NULL)
goto fail;
while (n--)
prc = stpcpy(prc, "../");
strcpy(prc, absfile + ptr);
free(cwd);
free(absfile);
free(absref);
return rc;
fail:
saved_errno = errno;
free(cwd);
free(absfile);
free(absref);
errno = saved_errno;
return NULL;
}
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