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/* Return the canonical absolute name of a given file.
Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
/* Return the canonical absolute name of file NAME. A canonical name
does not contain any `.', `..' components nor any repeated path
separators ('/') or symlinks. All path components must exist. If
RESOLVED is null, the result is malloc'd; otherwise, if the
canonical name is PATH_MAX chars or more, returns null with `errno'
set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
returns the name in RESOLVED. If the name cannot be resolved and
RESOLVED is non-NULL, it contains the path of the first component
that cannot be resolved. If the path can be resolved, RESOLVED
holds the same value as the value returned. */
static char *
canonicalize (const char *name, char *resolved)
{
char *rpath, *dest, *extra_buf = NULL;
const char *start, *end, *rpath_limit;
long int path_max;
int num_links = 0;
#ifdef PATH_MAX
path_max = PATH_MAX;
#else
path_max = pathconf (name, _PC_PATH_MAX);
if (path_max <= 0)
path_max = 1024;
#endif
rpath = resolved;
rpath_limit = rpath + path_max;
if (!resolved)
rpath = malloc (path_max);
strcpy (rpath, "/");
if (name[0] != '/' && !getcwd (rpath, path_max))
goto error;
dest = rpath + strlen (rpath);
for (start = end = name; *start; start = end)
{
struct stat st;
int n;
/* skip sequence of multiple path-separators: */
while (*start == '/') ++start;
/* find end of path component: */
for (end = start; *end && *end != '/'; ++end);
if (end - start == 0)
break;
else if (strncmp (start, ".", end - start) == 0)
/* nothing */;
else if (strncmp (start, "..", end - start) == 0) {
/* back up to previous component, ignore if at root already: */
if (dest > rpath + 1)
while ((--dest)[-1] != '/');
} else
{
size_t new_size;
if (dest[-1] != '/')
*dest++ = '/';
if (dest + (end - start) >= rpath_limit)
{
if (resolved)
{
__set_errno (ENAMETOOLONG);
goto error;
}
new_size = rpath_limit - rpath;
if (end - start + 1 > path_max)
new_size += end - start + 1;
else
new_size += path_max;
rpath = realloc (rpath, new_size);
rpath_limit = rpath + new_size;
if (!rpath)
return NULL;
}
memcpy (dest, start, end - start);
dest += end - start;
*dest = '\0';
if (__lstat (rpath, &st) < 0)
goto error;
if (S_ISLNK (st.st_mode))
{
char * buf = __alloca(path_max);
if (++num_links > MAXSYMLINKS)
{
__set_errno (ELOOP);
goto error;
}
n = readlink (rpath, buf, path_max);
if (n < 0)
goto error;
buf[n] = '\0';
if (!extra_buf)
extra_buf = __alloca (path_max);
if ((long int) (n + strlen (end)) >= path_max)
{
__set_errno (ENAMETOOLONG);
goto error;
}
/* careful here, end may be a pointer into extra_buf... */
strcat (buf, end);
strcpy (extra_buf, buf);
name = end = extra_buf;
if (buf[0] == '/')
dest = rpath + 1; /* it's an absolute symlink */
else
/* back up to previous component, ignore if at root already: */
if (dest > rpath + 1)
while ((--dest)[-1] != '/');
}
else
num_links = 0;
}
}
if (dest > rpath + 1 && dest[-1] == '/')
--dest;
*dest = '\0';
return rpath;
error:
if (!resolved)
free (rpath);
return NULL;
}
weak_alias (canonicalize, realpath)
char *
canonicalize_file_name (const char *name)
{
return canonicalize (name, NULL);
}
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