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/*
* realpath.c -- canonicalize pathname by removing symlinks
* Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
* Copyright (C) 2000-2006 Erik Andersen <andersen@uclibc.org>
*
* Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <limits.h> /* for PATH_MAX */
#include <sys/param.h> /* for MAXPATHLEN */
#include <errno.h>
#include <stdlib.h>
#include <sys/stat.h> /* for S_IFLNK */
/* Experimentally off - libc_hidden_proto(strcat) */
/* Experimentally off - libc_hidden_proto(strcpy) */
/* Experimentally off - libc_hidden_proto(strlen) */
/* libc_hidden_proto(readlink) */
/* libc_hidden_proto(getcwd) */
#ifndef PATH_MAX
#ifdef _POSIX_VERSION
#define PATH_MAX _POSIX_PATH_MAX
#else
#ifdef MAXPATHLEN
#define PATH_MAX MAXPATHLEN
#else
#define PATH_MAX 1024
#endif
#endif
#endif
#define MAX_READLINKS 32
#ifdef __STDC__
char *realpath(const char *path, char got_path[])
#else
char *realpath(path, got_path)
const char *path;
char got_path[];
#endif
{
char copy_path[PATH_MAX];
/* use user supplied buffer directly - reduces stack usage */
/* char got_path[PATH_MAX]; */
char *max_path;
char *new_path;
size_t path_len;
int readlinks = 0;
#ifdef S_IFLNK
int link_len;
#endif
if (path == NULL) {
__set_errno(EINVAL);
return NULL;
}
if (*path == '\0') {
__set_errno(ENOENT);
return NULL;
}
/* Make a copy of the source path since we may need to modify it. */
path_len = strlen(path);
if (path_len >= PATH_MAX - 2) {
__set_errno(ENAMETOOLONG);
return NULL;
}
/* Copy so that path is at the end of copy_path[] */
strcpy(copy_path + (PATH_MAX-1) - path_len, path);
path = copy_path + (PATH_MAX-1) - path_len;
max_path = got_path + PATH_MAX - 2; /* points to last non-NUL char */
new_path = got_path;
if (*path != '/') {
/* If it's a relative pathname use getcwd for starters. */
if (!getcwd(new_path, PATH_MAX - 1))
return NULL;
new_path += strlen(new_path);
if (new_path[-1] != '/')
*new_path++ = '/';
} else {
*new_path++ = '/';
path++;
}
/* Expand each slash-separated pathname component. */
while (*path != '\0') {
/* Ignore stray "/". */
if (*path == '/') {
path++;
continue;
}
if (*path == '.') {
/* Ignore ".". */
if (path[1] == '\0' || path[1] == '/') {
path++;
continue;
}
if (path[1] == '.') {
if (path[2] == '\0' || path[2] == '/') {
path += 2;
/* Ignore ".." at root. */
if (new_path == got_path + 1)
continue;
/* Handle ".." by backing up. */
while ((--new_path)[-1] != '/');
continue;
}
}
}
/* Safely copy the next pathname component. */
while (*path != '\0' && *path != '/') {
if (new_path > max_path) {
__set_errno(ENAMETOOLONG);
return NULL;
}
*new_path++ = *path++;
}
#ifdef S_IFLNK
/* Protect against infinite loops. */
if (readlinks++ > MAX_READLINKS) {
__set_errno(ELOOP);
return NULL;
}
path_len = strlen(path);
/* See if last (so far) pathname component is a symlink. */
*new_path = '\0';
{
int sv_errno = errno;
link_len = readlink(got_path, copy_path, PATH_MAX - 1);
if (link_len < 0) {
/* EINVAL means the file exists but isn't a symlink. */
if (errno != EINVAL) {
return NULL;
}
} else {
/* Safe sex check. */
if (path_len + link_len >= PATH_MAX - 2) {
__set_errno(ENAMETOOLONG);
return NULL;
}
/* Note: readlink doesn't add the null byte. */
/* copy_path[link_len] = '\0'; - we don't need it too */
if (*copy_path == '/')
/* Start over for an absolute symlink. */
new_path = got_path;
else
/* Otherwise back up over this component. */
while (*(--new_path) != '/');
/* Prepend symlink contents to path. */
memmove(copy_path + (PATH_MAX-1) - link_len - path_len, copy_path, link_len);
path = copy_path + (PATH_MAX-1) - link_len - path_len;
}
__set_errno(sv_errno);
}
#endif /* S_IFLNK */
*new_path++ = '/';
}
/* Delete trailing slash but don't whomp a lone slash. */
if (new_path != got_path + 1 && new_path[-1] == '/')
new_path--;
/* Make sure it's null terminated. */
*new_path = '\0';
return got_path;
}
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