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/* Determine whether two file names refer to the same file.
Copyright (C) 1997-2000, 2002-2006, 2009-2021 Free Software Foundation, Inc.
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 <https://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <limits.h>
#ifndef _POSIX_NAME_MAX
# define _POSIX_NAME_MAX 14
#endif
#include "same.h"
#include "dirname.h"
#include "error.h"
#include "same-inode.h"
#ifndef MIN
# define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif
/* Whether file name components are silently truncated (behavior that
POSIX stopped allowing in 2008). This enables checks whether
truncated base names are the same, while checking the directories. */
#if !_POSIX_NO_TRUNC && HAVE_FPATHCONF && defined _PC_NAME_MAX
# define CHECK_TRUNCATION true
#else
# define CHECK_TRUNCATION false
#endif
/* Return nonzero if SOURCE and DEST point to the same name in the same
directory. */
bool
same_name (const char *source, const char *dest)
{
return same_nameat (AT_FDCWD, source, AT_FDCWD, dest);
}
/* Likewise, but interpret the file names relative to SOURCE_FD and DEST_FD,
in the style of openat. */
bool
same_nameat (int source_dfd, char const *source,
int dest_dfd, char const *dest)
{
/* Compare the basenames. */
char const *source_basename = last_component (source);
char const *dest_basename = last_component (dest);
size_t source_baselen = base_len (source_basename);
size_t dest_baselen = base_len (dest_basename);
bool identical_basenames =
(source_baselen == dest_baselen
&& memcmp (source_basename, dest_basename, dest_baselen) == 0);
bool compare_dirs = identical_basenames;
bool same = false;
#if CHECK_TRUNCATION
size_t slen_max = HAVE_LONG_FILE_NAMES ? 255 : _POSIX_NAME_MAX;
size_t min_baselen = MIN (source_baselen, dest_baselen);
if (slen_max <= min_baselen
&& memcmp (source_basename, dest_basename, slen_max) == 0)
compare_dirs = true;
#endif
if (compare_dirs)
{
struct stat source_dir_stats;
struct stat dest_dir_stats;
/* Compare the parent directories (via the device and inode numbers). */
char *source_dirname = dir_name (source);
int flags = AT_SYMLINK_NOFOLLOW;
if (fstatat (source_dfd, source_dirname, &source_dir_stats, flags) != 0)
{
/* Shouldn't happen. */
error (1, errno, "%s", source_dirname);
}
free (source_dirname);
char *dest_dirname = dir_name (dest);
#if CHECK_TRUNCATION
int destdir_errno = 0;
int open_flags = O_SEARCH | O_CLOEXEC | O_DIRECTORY;
int destdir_fd = openat (dest_dfd, dest_dirname, open_flags);
if (destdir_fd < 0 || fstat (destdir_fd, &dest_dir_stats) != 0)
destdir_errno = errno;
else if (SAME_INODE (source_dir_stats, dest_dir_stats))
{
same = identical_basenames;
if (! same)
{
errno = 0;
long name_max = fpathconf (destdir_fd, _PC_NAME_MAX);
if (name_max < 0)
destdir_errno = errno;
else
same = (name_max <= min_baselen
&& (memcmp (source_basename, dest_basename, name_max)
== 0));
}
}
close (destdir_fd);
if (destdir_errno != 0)
{
/* Shouldn't happen. */
error (1, destdir_errno, "%s", dest_dirname);
}
#else
if (fstatat (dest_dfd, dest_dirname, &dest_dir_stats, flags) != 0)
{
/* Shouldn't happen. */
error (1, errno, "%s", dest_dirname);
}
same = SAME_INODE (source_dir_stats, dest_dir_stats);
#endif
free (dest_dirname);
}
return same;
}
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