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diff: optimize diffing of files with the same metadata

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Signed-off-by: Roman Borisov <ext-roman.borisov@nokia.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Roman Borisov 2011-03-27 23:24:09 +02:00 committed by Denys Vlasenko
parent 1f4447b2d4
commit 95f5c52e6f
1 changed files with 25 additions and 0 deletions
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editors/diff.c
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@ -952,6 +952,31 @@ int diff_main(int argc UNUSED_PARAM, char **argv)
if (gotstdin && (S_ISDIR(stb[0].st_mode) || S_ISDIR(stb[1].st_mode)))
bb_error_msg_and_die("can't compare stdin to a directory");
/* Compare metadata to check if the files are the same physical file.
*
* Comment from diffutils source says:
* POSIX says that two files are identical if st_ino and st_dev are
* the same, but many file systems incorrectly assign the same (device,
* inode) pair to two distinct files, including:
* GNU/Linux NFS servers that export all local file systems as a
* single NFS file system, if a local device number (st_dev) exceeds
* 255, or if a local inode number (st_ino) exceeds 16777215.
*/
if (ENABLE_DESKTOP
&& stb[0].st_ino == stb[1].st_ino
&& stb[0].st_dev == stb[1].st_dev
&& stb[0].st_size == stb[1].st_size
&& stb[0].st_mtime == stb[1].st_mtime
&& stb[0].st_ctime == stb[1].st_ctime
&& stb[0].st_mode == stb[1].st_mode
&& stb[0].st_nlink == stb[1].st_nlink
&& stb[0].st_uid == stb[1].st_uid
&& stb[0].st_gid == stb[1].st_gid
) {
/* files are physically the same; no need to compare them */
return STATUS_SAME;
}
if (S_ISDIR(stb[0].st_mode) && S_ISDIR(stb[1].st_mode)) {
#if ENABLE_FEATURE_DIFF_DIR
diffdir(file, s_start);