79 lines
3.6 KiB
C
79 lines
3.6 KiB
C
|
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
||
|
|
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
|
||
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
||
|
|
│ Copyright 2020 Justine Alexandra Roberts Tunney │
|
||
|
|
│ │
|
||
|
|
│ 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; version 2 of the License. │
|
||
|
|
│ │
|
||
|
|
│ 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, write to the Free Software │
|
||
|
|
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
|
||
|
|
│ 02110-1301 USA │
|
||
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
||
|
|
#include "libc/alg/alg.h"
|
||
|
|
#include "libc/bits/safemacros.h"
|
||
|
|
#include "libc/calls/calls.h"
|
||
|
|
#include "libc/errno.h"
|
||
|
|
#include "libc/str/str.h"
|
||
|
|
#include "libc/sysv/consts/madv.h"
|
||
|
|
#include "libc/sysv/consts/map.h"
|
||
|
|
#include "libc/sysv/consts/o.h"
|
||
|
|
#include "libc/sysv/consts/prot.h"
|
||
|
|
|
||
|
|
static void *filecmp$mmap(int fd, size_t size) {
|
||
|
|
return size ? mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0) : NULL;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Compares contents of files with memcmp().
|
||
|
|
*
|
||
|
|
* @return ≤0, 0, or ≥0 based on comparison; or ≠0 on error, in which
|
||
|
|
* case we make our best effort to sift failing filenames rightward,
|
||
|
|
* and errno can be set to 0 beforehand to differentiate errors
|
||
|
|
*/
|
||
|
|
int filecmp(const char *pathname1, const char *pathname2) {
|
||
|
|
int res, olderr;
|
||
|
|
int fd1 = -1;
|
||
|
|
int fd2 = -1;
|
||
|
|
char *addr1 = MAP_FAILED;
|
||
|
|
char *addr2 = MAP_FAILED;
|
||
|
|
size_t size1 = 0;
|
||
|
|
size_t size2 = 0;
|
||
|
|
if ((fd1 = open(pathname1, O_RDONLY)) != -1 &&
|
||
|
|
(fd2 = open(pathname2, O_RDONLY)) != -1 &&
|
||
|
|
(size1 = getfiledescriptorsize(fd1)) != -1 &&
|
||
|
|
(size2 = getfiledescriptorsize(fd2)) != -1 &&
|
||
|
|
(addr1 = filecmp$mmap(fd1, size1)) != MAP_FAILED &&
|
||
|
|
(addr2 = filecmp$mmap(fd2, size2)) != MAP_FAILED) {
|
||
|
|
olderr = errno;
|
||
|
|
madvise(addr1, size1, MADV_WILLNEED | MADV_SEQUENTIAL);
|
||
|
|
madvise(addr2, size2, MADV_WILLNEED | MADV_SEQUENTIAL);
|
||
|
|
errno = olderr;
|
||
|
|
res = memcmp(addr1, addr2, min(size1, size2));
|
||
|
|
if (!res && size1 != size2) {
|
||
|
|
char kNul = '\0';
|
||
|
|
if (size1 > size2) {
|
||
|
|
res = cmpub(addr1 + size2, &kNul);
|
||
|
|
} else {
|
||
|
|
res = cmpub(addr2 + size1, &kNul);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
res = cmpuq(&fd1, &fd2) | 1;
|
||
|
|
}
|
||
|
|
olderr = errno;
|
||
|
|
munmap(addr1, size1);
|
||
|
|
munmap(addr2, size2);
|
||
|
|
close(fd1);
|
||
|
|
close(fd2);
|
||
|
|
errno = olderr;
|
||
|
|
return res;
|
||
|
|
}
|