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 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/alg/alg.h"
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#include "libc/bits/safemacros.h"
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#include "libc/calls/calls.h"
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#include "libc/errno.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/madv.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/consts/prot.h"
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static void *filecmp$mmap(int fd, size_t size) {
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return size ? mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0) : NULL;
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}
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/**
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* Compares contents of files with memcmp().
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*
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* @return ≤0, 0, or ≥0 based on comparison; or ≠0 on error, in which
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* case we make our best effort to sift failing filenames rightward,
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* and errno can be set to 0 beforehand to differentiate errors
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*/
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int filecmp(const char *pathname1, const char *pathname2) {
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int res, olderr;
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int fd1 = -1;
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int fd2 = -1;
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char *addr1 = MAP_FAILED;
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char *addr2 = MAP_FAILED;
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size_t size1 = 0;
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size_t size2 = 0;
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if ((fd1 = open(pathname1, O_RDONLY)) != -1 &&
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(fd2 = open(pathname2, O_RDONLY)) != -1 &&
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(size1 = getfiledescriptorsize(fd1)) != -1 &&
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(size2 = getfiledescriptorsize(fd2)) != -1 &&
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(addr1 = filecmp$mmap(fd1, size1)) != MAP_FAILED &&
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(addr2 = filecmp$mmap(fd2, size2)) != MAP_FAILED) {
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olderr = errno;
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madvise(addr1, size1, MADV_WILLNEED | MADV_SEQUENTIAL);
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madvise(addr2, size2, MADV_WILLNEED | MADV_SEQUENTIAL);
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errno = olderr;
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res = memcmp(addr1, addr2, min(size1, size2));
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if (!res && size1 != size2) {
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char kNul = '\0';
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if (size1 > size2) {
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res = cmpub(addr1 + size2, &kNul);
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} else {
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res = cmpub(addr2 + size1, &kNul);
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}
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}
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} else {
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res = cmpuq(&fd1, &fd2) | 1;
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}
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olderr = errno;
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munmap(addr1, size1);
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munmap(addr2, size2);
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close(fd1);
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close(fd2);
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errno = olderr;
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return res;
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}
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