cosmopolitan/third_party/musl/lockf.c

/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
│ vi: set noet ft=c ts=8 tw=8 fenc=utf-8                                   :vi │
╚──────────────────────────────────────────────────────────────────────────────╝
│                                                                              │
│  Musl Libc                                                                   │
│  Copyright © 2005-2014 Rich Felker, et al.                                   │
│                                                                              │
│  Permission is hereby granted, free of charge, to any person obtaining       │
│  a copy of this software and associated documentation files (the             │
│  "Software"), to deal in the Software without restriction, including         │
│  without limitation the rights to use, copy, modify, merge, publish,         │
│  distribute, sublicense, and/or sell copies of the Software, and to          │
│  permit persons to whom the Software is furnished to do so, subject to       │
│  the following conditions:                                                   │
│                                                                              │
│  The above copyright notice and this permission notice shall be              │
│  included in all copies or substantial portions of the Software.             │
│                                                                              │
│  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,             │
│  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF          │
│  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.      │
│  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY        │
│  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,        │
│  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE           │
│  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                      │
│                                                                              │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "third_party/musl/lockf.h"
#include "libc/calls/calls.h"
#include "libc/calls/struct/flock.h"
#include "libc/calls/weirdtypes.h"
#include "libc/errno.h"
#include "libc/sysv/consts/f.h"
#include "libc/sysv/errfuns.h"

asm(".ident\t\"\\n\\n\
Musl libc (MIT License)\\n\
Copyright 2005-2014 Rich Felker, et. al.\"");
asm(".include \"libc/disclaimer.inc\"");

/**
 * Locks file.
 *
 * @cancelationpoint when `op` is `F_LOCK`
 */
int lockf(int fd, int op, off_t size)
{
	struct flock l = {
		.l_type = F_WRLCK,
		.l_whence = SEEK_CUR,
		.l_len = size,
	};
	switch (op) {
	case F_TEST:
		l.l_type = F_RDLCK;
		if (fcntl(fd, F_GETLK, &l) < 0)
			return -1;
		if (l.l_type == F_UNLCK || l.l_pid == getpid())
			return 0;
		return eacces();
	case F_ULOCK:
		l.l_type = F_UNLCK;
	case F_TLOCK:
		return fcntl(fd, F_SETLK, &l);
	case F_LOCK:
		return fcntl(fd, F_SETLKW, &l);
	}
	return einval();
}

__weak_reference(lockf, lockf64);