* Copyright 2008, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
* Distributed under the terms of the MIT License.
*/
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
extern const char *__progname;
const char* kTemporaryFile = "/tmp/axels-lock-test";
const char*
type_name(int type)
{
return type == F_RDLCK ? "shared" : type == F_WRLCK
? "exclusive" : "remove";
}
int
do_lock(int fd, int type, off_t start, off_t length)
{
printf("%s lock %lld:%lld\n", type_name(type), start, length);
struct flock flock;
flock.l_type = type;
flock.l_whence = SEEK_SET;
flock.l_start = start;
flock.l_len = length;
if (fcntl(fd, F_SETLK, &flock) != 0) {
fprintf(stderr, "ERROR: %s lock %lld:%lld failed: %s\n", type_name(type),
start, length, strerror(errno));
return -1;
}
return 0;
}
int
shared_lock(int fd, off_t start, off_t length)
{
return do_lock(fd, F_RDLCK, start, length);
}
int
exclusive_lock(int fd, off_t start, off_t length)
{
return do_lock(fd, F_WRLCK, start, length);
}
int
remove_lock(int fd, off_t start, off_t length)
{
return do_lock(fd, F_UNLCK, start, length);
}
void
wait_for_enter()
{
puts("wait for <enter>...");
char buffer[64];
fgets(buffer, sizeof(buffer), stdin);
}
void
usage()
{
fprintf(stderr, "usage: %s [shared|exclusive|unlock <start> <length>] "
"[wait] [...]\n", __progname);
exit(1);
}
bool
is_command(const char* op, const char* command1, const char* command2)
{
int length = strlen(op);
if (length == 0)
return false;
return command1 != NULL && !strncmp(op, command1, length)
|| command2 != NULL && !strncmp(op, command2, length);
}
int
main(int argc, char** argv)
{
int fd = open(kTemporaryFile, O_CREAT | O_RDWR, 0644);
if (fd < 0) {
fprintf(stderr, "Could not create lock file: %s\n", strerror(errno));
return 1;
}
while (argc > 1) {
const char* op = argv[1];
if (is_command(op, "wait", NULL)) {
wait_for_enter();
argv++;
argc--;
continue;
}
if (argc < 3)
usage();
off_t start = strtoll(argv[2], NULL, 0);
off_t length = strtoll(argv[3], NULL, 0);
int type = 0;
if (is_command(op, "read", "shared"))
type = F_RDLCK;
else if (is_command(op, "write", "exclusive"))
type = F_WRLCK;
else if (is_command(op, "unlock", "remove"))
type = F_UNLCK;
else
usage();
do_lock(fd, type, start, length);
argc -= 3;
argv += 3;
}
close(fd);
return 0;
}
