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module filelock
import time
#include <sys/file.h>
fn C.unlink(&char) int
fn C.open(&char, int, int) int
fn C.flock(int, int) int
[unsafe]
pub fn (mut l FileLock) unlink() {
if l.fd != -1 {
C.close(l.fd)
l.fd = -1
}
C.unlink(&char(l.name.str))
}
pub fn (mut l FileLock) acquire() ?bool {
if l.fd != -1 {
// lock already acquired by this instance
return false
}
fd := open_lockfile(l.name)
if fd == -1 {
return error('cannot create lock file $l.name')
}
if C.flock(fd, C.LOCK_EX) == -1 {
C.close(fd)
return error('cannot lock')
}
l.fd = fd
return true
}
pub fn (mut l FileLock) release() bool {
if l.fd != -1 {
unsafe {
l.unlink()
}
return true
}
return false
}
pub fn (mut l FileLock) wait_acquire(s int) ?bool {
fin := time.now().add(s)
for time.now() < fin {
if l.try_acquire() {
return true
}
C.usleep(1000)
}
return false
}
fn open_lockfile(f string) int {
mut fd := C.open(&char(f.str), C.O_CREAT, 0o644)
if fd == -1 {
// if stat is too old delete lockfile
fd = C.open(&char(f.str), C.O_RDONLY, 0)
}
return fd
}
pub fn (mut l FileLock) try_acquire() bool {
if l.fd != -1 {
return true
}
fd := open_lockfile('$l.name')
if fd != -1 {
err := C.flock(fd, C.LOCK_EX | C.LOCK_NB)
if err == -1 {
C.close(fd)
return false
}
l.fd = fd
return true
}
return false
}
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