Beispiel #1
0
// flock acquires an advisory lock on a file descriptor.
func flock(f *os.File, exclusive bool, timeout time.Duration) error {
	var t time.Time
	for {
		// If we're beyond our timeout then return an error.
		// This can only occur after we've attempted a flock once.
		if t.IsZero() {
			t = time.Now()
		} else if timeout > 0 && time.Since(t) > timeout {
			return ErrTimeout
		}
		var lock syscall.Flock_t
		lock.Start = 0
		lock.Len = 0
		lock.Pid = 0
		lock.Whence = 0
		lock.Pid = 0
		if exclusive {
			lock.Type = syscall.F_WRLCK
		} else {
			lock.Type = syscall.F_RDLCK
		}
		err := syscall.FcntlFlock(f.Fd(), syscall.F_SETLK, &lock)
		if err == nil {
			return nil
		} else if err != syscall.EAGAIN {
			return err
		}

		// Wait for a bit and try again.
		time.Sleep(50 * time.Millisecond)
	}
}
Beispiel #2
0
// funlock releases an advisory lock on a file descriptor.
func funlock(f *os.File) error {
	var lock syscall.Flock_t
	lock.Start = 0
	lock.Len = 0
	lock.Type = syscall.F_UNLCK
	lock.Whence = 0
	return syscall.FcntlFlock(uintptr(f.Fd()), syscall.F_SETLK, &lock)
}
Beispiel #3
0
// Lock acquires exclusivity on the lock without blocking
func (l *lock) Lock() error {
	var lock syscall.Flock_t
	lock.Start = 0
	lock.Len = 0
	lock.Type = syscall.F_WRLCK
	lock.Whence = 0
	lock.Pid = 0
	return syscall.FcntlFlock(uintptr(l.fd), syscall.F_SETLK, &lock)
}
Beispiel #4
0
// Unlock unlocks the lock
func (l *lock) Unlock() error {
	var lock syscall.Flock_t
	lock.Start = 0
	lock.Len = 0
	lock.Type = syscall.F_UNLCK
	lock.Whence = 0
	err := syscall.FcntlFlock(uintptr(l.fd), syscall.F_SETLK, &lock)
	if err != nil && err == syscall.EAGAIN {
		return ErrLocked
	}
	return err
}
Beispiel #5
0
func LockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
	var lock syscall.Flock_t
	lock.Start = 0
	lock.Len = 0
	lock.Pid = 0
	lock.Type = syscall.F_WRLCK
	lock.Whence = 0
	f, err := os.OpenFile(path, flag, perm)
	if err != nil {
		return nil, err
	}
	if err = syscall.FcntlFlock(f.Fd(), syscall.F_SETLKW, &lock); err != nil {
		f.Close()
		return nil, err
	}
	return &LockedFile{f}, nil
}