// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build darwin || dragonfly || freebsd || illumos || linux || netbsd || openbsd

package filelock

import (
	"io/fs"
	"syscall"
)

type lockType int16

const (
	readLock  lockType = syscall.LOCK_SH
	writeLock lockType = syscall.LOCK_EX
)

func lock(f File, lt lockType) (err error) {
	for {
		err = syscall.Flock(int(f.Fd()), int(lt))
		if err != syscall.EINTR {
			break
		}
	}
	if err != nil {
		return &fs.PathError{
			Op:   lt.String(),
			Path: f.Name(),
			Err:  err,
		}
	}
	return nil
}

func unlock(f File) error {
	return lock(f, syscall.LOCK_UN)
}