kv/mstorage/file_storage_unix.go

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// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// +build darwin dragonfly freebsd linux netbsd openbsd

package mstorage

import (
	"os"
	"syscall"
)

type unixFileLock struct {
	f *os.File
}

func (fl *unixFileLock) release() error {
	if err := setFileLock(fl.f, false, false); err != nil {
		return err
	}
	return fl.f.Close()
}

func newFileLock(path string, readOnly bool) (fl fileLock, err error) {
	var flag int
	if readOnly {
		flag = os.O_RDONLY
	} else {
		flag = os.O_RDWR
	}
	f, err := os.OpenFile(path, flag, 0)
	if os.IsNotExist(err) {
		f, err = os.OpenFile(path, flag|os.O_CREATE, 0644)
	}
	if err != nil {
		return
	}
	err = setFileLock(f, readOnly, true)
	if err != nil {
		f.Close()
		return
	}
	fl = &unixFileLock{f: f}
	return
}

func setFileLock(f *os.File, readOnly, lock bool) error {
	how := syscall.LOCK_UN
	if lock {
		if readOnly {
			how = syscall.LOCK_SH
		} else {
			how = syscall.LOCK_EX
		}
	}
	return syscall.Flock(int(f.Fd()), how|syscall.LOCK_NB)
}