file_unix.go

// +build !windows

/*
 * Copyright 2020 Saffat Technologies, Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package unitdb

import (
	"os"
	"syscall"
)

type _UnixFileLock struct {
	f    *os.File
	name string
}

// Unlock removes the lock from file.
func (fl *_UnixFileLock) unlock() error {
	if err := os.Remove(fl.name); err != nil {
		return err
	}
	return fl.f.Close()
}

func lockFile(f *os.File) error {
	if err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
		if err == syscall.EWOULDBLOCK {
			err = os.ErrExist
		}
		return err
	}
	return nil
}

func newLockFile(name string) (_LockFile, error) {
	f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		return nil, err
	}
	if err := lockFile(f); err != nil {
		f.Close()
		return nil, err
	}
	return &_UnixFileLock{f, name}, nil
}