78 lines
1.6 KiB
Go
78 lines
1.6 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build darwin dragonfly freebsd linux netbsd openbsd
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package filemutex
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import (
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"syscall"
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)
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const (
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mkdirPerm = 0750
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)
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// FileMutex is similar to sync.RWMutex, but also synchronizes across processes.
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// This implementation is based on flock syscall.
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type FileMutex struct {
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fd int
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}
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func New(filename string) (*FileMutex, error) {
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fd, err := syscall.Open(filename, syscall.O_CREAT|syscall.O_RDONLY, mkdirPerm)
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if err != nil {
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return nil, err
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}
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return &FileMutex{fd: fd}, nil
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}
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func (m *FileMutex) Lock() error {
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if err := syscall.Flock(m.fd, syscall.LOCK_EX); err != nil {
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return err
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}
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return nil
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}
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func (m *FileMutex) TryLock() error {
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if err := syscall.Flock(m.fd, syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
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if errno, ok := err.(syscall.Errno); ok {
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if errno == syscall.EWOULDBLOCK {
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return AlreadyLocked
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}
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}
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return err
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}
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return nil
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}
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func (m *FileMutex) Unlock() error {
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if err := syscall.Flock(m.fd, syscall.LOCK_UN); err != nil {
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return err
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}
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return nil
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}
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func (m *FileMutex) RLock() error {
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if err := syscall.Flock(m.fd, syscall.LOCK_SH); err != nil {
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return err
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}
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return nil
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}
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func (m *FileMutex) RUnlock() error {
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if err := syscall.Flock(m.fd, syscall.LOCK_UN); err != nil {
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return err
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}
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return nil
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}
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// Close unlocks the lock and closes the underlying file descriptor.
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func (m *FileMutex) Close() error {
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if err := syscall.Flock(m.fd, syscall.LOCK_UN); err != nil {
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return err
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}
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return syscall.Close(m.fd)
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}
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