77 lines
1.6 KiB
Go
77 lines
1.6 KiB
Go
// Copyright 2015 CoreOS, Inc.
|
|
//
|
|
// 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.
|
|
|
|
// +build !windows,!plan9
|
|
|
|
package fileutil
|
|
|
|
import (
|
|
"errors"
|
|
"os"
|
|
"syscall"
|
|
)
|
|
|
|
var (
|
|
ErrLocked = errors.New("file already locked")
|
|
)
|
|
|
|
type Lock interface {
|
|
Name() string
|
|
TryLock() error
|
|
Lock() error
|
|
Unlock() error
|
|
Destroy() error
|
|
}
|
|
|
|
type lock struct {
|
|
fd int
|
|
file *os.File
|
|
}
|
|
|
|
func (l *lock) Name() string {
|
|
return l.file.Name()
|
|
}
|
|
|
|
// TryLock acquires exclusivity on the lock without blocking
|
|
func (l *lock) TryLock() error {
|
|
err := syscall.Flock(l.fd, syscall.LOCK_EX|syscall.LOCK_NB)
|
|
if err != nil && err == syscall.EWOULDBLOCK {
|
|
return ErrLocked
|
|
}
|
|
return err
|
|
}
|
|
|
|
// Lock acquires exclusivity on the lock without blocking
|
|
func (l *lock) Lock() error {
|
|
return syscall.Flock(l.fd, syscall.LOCK_EX)
|
|
}
|
|
|
|
// Unlock unlocks the lock
|
|
func (l *lock) Unlock() error {
|
|
return syscall.Flock(l.fd, syscall.LOCK_UN)
|
|
}
|
|
|
|
func (l *lock) Destroy() error {
|
|
return l.file.Close()
|
|
}
|
|
|
|
func NewLock(file string) (Lock, error) {
|
|
f, err := os.Open(file)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
l := &lock{int(f.Fd()), f}
|
|
return l, nil
|
|
}
|