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lock_unix.go
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lock_unix.go
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// 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,!solaris
package fileutil
import (
"errors"
"os"
"syscall"
)
var (
ErrLocked = errors.New("file already locked")
)
type lock struct {
fd int
file *os.File
}
func (l *lock) Name() string {
return l.file.Name()
}
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
}
func (l *lock) Lock() error {
return syscall.Flock(l.fd, syscall.LOCK_EX)
}
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
}