| // 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 |
| } |