github.com/gochain-io/gochain@v2.2.26+incompatible/flock/flock_unix.go (about)

     1  // Copyright 2016 The Prometheus Authors
     2  // Licensed under the Apache License, Version 2.0 (the "License");
     3  // you may not use this file except in compliance with the License.
     4  // You may obtain a copy of the License at
     5  //
     6  //     http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  // +build darwin dragonfly freebsd linux netbsd openbsd
    15  
    16  package flock
    17  
    18  import (
    19  	"os"
    20  	"syscall"
    21  )
    22  
    23  type unixLock struct {
    24  	f *os.File
    25  }
    26  
    27  func (l *unixLock) Release() error {
    28  	if err := l.set(false); err != nil {
    29  		return err
    30  	}
    31  	return l.f.Close()
    32  }
    33  
    34  func (l *unixLock) set(lock bool) error {
    35  	how := syscall.LOCK_UN
    36  	if lock {
    37  		how = syscall.LOCK_EX
    38  	}
    39  	return syscall.Flock(int(l.f.Fd()), how|syscall.LOCK_NB)
    40  }
    41  
    42  func newLock(fileName string) (Releaser, error) {
    43  	f, err := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE, 0644)
    44  	if err != nil {
    45  		return nil, err
    46  	}
    47  	l := &unixLock{f}
    48  	err = l.set(true)
    49  	if err != nil {
    50  		f.Close()
    51  		return nil, err
    52  	}
    53  	return l, nil
    54  }