Official Go implementation of the Ethereum protocol
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go-ethereum/vendor/github.com/prometheus/tsdb/fileutil/flock.go

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// Copyright 2016 The Prometheus Authors
// 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.
package fileutil
import (
"os"
"path/filepath"
)
// Releaser provides the Release method to release a file lock.
type Releaser interface {
Release() error
}
// Flock locks the file with the provided name. If the file does not exist, it is
// created. The returned Releaser is used to release the lock. existed is true
// if the file to lock already existed. A non-nil error is returned if the
// locking has failed. Neither this function nor the returned Releaser is
// goroutine-safe.
func Flock(fileName string) (r Releaser, existed bool, err error) {
if err = os.MkdirAll(filepath.Dir(fileName), 0755); err != nil {
return nil, false, err
}
_, err = os.Stat(fileName)
existed = err == nil
r, err = newLock(fileName)
return r, existed, err
}