lock_plan9.go

Documentation: go.etcd.io/etcd/client/pkg/v3/fileutil

     1  // Copyright 2015 The etcd Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package fileutil
    16  
    17  import (
    18  	"os"
    19  	"syscall"
    20  	"time"
    21  )
    22  
    23  func TryLockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
    24  	if err := os.Chmod(path, syscall.DMEXCL|PrivateFileMode); err != nil {
    25  		return nil, err
    26  	}
    27  	f, err := os.Open(path, flag, perm)
    28  	if err != nil {
    29  		return nil, ErrLocked
    30  	}
    31  	return &LockedFile{f}, nil
    32  }
    33  
    34  func LockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
    35  	if err := os.Chmod(path, syscall.DMEXCL|PrivateFileMode); err != nil {
    36  		return nil, err
    37  	}
    38  	for {
    39  		f, err := os.OpenFile(path, flag, perm)
    40  		if err == nil {
    41  			return &LockedFile{f}, nil
    42  		}
    43  		time.Sleep(10 * time.Millisecond)
    44  	}
    45  }
    46
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