1 /* 2 * Copyright 2009 The WebRTC Project Authors. All rights reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef WEBRTC_BASE_FILELOCK_H_ 12 #define WEBRTC_BASE_FILELOCK_H_ 13 14 #include <string> 15 16 #include "webrtc/base/constructormagic.h" 17 #include "webrtc/base/scoped_ptr.h" 18 19 namespace rtc { 20 21 class FileStream; 22 23 // Implements a very simple cross process lock based on a file. 24 // When Lock(...) is called we try to open/create the file in read/write 25 // mode without any sharing. (Or locking it with flock(...) on Unix) 26 // If the process crash the OS will make sure that the file descriptor 27 // is released and another process can accuire the lock. 28 // This doesn't work on ancient OSX/Linux versions if used on NFS. 29 // (Nfs-client before: ~2.6 and Linux Kernel < 2.6.) 30 class FileLock { 31 public: 32 virtual ~FileLock(); 33 34 // Attempts to lock the file. The caller owns the returned 35 // lock object. Returns NULL if the file already was locked. 36 static FileLock* TryLock(const std::string& path); 37 void Unlock(); 38 39 protected: 40 FileLock(const std::string& path, FileStream* file); 41 42 private: 43 void MaybeUnlock(); 44 45 std::string path_; 46 scoped_ptr<FileStream> file_; 47 48 DISALLOW_EVIL_CONSTRUCTORS(FileLock); 49 }; 50 51 } // namespace rtc 52 53 #endif // WEBRTC_BASE_FILELOCK_H_ 54
