1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_BASE_SCOPED_FLOCK_H_ 18 #define ART_RUNTIME_BASE_SCOPED_FLOCK_H_ 19 20 #include <memory> 21 #include <string> 22 23 #include "base/macros.h" 24 #include "os.h" 25 26 namespace art { 27 28 class ScopedFlock { 29 public: 30 ScopedFlock(); 31 32 // Attempts to acquire an exclusive file lock (see flock(2)) on the file 33 // at filename, and blocks until it can do so. 34 // 35 // Returns true if the lock could be acquired, or false if an error occurred. 36 // It is an error if its inode changed (usually due to a new file being 37 // created at the same path) between attempts to lock it. In blocking mode, 38 // locking will be retried if the file changed. In non-blocking mode, false 39 // is returned and no attempt is made to re-acquire the lock. 40 // 41 // The file is opened with the provided flags. 42 bool Init(const char* filename, int flags, bool block, std::string* error_msg); 43 // Calls Init(filename, O_CREAT | O_RDWR, true, errror_msg) 44 bool Init(const char* filename, std::string* error_msg); 45 // Attempt to acquire an exclusive file lock (see flock(2)) on 'file'. 46 // Returns true if the lock could be acquired or false if an error 47 // occured. 48 bool Init(File* file, std::string* error_msg); 49 50 // Returns the (locked) file associated with this instance. 51 File* GetFile() const; 52 53 // Returns whether a file is held. 54 bool HasFile(); 55 56 ~ScopedFlock(); 57 58 private: 59 std::unique_ptr<File> file_; 60 DISALLOW_COPY_AND_ASSIGN(ScopedFlock); 61 }; 62 63 } // namespace art 64 65 #endif // ART_RUNTIME_BASE_SCOPED_FLOCK_H_ 66