scoped_flock.h revision a59dd80f9f48cb750d329d4d4af2d99d72b484d1 
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
26namespace art {
27
28class 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
36  // occurred. It is an error if the file does not exist, or if its inode
37  // changed (usually due to a new file being created at the same path)
38  // between attempts to lock it.
39  bool Init(const char* filename, std::string* error_msg);
40  // Attempt to acquire an exclusive file lock (see flock(2)) on 'file'.
41  // Returns true if the lock could be acquired or false if an error
42  // occured.
43  bool Init(File* file, std::string* error_msg);
44
45  // Returns the (locked) file associated with this instance.
46  File* GetFile();
47
48  // Returns whether a file is held.
49  bool HasFile();
50
51  ~ScopedFlock();
52
53 private:
54  std::unique_ptr<File> file_;
55  DISALLOW_COPY_AND_ASSIGN(ScopedFlock);
56};
57
58}  // namespace art
59
60#endif  // ART_RUNTIME_BASE_SCOPED_FLOCK_H_
61