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
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