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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // See net/disk_cache/disk_cache.h for the public interface of the cache. | 5 // See net/disk_cache/disk_cache.h for the public interface of the cache. |
6 | 6 |
7 #ifndef NET_DISK_CACHE_FILE_LOCK_H__ | 7 #ifndef NET_DISK_CACHE_FILE_LOCK_H__ |
8 #define NET_DISK_CACHE_FILE_LOCK_H__ | 8 #define NET_DISK_CACHE_FILE_LOCK_H__ |
9 #pragma once | 9 #pragma once |
10 | 10 |
11 #include "net/base/net_api.h" | 11 #include "net/base/net_export.h" |
12 #include "net/disk_cache/disk_format.h" | 12 #include "net/disk_cache/disk_format.h" |
13 | 13 |
14 namespace disk_cache { | 14 namespace disk_cache { |
15 | 15 |
16 // This class implements a file lock that lives on the header of a memory mapped | 16 // This class implements a file lock that lives on the header of a memory mapped |
17 // file. This is NOT a thread related lock, it is a lock to detect corruption | 17 // file. This is NOT a thread related lock, it is a lock to detect corruption |
18 // of the file when the process crashes in the middle of an update. | 18 // of the file when the process crashes in the middle of an update. |
19 // The lock is acquired on the constructor and released on the destructor. | 19 // The lock is acquired on the constructor and released on the destructor. |
20 // The typical use of the class is: | 20 // The typical use of the class is: |
21 // { | 21 // { |
22 // BlockFileHeader* header = GetFileHeader(); | 22 // BlockFileHeader* header = GetFileHeader(); |
23 // FileLock lock(header); | 23 // FileLock lock(header); |
24 // header->max_entries = num_entries; | 24 // header->max_entries = num_entries; |
25 // // At this point the destructor is going to release the lock. | 25 // // At this point the destructor is going to release the lock. |
26 // } | 26 // } |
27 // It is important to perform Lock() and Unlock() operations in the right order, | 27 // It is important to perform Lock() and Unlock() operations in the right order, |
28 // because otherwise the desired effect of the "lock" will not be achieved. If | 28 // because otherwise the desired effect of the "lock" will not be achieved. If |
29 // the operations are inlined / optimized, the "locked" operations can happen | 29 // the operations are inlined / optimized, the "locked" operations can happen |
30 // outside the lock. | 30 // outside the lock. |
31 class NET_TEST FileLock { | 31 class NET_EXPORT_PRIVATE FileLock { |
32 public: | 32 public: |
33 explicit FileLock(BlockFileHeader* header); | 33 explicit FileLock(BlockFileHeader* header); |
34 virtual ~FileLock(); | 34 virtual ~FileLock(); |
35 | 35 |
36 // Virtual to make sure the compiler never inlines the calls. | 36 // Virtual to make sure the compiler never inlines the calls. |
37 virtual void Lock(); | 37 virtual void Lock(); |
38 virtual void Unlock(); | 38 virtual void Unlock(); |
39 private: | 39 private: |
40 bool acquired_; | 40 bool acquired_; |
41 volatile int32* updating_; | 41 volatile int32* updating_; |
42 }; | 42 }; |
43 | 43 |
44 } // namespace disk_cache | 44 } // namespace disk_cache |
45 | 45 |
46 #endif // NET_DISK_CACHE_FILE_LOCK_H__ | 46 #endif // NET_DISK_CACHE_FILE_LOCK_H__ |
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