1/*
2 *  Copyright 2011 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_SHAREDEXCLUSIVELOCK_H_
12#define WEBRTC_BASE_SHAREDEXCLUSIVELOCK_H_
13
14#include "webrtc/base/constructormagic.h"
15#include "webrtc/base/criticalsection.h"
16#include "webrtc/base/event.h"
17
18namespace rtc {
19
20// This class provides shared-exclusive lock. It can be used in cases like
21// multiple-readers/single-writer model.
22class LOCKABLE SharedExclusiveLock {
23 public:
24  SharedExclusiveLock();
25
26  // Locking/unlocking methods. It is encouraged to use SharedScope or
27  // ExclusiveScope for protection.
28  void LockExclusive() EXCLUSIVE_LOCK_FUNCTION();
29  void UnlockExclusive() UNLOCK_FUNCTION();
30  void LockShared();
31  void UnlockShared();
32
33 private:
34  rtc::CriticalSection cs_exclusive_;
35  rtc::CriticalSection cs_shared_;
36  rtc::Event shared_count_is_zero_;
37  int shared_count_;
38
39  DISALLOW_COPY_AND_ASSIGN(SharedExclusiveLock);
40};
41
42class SCOPED_LOCKABLE SharedScope {
43 public:
44  explicit SharedScope(SharedExclusiveLock* lock) SHARED_LOCK_FUNCTION(lock)
45      : lock_(lock) {
46    lock_->LockShared();
47  }
48
49  ~SharedScope() UNLOCK_FUNCTION() { lock_->UnlockShared(); }
50
51 private:
52  SharedExclusiveLock* lock_;
53
54  DISALLOW_COPY_AND_ASSIGN(SharedScope);
55};
56
57class SCOPED_LOCKABLE ExclusiveScope {
58 public:
59  explicit ExclusiveScope(SharedExclusiveLock* lock)
60      EXCLUSIVE_LOCK_FUNCTION(lock)
61      : lock_(lock) {
62    lock_->LockExclusive();
63  }
64
65  ~ExclusiveScope() UNLOCK_FUNCTION() { lock_->UnlockExclusive(); }
66
67 private:
68  SharedExclusiveLock* lock_;
69
70  DISALLOW_COPY_AND_ASSIGN(ExclusiveScope);
71};
72
73}  // namespace rtc
74
75#endif  // WEBRTC_BASE_SHAREDEXCLUSIVELOCK_H_
76