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      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 
     18 namespace rtc {
     19 
     20 // This class provides shared-exclusive lock. It can be used in cases like
     21 // multiple-readers/single-writer model.
     22 class 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 
     42 class 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 
     57 class 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