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      1 /*
      2  *  Copyright (c) 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_SYSTEM_WRAPPERS_INTERFACE_RW_LOCK_WRAPPER_H_
     12 #define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_RW_LOCK_WRAPPER_H_
     13 
     14 #include "webrtc/base/thread_annotations.h"
     15 
     16 // Note, Windows pre-Vista version of RW locks are not supported natively. For
     17 // these OSs regular critical sections have been used to approximate RW lock
     18 // functionality and will therefore have worse performance.
     19 
     20 namespace webrtc {
     21 
     22 class LOCKABLE RWLockWrapper {
     23  public:
     24   static RWLockWrapper* CreateRWLock();
     25   virtual ~RWLockWrapper() {}
     26 
     27   virtual void AcquireLockExclusive() EXCLUSIVE_LOCK_FUNCTION() = 0;
     28   virtual void ReleaseLockExclusive() UNLOCK_FUNCTION() = 0;
     29 
     30   virtual void AcquireLockShared() SHARED_LOCK_FUNCTION() = 0;
     31   virtual void ReleaseLockShared() UNLOCK_FUNCTION() = 0;
     32 };
     33 
     34 // RAII extensions of the RW lock. Prevents Acquire/Release missmatches and
     35 // provides more compact locking syntax.
     36 class SCOPED_LOCKABLE ReadLockScoped {
     37  public:
     38   ReadLockScoped(RWLockWrapper& rw_lock) SHARED_LOCK_FUNCTION(rw_lock)
     39       : rw_lock_(rw_lock) {
     40     rw_lock_.AcquireLockShared();
     41   }
     42 
     43   ~ReadLockScoped() UNLOCK_FUNCTION() {
     44     rw_lock_.ReleaseLockShared();
     45   }
     46 
     47  private:
     48   RWLockWrapper& rw_lock_;
     49 };
     50 
     51 class SCOPED_LOCKABLE WriteLockScoped {
     52  public:
     53   WriteLockScoped(RWLockWrapper& rw_lock) EXCLUSIVE_LOCK_FUNCTION(rw_lock)
     54       : rw_lock_(rw_lock) {
     55     rw_lock_.AcquireLockExclusive();
     56   }
     57 
     58   ~WriteLockScoped() UNLOCK_FUNCTION() {
     59     rw_lock_.ReleaseLockExclusive();
     60   }
     61 
     62  private:
     63   RWLockWrapper& rw_lock_;
     64 };
     65 
     66 }  // namespace webrtc
     67 
     68 #endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_RW_LOCK_WRAPPER_H_
     69