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      1 /*
      2  *  Copyright 2004 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_CRITICALSECTION_H_
     12 #define WEBRTC_BASE_CRITICALSECTION_H_
     13 
     14 #include "webrtc/base/atomicops.h"
     15 #include "webrtc/base/constructormagic.h"
     16 #include "webrtc/base/thread_annotations.h"
     17 
     18 #if defined(WEBRTC_WIN)
     19 // Include winsock2.h before including <windows.h> to maintain consistency with
     20 // win32.h.  We can't include win32.h directly here since it pulls in
     21 // headers such as basictypes.h which causes problems in Chromium where webrtc
     22 // exists as two separate projects, webrtc and libjingle.
     23 #include <winsock2.h>
     24 #include <windows.h>
     25 #include <sal.h>  // must come after windows headers.
     26 #endif  // defined(WEBRTC_WIN)
     27 
     28 #if defined(WEBRTC_POSIX)
     29 #include <pthread.h>
     30 #endif
     31 
     32 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
     33 #define CS_DEBUG_CHECKS 1
     34 #endif
     35 
     36 #if CS_DEBUG_CHECKS
     37 #define CS_DEBUG_CODE(x) x
     38 #else  // !CS_DEBUG_CHECKS
     39 #define CS_DEBUG_CODE(x)
     40 #endif  // !CS_DEBUG_CHECKS
     41 
     42 namespace rtc {
     43 
     44 class LOCKABLE CriticalSection {
     45  public:
     46   CriticalSection();
     47   ~CriticalSection();
     48 
     49   void Enter() EXCLUSIVE_LOCK_FUNCTION();
     50   bool TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true);
     51   void Leave() UNLOCK_FUNCTION();
     52 
     53   // Use only for RTC_DCHECKing.
     54   bool CurrentThreadIsOwner() const;
     55   // Use only for RTC_DCHECKing.
     56   bool IsLocked() const;
     57 
     58  private:
     59 #if defined(WEBRTC_WIN)
     60   CRITICAL_SECTION crit_;
     61 #elif defined(WEBRTC_POSIX)
     62   pthread_mutex_t mutex_;
     63   CS_DEBUG_CODE(pthread_t thread_);
     64   CS_DEBUG_CODE(int recursion_count_);
     65 #endif
     66 };
     67 
     68 // CritScope, for serializing execution through a scope.
     69 class SCOPED_LOCKABLE CritScope {
     70  public:
     71   explicit CritScope(CriticalSection* cs) EXCLUSIVE_LOCK_FUNCTION(cs);
     72   ~CritScope() UNLOCK_FUNCTION();
     73  private:
     74   CriticalSection* const cs_;
     75   RTC_DISALLOW_COPY_AND_ASSIGN(CritScope);
     76 };
     77 
     78 // Tries to lock a critical section on construction via
     79 // CriticalSection::TryEnter, and unlocks on destruction if the
     80 // lock was taken. Never blocks.
     81 //
     82 // IMPORTANT: Unlike CritScope, the lock may not be owned by this thread in
     83 // subsequent code. Users *must* check locked() to determine if the
     84 // lock was taken. If you're not calling locked(), you're doing it wrong!
     85 class TryCritScope {
     86  public:
     87   explicit TryCritScope(CriticalSection* cs);
     88   ~TryCritScope();
     89 #if defined(WEBRTC_WIN)
     90   _Check_return_ bool locked() const;
     91 #else
     92   bool locked() const __attribute__ ((__warn_unused_result__));
     93 #endif
     94  private:
     95   CriticalSection* const cs_;
     96   const bool locked_;
     97   CS_DEBUG_CODE(mutable bool lock_was_called_);
     98   RTC_DISALLOW_COPY_AND_ASSIGN(TryCritScope);
     99 };
    100 
    101 // A POD lock used to protect global variables. Do NOT use for other purposes.
    102 // No custom constructor or private data member should be added.
    103 class LOCKABLE GlobalLockPod {
    104  public:
    105   void Lock() EXCLUSIVE_LOCK_FUNCTION();
    106 
    107   void Unlock() UNLOCK_FUNCTION();
    108 
    109   volatile int lock_acquired;
    110 };
    111 
    112 class GlobalLock : public GlobalLockPod {
    113  public:
    114   GlobalLock();
    115 };
    116 
    117 // GlobalLockScope, for serializing execution through a scope.
    118 class SCOPED_LOCKABLE GlobalLockScope {
    119  public:
    120   explicit GlobalLockScope(GlobalLockPod* lock) EXCLUSIVE_LOCK_FUNCTION(lock);
    121   ~GlobalLockScope() UNLOCK_FUNCTION();
    122  private:
    123   GlobalLockPod* const lock_;
    124   RTC_DISALLOW_COPY_AND_ASSIGN(GlobalLockScope);
    125 };
    126 
    127 } // namespace rtc
    128 
    129 #endif // WEBRTC_BASE_CRITICALSECTION_H_
    130