Make rtc::CriticalSection lockable from f() const.

webrtc/base/criticalsection.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 23 matching lines @@
 #endif
 
 #if CS_DEBUG_CHECKS
 #define CS_DEBUG_CODE(x) x
 #else  // !CS_DEBUG_CHECKS
 #define CS_DEBUG_CODE(x)
 #endif  // !CS_DEBUG_CHECKS
 
 namespace rtc {
 
+// Locking methods (Enter, TryEnter, Leave)are const to permit protecting
+// members inside a const context without requiring mutable CriticalSections
+// everywhere.
 class LOCKABLE CriticalSection {
  public:
   CriticalSection();
   ~CriticalSection();
 
-  void Enter() EXCLUSIVE_LOCK_FUNCTION();
-  bool TryEnter() EXCLUSIVE_TRYLOCK_FUNCTION(true);
-  void Leave() UNLOCK_FUNCTION();
+  void Enter() const EXCLUSIVE_LOCK_FUNCTION();
+  bool TryEnter() const EXCLUSIVE_TRYLOCK_FUNCTION(true);
+  void Leave() const UNLOCK_FUNCTION();
 
   // Use only for RTC_DCHECKing.
   bool CurrentThreadIsOwner() const;
   // Use only for RTC_DCHECKing.
   bool IsLocked() const;
 
  private:
 #if defined(WEBRTC_WIN)
-  CRITICAL_SECTION crit_;
+  mutable CRITICAL_SECTION crit_;
 #elif defined(WEBRTC_POSIX)
-  pthread_mutex_t mutex_;
-  CS_DEBUG_CODE(pthread_t thread_);
-  CS_DEBUG_CODE(int recursion_count_);
+  mutable pthread_mutex_t mutex_;
+  CS_DEBUG_CODE(mutable pthread_t thread_);
+  CS_DEBUG_CODE(mutable int recursion_count_);
 #endif
 };
 
 // CritScope, for serializing execution through a scope.
 class SCOPED_LOCKABLE CritScope {
  public:
-  explicit CritScope(CriticalSection* cs) EXCLUSIVE_LOCK_FUNCTION(cs);
+  explicit CritScope(const CriticalSection* cs) EXCLUSIVE_LOCK_FUNCTION(cs);
   ~CritScope() UNLOCK_FUNCTION();
  private:
-  CriticalSection* const cs_;
+  const CriticalSection* const cs_;
   RTC_DISALLOW_COPY_AND_ASSIGN(CritScope);
 };
 
 // Tries to lock a critical section on construction via
 // CriticalSection::TryEnter, and unlocks on destruction if the
 // lock was taken. Never blocks.
 //
 // IMPORTANT: Unlike CritScope, the lock may not be owned by this thread in
 // subsequent code. Users *must* check locked() to determine if the
 // lock was taken. If you're not calling locked(), you're doing it wrong!
 class TryCritScope {
  public:
-  explicit TryCritScope(CriticalSection* cs);
+  explicit TryCritScope(const CriticalSection* cs);
   ~TryCritScope();
 #if defined(WEBRTC_WIN)
   _Check_return_ bool locked() const;
 #else
   bool locked() const __attribute__ ((__warn_unused_result__));
 #endif
  private:
-  CriticalSection* const cs_;
+  const CriticalSection* const cs_;
   const bool locked_;
   CS_DEBUG_CODE(mutable bool lock_was_called_);
   RTC_DISALLOW_COPY_AND_ASSIGN(TryCritScope);
 };
 
 // A POD lock used to protect global variables. Do NOT use for other purposes.
 // No custom constructor or private data member should be added.
 class LOCKABLE GlobalLockPod {
  public:
   void Lock() EXCLUSIVE_LOCK_FUNCTION();
@@ skipping 14 matching lines @@
   explicit GlobalLockScope(GlobalLockPod* lock) EXCLUSIVE_LOCK_FUNCTION(lock);
   ~GlobalLockScope() UNLOCK_FUNCTION();
  private:
   GlobalLockPod* const lock_;
   RTC_DISALLOW_COPY_AND_ASSIGN(GlobalLockScope);
 };
 
 } // namespace rtc
 
 #endif // WEBRTC_BASE_CRITICALSECTION_H_