text: // Copyright 2014 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef MOJO_PUBLIC_CPP_UTILITY_MUTEX_H_
  #define MOJO_PUBLIC_CPP_UTILITY_MUTEX_H_
  
  #ifdef _WIN32
  #error "Not implemented: See crbug.com/342893."
  #endif
  
  #include <pthread.h>
  
  #include "mojo/public/cpp/system/macros.h"
  
  namespace mojo {
  
  #ifdef NDEBUG
  // Note: Make a C++ constant for |PTHREAD_MUTEX_INITIALIZER|. (We can't directly
  // use the C macro in an initializer list, since it might expand to |{ ... }|.)
  namespace internal {
  const pthread_mutex_t kPthreadMutexInitializer = PTHREAD_MUTEX_INITIALIZER;
  }
  #endif
  
  class Mutex {
   public:
  #ifdef NDEBUG
    Mutex() : mutex_(internal::kPthreadMutexInitializer) {}
    ~Mutex() { pthread_mutex_destroy(&mutex_); }
  
    void Lock() { pthread_mutex_lock(&mutex_); }
    void Unlock() { pthread_mutex_unlock(&mutex_); }
    bool TryLock() { return pthread_mutex_trylock(&mutex_) == 0; }
  
    void AssertHeld() {}
  #else
    Mutex();
    ~Mutex();
  
    void Lock();
    void Unlock();
    bool TryLock();
  
    void AssertHeld();
  #endif
  
   private:
    pthread_mutex_t mutex_;
  
    MOJO_DISALLOW_COPY_AND_ASSIGN(Mutex);
  };
  
  class MutexLock {
   public:
    explicit MutexLock(Mutex* mutex) : mutex_(mutex) { mutex_->Lock(); }
    ~MutexLock() { mutex_->Unlock(); }
  
   private:
    Mutex* const mutex_;
  
    MOJO_DISALLOW_COPY_AND_ASSIGN(MutexLock);
  };
  
  // Catch bug where variable name is omitted (e.g., |MutexLock (&mu)|).
  #define MutexLock(x) MOJO_COMPILE_ASSERT(0, mutex_lock_missing_variable_name);
  
  }  // namespace mojo
  
  #endif  // MOJO_PUBLIC_CPP_UTILITY_MUTEX_H_
  