WebRTC-线程模型（1）

在介绍WebRTC的线程模型之前，先介绍webrtc线程模型中用到的几个简单、常用的模块或函数。webrtc是一个代码宝库，且它本身跨平台（windows，linux，ios，android），不管是哪个平台上面开发，都可以从中学习到很多有用的东西。

一、 设置线程名

platform_thread.cc

void SetCurrentThreadName(const char* name) {
#if defined(WEBRTC_WIN)
  struct {
    DWORD dwType;
    LPCSTR szName;
    DWORD dwThreadID;
    DWORD dwFlags;
  } threadname_info = {0x1000, name, static_cast<DWORD>(-1), 0};

  __try {
    ::RaiseException(0x406D1388, 0, sizeof(threadname_info) / sizeof(DWORD),
                     reinterpret_cast<ULONG_PTR*>(&threadname_info));
  } __except (EXCEPTION_EXECUTE_HANDLER) {
  }
#elif defined(WEBRTC_LINUX) || defined(WEBRTC_ANDROID)
  prctl(PR_SET_NAME, reinterpret_cast<unsigned long>(name));
#elif defined(WEBRTC_MAC) || defined(WEBRTC_IOS)
  pthread_setname_np(name);
#endif
}

调用示例 thread.cc Thread::SetName

bool Thread::SetName(const std::string& name, const void* obj) {
  if (running()) return false;
  name_ = name;
  if (obj) {
    char buf[20];
    sprintfn(buf, sizeof(buf), " 0x%p", obj);
    name_ += buf;
  }
  return true;
}

二、 原子操作

atomicops.h

class AtomicOps {
 public:
#if defined(WEBRTC_WIN)
  // Assumes sizeof(int) == sizeof(LONG), which it is on Win32 and Win64.
  static int Increment(volatile int* i) {
    return ::InterlockedIncrement(reinterpret_cast<volatile LONG*>(i));
  }
  static int Decrement(volatile int* i) {
    return ::InterlockedDecrement(reinterpret_cast<volatile LONG*>(i));
  }
  static int AcquireLoad(volatile const int* i) {
    return *i;
  }
  static void ReleaseStore(volatile int* i, int value) {
    *i = value;
  }
  static int CompareAndSwap(volatile int* i, int old_value, int new_value) {
    return ::InterlockedCompareExchange(reinterpret_cast<volatile LONG*>(i),
                                        new_value,
                                        old_value);
  }
  // Pointer variants.
  template <typename T>
  static T* AcquireLoadPtr(T* volatile* ptr) {
    return *ptr;
  }
  template <typename T>
  static T* CompareAndSwapPtr(T* volatile* ptr, T* old_value, T* new_value) {
    return static_cast<T*>(::InterlockedCompareExchangePointer(
        reinterpret_cast<PVOID volatile*>(ptr), new_value, old_value));
  }
#else
  static int Increment(volatile int* i) {
    return __sync_add_and_fetch(i, 1);
  }
  static int Decrement(volatile int* i) {
    return __sync_sub_and_fetch(i, 1);
  }
  static int AcquireLoad(volatile const int* i) {
    return __atomic_load_n(i, __ATOMIC_ACQUIRE);
  }
  static void ReleaseStore(volatile int* i, int value) {
    __atomic_store_n(i, value, __ATOMIC_RELEASE);
  }
  static int CompareAndSwap(volatile int* i, int old_value, int new_value) {
    return __sync_val_compare_and_swap(i, old_value, new_value);
  }
  // Pointer variants.
  template <typename T>
  static T* AcquireLoadPtr(T* volatile* ptr) {
    return __atomic_load_n(ptr, __ATOMIC_ACQUIRE);
  }
  template <typename T>
  static T* CompareAndSwapPtr(T* volatile* ptr, T* old_value, T* new_value) {
    return __sync_val_compare_and_swap(ptr, old_value, new_value);
  }
#endif
};

使用示例

bool MessageQueue::IsQuitting() {
  return AtomicOps::AcquireLoad(&stop_) != 0;
}

来源：CSDN

作者：china_jeffery

链接：https://blog.csdn.net/china_jeffery/article/details/78614268