Analysis of muduo library - base (4) Mutex

In order to facilitate development, the management class of mutex is generally created, and the lock and unlock class (RALL technology) is created at the same time.

class MutexLock : boost::noncopyable
{
 public:
  MutexLock()
    : holder_(0) //Thread holder
  {
    MCHECK(pthread_mutex_init(&mutex_, NULL)); //mutex dynamic initialization
  }

  ~MutexLock()
  {
    assert(holder_ == 0); // no holder
    MCHECK(pthread_mutex_destroy(&mutex_));	//销毁mutex
  }

bool isLockedByThisThread() const //Can only be called when locked
  {
    return holder_ == CurrentThread::tid(); //Determine whether the holder and the current thread are the same
  }

void lock()
  {
    MCHECK(pthread_mutex_lock(&mutex_));	//上锁
    assignHolder(); //Set the holder
  }

void unlock()
  {
    unassignHolder(); //Clear the holder
    MCHECK(pthread_mutex_unlock(&mutex_));	//解锁
  }

pthread_mutex_t* getPthreadMutex() /* non-const */
  {
    return &mutex_; //Get the lock, because the condition variable sometimes needs a lock, so return its address
  }

private:
  friend class Condition; //friend class condition variable

//After the condition variable is locked, when the wait operation is performed, the thread binding is released to prevent the call from failing when other threads are locked.
  class UnassignGuard : boost::noncopyable	

class MutexLockGuard : boost::noncopyable
{
 public:
  explicit MutexLockGuard(MutexLock& mutex)
    : mutex_(mutex)
  {
    mutex_.lock(); //Using RALL technology, resources are obtained when constructing, and resources are released when destructing
  }

  ~MutexLockGuard()
  {
    mutex_.unlock();	
  }