muduo庫源碼學習(base)Condition

#ifndef MUDUO_BASE_CONDITION_H
#define MUDUO_BASE_CONDITION_H

#include "./Mutex.h"

#include <boost/noncopyable.hpp>
#include <pthread.h>

namespace muduo
{

class Condition : boost::noncopyable
{
 public:
  explicit Condition(MutexLock& mutex)
    : mutex_(mutex)
  {
    MCHECK(pthread_cond_init(&pcond_, NULL));
  }

  ~Condition()
  {
    MCHECK(pthread_cond_destroy(&pcond_));
  }

  //notify_all的時候會喚醒多個線程。
  //要實現類似於
  /*
  lock();
  while(queue.empty()) wait();
 queue.take();unlock();
  */
  void wait()//切記處理虛假喚醒的問題，或使用標準C++的wait處理spurious wakeup
  {
    MutexLock::UnassignGuard ug(mutex_);
    MCHECK(pthread_cond_wait(&pcond_, mutex_.getPthreadMutex()));
  }

  // returns true if time out, false otherwise.
  bool waitForSeconds(double seconds);

  void notify()
  {
    MCHECK(pthread_cond_signal(&pcond_));
  }

  void notifyAll()
  {
    MCHECK(pthread_cond_broadcast(&pcond_));
  }

 private:
  MutexLock& mutex_;
  pthread_cond_t pcond_;
};

}
#endif  // MUDUO_BASE_CONDITION_H

#include <errno.h>

// returns true if time out, false otherwise.
bool muduo::Condition::waitForSeconds(double seconds)
{
  struct timespec abstime;
  // FIXME: use CLOCK_MONOTONIC or CLOCK_MONOTONIC_RAW to prevent time rewind.
  clock_gettime(CLOCK_REALTIME, &abstime);

  const int64_t kNanoSecondsPerSecond = 1e9;
  int64_t nanoseconds = static_cast<int64_t>(seconds * kNanoSecondsPerSecond);

  abstime.tv_sec += static_cast<time_t>((abstime.tv_nsec + nanoseconds) / kNanoSecondsPerSecond);
  abstime.tv_nsec = static_cast<long>((abstime.tv_nsec + nanoseconds) % kNanoSecondsPerSecond);
  //在等待之前，先釋放mutex的線程擁有標識
  MutexLock::UnassignGuard ug(mutex_);
  return ETIMEDOUT == pthread_cond_timedwait(&pcond_, mutex_.getPthreadMutex(), &abstime);
}