c++11实现写优先的读写锁

先直接贴出代码：

#ifndef __WRITE_FIRST_RW_LOCK_H
#define __WRITE_FIRST_RW_LOCK_H

#include <mutex>
#include <condition_variable>

class WfirstRWLock
{
public:
	WfirstRWLock() = default;
	~WfirstRWLock() = default;
public:
	void lock_read()
	{
		std::unique_lock<std::mutex> ulk(counter_mutex);
		cond_r.wait(ulk, [=]()->bool {return write_cnt == 0; });
		++read_cnt;
	}
	void lock_write()
	{
		std::unique_lock<std::mutex> ulk(counter_mutex);
		++write_cnt;
		cond_w.wait(ulk, [=]()->bool {return read_cnt == 0 && !inwriteflag; });
		inwriteflag = true;
	}
	void release_read()
	{
		std::unique_lock<std::mutex> ulk(counter_mutex);
		if (--read_cnt == 0 && write_cnt > 0)
		{
			cond_w.notify_one();
		}
	}
	void release_write()
	{
		std::unique_lock<std::mutex> ulk(counter_mutex);
		if (--write_cnt == 0)
		{
			cond_r.notify_all();
		}
		else
		{
			cond_w.notify_one();
		}
		inwriteflag = false