一種基於copy-on-write的多生產者消費者模型

#ifndef _CREATEONCOSUME
#define _CREATEONCOSUME
#include <vector>
#include <memory>
#include <mutex>
#include <queue>
using namespace std;

template<typename T>
class CreateOnConsume {
public:
	CreateOnConsume()
		: m_forProduce(make_shared<vector<T> >()) {};
	virtual void consumeEachVec(vector<T> &vec) = 0;
	void push(T &t) {
		lock_guard<mutex> lock(m_mtx);
		m_forProduce->push_back(t);
	};
	void consumeAll() {
		move2ForConsume();
		while (!m_forConsume.empty()) {
			auto &head = m_forConsume.front();
			consumeEachVec(*head);
			m_forConsume.pop();
		}
	};
	
protected:
	shared_ptr<vector<T> > m_forProduce;
	mutex m_mtx;
	queue<shared_ptr<vector<T> > > m_forConsume;//?
	void move2ForConsume() {
		lock_guard<mutex> lock(m_mtx);
		if (!m_forProduce->empty()) {
			m_forConsume.push(m_forProduce);
			m_forProduce = make_shared<vector<T> >();
		}
	};
};
#endif

子類只需要重載consumeEachVec即可。

生產過程的鎖粒度很低，只是往std::vector push。

消費過程的鎖只在move2ForCosume中作用。第一步判斷生產用的vector是否爲空，第二步搬運這個vector指針，第三步給生產者再創建一個vector。