生產者-消費者(producer-consumer)問題,也稱作有界緩衝區(bounded-buffer)問題,兩個進程共享一個公共的固定大小的緩衝區。其中一個是生產者,用於將消息放入緩衝區;另外一個是消費者,用於從緩衝區中取出消息。問題出現在當緩衝區已經滿了,而此時生產者還想向其中放入一個新的數據項的情形,其解決方法是讓生產者此時進行休眠,等待消費者從緩衝區中取走了一個或者多個數據後再去喚醒它。同樣地,當緩衝區已經空了,而消費者還想去取消息,此時也可以讓消費者進行休眠,等待生產者放入一個或者多個數據時再喚醒它。
頭文件:
#include<memory>
#include<chrono>
#include<iostream>
#include<thread>
#include<condition_variable>
#include<mutex>
#include<cstdlib>
#include<chrono>
代碼:
#include "stdafx.h"
class loop_list {
public:
enum { kItemRepositorySize = 10, kItemsToProduce = 1000};
private:
struct ItemRepository {
std::condition_variable repo_not_empty;
std::condition_variable repo_not_full;
std::mutex mtx;
size_t write_position = 0;
size_t read_position = 0;
int item_buffer[kItemRepositorySize]{ 0 };
int cnt = 0;
};
typedef struct ItemRepository ItemRepository;
ItemRepository ir;
size_t _stop; //count about pop numbers
public:
void push(int _item) {
std::unique_lock<std::mutex> lock(ir.mtx);
while ((ir.write_position+1)% kItemRepositorySize
== ir.read_position){
std::cout << "please pop..." << std::endl;
ir.repo_not_full.wait(lock);
}
ir.item_buffer[ir.write_position] = _item;
(ir.write_position)++;
if (ir.write_position >= kItemRepositorySize)
ir.write_position = 0;
lock.unlock();
ir.repo_not_empty.notify_all();
}
std::shared_ptr<int> pop(){
std::unique_lock<std::mutex> lock(ir.mtx);
while (ir.write_position == ir.read_position) {
std::cout << "please push..." << std::endl;
ir.repo_not_empty.wait(lock);
}
std::shared_ptr<int> _result = std::make_shared<int>(ir.item_buffer[ir.read_position]);
(ir.read_position)++;
if (ir.read_position >= kItemRepositorySize)
ir.read_position = 0;
lock.unlock();
ir.repo_not_full.notify_all();
return _result;
}
size_t _count() const {
return _stop;
}
public:
loop_list(int _count = kItemsToProduce):_stop(_count) {};
};
//生產者
void ProducerTask(loop_list& ir) {
for (int i = 1; i <= ir._count(); ++i) {
// std::this_thread::sleep_for( std::chrono::seconds(2));
std::cout <<"the id : "<<std::this_thread::get_id()<< ". Produce the " << i << "^th item..." << std::endl;
ir.push(i);
}
}
//消費者
void ConsumerTask(loop_list& ir,int ProducerTasknumber) //ProducerTasknumber 生產者數目
{
static int _count = 0;
while (true) {
// std::this_thread::sleep_for(std::chrono::seconds(1));
auto item = ir.pop();
std::cout << " Consume the " << *item << "^th item" << std::endl;
if (++_count == ProducerTasknumber*ir._count()) break;
}
}
int main(){
loop_list i;
std::thread one(ProducerTask, std::ref(i));
std::thread two(ProducerTask, std::ref(i));
std::thread thr(ConsumerTask, std::ref(i),2);
one.join();
two.join();
thr.join();
system("pause");
return 0;
}
將緩存區封裝成一個類,將所有基本操作賦該類,並決定鎖的粒度。將生產者與消費者操作封裝成函數。生產者消費者互相不知道對方的存在,每個方法只是與緩存區交互。這種寫法,我們在操作時只要確定生產產品與消費產品的數目後,再對操作進行修改,就不會牽一髮而動全身。具有好的封裝性。
部分參考: