生产者与消费者问题的实现

生产者与消费者问题的实现。创建一组“生产者”线程和一组“消费者”线程，并建立一个长度为N的全局数组作为共享缓冲区。“生产者”向缓冲区输入数据，“消费者”从缓冲区读出数据。当缓冲区满时，“生产者”必须阻塞，等待“消费者”取走缓冲区数据后将其唤醒。当缓冲区空时，“消费者”阻塞，等待“生产者”生产了产品后将其唤醒。试用信号量实现“生产者”与“消费者”线程之间的同步。

#include <windows.h>
#include <iostream>

const unsigned short SIZE_OF_BUFFER = 10; //缓冲区长度
unsigned short ProductID = 0;    //产品号
unsigned short ConsumeID = 0;    //将被消耗的产品号
unsigned short in = 0;      //产品进缓冲区时的缓冲区下标
unsigned short out = 0;      //产品出缓冲区时的缓冲区下标

int g_buffer[SIZE_OF_BUFFER];    //缓冲区是个循环队列
bool g_continue = true;      //控制程序结束
HANDLE g_hMutex;       //用于线程间的互斥
HANDLE g_hFullSemaphore;     //当缓冲区满时迫使生产者等待
HANDLE g_hEmptySemaphore;     //当缓冲区空时迫使消费者等待

DWORD WINAPI Producer(LPVOID);    //生产者线程
DWORD WINAPI Consumer(LPVOID);    //消费者线程

int main()
{
    //创建各个互斥信号
    g_hMutex = CreateMutex(NULL,FALSE,NULL);
    g_hFullSemaphore = CreateSemaphore(NULL,SIZE_OF_BUFFER-1,SIZE_OF_BUFFER-1,NULL);
    g_hEmptySemaphore = CreateSemaphore(NULL,0,SIZE_OF_BUFFER-1,NULL);

    //调整下面的数值，可以发现，当生产者个数多于消费者个数时，
    //生产速度快，生产者经常等待消费者；反之，消费者经常等待
    const unsigned short PRODUCERS_COUNT = 3;  //生产者的个数
    const unsigned short CONSUMERS_COUNT = 1;  //消费者的个数

    //总的线程数
    const unsigned short THREADS_COUNT = PRODUCERS_COUNT+CONSUMERS_COUNT;

    HANDLE hThreads[PRODUCERS_COUNT]; //各线程的handle
    DWORD producerID[CONSUMERS_COUNT]; //生产者线程的标识符
    DWORD consumerID[THREADS_COUNT]; //消费者线程的标识符

    //创建生产者线程
    for (int i=0;i<PRODUCERS_COUNT;++i){
        hThreads[i]=CreateThread(NULL,0,Producer,NULL,0,&producerID[i]);
        if (hThreads[i]==NULL) return -1;
    }
    //创建消费者线程
    for (i=0;i<CONSUMERS_COUNT;++i){
        hThreads[PRODUCERS_COUNT+i]=CreateThread(NULL,0,Consumer,NULL,0,&consumerID[i]);
        if (hThreads[i]==NULL) return -1;
    }

    while(g_continue){
        if(getchar()){ //按回车后终止程序运行
            g_continue = false;
        }
    }

    return 0;
}

//生产一个产品。简单模拟了一下，仅输出新产品的ID号
void Produce()
{
    std::cerr << "Producing " << ++ProductID << " ... ";
    std::cerr << "Succeed" << std::endl;
}

//把新生产的产品放入缓冲区
void Append()
{
    std::cerr << "Appending a product ... ";
    g_buffer[in] = ProductID;
    in = (in+1)%SIZE_OF_BUFFER;
    std::cerr << "Succeed" << std::endl;

    //输出缓冲区当前的状态
    for (int i=0;i<SIZE_OF_BUFFER;++i){
        std::cout << i <<": " << g_buffer[i];
        if (i==in) std::cout << " <-- 生产";
        if (i==out) std::cout << " <-- 消费";
        std::cout << std::endl;
    }
}

//从缓冲区中取出一个产品
void Take()
{
    std::cerr << "Taking a product ... ";
    ConsumeID = g_buffer[out];
    out = (out+1)%SIZE_OF_BUFFER;
    std::cerr << "Succeed" << std::endl;

    //输出缓冲区当前的状态
    for (int i=0;i<SIZE_OF_BUFFER;++i){
        std::cout << i <<": " << g_buffer[i];
        if (i==in) std::cout << " <-- 生产";
        if (i==out) std::cout << " <-- 消费";
        std::cout << std::endl;
    }
}

//消耗一个产品
void Consume()
{
    std::cerr << "Consuming " << ConsumeID << " ... ";
    std::cerr << "Succeed" << std::endl;
}

//生产者
DWORD  WINAPI Producer(LPVOID lpPara)
{
    while(g_continue){
        WaitForSingleObject(g_hFullSemaphore,INFINITE);
        WaitForSingleObject(g_hMutex,INFINITE);
        Produce();
        Append();
        Sleep(1500);
        ReleaseMutex(g_hMutex);
        ReleaseSemaphore(g_hEmptySemaphore,1,NULL);
    }
    return 0;
}

//消费者
DWORD  WINAPI Consumer(LPVOID lpPara)
{
    while(g_continue){
        WaitForSingleObject(g_hEmptySemaphore,INFINITE);
        WaitForSingleObject(g_hMutex,INFINITE);
        Take();
        Consume();
        Sleep(1500);
        ReleaseMutex(g_hMutex);
        ReleaseSemaphore(g_hFullSemaphore,1,NULL);
    }
    return 0;
}