生产者-消费者问题实现 (windows)

生产者-消费者问题是一个经典的进程同步问题，该问题最早由Dijkstra提出，用以演示他提出的信号量机制。在同一个进程地址空间内执行的两个线程。生产者线程生产物品，然后将物品放置在一个空缓冲区中供消费者线程消费。消费者线程从缓冲区中获得物品，然后释放缓冲区。当生产者线程生产物品时，如果没有空缓冲区可用，那么生产者线程必须等待消费者线程释放出一个空缓冲区。当消费者线程消费物品时，如果没有满的缓冲区，那么消费者线程将被阻塞，直到新的物品被生产出来。

#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 (int 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;

}