浅析生产者消费者模型

生产者消费者模型是经典的线程同步问题，该模型如下：生产者生产产品，并将产品放在一个缓冲区中，供消费者消费。显然消费者和生产者之间必须保持同步，即不允许消费者在一个空的缓冲区中取产品，也不允许生产者向一个满的缓冲区中投放产品。

同步所要解决的问题，即对缓冲区的访问，可以用关键段和信号量来解决。

假设现在需要解决的问题如下：生产者每次生产一个数据，生产五次，然后通知消费者一次消费这五次数据

     

<pre name="code" class="cpp">#include <process.h>#include <windows.h>int ret[5] = {1,2,3,4,5};int num = 0;//表示生产者生产次数int data_buffer[25] = {0}; //float *cur = data_buffer;CRITICAL_SECTION data_cs;HANDLE databufNotEmpty, databufNotFull;void inition(){InitializeCriticalSection(&data_cs);  //初始化信号量;    databufNotEmpty = CreateSemaphore(NULL, 0, 1, NULL);//表示databufNotEmpty的初始值为0databufNotFull = CreateSemaphore(NULL, 5, 5, NULL);//表示databufNotFull的初始值为5，表示生产者可以生产5次//将data_buffer内存初始化为0;memset(data_buffer,0,sizeof(data_buffer));//sizeof(data_buffer)=sizeof(float)*25;}unsigned int _stdcall  producer(LPVOID lp)   //生产者{while (1){//缓冲区非满;P()WaitForSingleObject(databufNotFull, INFINITE);EnterCriticalSection(&data_cs);memcpy(data_buffer+num, ret, sizeof(ret));//内存复制，将ret内存拷贝到cur; num = num + 5;printf("******producer*****\n");LeaveCriticalSection(&data_cs);if (num == 25) //等待缓冲区满{ReleaseSemaphore(databufNotEmpty, 1, NULL);}}return 0;}unsigned int _stdcall  consumer(LPVOID lp){while (1){//等待缓冲区非空WaitForSingleObject(databufNotEmpty, INFINITE);EnterCriticalSection(&data_cs);memset(data_buffer, 0, sizeof(data_buffer));printf("******consumer******\n");num = 0;LeaveCriticalSection(&data_cs);ReleaseSemaphore(databufNotFull, 5, NULL);}return 0;}int main(){inition();HANDLE h_Thread[2];h_Thread[0] = (HANDLE)_beginthreadex(NULL, 0, producer, NULL, 0, NULL);h_Thread[1] = (HANDLE)_beginthreadex(NULL, 0, consumer, NULL, 0, NULL);WaitForMultipleObjects(2,h_Thread,true,INFINITE);CloseHandle(h_Thread[0]);CloseHandle(h_Thread[1]);getchar();return 0;}

结果如下：