生产者消费者问题——C++ windows版 多生产者多消费者的队列实现

　　最进要写一个多线程加载资源的资源管理器(ResourceManager)和多线程音频解码器(MultiThread Decoder)。因为距最近一次用到多线程放下好久了，所以今天把生产者消费者问题练一下手。

　　为什么选择生产者消费者问题，因为他比较接近资源管理器和多线程音频解码器的原型。

　　比如，对于音频解码器，音频线程去流式的解码一段MP3格式的内存，就类似生产者生产产品的过程;而音频播放API(如OpenAL，OpenSL)通常需要的是PCM数据，也就是生产者生产的产品，所以播放逻辑充当消费者的角色，典型的生产者消费者问题。

　　再对于资源管理器，加载Mesh和Texture类似生产单个Resource的过程，而相应的渲染逻辑去使用资源就相当于消费资源的过程，但不同的是最后当不再使用这个资源的时候，这个资源才会被释放，而非使用一次。

　　今天抽时间，写了一个C++ windows版 多生产者多消费者的队列实现，pthread版估计等需要做跨平台的时候再做，如果想方便直接用OpenMP或者TBB也是可以的，但是对于轻量级引擎，自己实现资源加载器完全足够了。

　　

#include <Windows.h>
#include <map>
#include <queue>

CRITICAL_SECTION g_cs;    // mutex

HANDLE    g_hEmptyBufferSemaphore;
HANDLE  g_hFullBufferSemaphore;

#define INVALID  -1

#define PRODUCER 5
#define CUSTOMER 5

#define NUM_COUNT 8
#define BUFF_SIZE 4

static std::queue<int> bufferQueue;
static std::map< DWORD,int > countMap;

bool ProducerFinish = false;

//设置控制台输出颜色
BOOL SetConsoleColor(WORD wAttributes)
{
    HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
    if (hConsole == INVALID_HANDLE_VALUE)
        return FALSE;    
    return SetConsoleTextAttribute(hConsole, wAttributes);
}

DWORD WINAPI ProducerFunc(LPVOID param)
{
    
    while(true)
    {
        WaitForSingleObject( g_hEmptyBufferSemaphore, INFINITE);

        EnterCriticalSection(&g_cs);

        DWORD threadId = GetCurrentThreadId();
        if(countMap.find(threadId) == countMap.end())
            countMap[threadId] = 0;

        int productID = ++countMap[threadId];

        bufferQueue.push( productID);
        printf("生产者%d , 生产%d
", threadId, productID);

        if( productID == NUM_COUNT )
        {
            SetConsoleColor(FOREGROUND_RED);
            printf("生产者%d生产完毕
",GetCurrentThreadId());
            SetConsoleColor(FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE);

            LeaveCriticalSection(&g_cs);
            ReleaseSemaphore(g_hFullBufferSemaphore, 1, NULL);

            break;
        }

        LeaveCriticalSection(&g_cs);

        ReleaseSemaphore(g_hFullBufferSemaphore, 1, NULL);
    }

    return NULL;
}

DWORD WINAPI CustomerFunc(LPVOID param)
{
    while (true)
    {
        WaitForSingleObject( g_hFullBufferSemaphore, INFINITE);

        EnterCriticalSection(&g_cs);

        int buffer = -1;
        
        if(!bufferQueue.empty())
        {
            buffer = bufferQueue.front();
            bufferQueue.pop();
        }


        if(buffer != INVALID )
            printf("消费者%d ,消费%d
", GetCurrentThreadId() , buffer);

        if( bufferQueue.empty() && ProducerFinish)
        {
            printf("消费者%d 结束
",GetCurrentThreadId());
            LeaveCriticalSection(&g_cs);

            // 通知其他消费者可以结束了
            ReleaseSemaphore( g_hFullBufferSemaphore, 1, NULL);
            break;
        }

        LeaveCriticalSection(&g_cs);

        ReleaseSemaphore( g_hEmptyBufferSemaphore, 1, NULL);
    }


    return NULL;
}

int _tmain(int argc, _TCHAR* argv[])
{
    InitializeCriticalSection(&g_cs);  

    g_hEmptyBufferSemaphore = CreateSemaphore( NULL, 4, 4, NULL);
    g_hFullBufferSemaphore = CreateSemaphore( NULL, 0, 4, NULL);
    
    HANDLE producerThreads[PRODUCER];
    HANDLE customerThreads[CUSTOMER];

    // producer
    for (int i = 0; i < PRODUCER; ++i)
    {
        producerThreads[i] = CreateThread( NULL, 0, ProducerFunc, NULL, NULL, NULL);
    }
    
    // customers
    for (int i = 0; i < CUSTOMER; ++i)
        customerThreads[i] = CreateThread( NULL, 0, CustomerFunc, NULL, NULL, NULL);


    WaitForMultipleObjects( PRODUCER, producerThreads, TRUE, INFINITE);
    ProducerFinish = true;

    WaitForMultipleObjects( CUSTOMER, customerThreads, TRUE, INFINITE);


    for (int i = 0; i < PRODUCER; ++i)
        CloseHandle(producerThreads[i]);

    for (int i = 0; i < CUSTOMER; ++i)
        CloseHandle(customerThreads[i]);


    CloseHandle(g_hEmptyBufferSemaphore);
    CloseHandle(g_hFullBufferSemaphore);

    DeleteCriticalSection(&g_cs);

    countMap.clear();

    return 0;
}