转载一份C++线程池的代码，非常实用 .

#ifndef _ThreadPool_H_
#define _ThreadPool_H_
#pragma warning(disable: 4530)
#pragma warning(disable: 4786)
#include <cassert>
#include <vector>
#include <queue>
#include <windows.h>

using namespace std;

class ThreadJob //工作基类
{
public:
//供线程池调用的虚函数
virtual void DoJob(void *pPara) = 0;
};
class ThreadPool
{
public:
//dwNum 线程池规模
ThreadPool(DWORD dwNum = 4) : _lThreadNum(0), _lRunningNum(0)
{
InitializeCriticalSection(&_csThreadVector);
InitializeCriticalSection(&_csWorkQueue);
_EventComplete = CreateEvent(0, false, false, NULL);
_EventEnd = CreateEvent(0, true, false, NULL);
_SemaphoreCall = CreateSemaphore(0, 0, 0x7FFFFFFF, NULL);
_SemaphoreDel = CreateSemaphore(0, 0, 0x7FFFFFFF, NULL);
assert(_SemaphoreCall != INVALID_HANDLE_VALUE);
assert(_EventComplete != INVALID_HANDLE_VALUE);
assert(_EventEnd != INVALID_HANDLE_VALUE);
assert(_SemaphoreDel != INVALID_HANDLE_VALUE);
AdjustSize(dwNum <= 0 ? 4 : dwNum);
}
~ThreadPool()
{
DeleteCriticalSection(&_csWorkQueue);
CloseHandle(_EventEnd);
CloseHandle(_EventComplete);
CloseHandle(_SemaphoreCall);
CloseHandle(_SemaphoreDel);

vector<ThreadItem*>::iterator iter;
for(iter = _ThreadVector.begin(); iter != _ThreadVector.end(); iter++)
{
if(*iter)
delete *iter;
}
DeleteCriticalSection(&_csThreadVector);
}
//调整线程池规模
int AdjustSize(int iNum)
{
if(iNum > 0)
{
ThreadItem *pNew;
EnterCriticalSection(&_csThreadVector);
for(int _i=0; _i<iNum; _i++)
{
_ThreadVector.push_back(pNew = new ThreadItem(this));
assert(pNew);
pNew->_Handle = CreateThread(NULL, 0, DefaultJobProc, pNew, 0, NULL);
// set priority
SetThreadPriority(pNew->_Handle, THREAD_PRIORITY_BELOW_NORMAL);
assert(pNew->_Handle);
}
LeaveCriticalSection(&_csThreadVector);
}
else
{
iNum *= -1;
ReleaseSemaphore(_SemaphoreDel, iNum > _lThreadNum ? _lThreadNum : iNum, NULL);
}
return (int)_lThreadNum;
}
//调用线程池
void Call(void (*pFunc)(void *), void *pPara = NULL)
{
assert(pFunc);
EnterCriticalSection(&_csWorkQueue);
_JobQueue.push(new JobItem(pFunc, pPara));
LeaveCriticalSection(&_csWorkQueue);
ReleaseSemaphore(_SemaphoreCall, 1, NULL);
}
//调用线程池
inline void Call(ThreadJob * p, void *pPara = NULL)
{
Call(CallProc, new CallProcPara(p, pPara));
}
//结束线程池, 并同步等待
bool EndAndWait(DWORD dwWaitTime = INFINITE)
{
SetEvent(_EventEnd);
return WaitForSingleObject(_EventComplete, dwWaitTime) == WAIT_OBJECT_0;
}
//结束线程池
inline void End()
{
SetEvent(_EventEnd);
}
inline DWORD Size()
{
return (DWORD)_lThreadNum;
}
inline DWORD GetRunningSize()
{
return (DWORD)_lRunningNum;
}
bool IsRunning()
{
return _lRunningNum > 0;
}
protected:
//工作线程
static DWORD WINAPI DefaultJobProc(LPVOID lpParameter = NULL)
{
ThreadItem *pThread = static_cast<ThreadItem*>(lpParameter);
assert(pThread);
ThreadPool *pThreadPoolObj = pThread->_pThis;
assert(pThreadPoolObj);
InterlockedIncrement(&pThreadPoolObj->_lThreadNum);
HANDLE hWaitHandle[3];
hWaitHandle[0] = pThreadPoolObj->_SemaphoreCall;
hWaitHandle[1] = pThreadPoolObj->_SemaphoreDel;
hWaitHandle[2] = pThreadPoolObj->_EventEnd;
JobItem *pJob;
bool fHasJob;

for(;;)
{
DWORD wr = WaitForMultipleObjects(3, hWaitHandle, false, INFINITE);
//响应删除线程信号
if(wr == WAIT_OBJECT_0 + 1)
break;

//从队列里取得用户作业
EnterCriticalSection(&pThreadPoolObj->_csWorkQueue);
if(fHasJob = !pThreadPoolObj->_JobQueue.empty())
{
pJob = pThreadPoolObj->_JobQueue.front();
pThreadPoolObj->_JobQueue.pop();
assert(pJob);
}
LeaveCriticalSection(&pThreadPoolObj->_csWorkQueue);
//受到结束线程信号 确定是否结束线程(结束线程信号 && 是否还有工作)
if(wr == WAIT_OBJECT_0 + 2 && !fHasJob)
break;
if(fHasJob && pJob)
{
InterlockedIncrement(&pThreadPoolObj->_lRunningNum);
pThread->_dwLastBeginTime = GetTickCount();
pThread->_dwCount++;
pThread->_fIsRunning = true;
pJob->_pFunc(pJob->_pPara); //运行用户作业
delete pJob;
pThread->_fIsRunning = false;
InterlockedDecrement(&pThreadPoolObj->_lRunningNum);
}
}
//删除自身结构
EnterCriticalSection(&pThreadPoolObj->_csThreadVector);
pThreadPoolObj->_ThreadVector.erase(find(pThreadPoolObj->_ThreadVector.begin(), pThreadPoolObj->_ThreadVector.end(), pThread));
LeaveCriticalSection(&pThreadPoolObj->_csThreadVector);
delete pThread;
InterlockedDecrement(&pThreadPoolObj->_lThreadNum);
if(!pThreadPoolObj->_lThreadNum) //所有线程结束
SetEvent(pThreadPoolObj->_EventComplete);
return 0;
}
//调用用户对象虚函数
static void CallProc(void *pPara)
{
CallProcPara *cp = static_cast<CallProcPara *>(pPara);
assert(cp);
if(cp)
{
cp->_pObj->DoJob(cp->_pPara);
delete cp;
}
}
//用户对象结构
struct CallProcPara
{
ThreadJob* _pObj;//用户对象
void *_pPara;//用户参数
CallProcPara(ThreadJob* p, void *pPara) : _pObj(p), _pPara(pPara) { };
};
//用户函数结构
struct JobItem
{
void (*_pFunc)(void *);//函数
void *_pPara; //参数
JobItem(void (*pFunc)(void *) = NULL, void *pPara = NULL) : _pFunc(pFunc), _pPara(pPara) { };
};
//线程池中的线程结构
struct ThreadItem
{
HANDLE _Handle; //线程句柄
ThreadPool *_pThis; //线程池的指针
DWORD _dwLastBeginTime; //最后一次运行开始时间
DWORD _dwCount; //运行次数
bool _fIsRunning;
ThreadItem(ThreadPool *pthis) : _pThis(pthis), _Handle(NULL), _dwLastBeginTime(0), _dwCount(0), _fIsRunning(false) { };
~ThreadItem()
{
if(_Handle)
{
CloseHandle(_Handle);
_Handle = NULL;
}
}
};

std::queue<JobItem *> _JobQueue; //工作队列
std::vector<ThreadItem *> _ThreadVector; //线程数据
CRITICAL_SECTION _csThreadVector, _csWorkQueue; //工作队列临界, 线程数据临界
HANDLE _EventEnd, _EventComplete, _SemaphoreCall, _SemaphoreDel;//结束通知, 完成事件, 工作信号， 删除线程信号
long _lThreadNum, _lRunningNum; //线程数, 运行的线程数
};
#endif //_ThreadPool_H_

转载自 http://blog.csdn.net/pjchen/archive/2004/11/06/170606.aspx
基本上是拿来就用了，对WIN32 API不熟，但对线程池的逻辑还是比较熟的，认为这个线程池写得很清晰，我拿来用在一个多线程下载的模块中。很实用的东东。
调用方法
void threadfunc(void *p)
{
YourClass* yourObject = (YourClass*) p;

//...

}

ThreadPool tp;

for(i=0; i<100; i++)

tp.Call(threadfunc);

ThreadPool tp(20);//20为初始线程池规模

tp.Call(threadfunc, lpPara);



使用时注意几点：
1. ThreadJob 没什么用，直接写线程函数吧。
2. 线程函数（threadfunc）的入口参数void* 可以转成自定义的类型对象，这个对象可以记录下线程运行中的数据，并设置线程当前状态，以此与线程进行交互。
3. 线程池有一个EndAndWait函数，用于让线程池中所有计算正常结束。有时线程池中的一个线程可能要运行很长时间，怎么办？可以通过线程函数threadfunc的入口参数对象来处理，比如：
class YourClass {
int cmd; // cmd = 1是上线程停止计算，正常退出。
};
threadfunc(void* p) {
YourClass* yourObject = (YourClass*)p;
while (true) {
// do some calculation
if (yourClass->cmd == 1)
break;
}
}
在主线程中设置yourClass->cmd = 1，该线程就会自然结束。
很简洁通用的线程池实现。