c++ - 如何使用 Win32 线程池 API？

Question

此版本(基于 this 文章)有效:

#include <windows.h>
#include <tchar.h>
#include <stdio.h>

VOID
CALLBACK
MyWorkCallback(
    PTP_CALLBACK_INSTANCE Instance,
    PVOID                 Parameter,
    PTP_WORK              Work
)
{
    // Instance, Parameter, and Work not used in this example.
    UNREFERENCED_PARAMETER(Instance);
    UNREFERENCED_PARAMETER(Parameter);
    UNREFERENCED_PARAMETER(Work);

    DWORD threadId = GetCurrentThreadId();

    BOOL bRet = FALSE;

    //
    // Do something when the work callback is invoked.
    //
    {
        _tprintf(_T("MyWorkCallback: ThreadId = %d Task performed.\n"), threadId);
    }

    return;
}

int main()
{
    TP_CALLBACK_ENVIRON CallBackEnviron;
    PTP_POOL pool = NULL;
    PTP_CLEANUP_GROUP cleanupgroup = NULL;
    PTP_WORK_CALLBACK workcallback = MyWorkCallback;
    PTP_TIMER timer = NULL;
    PTP_WORK work = NULL;


    InitializeThreadpoolEnvironment(&CallBackEnviron);
    pool = CreateThreadpool(NULL);
    SetThreadpoolThreadMaximum(pool, 1);
    SetThreadpoolThreadMinimum(pool, 3);
    cleanupgroup = CreateThreadpoolCleanupGroup();
    SetThreadpoolCallbackPool(&CallBackEnviron, pool);
    SetThreadpoolCallbackCleanupGroup(&CallBackEnviron, cleanupgroup, NULL);
    work = CreateThreadpoolWork(workcallback, NULL, &CallBackEnviron);
    for (int i = 0; i < 10; ++i)
    {
        SubmitThreadpoolWork(work);
    }
}

但是，这个版本也可以工作(与上面的工作函数相同):

int main()
{
    PTP_WORK = CreateThreadpoolWork(workcallback, NULLPTR, NULLPTR);
    for (int i = 0; i < 10; ++i)
    { 
        SubmitThreadpoolWork(work);
    }
}

这两个版本有什么区别(最小和最大线程数除外)？
为什么我要使用一个版本而不是另一个版本？

Answer 1

InitializeThreadpoolEnvironment 的文档中对此进行了介绍:

Create a callback environment if you plan to call one of the following functions to modify the environment:

• SetThreadpoolCallbackCleanupGroup

• SetThreadpoolCallbackLibrary

• SetThreadpoolCallbackPool

• SetThreadpoolCallbackPriority

• SetThreadpoolCallbackRunsLong

如果您需要一个或多个列出的函数提供的功能，那么您需要创建一个回调环境。如果你不这样做，你就不会。

如果在开始新项目时有疑问，请使用简单的方法开始，看看它是否满足您的需求。如果有必要，您可以随时返回并切换到更复杂的变体。