winapi - 完成端口上的 WaitForSingleObject()？

Question

今天我了解到我可以调用CreateIoCompletionPort()，然后将返回的HANDLE传递给WaitForSingleObject():

#include <Windows.h>

int main()
{
    HANDLE h = CreateIoCompletionPort(INVALID_HANDLE_VALUE, nullptr, 0, 0);
    auto bRes = PostQueuedCompletionStatus(h, 1, 2, 0);
    if (!bRes) {
        abort();
    }

    auto dwRes = WaitForSingleObject(h, INFINITE);
    if (dwRes != WAIT_OBJECT_0){
        abort();
    }

    LPOVERLAPPED pOvr;
    DWORD cb;
    ULONG_PTR key;
    bRes = GetQueuedCompletionStatus(
        h, &cb, &key, &pOvr, INFINITE); // <-- returns 1, 2, nullptr

    if (!bRes) {
        abort();
    }

    dwRes = WaitForSingleObject(h, INFINITE); // <-- blocks here
    return 0;
}

它在我的 Windows 10 机器上按预期工作。

这种行为是否已知或合法或有记录？我找不到任何相关信息。

Answer 1

如果您阅读 WaitForSingleObject() documentation ，I/O 完成端口不是允许的句柄类型:

The WaitForSingleObject function can wait for the following objects:

• Change notification
• Console input
• Event
• Memory resource notification
• Mutex
• Process
• Semaphore
• Thread
• Waitable timer

要等待完成事件到达端口，您必须自行将句柄传递给 GetQueuedCompletionStatus() 并让它阻塞，直到事件到达或发生超时。

#include <Windows.h>

int main()
{
    HANDLE h = CreateIoCompletionPort(INVALID_HANDLE_VALUE, nullptr, 0, 0);
    auto bRes = PostQueuedCompletionStatus(h, 1, 2, 0);
    if (!bRes) {
        abort();
    }

    LPOVERLAPPED pOvr;
    DWORD cb;
    ULONG_PTR key;
    bRes = GetQueuedCompletionStatus(
        h, &cb, &key, &pOvr, INFINITE); // <-- returns 1, 2, nullptr

    if (!bRes) {
        abort();
    }

    bRes = GetQueuedCompletionStatus(
        h, &cb, &key, &pOvr, INFINITE); // <-- blocks here

    return 0;
}