Winsock 完成端口模型简介

$ynA ou0注：CreateIoCompletionPort ，PostQueuedCompletionStatus ，GetQueuedCompletionStatus 等函数的用法说明。

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I/O completion ports are the mechanism by which an application uses a pool of threads that was created when the application was started to process asynchronous I/O requests. These threads are created for the sole purpose of processing I/O requests. Applications that process many concurrent asynchronous I/O requests can do so more quickly and efficiently by using I/O completion ports than by using creating threads at the time of the I/O request. pcMing工作室nk` E [ P:a_%kV

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I/O完成端口(s)是一种机制，通过这个机制，应用程序在启动时会首先创建一个线程池，然后该应用程序使用线程池处理异步I/O请求。这些线程被创建的唯一目的就是用于处理I/O请求。对于处理大量并发异步I/O请求的应用程序来说，相比于在I/O请求发生时创建线程来说，使用完成端口(s)它就可以做的更快且更有效率。

The CreateIoCompletionPort function associates an I/O completion port with one or more file handles. When an asynchronous I/O operation started on a file handle associated with a completion port is completed, an I/O completion packet is queued to the port. This can be used to combine the synchronization point for multiple file handles into a single object. pcMing工作室{ oQ
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CreateIoCompletionPort函数会使一个I/O完成端口与一个或多个文件句柄发生关联。当与一个完成端口相关的文件句柄上启动的异步I/O操作完成时，一个I/O完成包就会进入到该完成端口的队列中。对于多个文件句柄来说，就可以把这些多个文件句柄合并成一个单独的对象，这个可以被用来结合同步点？ pcMing工作室 t9q.d(Jp*~

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A thread uses the GetQueuedCompletionStatus function to wait for a completion packet to be queued to the completion port, rather than waiting directly for the asynchronous I/O to complete. Threads that block their execution on a completion port are released in last-in-first-out (LIFO) order. This means that when a completion packet is queued to the completion port, the system releases the last thread to block its execution on the port.

调用 GetQueuedCompletionStatus函数，某个线程就会等待一个完成包进入到完成端口的队列中，而不是直接等待异步I/O请求完成。线程（们）就会阻塞于它们的运行在完成端口（按照后进先出队列顺序的被释放）。这就意味着当一个完成包进入到完成端口的队列中时，系统会释放最近被阻塞在该完成端口的线程。

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When a thread calls GetQueuedCompletionStatus, it is associated with the specified completion port until it exits, specifies a different completion port, or frees the completion port. A thread can be associated with at most one completion port.

调用GetQueuedCompletionStatus，线程就会将会与某个指定的完成端口建立联系，一直延续其该线程的存在周期，或被指定了不同的完成端口，或者释放了与完成端口的联系。一个线程只能与最多不超过一个的完成端口发生联系。

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