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POWhen are IO completion port packets sent and when not?
 

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    <p>I'm currently working on an IPC mechanism based on named pipes using a IO completion port.</p> <p>Unfortunately I have some troubles with the msdn documentation because it's quite unclear to me in which cases calls to ReadFile/WriteFile result in a completion packet.</p> <p>The case when FALSE is returned with ERROR_IO_PENDING is clear, but what about the apparently possible case, when ERROR_MORE_DATA is returned? Will there be a completion packet in this case? Moreover, what if other errors are returned? In which cases do i have to handle the result and free resources directly and not in the completion handler?</p> <p>Another case would be if ReadFile/WriteFile even succeed, which apparently is possible, too. MSDN is thankfully pretty clear about this <a href="http://msdn.microsoft.com/en-us/library/aa365683%28v=VS.85%29.aspx" rel="nofollow noreferrer">here</a>:</p> <blockquote> <p>Further, the WriteFile function will sometimes return TRUE with a GetLastError value of ERROR_SUCCESS, even though it is using an asynchronous handle (which can also return FALSE with ERROR_IO_PENDING). ... In this example, the recommendation would be to allow the completion port routine to be solely responsible for all freeing operations for such resources.</p> </blockquote> <p>Is this recommendation correct in all cases, and the result of an ReadFile/WriteFile operation for handles assigned to a completion port could (and should) in fact be ignored completely, because a packet is sent to the port anyways?</p>
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