看到别人写的一段IOCP代码

if (SI->BytesRECV > SI->BytesSEND)
   {

      // Post another WSASend() request.
      // Since WSASend() is not gauranteed to send all of the bytes requested,
      // continue posting WSASend() calls until all received bytes are sent.

      ZeroMemory(&(SI->Overlapped), sizeof(WSAOVERLAPPED));

      SI->DataBuf.buf = SI->Buffer + SI->BytesSEND;
      SI->DataBuf.len = SI->BytesRECV - SI->BytesSEND;

      if (WSASend(SI->Socket, &(SI->DataBuf), 1, &SendBytes, 0,
         &(SI->Overlapped), WorkerRoutine) == SOCKET_ERROR)
      {
         if (WSAGetLastError() != WSA_IO_PENDING)
         {
            printf("WSASend() failed with error %d\n", WSAGetLastError());
            return;
         }
      }
   }