在win平台如何将select操作变成异步基于iocp的一种办法

sevencat

这个巧妙的做法是取得socket底层的afd的句柄，然后将select的调用变成NtDeviceIoControlFile调用，就可以跟iocp进行关联起来了。
有人可能说这个没有用，这个的用处在于使用第三方库。
注：在xp,2003平台上无效，具体原因看代码。

int uv_poll_init_socket(uv_loop_t* loop, uv_poll_t* handle,
    uv_os_sock_t socket) {
  WSAPROTOCOL_INFOW protocol_info;
  int len;
  SOCKET peer_socket, base_socket;
  DWORD bytes;
  DWORD yes = 1;

  /* Set the socket to nonblocking mode */
  if (ioctlsocket(socket, FIONBIO, &yes) == SOCKET_ERROR)
    return uv_translate_sys_error(WSAGetLastError());

  /* Try to obtain a base handle for the socket. This increases this chances */
  /* that we find an AFD handle and are able to use the fast poll mechanism. */
  /* This will always fail on windows XP/2k3, since they don't support the */
  /* SIO_BASE_HANDLE ioctl. */
#ifndef NDEBUG
  base_socket = INVALID_SOCKET;
#endif

  if (WSAIoctl(socket,
               SIO_BASE_HANDLE,
               NULL,
               0,
               &base_socket,
               sizeof base_socket,
               &bytes,
               NULL,
               NULL) == 0) {
    assert(base_socket != 0 && base_socket != INVALID_SOCKET);
    socket = base_socket;
  }

  uv__handle_init(loop, (uv_handle_t*) handle, UV_POLL);
  handle->socket = socket;
  handle->events = 0;

  /* Obtain protocol information about the socket. */
  len = sizeof protocol_info;
  if (getsockopt(socket,
                 SOL_SOCKET,
                 SO_PROTOCOL_INFOW,
                 (char*) &protocol_info,
                 &len) != 0) {
    return uv_translate_sys_error(WSAGetLastError());
  }

  /* Get the peer socket that is needed to enable fast poll. If the returned */
  /* value is NULL, the protocol is not implemented by MSAFD and we'll have */
  /* to use slow mode. */
  peer_socket = uv__fast_poll_get_peer_socket(loop, &protocol_info);

  if (peer_socket != INVALID_SOCKET) {
    /* Initialize fast poll specific fields. */
    handle->peer_socket = peer_socket;
  } else {
    /* Initialize slow poll specific fields. */
    handle->flags |= UV_HANDLE_POLL_SLOW;
  }

  /* Initialize 2 poll reqs. */
  handle->submitted_events_1 = 0;
  uv_req_init(loop, (uv_req_t*) &(handle->poll_req_1));
  handle->poll_req_1.type = UV_POLL_REQ;
  handle->poll_req_1.data = handle;

  handle->submitted_events_2 = 0;
  uv_req_init(loop, (uv_req_t*) &(handle->poll_req_2));
  handle->poll_req_2.type = UV_POLL_REQ;
  handle->poll_req_2.data = handle;

  return 0;
}



static void uv__fast_poll_submit_poll_req(uv_loop_t* loop, uv_poll_t* handle) {
  uv_req_t* req;
  AFD_POLL_INFO* afd_poll_info;
  DWORD result;

  /* Find a yet unsubmitted req to submit. */
  if (handle->submitted_events_1 == 0) {
    req = &handle->poll_req_1;
    afd_poll_info = &handle->afd_poll_info_1;
    handle->submitted_events_1 = handle->events;
    handle->mask_events_1 = 0;
    handle->mask_events_2 = handle->events;
  } else if (handle->submitted_events_2 == 0) {
    req = &handle->poll_req_2;
    afd_poll_info = &handle->afd_poll_info_2;
    handle->submitted_events_2 = handle->events;
    handle->mask_events_1 = handle->events;
    handle->mask_events_2 = 0;
  } else {
    assert(0);
    return;
  }

  /* Setting Exclusive to TRUE makes the other poll request return if there */
  /* is any. */
  afd_poll_info->Exclusive = TRUE;
  afd_poll_info->NumberOfHandles = 1;
  afd_poll_info->Timeout.QuadPart = INT64_MAX;
  afd_poll_info->Handles[0].Handle = (HANDLE) handle->socket;
  afd_poll_info->Handles[0].Status = 0;
  afd_poll_info->Handles[0].Events = 0;

  if (handle->events & UV_READABLE) {
    afd_poll_info->Handles[0].Events |= AFD_POLL_RECEIVE |
        AFD_POLL_DISCONNECT | AFD_POLL_ACCEPT | AFD_POLL_ABORT;
  }
  if (handle->events & UV_WRITABLE) {
    afd_poll_info->Handles[0].Events |= AFD_POLL_SEND | AFD_POLL_CONNECT_FAIL;
  }

  memset(&req->u.io.overlapped, 0, sizeof req->u.io.overlapped);

  result = uv_msafd_poll((SOCKET) handle->peer_socket,
                         afd_poll_info,
                         afd_poll_info,
                         &req->u.io.overlapped);
  if (result != 0 && WSAGetLastError() != WSA_IO_PENDING) {
    /* Queue this req, reporting an error. */
    SET_REQ_ERROR(req, WSAGetLastError());
    uv_insert_pending_req(loop, req);
  }
}


int WSAAPI uv_msafd_poll(SOCKET socket, AFD_POLL_INFO* info_in,
    AFD_POLL_INFO* info_out, OVERLAPPED* overlapped) {
  IO_STATUS_BLOCK iosb;
  IO_STATUS_BLOCK* iosb_ptr;
  HANDLE event = NULL;
  void* apc_context;
  NTSTATUS status;
  DWORD error;

  if (overlapped != NULL) {
    /* Overlapped operation. */
    iosb_ptr = (IO_STATUS_BLOCK*) &overlapped->Internal;
    event = overlapped->hEvent;

    /* Do not report iocp completion if hEvent is tagged. */
    if ((uintptr_t) event & 1) {
      event = (HANDLE)((uintptr_t) event & ~(uintptr_t) 1);
      apc_context = NULL;
    } else {
      apc_context = overlapped;
    }

  } else {
    /* Blocking operation. */
    iosb_ptr = &iosb;
    event = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (event == NULL) {
      return SOCKET_ERROR;
    }
    apc_context = NULL;
  }

  iosb_ptr->Status = STATUS_PENDING;
  status = pNtDeviceIoControlFile((HANDLE) socket,
                                  event,
                                  NULL,
                                  apc_context,
                                  iosb_ptr,
                                  IOCTL_AFD_POLL,
                                  info_in,
                                  sizeof *info_in,
                                  info_out,
                                  sizeof *info_out);

  if (overlapped == NULL) {
    /* If this is a blocking operation, wait for the event to become */
    /* signaled, and then grab the real status from the io status block. */
    if (status == STATUS_PENDING) {
      DWORD r = WaitForSingleObject(event, INFINITE);

      if (r == WAIT_FAILED) {
        DWORD saved_error = GetLastError();
        CloseHandle(event);
        WSASetLastError(saved_error);
        return SOCKET_ERROR;
      }

      status = iosb.Status;
    }

    CloseHandle(event);
  }

  switch (status) {
    case STATUS_SUCCESS:
      error = ERROR_SUCCESS;
      break;

    case STATUS_PENDING:
      error = WSA_IO_PENDING;
      break;

    default:
      error = uv_ntstatus_to_winsock_error(status);
      break;
  }

  WSASetLastError(error);

  if (error == ERROR_SUCCESS) {
    return 0;
  } else {
    return SOCKET_ERROR;
  }
}

winston

没想过这个方案，确实有一套！