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3rdparty/c-ares-1.18.1/src/lib/ares_fds.c 1.92 KB
73ef4ff3   Hu Chunming   提交三方库
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  /* Copyright 1998 by the Massachusetts Institute of Technology.
   *
   * Permission to use, copy, modify, and distribute this
   * software and its documentation for any purpose and without
   * fee is hereby granted, provided that the above copyright
   * notice appear in all copies and that both that copyright
   * notice and this permission notice appear in supporting
   * documentation, and that the name of M.I.T. not be used in
   * advertising or publicity pertaining to distribution of the
   * software without specific, written prior permission.
   * M.I.T. makes no representations about the suitability of
   * this software for any purpose.  It is provided "as is"
   * without express or implied warranty.
   */
  
  #include "ares_setup.h"
  
  #include "ares.h"
  #include "ares_nowarn.h"
  #include "ares_private.h"
  
  int ares_fds(ares_channel channel, fd_set *read_fds, fd_set *write_fds)
  {
    struct server_state *server;
    ares_socket_t nfds;
    int i;
  
    /* Are there any active queries? */
    int active_queries = !ares__is_list_empty(&(channel->all_queries));
  
    nfds = 0;
    for (i = 0; i < channel->nservers; i++)
      {
        server = &channel->servers[i];
        /* We only need to register interest in UDP sockets if we have
         * outstanding queries.
         */
        if (active_queries && server->udp_socket != ARES_SOCKET_BAD)
          {
            FD_SET(server->udp_socket, read_fds);
            if (server->udp_socket >= nfds)
              nfds = server->udp_socket + 1;
          }
        /* We always register for TCP events, because we want to know
         * when the other side closes the connection, so we don't waste
         * time trying to use a broken connection.
         */
        if (server->tcp_socket != ARES_SOCKET_BAD)
         {
           FD_SET(server->tcp_socket, read_fds);
           if (server->qhead)
             FD_SET(server->tcp_socket, write_fds);
           if (server->tcp_socket >= nfds)
             nfds = server->tcp_socket + 1;
  	}
      }
    return (int)nfds;
  }