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      1 
      2 /* Copyright 1998 by the Massachusetts Institute of Technology.
      3  *
      4  * Permission to use, copy, modify, and distribute this
      5  * software and its documentation for any purpose and without
      6  * fee is hereby granted, provided that the above copyright
      7  * notice appear in all copies and that both that copyright
      8  * notice and this permission notice appear in supporting
      9  * documentation, and that the name of M.I.T. not be used in
     10  * advertising or publicity pertaining to distribution of the
     11  * software without specific, written prior permission.
     12  * M.I.T. makes no representations about the suitability of
     13  * this software for any purpose.  It is provided "as is"
     14  * without express or implied warranty.
     15  */
     16 
     17 #include "ares_setup.h"
     18 
     19 #ifdef HAVE_SYS_TIME_H
     20 #include <sys/time.h>
     21 #endif
     22 
     23 #include <time.h>
     24 
     25 #include "ares.h"
     26 #include "ares_private.h"
     27 
     28 /* WARNING: Beware that this is linear in the number of outstanding
     29  * requests! You are probably far better off just calling ares_process()
     30  * once per second, rather than calling ares_timeout() to figure out
     31  * when to next call ares_process().
     32  */
     33 struct timeval *ares_timeout(ares_channel channel, struct timeval *maxtv,
     34                              struct timeval *tvbuf)
     35 {
     36   struct query *query;
     37   struct list_node* list_head;
     38   struct list_node* list_node;
     39   struct timeval now;
     40   struct timeval nextstop;
     41   long offset, min_offset;
     42 
     43   /* No queries, no timeout (and no fetch of the current time). */
     44   if (ares__is_list_empty(&(channel->all_queries)))
     45     return maxtv;
     46 
     47   /* Find the minimum timeout for the current set of queries. */
     48   now = ares__tvnow();
     49   min_offset = -1;
     50 
     51   list_head = &(channel->all_queries);
     52   for (list_node = list_head->next; list_node != list_head;
     53        list_node = list_node->next)
     54     {
     55       query = list_node->data;
     56       if (query->timeout.tv_sec == 0)
     57         continue;
     58       offset = ares__timeoffset(&now, &query->timeout);
     59       if (offset < 0)
     60         offset = 0;
     61       if (min_offset == -1 || offset < min_offset)
     62         min_offset = offset;
     63     }
     64 
     65   if(min_offset != -1) {
     66     nextstop.tv_sec = min_offset/1000;
     67     nextstop.tv_usec = (min_offset%1000)*1000;
     68   }
     69 
     70   /* If we found a minimum timeout and it's sooner than the one specified in
     71    * maxtv (if any), return it.  Otherwise go with maxtv.
     72    */
     73   if (min_offset != -1 && (!maxtv || ares__timedout(maxtv, &nextstop)))
     74     {
     75       *tvbuf = nextstop;
     76       return tvbuf;
     77     }
     78   else
     79     return maxtv;
     80 }
     81