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      1 
      2 /* Copyright (C) 2008 by Daniel Stenberg et al
      3  *
      4  * Permission to use, copy, modify, and distribute this software and its
      5  * documentation for any purpose and without fee is hereby granted, provided
      6  * that the above copyright notice appear in all copies and that both that
      7  * copyright notice and this permission notice appear in supporting
      8  * documentation, and that the name of M.I.T. not be used in advertising or
      9  * publicity pertaining to distribution of the software without specific,
     10  * written prior permission.  M.I.T. makes no representations about the
     11  * suitability of this software for any purpose.  It is provided "as is"
     12  * without express or implied warranty.
     13  */
     14 
     15 #include "ares_setup.h"
     16 #include "ares.h"
     17 #include "ares_private.h"
     18 
     19 #if defined(WIN32) && !defined(MSDOS)
     20 
     21 struct timeval ares__tvnow(void)
     22 {
     23   /*
     24   ** GetTickCount() is available on _all_ Windows versions from W95 up
     25   ** to nowadays. Returns milliseconds elapsed since last system boot,
     26   ** increases monotonically and wraps once 49.7 days have elapsed.
     27   */
     28   struct timeval now;
     29   DWORD milliseconds = GetTickCount();
     30   now.tv_sec = milliseconds / 1000;
     31   now.tv_usec = (milliseconds % 1000) * 1000;
     32   return now;
     33 }
     34 
     35 #elif defined(HAVE_CLOCK_GETTIME_MONOTONIC)
     36 
     37 struct timeval ares__tvnow(void)
     38 {
     39   /*
     40   ** clock_gettime() is granted to be increased monotonically when the
     41   ** monotonic clock is queried. Time starting point is unspecified, it
     42   ** could be the system start-up time, the Epoch, or something else,
     43   ** in any case the time starting point does not change once that the
     44   ** system has started up.
     45   */
     46   struct timeval now;
     47   struct timespec tsnow;
     48   if(0 == clock_gettime(CLOCK_MONOTONIC, &tsnow)) {
     49     now.tv_sec = tsnow.tv_sec;
     50     now.tv_usec = tsnow.tv_nsec / 1000;
     51   }
     52   /*
     53   ** Even when the configure process has truly detected monotonic clock
     54   ** availability, it might happen that it is not actually available at
     55   ** run-time. When this occurs simply fallback to other time source.
     56   */
     57 #ifdef HAVE_GETTIMEOFDAY
     58   else
     59     (void)gettimeofday(&now, NULL);
     60 #else
     61   else {
     62     now.tv_sec = (long)time(NULL);
     63     now.tv_usec = 0;
     64   }
     65 #endif
     66   return now;
     67 }
     68 
     69 #elif defined(HAVE_GETTIMEOFDAY)
     70 
     71 struct timeval ares__tvnow(void)
     72 {
     73   /*
     74   ** gettimeofday() is not granted to be increased monotonically, due to
     75   ** clock drifting and external source time synchronization it can jump
     76   ** forward or backward in time.
     77   */
     78   struct timeval now;
     79   (void)gettimeofday(&now, NULL);
     80   return now;
     81 }
     82 
     83 #else
     84 
     85 struct timeval ares__tvnow(void)
     86 {
     87   /*
     88   ** time() returns the value of time in seconds since the Epoch.
     89   */
     90   struct timeval now;
     91   now.tv_sec = (long)time(NULL);
     92   now.tv_usec = 0;
     93   return now;
     94 }
     95 
     96 #endif
     97 
     98 #if 0 /* Not used */
     99 /*
    100  * Make sure that the first argument is the more recent time, as otherwise
    101  * we'll get a weird negative time-diff back...
    102  *
    103  * Returns: the time difference in number of milliseconds.
    104  */
    105 long ares__tvdiff(struct timeval newer, struct timeval older)
    106 {
    107   return (newer.tv_sec-older.tv_sec)*1000+
    108     (newer.tv_usec-older.tv_usec)/1000;
    109 }
    110 #endif
    111 
    112