contrib/ntp/sntp/timing.c

   1 /*  Copyright (C) 1996 N.M. Maclaren
   2     Copyright (C) 1996 The University of Cambridge
   3
   4 This includes all of the code needed to handle the time.  It assumes rather
   5 more than is defined by POSIX, unfortunately.  Systems that do not have the
   6 'X/Open' extensions may need changes. */
   7
   8
   9
  10 #include "header.h"
  11
  12 #include <sys/types.h>
  13 #include <sys/time.h>
  14
  15 #define TIMING
  16 #include "kludges.h"
  17 #undef TIMING
  18
  19
  20
  21 #define MILLION_L    1000000l          /* For conversion to/from timeval */
  22 #define MILLION_D       1.0e6          /* Must be equal to MILLION_L */
  23
  24
  25
  26 double current_time (double offset) {
  27
  28 /* Get the current UTC time in seconds since the Epoch plus an offset (usually
  29 the time from the beginning of the century to the Epoch!) */
  30
  31     struct timeval current;
  32
  33     errno = 0;
  34     if (gettimeofday(&current,NULL))
  35         fatal(1,"unable to read current machine/system time",NULL);
  36     return offset+current.tv_sec+1.0e-6*current.tv_usec;
  37 }
  38
  39
  40
  41 time_t convert_time (double value, int *millisecs) {
  42
  43 /* Convert the time to the ANSI C form. */
  44
  45     time_t result = (time_t)value;
  46
  47     if ((*millisecs = (int)(1000.0*(value-result))) >= 1000) {
  48         *millisecs = 0;
  49         ++result;
  50     }
  51     return result;
  52 }
  53
  54
  55
  56 void adjust_time (double difference, int immediate, double ignore) {
  57
  58 /* Adjust the current UTC time.  This is portable, even if struct timeval uses
  59 an unsigned long for tv_sec. */
  60
  61     struct timeval old, new, adjust, previous;
  62     char text[40];
  63     long n;
  64
  65 /* Start by converting to timeval format. Note that we have to cater for
  66 negative, unsigned values. */
  67
  68     if ((n = (long)difference) > difference) --n;
  69     adjust.tv_sec = n;
  70     adjust.tv_usec = (long)(MILLION_D*(difference-n));
  71     errno = 0;
  72     if (gettimeofday(&old,NULL))
  73         fatal(1,"unable to read machine/system time",NULL);
  74     new.tv_sec = old.tv_sec+adjust.tv_sec;
  75     new.tv_usec = (n = (long)old.tv_usec+(long)adjust.tv_usec);
  76     if (n < 0) {
  77         new.tv_usec += MILLION_L;
  78         --new.tv_sec;
  79     } else if (n >= MILLION_L) {
  80         new.tv_usec -= MILLION_L;
  81         ++new.tv_sec;
  82     }
  83
  84 /* Now diagnose the situation if necessary, and perform the dirty deed. */
  85
  86     if (verbose > 2)
  87         fprintf(stderr,
  88             "Times: old=(%ld,%.6ld) new=(%ld,%.6ld) adjust=(%ld,%.6ld)\n",
  89             (long)old.tv_sec,(long)old.tv_usec,
  90             (long)new.tv_sec,(long)new.tv_usec,
  91             (long)adjust.tv_sec,(long)adjust.tv_usec);
  92     if (immediate) {
  93         errno = 0;
  94         if (settimeofday(&new,NULL))
  95             fatal(1,"unable to reset current system time",NULL);
  96     } else {
  97         previous.tv_sec  = 0;
  98         previous.tv_usec = 0;
  99         errno = 0;
 100         if (adjtime(&adjust,&previous))
 101             fatal(1,"unable to adjust current system time",NULL);
 102         if (previous.tv_sec != 0 || previous.tv_usec != 0) {
 103             sprintf(text,"(%ld,%.6ld)",
 104                 (long)previous.tv_sec,(long)previous.tv_usec);
 105             if (previous.tv_sec+1.0e-6*previous.tv_usec > ignore)
 106                 fatal(0,"outstanding time adjustment %s",text);
 107             else if (verbose)
 108                 fprintf(stderr,"%s: outstanding time adjustment %s\n",
 109                     argv0,text);
 110         }
 111     }
 112 }