unix4lyfe git - darkstat/blob - now.c

   1 /* darkstat 3
   2  * copyright (c) 2012 Emil Mikulic.
   3  *
   4  * now.c: a cache of the current time.
   5  *
   6  * Permission to use, copy, modify, and distribute this file for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18 #include "err.h"
  19 #include "now.h"
  20
  21 #include <assert.h>
  22 #include <string.h>
  23 #include <time.h>
  24
  25 static struct timespec clock_real, clock_mono;
  26 static int now_initialized = 0;
  27
  28 long now_real(void) {
  29    assert(now_initialized);
  30    return clock_real.tv_sec;
  31 }
  32
  33 long now_mono(void) {
  34    assert(now_initialized);
  35    return clock_mono.tv_sec;
  36 }
  37
  38 static int before(const struct timespec *a, const struct timespec *b) {
  39    if (a->tv_sec < b->tv_sec)
  40       return 1;
  41    if (a->tv_sec == b->tv_sec && a->tv_nsec < b->tv_nsec)
  42       return 1;
  43    return 0;
  44 }
  45
  46 static void clock_update(const clockid_t clk_id,
  47                          struct timespec *dest,
  48                          const char *name) {
  49    struct timespec t;
  50
  51    clock_gettime(clk_id, &t);
  52    if (now_initialized && before(&t, dest)) {
  53       verbosef("%s clock went backwards from %ld.%09ld to %ld.%09ld",
  54                name,
  55                (long)dest->tv_sec,
  56                (long)dest->tv_nsec,
  57                (long)t.tv_sec,
  58                (long)t.tv_nsec);
  59    }
  60    memcpy(dest, &t, sizeof(t));
  61 }
  62
  63 static void all_clocks_update(void) {
  64    clock_update(CLOCK_REALTIME,  &clock_real, "realtime");
  65    clock_update(CLOCK_MONOTONIC, &clock_mono, "monotonic");
  66 }
  67
  68 void now_init(void) {
  69    assert(!now_initialized);
  70    all_clocks_update();
  71    now_initialized = 1;
  72 }
  73
  74 void now_update(void) {
  75    assert(now_initialized);
  76    all_clocks_update();
  77 }
  78
  79 long mono_to_real(const long t) {
  80    assert(now_initialized);
  81    return t - clock_mono.tv_sec + clock_real.tv_sec;
  82 }
  83
  84 long real_to_mono(const long t) {
  85    assert(now_initialized);
  86    return t - clock_real.tv_sec + clock_mono.tv_sec;
  87 }
  88
  89 /* vim:set ts=3 sw=3 tw=80 et: */