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timespec_str.c 1.6KB

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  1. /*
  2. * We also need to set the value high enough to signal inclusion of
  3. * newer features (like clock_gettime). See the POSIX spec for more info:
  4. * http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_02_01_02
  5. *
  6. * This file is Copyright (c) 2010-2018 by the GPSD project
  7. * SPDX-License-Identifier: BSD-2-clause
  8. */
  9. #include "gpsd_config.h" /* must be before all includes */
  10. #include <ctype.h>
  11. #include <errno.h>
  12. #include <math.h>
  13. #include <stdio.h>
  14. #include <stdlib.h>
  15. #include <string.h>
  16. #include <sys/time.h>
  17. #include <time.h>
  18. #include "timespec.h"
  19. /* Convert a normalized timespec to a nice string
  20. * put in it *buf, buf should be at least 22 bytes
  21. *
  22. * the returned buffer will look like, shortest case:
  23. * sign character ' ' or '-'
  24. * one digit of seconds
  25. * decmal point '.'
  26. * 9 digits of nanoSec
  27. *
  28. * So 12 chars, like this: "-0.123456789"
  29. *
  30. * Probable worst case is 10 digits of seconds,
  31. * but standards do not provide hard limits to time_t
  32. * So 21 characters like this: "-2147483647.123456789"
  33. *
  34. * date --date='@2147483647' is: Mon Jan 18 19:14:07 PST 2038
  35. * date --date='@9999999999' is: Sat Nov 20 09:46:39 PST 2286
  36. *
  37. */
  38. const char *timespec_str(const struct timespec *ts, char *buf, size_t buf_size)
  39. {
  40. char sign = ' ';
  41. if (!TS_GEZ(ts)) {
  42. sign = '-';
  43. }
  44. /* %lld and (long long) because some time_t is bigger than a long
  45. * mostly on 32-bit systems. */
  46. (void)snprintf(buf, buf_size, "%c%lld.%09ld",
  47. sign,
  48. (long long)llabs(ts->tv_sec),
  49. (long)labs(ts->tv_nsec));
  50. return buf;
  51. }
  52. /* end */