libc-bottom-half/cloudlibc/src/common/time.h

   1 // Copyright (c) 2015-2016 Nuxi, https://nuxi.nl/
   2 //
   3 // SPDX-License-Identifier: BSD-2-Clause
   4
   5 #ifndef COMMON_TIME_H
   6 #define COMMON_TIME_H
   7
   8 #include <common/limits.h>
   9 #include <common/overflow.h>
  10
  11 #include <sys/time.h>
  12
  13 #include <wasi/core.h>
  14 #include <stdbool.h>
  15 #include <time.h>
  16
  17 #define NSEC_PER_SEC 1000000000
  18
  19 // Timezone agnostic conversion routines.
  20 int __localtime_utc(time_t, struct tm *);
  21 void __mktime_utc(const struct tm *, struct timespec *);
  22
  23 static inline bool is_leap(time_t year) {
  24   year %= 400;
  25   if (year < 0)
  26     year += 400;
  27   return ((year % 4) == 0 && (year % 100) != 0) || year == 100;
  28 }
  29
  30 // Gets the length of the months in a year.
  31 static inline const char *get_months(time_t year) {
  32   static const char leap[12] = {
  33       31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
  34   };
  35   static const char common[12] = {
  36       31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
  37   };
  38   return is_leap(year) ? leap : common;
  39 }
  40
  41 // Gets the cumulative length of the months in a year.
  42 static inline const short *get_months_cumulative(time_t year) {
  43   static const short leap[13] = {
  44       0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366,
  45   };
  46   static const short common[13] = {
  47       0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365,
  48   };
  49   return is_leap(year) ? leap : common;
  50 }
  51
  52 static inline short get_ydays(time_t year) {
  53   return is_leap(year) ? 366 : 365;
  54 }
  55
  56 static inline bool timespec_to_timestamp_exact(
  57     const struct timespec *timespec, __wasi_timestamp_t *timestamp) {
  58   // Invalid nanoseconds field.
  59   if (timespec->tv_nsec < 0 || timespec->tv_nsec >= NSEC_PER_SEC)
  60     return false;
  61
  62   // Timestamps before the Epoch are not supported.
  63   if (timespec->tv_sec < 0)
  64     return false;
  65
  66   // Make sure our timestamp does not overflow.
  67   return !mul_overflow(timespec->tv_sec, NSEC_PER_SEC, timestamp) &&
  68          !add_overflow(*timestamp, timespec->tv_nsec, timestamp);
  69 }
  70
  71 static inline bool timespec_to_timestamp_clamp(
  72     const struct timespec *timespec, __wasi_timestamp_t *timestamp) {
  73   // Invalid nanoseconds field.
  74   if (timespec->tv_nsec < 0 || timespec->tv_nsec >= NSEC_PER_SEC)
  75     return false;
  76
  77   if (timespec->tv_sec < 0) {
  78     // Timestamps before the Epoch are not supported.
  79     *timestamp = 0;
  80   } else if (mul_overflow(timespec->tv_sec, NSEC_PER_SEC, timestamp) ||
  81              add_overflow(*timestamp, timespec->tv_nsec, timestamp)) {
  82     // Make sure our timestamp does not overflow.
  83     *timestamp = NUMERIC_MAX(__wasi_timestamp_t);
  84   }
  85   return true;
  86 }
  87
  88 static inline struct timespec timestamp_to_timespec(
  89     __wasi_timestamp_t timestamp) {
  90   // Decompose timestamp into seconds and nanoseconds.
  91   return (struct timespec){.tv_sec = timestamp / NSEC_PER_SEC,
  92                            .tv_nsec = timestamp % NSEC_PER_SEC};
  93 }
  94
  95 static inline struct timeval timestamp_to_timeval(
  96     __wasi_timestamp_t timestamp) {
  97   struct timespec ts = timestamp_to_timespec(timestamp);
  98   return (struct timeval){.tv_sec = ts.tv_sec, ts.tv_nsec / 1000};
  99 }
 100
 101 #endif