libc/src/time/time_utils.h

   1 //===-- Collection of utils for mktime and friends --------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC_TIME_TIME_UTILS_H
  10 #define LLVM_LIBC_SRC_TIME_TIME_UTILS_H
  11
  12 #include <stddef.h> // For size_t.
  13
  14 #include "src/__support/common.h"
  15 #include "src/errno/libc_errno.h"
  16 #include "src/time/mktime.h"
  17
  18 #include <stdint.h>
  19
  20 namespace __llvm_libc {
  21 namespace time_utils {
  22
  23 enum Month : int {
  24   JANUARY,
  25   FEBRUARY,
  26   MARCH,
  27   APRIL,
  28   MAY,
  29   JUNE,
  30   JULY,
  31   AUGUST,
  32   SEPTEMBER,
  33   OCTOBER,
  34   NOVEMBER,
  35   DECEMBER
  36 };
  37
  38 struct TimeConstants {
  39   static constexpr int SECONDS_PER_MIN = 60;
  40   static constexpr int MINUTES_PER_HOUR = 60;
  41   static constexpr int HOURS_PER_DAY = 24;
  42   static constexpr int DAYS_PER_WEEK = 7;
  43   static constexpr int MONTHS_PER_YEAR = 12;
  44   static constexpr int DAYS_PER_NON_LEAP_YEAR = 365;
  45   static constexpr int DAYS_PER_LEAP_YEAR = 366;
  46
  47   static constexpr int SECONDS_PER_HOUR = SECONDS_PER_MIN * MINUTES_PER_HOUR;
  48   static constexpr int SECONDS_PER_DAY = SECONDS_PER_HOUR * HOURS_PER_DAY;
  49   static constexpr int NUMBER_OF_SECONDS_IN_LEAP_YEAR =
  50       DAYS_PER_LEAP_YEAR * SECONDS_PER_DAY;
  51
  52   static constexpr int TIME_YEAR_BASE = 1900;
  53   static constexpr int EPOCH_YEAR = 1970;
  54   static constexpr int EPOCH_WEEK_DAY = 4;
  55
  56   // For asctime the behavior is undefined if struct tm's tm_wday or tm_mon are
  57   // not within the normal ranges as defined in <time.h>, or if struct tm's
  58   // tm_year exceeds {INT_MAX}-1990, or if the below asctime_internal algorithm
  59   // would attempt to generate more than 26 bytes of output (including the
  60   // terminating null).
  61   static constexpr int ASCTIME_BUFFER_SIZE = 256;
  62   static constexpr int ASCTIME_MAX_BYTES = 26;
  63
  64   /* 2000-03-01 (mod 400 year, immediately after feb29 */
  65   static constexpr int64_t SECONDS_UNTIL2000_MARCH_FIRST =
  66       (946684800LL + SECONDS_PER_DAY * (31 + 29));
  67   static constexpr int WEEK_DAY_OF2000_MARCH_FIRST = 3;
  68
  69   static constexpr int DAYS_PER400_YEARS =
  70       (DAYS_PER_NON_LEAP_YEAR * 400) + (400 / 4) - 3;
  71   static constexpr int DAYS_PER100_YEARS =
  72       (DAYS_PER_NON_LEAP_YEAR * 100) + (100 / 4) - 1;
  73   static constexpr int DAYS_PER4_YEARS = (DAYS_PER_NON_LEAP_YEAR * 4) + 1;
  74
  75   // The latest time that can be represented in this form is 03:14:07 UTC on
  76   // Tuesday, 19 January 2038 (corresponding to 2,147,483,647 seconds since the
  77   // start of the epoch). This means that systems using a 32-bit time_t type are
  78   // susceptible to the Year 2038 problem.
  79   static constexpr int END_OF32_BIT_EPOCH_YEAR = 2038;
  80
  81   static constexpr time_t OUT_OF_RANGE_RETURN_VALUE = -1;
  82 };
  83
  84 // Update the "tm" structure's year, month, etc. members from seconds.
  85 // "total_seconds" is the number of seconds since January 1st, 1970.
  86 extern int64_t update_from_seconds(int64_t total_seconds, struct tm *tm);
  87
  88 // TODO(michaelrj): move these functions to use ErrorOr instead of setting
  89 // errno. They always accompany a specific return value so we only need the one
  90 // variable.
  91
  92 // POSIX.1-2017 requires this.
  93 LIBC_INLINE time_t out_of_range() {
  94   libc_errno = EOVERFLOW;
  95   return static_cast<time_t>(-1);
  96 }
  97
  98 LIBC_INLINE void invalid_value() { libc_errno = EINVAL; }
  99
 100 LIBC_INLINE char *asctime(const struct tm *timeptr, char *buffer,
 101                           size_t bufferLength) {
 102   if (timeptr == nullptr || buffer == nullptr) {
 103     invalid_value();
 104     return nullptr;
 105   }
 106   if (timeptr->tm_wday < 0 ||
 107       timeptr->tm_wday > (TimeConstants::DAYS_PER_WEEK - 1)) {
 108     invalid_value();
 109     return nullptr;
 110   }
 111   if (timeptr->tm_mon < 0 ||
 112       timeptr->tm_mon > (TimeConstants::MONTHS_PER_YEAR - 1)) {
 113     invalid_value();
 114     return nullptr;
 115   }
 116
 117   // TODO(rtenneti): i18n the following strings.
 118   static const char *week_days_name[TimeConstants::DAYS_PER_WEEK] = {
 119       "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
 120
 121   static const char *months_name[TimeConstants::MONTHS_PER_YEAR] = {
 122       "Jan", "Feb", "Mar", "Apr", "May", "Jun",
 123       "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
 124
 125   // TODO(michaelr): look into removing this call to __builtin_snprintf that may
 126   // be emitted as a call to snprintf. Alternatively, look into using our
 127   // internal printf machinery.
 128   int written_size = __builtin_snprintf(
 129       buffer, bufferLength, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
 130       week_days_name[timeptr->tm_wday], months_name[timeptr->tm_mon],
 131       timeptr->tm_mday, timeptr->tm_hour, timeptr->tm_min, timeptr->tm_sec,
 132       TimeConstants::TIME_YEAR_BASE + timeptr->tm_year);
 133   if (written_size < 0)
 134     return nullptr;
 135   if (static_cast<size_t>(written_size) >= bufferLength) {
 136     out_of_range();
 137     return nullptr;
 138   }
 139   return buffer;
 140 }
 141
 142 LIBC_INLINE struct tm *gmtime_internal(const time_t *timer, struct tm *result) {
 143   int64_t seconds = *timer;
 144   // Update the tm structure's year, month, day, etc. from seconds.
 145   if (update_from_seconds(seconds, result) < 0) {
 146     out_of_range();
 147     return nullptr;
 148   }
 149
 150   return result;
 151 }
 152
 153 } // namespace time_utils
 154 } // namespace __llvm_libc
 155
 156 #endif // LLVM_LIBC_SRC_TIME_TIME_UTILS_H