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/__support/macros/config.h"
  16 #include "src/errno/libc_errno.h"
  17 #include "src/time/mktime.h"
  18
  19 #include <stdint.h>
  20
  21 namespace LIBC_NAMESPACE_DECL {
  22 namespace time_utils {
  23
  24 enum Month : int {
  25   JANUARY,
  26   FEBRUARY,
  27   MARCH,
  28   APRIL,
  29   MAY,
  30   JUNE,
  31   JULY,
  32   AUGUST,
  33   SEPTEMBER,
  34   OCTOBER,
  35   NOVEMBER,
  36   DECEMBER
  37 };
  38
  39 struct TimeConstants {
  40   static constexpr int SECONDS_PER_MIN = 60;
  41   static constexpr int MINUTES_PER_HOUR = 60;
  42   static constexpr int HOURS_PER_DAY = 24;
  43   static constexpr int DAYS_PER_WEEK = 7;
  44   static constexpr int MONTHS_PER_YEAR = 12;
  45   static constexpr int DAYS_PER_NON_LEAP_YEAR = 365;
  46   static constexpr int DAYS_PER_LEAP_YEAR = 366;
  47
  48   static constexpr int SECONDS_PER_HOUR = SECONDS_PER_MIN * MINUTES_PER_HOUR;
  49   static constexpr int SECONDS_PER_DAY = SECONDS_PER_HOUR * HOURS_PER_DAY;
  50   static constexpr int NUMBER_OF_SECONDS_IN_LEAP_YEAR =
  51       DAYS_PER_LEAP_YEAR * SECONDS_PER_DAY;
  52
  53   static constexpr int TIME_YEAR_BASE = 1900;
  54   static constexpr int EPOCH_YEAR = 1970;
  55   static constexpr int EPOCH_WEEK_DAY = 4;
  56
  57   // For asctime the behavior is undefined if struct tm's tm_wday or tm_mon are
  58   // not within the normal ranges as defined in <time.h>, or if struct tm's
  59   // tm_year exceeds {INT_MAX}-1990, or if the below asctime_internal algorithm
  60   // would attempt to generate more than 26 bytes of output (including the
  61   // terminating null).
  62   static constexpr int ASCTIME_BUFFER_SIZE = 256;
  63   static constexpr int ASCTIME_MAX_BYTES = 26;
  64
  65   /* 2000-03-01 (mod 400 year, immediately after feb29 */
  66   static constexpr int64_t SECONDS_UNTIL2000_MARCH_FIRST =
  67       (946684800LL + SECONDS_PER_DAY * (31 + 29));
  68   static constexpr int WEEK_DAY_OF2000_MARCH_FIRST = 3;
  69
  70   static constexpr int DAYS_PER400_YEARS =
  71       (DAYS_PER_NON_LEAP_YEAR * 400) + (400 / 4) - 3;
  72   static constexpr int DAYS_PER100_YEARS =
  73       (DAYS_PER_NON_LEAP_YEAR * 100) + (100 / 4) - 1;
  74   static constexpr int DAYS_PER4_YEARS = (DAYS_PER_NON_LEAP_YEAR * 4) + 1;
  75
  76   // The latest time that can be represented in this form is 03:14:07 UTC on
  77   // Tuesday, 19 January 2038 (corresponding to 2,147,483,647 seconds since the
  78   // start of the epoch). This means that systems using a 32-bit time_t type are
  79   // susceptible to the Year 2038 problem.
  80   static constexpr int END_OF32_BIT_EPOCH_YEAR = 2038;
  81
  82   static constexpr time_t OUT_OF_RANGE_RETURN_VALUE = -1;
  83 };
  84
  85 // Update the "tm" structure's year, month, etc. members from seconds.
  86 // "total_seconds" is the number of seconds since January 1st, 1970.
  87 extern int64_t update_from_seconds(int64_t total_seconds, struct tm *tm);
  88
  89 // TODO(michaelrj): move these functions to use ErrorOr instead of setting
  90 // errno. They always accompany a specific return value so we only need the one
  91 // variable.
  92
  93 // POSIX.1-2017 requires this.
  94 LIBC_INLINE time_t out_of_range() {
  95 #ifdef EOVERFLOW
  96   // For non-POSIX uses of the standard C time functions, where EOVERFLOW is
  97   // not defined, it's OK not to set errno at all. The plain C standard doesn't
  98   // require it.
  99   libc_errno = EOVERFLOW;
 100 #endif
 101   return TimeConstants::OUT_OF_RANGE_RETURN_VALUE;
 102 }
 103
 104 LIBC_INLINE void invalid_value() { libc_errno = EINVAL; }
 105
 106 LIBC_INLINE char *asctime(const struct tm *timeptr, char *buffer,
 107                           size_t bufferLength) {
 108   if (timeptr == nullptr || buffer == nullptr) {
 109     invalid_value();
 110     return nullptr;
 111   }
 112   if (timeptr->tm_wday < 0 ||
 113       timeptr->tm_wday > (TimeConstants::DAYS_PER_WEEK - 1)) {
 114     invalid_value();
 115     return nullptr;
 116   }
 117   if (timeptr->tm_mon < 0 ||
 118       timeptr->tm_mon > (TimeConstants::MONTHS_PER_YEAR - 1)) {
 119     invalid_value();
 120     return nullptr;
 121   }
 122
 123   // TODO(rtenneti): i18n the following strings.
 124   static const char *week_days_name[TimeConstants::DAYS_PER_WEEK] = {
 125       "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
 126
 127   static const char *months_name[TimeConstants::MONTHS_PER_YEAR] = {
 128       "Jan", "Feb", "Mar", "Apr", "May", "Jun",
 129       "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
 130
 131   // TODO(michaelr): look into removing this call to __builtin_snprintf that may
 132   // be emitted as a call to snprintf. Alternatively, look into using our
 133   // internal printf machinery.
 134   int written_size = __builtin_snprintf(
 135       buffer, bufferLength, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
 136       week_days_name[timeptr->tm_wday], months_name[timeptr->tm_mon],
 137       timeptr->tm_mday, timeptr->tm_hour, timeptr->tm_min, timeptr->tm_sec,
 138       TimeConstants::TIME_YEAR_BASE + timeptr->tm_year);
 139   if (written_size < 0)
 140     return nullptr;
 141   if (static_cast<size_t>(written_size) >= bufferLength) {
 142     out_of_range();
 143     return nullptr;
 144   }
 145   return buffer;
 146 }
 147
 148 LIBC_INLINE struct tm *gmtime_internal(const time_t *timer, struct tm *result) {
 149   int64_t seconds = *timer;
 150   // Update the tm structure's year, month, day, etc. from seconds.
 151   if (update_from_seconds(seconds, result) < 0) {
 152     out_of_range();
 153     return nullptr;
 154   }
 155
 156   return result;
 157 }
 158
 159 // TODO: localtime is not yet implemented and a temporary solution is to
 160 //       use gmtime, https://github.com/llvm/llvm-project/issues/107597
 161 LIBC_INLINE struct tm *localtime(const time_t *t_ptr) {
 162   static struct tm result;
 163   return time_utils::gmtime_internal(t_ptr, &result);
 164 }
 165
 166 } // namespace time_utils
 167 } // namespace LIBC_NAMESPACE_DECL
 168
 169 #endif // LLVM_LIBC_SRC_TIME_TIME_UTILS_H