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.
out_of_range()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
invalid_value()104 LIBC_INLINE void invalid_value() { libc_errno = EINVAL; }
105
asctime(const struct tm * timeptr,char * buffer,size_t bufferLength)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
gmtime_internal(const time_t * timer,struct tm * result)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
localtime(const time_t * t_ptr)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
170