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 "include/errno.h"
15
16 #include "src/errno/llvmlibc_errno.h"
17 #include "src/time/mktime.h"
18
19 #include <stdint.h>
20
21 namespace __llvm_libc {
22 namespace time_utils {
23
24 struct TimeConstants {
25 static constexpr int SecondsPerMin = 60;
26 static constexpr int SecondsPerHour = 3600;
27 static constexpr int SecondsPerDay = 86400;
28 static constexpr int DaysPerWeek = 7;
29 static constexpr int MonthsPerYear = 12;
30 static constexpr int DaysPerNonLeapYear = 365;
31 static constexpr int DaysPerLeapYear = 366;
32 static constexpr int TimeYearBase = 1900;
33 static constexpr int EpochYear = 1970;
34 static constexpr int EpochWeekDay = 4;
35 static constexpr int NumberOfSecondsInLeapYear =
36 (DaysPerNonLeapYear + 1) * SecondsPerDay;
37
38 // For asctime the behavior is undefined if struct tm's tm_wday or tm_mon are
39 // not within the normal ranges as defined in <time.h>, or if struct tm's
40 // tm_year exceeds {INT_MAX}-1990, or if the below asctime_internal algorithm
41 // would attempt to generate more than 26 bytes of output (including the
42 // terminating null).
43 static constexpr int AsctimeBufferSize = 256;
44 static constexpr int AsctimeMaxBytes = 26;
45
46 /* 2000-03-01 (mod 400 year, immediately after feb29 */
47 static constexpr int64_t SecondsUntil2000MarchFirst =
48 (946684800LL + SecondsPerDay * (31 + 29));
49 static constexpr int WeekDayOf2000MarchFirst = 3;
50
51 static constexpr int DaysPer400Years =
52 (DaysPerNonLeapYear * 400 + (400 / 4) - 3);
53 static constexpr int DaysPer100Years =
54 (DaysPerNonLeapYear * 100 + (100 / 4) - 1);
55 static constexpr int DaysPer4Years = (DaysPerNonLeapYear * 4 + 1);
56
57 // The latest time that can be represented in this form is 03:14:07 UTC on
58 // Tuesday, 19 January 2038 (corresponding to 2,147,483,647 seconds since the
59 // start of the epoch). This means that systems using a 32-bit time_t type are
60 // susceptible to the Year 2038 problem.
61 static constexpr int EndOf32BitEpochYear = 2038;
62
63 static constexpr time_t OutOfRangeReturnValue = -1;
64 };
65
66 // Update the "tm" structure's year, month, etc. members from seconds.
67 // "total_seconds" is the number of seconds since January 1st, 1970.
68 extern int64_t UpdateFromSeconds(int64_t total_seconds, struct tm *tm);
69
70 // POSIX.1-2017 requires this.
OutOfRange()71 static inline time_t OutOfRange() {
72 llvmlibc_errno = EOVERFLOW;
73 return static_cast<time_t>(-1);
74 }
75
InvalidValue()76 static inline void InvalidValue() { llvmlibc_errno = EINVAL; }
77
asctime(const struct tm * timeptr,char * buffer,size_t bufferLength)78 static inline char *asctime(const struct tm *timeptr, char *buffer,
79 size_t bufferLength) {
80 if (timeptr == nullptr || buffer == nullptr) {
81 InvalidValue();
82 return nullptr;
83 }
84 if (timeptr->tm_wday < 0 ||
85 timeptr->tm_wday > (TimeConstants::DaysPerWeek - 1)) {
86 InvalidValue();
87 return nullptr;
88 }
89 if (timeptr->tm_mon < 0 ||
90 timeptr->tm_mon > (TimeConstants::MonthsPerYear - 1)) {
91 InvalidValue();
92 return nullptr;
93 }
94
95 // TODO(rtenneti): i18n the following strings.
96 static const char *WeekDaysName[TimeConstants::DaysPerWeek] = {
97 "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
98
99 static const char *MonthsName[TimeConstants::MonthsPerYear] = {
100 "Jan", "Feb", "Mar", "Apr", "May", "Jun",
101 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
102 int written_size = __builtin_snprintf(
103 buffer, bufferLength, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
104 WeekDaysName[timeptr->tm_wday], MonthsName[timeptr->tm_mon],
105 timeptr->tm_mday, timeptr->tm_hour, timeptr->tm_min, timeptr->tm_sec,
106 TimeConstants::TimeYearBase + timeptr->tm_year);
107 if (written_size < 0)
108 return nullptr;
109 if (static_cast<size_t>(written_size) >= bufferLength) {
110 OutOfRange();
111 return nullptr;
112 }
113 return buffer;
114 }
115
gmtime_internal(const time_t * timer,struct tm * result)116 static inline struct tm *gmtime_internal(const time_t *timer,
117 struct tm *result) {
118 int64_t seconds = *timer;
119 // Update the tm structure's year, month, day, etc. from seconds.
120 if (UpdateFromSeconds(seconds, result) < 0) {
121 OutOfRange();
122 return nullptr;
123 }
124
125 return result;
126 }
127
128 } // namespace time_utils
129 } // namespace __llvm_libc
130
131 #endif // LLVM_LIBC_SRC_TIME_TIME_UTILS_H
132