diff options
Diffstat (limited to 'src/xtime.c')
| -rw-r--r-- | src/xtime.c | 316 |
1 files changed, 316 insertions, 0 deletions
diff --git a/src/xtime.c b/src/xtime.c new file mode 100644 index 0000000..91ed915 --- /dev/null +++ b/src/xtime.c @@ -0,0 +1,316 @@ +// Copyright © Tavian Barnes <tavianator@tavianator.com> +// SPDX-License-Identifier: 0BSD + +#include "prelude.h" +#include "xtime.h" +#include "bfstd.h" +#include "diag.h" +#include <errno.h> +#include <limits.h> +#include <sys/time.h> +#include <time.h> +#include <unistd.h> + +int xmktime(struct tm *tm, time_t *timep) { + *timep = mktime(tm); + + if (*timep == -1) { + int error = errno; + + struct tm tmp; + if (!localtime_r(timep, &tmp)) { + bfs_bug("localtime_r(-1): %s", xstrerror(errno)); + return -1; + } + + if (tm->tm_year != tmp.tm_year || tm->tm_yday != tmp.tm_yday + || tm->tm_hour != tmp.tm_hour || tm->tm_min != tmp.tm_min || tm->tm_sec != tmp.tm_sec) { + errno = error; + return -1; + } + } + + return 0; +} + +static int safe_add(int *value, int delta) { + if (*value >= 0) { + if (delta > INT_MAX - *value) { + return -1; + } + } else { + if (delta < INT_MIN - *value) { + return -1; + } + } + + *value += delta; + return 0; +} + +static int floor_div(int n, int d) { + int a = n < 0; + return (n + a) / d - a; +} + +static int wrap(int *value, int max, int *next) { + int carry = floor_div(*value, max); + *value -= carry * max; + return safe_add(next, carry); +} + +static int month_length(int year, int month) { + static const int month_lengths[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; + int ret = month_lengths[month]; + if (month == 1 && year % 4 == 0 && (year % 100 != 0 || (year + 300) % 400 == 0)) { + ++ret; + } + return ret; +} + +int xtimegm(struct tm *tm, time_t *timep) { + struct tm copy = *tm; + copy.tm_isdst = 0; + + if (wrap(©.tm_sec, 60, ©.tm_min) != 0) { + goto overflow; + } + if (wrap(©.tm_min, 60, ©.tm_hour) != 0) { + goto overflow; + } + if (wrap(©.tm_hour, 24, ©.tm_mday) != 0) { + goto overflow; + } + + // In order to wrap the days of the month, we first need to know what + // month it is + if (wrap(©.tm_mon, 12, ©.tm_year) != 0) { + goto overflow; + } + + if (copy.tm_mday < 1) { + do { + --copy.tm_mon; + if (wrap(©.tm_mon, 12, ©.tm_year) != 0) { + goto overflow; + } + + copy.tm_mday += month_length(copy.tm_year, copy.tm_mon); + } while (copy.tm_mday < 1); + } else { + while (true) { + int days = month_length(copy.tm_year, copy.tm_mon); + if (copy.tm_mday <= days) { + break; + } + + copy.tm_mday -= days; + ++copy.tm_mon; + if (wrap(©.tm_mon, 12, ©.tm_year) != 0) { + goto overflow; + } + } + } + + copy.tm_yday = 0; + for (int i = 0; i < copy.tm_mon; ++i) { + copy.tm_yday += month_length(copy.tm_year, i); + } + copy.tm_yday += copy.tm_mday - 1; + + int leap_days; + // Compute floor((year - 69)/4) - floor((year - 1)/100) + floor((year + 299)/400) without overflows + if (copy.tm_year >= 0) { + leap_days = floor_div(copy.tm_year - 69, 4) - floor_div(copy.tm_year - 1, 100) + floor_div(copy.tm_year - 101, 400) + 1; + } else { + leap_days = floor_div(copy.tm_year + 3, 4) - floor_div(copy.tm_year + 99, 100) + floor_div(copy.tm_year + 299, 400) - 17; + } + + long long epoch_days = 365LL * (copy.tm_year - 70) + leap_days + copy.tm_yday; + copy.tm_wday = (epoch_days + 4) % 7; + if (copy.tm_wday < 0) { + copy.tm_wday += 7; + } + + long long epoch_time = copy.tm_sec + 60 * (copy.tm_min + 60 * (copy.tm_hour + 24 * epoch_days)); + time_t time = (time_t)epoch_time; + if ((long long)time != epoch_time) { + goto overflow; + } + + *tm = copy; + *timep = time; + return 0; + +overflow: + errno = EOVERFLOW; + return -1; +} + +/** Parse a decimal digit. */ +static int xgetdigit(char c) { + int ret = c - '0'; + if (ret < 0 || ret > 9) { + return -1; + } else { + return ret; + } +} + +/** Parse some digits from a timestamp. */ +static int xgetpart(const char **str, size_t n, int *result) { + *result = 0; + + for (size_t i = 0; i < n; ++i, ++*str) { + int dig = xgetdigit(**str); + if (dig < 0) { + return -1; + } + *result *= 10; + *result += dig; + } + + return 0; +} + +int xgetdate(const char *str, struct timespec *result) { + struct tm tm = { + .tm_isdst = -1, + }; + + int tz_hour = 0; + int tz_min = 0; + bool tz_negative = false; + bool local = true; + + // YYYY + if (xgetpart(&str, 4, &tm.tm_year) != 0) { + goto invalid; + } + tm.tm_year -= 1900; + + // MM + if (*str == '-') { + ++str; + } + if (xgetpart(&str, 2, &tm.tm_mon) != 0) { + goto invalid; + } + tm.tm_mon -= 1; + + // DD + if (*str == '-') { + ++str; + } + if (xgetpart(&str, 2, &tm.tm_mday) != 0) { + goto invalid; + } + + if (!*str) { + goto end; + } else if (*str == 'T' || *str == ' ') { + ++str; + } + + // hh + if (xgetpart(&str, 2, &tm.tm_hour) != 0) { + goto invalid; + } + + // mm + if (!*str) { + goto end; + } else if (*str == ':') { + ++str; + } else if (xgetdigit(*str) < 0) { + goto zone; + } + if (xgetpart(&str, 2, &tm.tm_min) != 0) { + goto invalid; + } + + // ss + if (!*str) { + goto end; + } else if (*str == ':') { + ++str; + } else if (xgetdigit(*str) < 0) { + goto zone; + } + if (xgetpart(&str, 2, &tm.tm_sec) != 0) { + goto invalid; + } + +zone: + if (!*str) { + goto end; + } else if (*str == 'Z') { + local = false; + ++str; + } else if (*str == '+' || *str == '-') { + local = false; + tz_negative = *str == '-'; + ++str; + + // hh + if (xgetpart(&str, 2, &tz_hour) != 0) { + goto invalid; + } + + // mm + if (!*str) { + goto end; + } else if (*str == ':') { + ++str; + } + if (xgetpart(&str, 2, &tz_min) != 0) { + goto invalid; + } + } else { + goto invalid; + } + + if (*str) { + goto invalid; + } + +end: + if (local) { + if (xmktime(&tm, &result->tv_sec) != 0) { + goto error; + } + } else { + if (xtimegm(&tm, &result->tv_sec) != 0) { + goto error; + } + + int offset = (tz_hour * 60 + tz_min) * 60; + if (tz_negative) { + result->tv_sec += offset; + } else { + result->tv_sec -= offset; + } + } + + result->tv_nsec = 0; + return 0; + +invalid: + errno = EINVAL; +error: + return -1; +} + +int xgettime(struct timespec *result) { +#if _POSIX_TIMERS > 0 + return clock_gettime(CLOCK_REALTIME, result); +#else + struct timeval tv; + int ret = gettimeofday(&tv, NULL); + if (ret == 0) { + result->tv_sec = tv.tv_sec; + result->tv_nsec = tv.tv_usec * 1000L; + } + return ret; +#endif +} |