ref: 51838a75bb42ae432048daf8ee040e40c73d598b
dir: /src/libc/time/mktime.c/
#include <limits.h> #include <time.h> #include "../libc.h" #undef mktime static int norm(int *val, int *next, int qty) { int v = *val, n = *next, d; if (v < 0) { d = -v / qty + 1; v += d * qty; if (n > INT_MAX - d) return 0; n += d; } if (v >= qty) { d = v / qty; v -= d * qty; if (n < INT_MIN + d) return 0; n -= d; } *val = v; *next = n; return 1; } static int normalize(struct tm *tm) { int mon, day, year; struct tm aux = *tm; if (!norm(&tm->tm_sec, &tm->tm_min, 60) || !norm(&tm->tm_min, &tm->tm_hour, 60) || !norm(&tm->tm_hour, &tm->tm_mday, 24) || !norm(&tm->tm_mon, &tm->tm_year, 12)) { return 0; } day = tm->tm_mday; year = EPOCH + tm->tm_year; _daysmon[FEB] = FEBDAYS(year); for (mon = tm->tm_mon; day < 1; --mon) { day += _daysmon[mon]; if (mon == JAN) { if (year == EPOCH) return -1; year--; _daysmon[FEB] = FEBDAYS(year); mon = DEC+1; } } for (; day > _daysmon[mon]; ++mon) { day -= _daysmon[mon]; if (mon == DEC) { if (year == _MAXYEAR) return -1; year++; _daysmon[FEB] = FEBDAYS(year); mon = JAN-1; } } tm->tm_mon = mon; tm->tm_year = year - EPOCH; tm->tm_mday = day; tm->tm_wday = (_newyear(tm->tm_year) + tm->tm_yday) % 7; return 1; } time_t mktime(struct tm *tm) { int i, year, dst; time_t t; struct tm *aux; if (!normalize(tm)) return -1; t = 0; year = tm->tm_year + 1900; for (i = EPOCH; i < year; i++) t += _daysyear(i) * SECDAY; for (i = 0; i < tm->tm_mon; i++) t += _daysmon[i] * SECDAY; t += tm->tm_sec; t += tm->tm_min * SECMIN; t += tm->tm_hour * SECHOUR; t += (tm->tm_mday-1) * SECDAY; aux = localtime(&t); dst = 0; if (tm->tm_isdst == 0 && aux->tm_isdst == 1) dst = -SECHOUR; else if (tm->tm_isdst == 1 && aux->tm_isdst == 0) dst = +SECHOUR; t += aux->tm_gmtoff + dst; return t; }