78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
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/*
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* tzcalc_limits.c
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* Original Author: Adapted from tzcode maintained by Arthur David Olson.
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* Modifications:
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* - Changed to mktm_r and added __tzcalc_limits - 04/10/02, Jeff Johnston
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* - Fixed bug in mday computations - 08/12/04, Alex Mogilnikov <alx@intellectronika.ru>
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* - Fixed bug in __tzcalc_limits - 08/12/04, Alex Mogilnikov <alx@intellectronika.ru>
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* - Moved __tzcalc_limits() to separate file - 05/09/14, Freddie Chopin <freddie_chopin@op.pl>
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*/
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#include "local.h"
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int
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_DEFUN (__tzcalc_limits, (year),
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int year)
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{
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int days, year_days, years;
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int i, j;
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__tzinfo_type *_CONST tz = __gettzinfo ();
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if (year < EPOCH_YEAR)
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return 0;
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tz->__tzyear = year;
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years = (year - EPOCH_YEAR);
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year_days = years * 365 +
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(years - 1 + EPOCH_YEARS_SINCE_LEAP) / 4 -
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(years - 1 + EPOCH_YEARS_SINCE_CENTURY) / 100 +
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(years - 1 + EPOCH_YEARS_SINCE_LEAP_CENTURY) / 400;
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for (i = 0; i < 2; ++i)
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{
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if (tz->__tzrule[i].ch == 'J')
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{
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/* The Julian day n (1 <= n <= 365). */
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days = year_days + tz->__tzrule[i].d +
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(isleap(year) && tz->__tzrule[i].d >= 60);
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/* Convert to yday */
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--days;
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}
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else if (tz->__tzrule[i].ch == 'D')
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days = year_days + tz->__tzrule[i].d;
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else
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{
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_CONST int yleap = isleap(year);
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int m_day, m_wday, wday_diff;
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_CONST int *_CONST ip = month_lengths[yleap];
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days = year_days;
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for (j = 1; j < tz->__tzrule[i].m; ++j)
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days += ip[j-1];
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m_wday = (EPOCH_WDAY + days) % DAYSPERWEEK;
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wday_diff = tz->__tzrule[i].d - m_wday;
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if (wday_diff < 0)
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wday_diff += DAYSPERWEEK;
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m_day = (tz->__tzrule[i].n - 1) * DAYSPERWEEK + wday_diff;
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while (m_day >= ip[j-1])
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m_day -= DAYSPERWEEK;
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days += m_day;
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}
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/* store the change-over time in GMT form by adding offset */
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tz->__tzrule[i].change = days * SECSPERDAY +
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tz->__tzrule[i].s + tz->__tzrule[i].offset;
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}
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tz->__tznorth = (tz->__tzrule[0].change < tz->__tzrule[1].change);
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return 1;
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}
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