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49 lines
1.5 KiB
C++
49 lines
1.5 KiB
C++
#include "time.h"
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#include <stdint.h>
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/*
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mktime replacement, originally from Samba
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*/
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time_t ap_mktime(const struct tm *t)
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{
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// days elapsed from 1 January to the 1st of each month, common year
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static const uint16_t cumdays[12] = {
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0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
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if (t->tm_year < 70) {
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return (time_t)-1;
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}
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/*
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every caller derives tm_mon from an external date field as
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"month - 1", so it can land outside 0-11 when the source reports
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a zero or out-of-range month. Both cases are kept as the month
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loop this replaced behaved: it walked its own month and year
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counters forward, so months past December rolled into the
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following years, and a negative month added nothing because the
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loop simply never ran.
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*/
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int mon = t->tm_mon;
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int year_off = t->tm_year;
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if (mon > 11) {
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year_off += mon / 12;
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mon %= 12;
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} else if (mon < 0) {
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mon = 0;
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}
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const uint32_t year = (uint32_t)year_off + 1900U;
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const uint32_t n = year - 1U;
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const bool leap = (year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0);
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// leap days since the epoch, as a closed form rather than a
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// per-year loop; 477 is the same count taken at 1969
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const uint32_t days = (uint32_t)(year_off - 70) * 365U
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+ (n/4U - n/100U + n/400U) - 477U
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+ cumdays[mon] + (leap && mon > 1)
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+ (uint32_t)t->tm_mday - 1U;
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return (time_t)days * 86400 + t->tm_hour*3600 + t->tm_min*60 + t->tm_sec;
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}
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