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	tm2sec.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	tm2sec.c (1900B)
	---
	1 #include <u.h>
	2 #include <libc.h>
	3
	4 #include "zoneinfo.h"
	5
	6 #define SEC2MIN 60L
	7 #define SEC2HOUR (60L*SEC2MIN)
	8 #define SEC2DAY (24L*SEC2HOUR)
	9
	10 /*
	11 * days per month plus days/year
	12 */
	13 static int dmsize[] =
	14 {
	15 365, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	16 };
	17 static int ldmsize[] =
	18 {
	19 366, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	20 };
	21
	22 /*
	23 * return the days/month for the given year
	24 */
	25 static int *
	26 yrsize(int y)
	27 {
	28 if((y%4) == 0 && ((y%100) != 0 \|\| (y%400) == 0))
	29 return ldmsize;
	30 else
	31 return dmsize;
	32 }
	33
	34 /*
	35 * compute seconds since Jan 1 1970 GMT
	36 * and convert to our timezone.
	37 */
	38 long
	39 tm2sec(Tm *tm)
	40 {
	41 Tinfo ti0, ti1, *ti;
	42 long secs;
	43 int i, yday, year, *d2m;
	44
	45 secs = 0;
	46
	47 /*
	48 * seconds per year
	49 */
	50 year = tm->year + 1900;
	51 for(i = 1970; i < year; i++){
	52 d2m = yrsize(i);
	53 secs += d2m[0] * SEC2DAY;
	54 }
	55
	56 /*
	57 * if mday is set, use mon and mday to compute yday
	58 */
	59 if(tm->mday){
	60 yday = 0;
	61 d2m = yrsize(year);
	62 for(i=0; i<tm->mon; i++)
	63 yday += d2m[i+1];
	64 yday += tm->mday-1;
	65 }else{
	66 yday = tm->yday;
	67 }
	68 secs += yday * SEC2DAY;
	69
	70 /*
	71 * hours, minutes, seconds
	72 */
	73 secs += tm->hour * SEC2HOUR;
	74 secs += tm->min * SEC2MIN;
	75 secs += tm->sec;
	76
	77 /*
	78 * Assume the local time zone if zone is not GMT
	79 */
	80 if(strcmp(tm->zone, "GMT") != 0) {
	81 i = zonelookuptinfo(&ti0, secs);
	82 ti = &ti0;
	83 if (i != -1)
	84 if (ti->tzoff!=0) {
	85 /*
	86 * to what local time period `secs' belongs?
	87 */
	88 if (ti->tzoff>0) {
	89 /*
	90 * east of GMT; check previous local tim…
	91 */
	92 if (ti->t+ti->tzoff > secs)
	93 if (zonetinfo(&ti1, i-1)!=-1)
	94 ti = &ti1;
	95 } else
	96 /*
	97 * west of GMT; check next local time tr…
	98 */
	99 if (zonetinfo(&ti1, i+1))
	100 if (ti1.t+ti->tzoff < secs)
	101 ti = &ti1;
	102 // fprint(2, "tt: %ld+%d %ld\n", (long)ti->t, ti-…
	103 secs -= ti->tzoff;
	104 }
	105 }
	106
	107 if(secs < 0)
	108 secs = 0;
	109 return secs;
	110 }