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	sfeed_time_libc.c - sfeed_tests - sfeed tests and RSS and Atom files
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	---
	sfeed_time_libc.c (3196B)
	---
	1 /*
	2 Test datetounix against timegm() libc implementation.
	3
	4 Extract datetounix() function from sfeed.c:
	5
	6 echo 'static long long'
	7 awk '/^datetounix/ { d=1; } d && /^}$/ { exit(0); } d' < sfeed.c
	8 echo '}'
	9 */
	10
	11 #include <err.h>
	12 #include <stdio.h>
	13 #include <stdlib.h>
	14 #include <string.h>
	15 #include <time.h>
	16
	17 static long long
	18 datetounix(long long year, int mon, int day, int hour, int min, int sec)
	19 {
	20 /* seconds in a month in a regular (non-leap) year */
	21 static const long secs_through_month[] = {
	22 0, 31 * 86400, 59 * 86400, 90 * 86400,
	23 120 * 86400, 151 * 86400, 181 * 86400, 212 * 86400,
	24 243 * 86400, 273 * 86400, 304 * 86400, 334 * 86400 };
	25 int is_leap = 0, cycles, centuries = 0, leaps = 0, rem;
	26 long long t;
	27
	28 /* optimization: handle common range year 1902 up to and includi…
	29 if (year - 2ULL <= 136) {
	30 /* amount of leap days relative to 1970: every 4 years */
	31 leaps = (year - 68) >> 2;
	32 if (!((year - 68) & 3)) {
	33 leaps--;
	34 is_leap = 1;
	35 } else {
	36 is_leap = 0;
	37 }
	38 t = 31536000 * (year - 70) + (86400 * leaps); /* 365 * 8…
	39 } else {
	40 /* general leap year calculation:
	41 leap years occur mostly every 4 years but every 100 y…
	42 a leap year is skipped unless the year is divisible b…
	43 cycles = (year - 100) / 400;
	44 rem = (year - 100) % 400;
	45 if (rem < 0) {
	46 cycles--;
	47 rem += 400;
	48 }
	49 if (!rem) {
	50 is_leap = 1;
	51 } else {
	52 if (rem >= 300) {
	53 centuries = 3;
	54 rem -= 300;
	55 } else if (rem >= 200) {
	56 centuries = 2;
	57 rem -= 200;
	58 } else if (rem >= 100) {
	59 centuries = 1;
	60 rem -= 100;
	61 }
	62 if (rem) {
	63 leaps = rem / 4U;
	64 rem %= 4U;
	65 is_leap = !rem;
	66 }
	67 }
	68 leaps += (97 * cycles) + (24 * centuries) - is_leap;
	69
	70 /* adjust 8 leap days from 1970 up to and including 2000:
	71 ((30 * 365) + 8) * 86400 = 946771200 */
	72 t = ((year - 100) * 31536000LL) + (leaps * 86400LL) + 94…
	73 }
	74 t += secs_through_month[mon];
	75 if (is_leap && mon >= 2)
	76 t += 86400;
	77 t += 86400LL * (day - 1);
	78 t += 3600LL * hour;
	79 t += 60LL * min;
	80 t += sec;
	81
	82 return t;
	83 }
	84
	85 void
	86 testtm(struct tm *tm)
	87 {
	88 time_t t1, t2; /* assume time_t is signed 64-bit */
	89 long long ll;
	90
	91 t1 = timegm(tm);
	92 if (t1 == (time_t)-1) {
	93 errx(1, "timegm failed for %d, %d, %d, %d, %d, %d\n",
	94 tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hou…
	95 }
	96
	97 ll = datetounix(tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hou…
	98 t2 = (time_t)ll;
	99
	100 if (t1 != t2) {
	101 printf("result: %lld != %lld\n", (long long)t1, (long lo…
	102 printf("for: %d, %d, %d, %d, %d, %d\n",
	103 tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hou…
	104 exit(1);
	105 }
	106 }
	107
	108 int
	109 main(void)
	110 {
	111 struct tm tm;
	112 int y, mon, d;
	113 long long counter = 0;
	114
	115 for (y = -2069; y < 2069; y++) {
	116 for (mon = 0; mon < 12; mon++) {
	117 for (d = 1; d <= 31; d++) {
	118 /* printf("DEBUG: comparing %d %d %d\n", …
	119
	120 memset(&tm, 0, sizeof(tm));
	121 tm.tm_year = y - 1900;
	122 tm.tm_mon = mon - 1;
	123 tm.tm_mday = d;
	124 tm.tm_hour = 0;
	125 tm.tm_min = 0;
	126 tm.tm_sec = 0;
	127 tm.tm_isdst = -1;
	128
	129 testtm(&tm);
	130 counter++;
	131 }
	132 }
	133 }
	134 printf("%lld dates compared, all OK\n", counter);
	135
	136 return 0;
	137 }