From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/time/tzset.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 173 insertions(+)
 create mode 100644 src/time/tzset.c

(limited to 'src/time/tzset.c')

diff --git a/src/time/tzset.c b/src/time/tzset.c
new file mode 100644
index 00000000..6d69957e
--- /dev/null
+++ b/src/time/tzset.c
@@ -0,0 +1,173 @@
+#include <time.h>
+#include <ctype.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include "libc.h"
+
+#include "__time.h"
+
+long  __timezone = 0;
+int   __daylight = 0;
+char *__tzname[2] = { 0, 0 };
+int   __dst_offset = 0;
+
+weak_alias(__timezone, timezone);
+weak_alias(__daylight, daylight);
+weak_alias(__tzname, tzname);
+weak_alias(__dst_offset, dst_offset);
+
+static char std_name[TZNAME_MAX+1];
+static char dst_name[TZNAME_MAX+1];
+
+/* all elements are zero-based */
+static struct rule {
+	char month;
+	char week;
+	short day;
+	int time;
+} __dst_start, __dst_end;
+
+static void zname(char *d, char **s)
+{
+	int i;
+	for (i=0; i<TZNAME_MAX && isalpha(d[i]=**s); i++, (*s)++);
+	d[i] = 0;
+}
+
+static int hhmmss(char **s)
+{
+	int ofs = strtol(*s, s, 10)*3600;
+	if (ofs >= 0) {
+		if (**s == ':') ofs += strtol(*s+1, s, 10)*60;
+		if (**s == ':') ofs += strtol(*s+1, s, 10);
+	} else {
+		if (**s == ':') ofs -= strtol(*s+1, s, 10)*60;
+		if (**s == ':') ofs -= strtol(*s+1, s, 10);
+	}
+	return ofs;
+}
+
+static int dstrule(struct rule *rule, char **s)
+{
+	if (**s != ',') return -1;
+	switch (*++*s) {
+	case 'J':
+		rule->month = 'J';
+		rule->day = strtol(*s+1, s, 10)-1;
+		break;
+	case 'M':
+		rule->month = strtol(*s+1, s, 10)-1;
+		if (**s != '.' || rule->month < 0 || rule->month > 11)
+			return -1;
+		rule->week = strtol(*s+1, s, 10)-1;
+		if (**s != '.' || rule->week < 0 || rule->week > 4)
+			return -1;
+		rule->day = strtol(*s+1, s, 10);
+		if (rule->day < 0 || rule->day > 6)
+			return -1;
+		break;
+	default:
+		rule->month = 'L';
+		rule->day = strtol(*s+1, s, 10);
+		break;
+	}
+	if (**s == '/') {
+		(*s)++;
+		rule->time = hhmmss(s);
+	} else rule->time = 7200;
+	return 0;
+}
+
+void tzset(void)
+{
+	char *z, *a;
+	
+	strcpy(std_name, "GMT");
+	strcpy(dst_name, "GMT");
+	__tzname[0] = std_name;
+	__tzname[1] = dst_name;
+	__timezone = 0;
+	__daylight = 0;
+	
+	if (!(z = getenv("TZ")) || !isalpha(*z)) return;
+
+	zname(std_name, &z);
+	__timezone = hhmmss(&z);
+
+	zname(dst_name, &z);
+	if (dst_name[0]) __daylight=1;
+	a = z;
+	__dst_offset = hhmmss(&z) - __timezone;
+	if (z==a) __dst_offset = -3600;
+
+	if (dstrule(&__dst_start, &z) || dstrule(&__dst_end, &z))
+		__daylight = 0;
+}
+
+void __tzset(void)
+{
+	static int lock, init;
+	if (init) return;
+	LOCK(&lock);
+	if (!init) tzset();
+	init=1;
+	UNLOCK(&lock);
+}
+
+static int is_leap(int year)
+{
+	year -= 100;
+	return !(year&3) && ((year%100) || !(year%400));
+}
+
+static int cutoff_yday(struct tm *tm, struct rule *rule)
+{
+	static const char days_in_month[] = {31,28,31,30,31,30,31,31,30,31,30,31};
+	static const int first_day[] = {0,31,59,90,120,151,181,212,243,273,304,335};
+	int yday, mday, leap;
+	
+	switch (rule->month) {
+	case 'J':
+		return rule->day + (tm->tm_mon > 1 && is_leap(tm->tm_year));
+	case 'L':
+		return rule->day;
+	default:
+		yday = first_day[rule->month];
+		leap = is_leap(tm->tm_year);
+		if (rule->month > 1 && leap) yday++;
+		mday = (rule->day - (yday + tm->tm_wday - tm->tm_yday) + 1400)%7 + 7*rule->week;
+		if (mday >= days_in_month[rule->month] + (leap && rule->month == 1))
+			mday -= 7;
+		return mday + yday;
+	}
+}
+
+struct tm *__dst_adjust(struct tm *tm)
+{
+	time_t t;
+	int start, end, secs;
+	int after_start, before_end;
+
+	if (tm->tm_isdst >= 0) return tm;
+	if (!__daylight) {
+		tm->tm_isdst = 0;
+		return tm;
+	}
+	
+	secs = tm->tm_hour*3600 + tm->tm_min*60 + tm->tm_sec;
+	start = cutoff_yday(tm, &__dst_start);
+	end = cutoff_yday(tm, &__dst_end);
+
+	after_start = (tm->tm_yday > start || (tm->tm_yday == start && secs >= __dst_start.time));
+	before_end = (tm->tm_yday < end || (tm->tm_yday == end && secs < __dst_end.time));
+
+	if ((after_start && before_end) || ((end < start) && (after_start || before_end))) {
+		tm->tm_sec -= __dst_offset;
+		tm->tm_isdst = 1;
+		t = __tm_to_time(tm);
+		return __time_to_tm(t, tm);
+	} else tm->tm_isdst = 0;
+
+	return tm;
+}
-- 
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