[or-cvs] Check in a working cross-platform timegm

[nickm@seul.org (Nick Mathewson)]

Update of /home/or/cvsroot/src/common
In directory moria.mit.edu:/tmp/cvs-serv32696/src/common

Modified Files:
	util.c 
Log Message:
Check in a working cross-platform timegm

Index: util.c
===================================================================
RCS file: /home/or/cvsroot/src/common/util.c,v
retrieving revision 1.37
retrieving revision 1.38
diff -u -d -r1.37 -r1.38
--- util.c	27 Oct 2003 10:26:44 -0000	1.37
+++ util.c	10 Nov 2003 06:28:52 -0000	1.38
@@ -112,19 +112,36 @@
   a->tv_usec %= 1000000;
 }
 
+
+#define IS_LEAPYEAR(y) (!(y % 4) && ((y % 100) || !(y % 400)))
+static int n_leapdays(int y1, int y2) {
+  --y1;
+  --y2;
+  return (y2/4 - y1/4) - (y2/100 - y1/100) + (y2/400 - y1/400);
+}
+static const int days_per_month[] = 
+  { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+
 time_t tor_timegm (struct tm *tm) {
+  /* This is a pretty ironclad timegm implementation, snarfed from Python2.2. 
+   * It's way more brute-force than fiddling with tzset().
+   */
   time_t ret;
-  char *tz;
-
-  tz = getenv("TZ");
-  setenv("TZ", "", 1);
-  tzset();
-  ret = mktime(tm);
-  if (tz)
-      setenv("TZ", tz, 1);
-  else
-      unsetenv("TZ");
-  tzset();
+  unsigned long year, days, hours, minutes;
+  int i;
+  year = tm->tm_year + 1900;
+  assert(year >= 1970);
+  assert(tm->tm_mon >= 0 && tm->tm_mon <= 11);
+  days = 365 * (year-1970) + n_leapdays(1970,year);
+  for (i = 0; i < tm->tm_mon; ++i)
+    days += days_per_month[i];
+  if (tm->tm_mon > 1 && IS_LEAPYEAR(year))
+    ++days;
+  days += tm->tm_mday - 1;
+  hours = days*24 + tm->tm_hour;
+  
+  minutes = hours*60 + tm->tm_min;
+  ret = minutes*60 + tm->tm_sec;
   return ret;
 }