Rewritten timegm replacement function

The algorithm is based on Python 2.7 calendar.timegm.

1 files changed, 59 insertions, 50 deletions

diff --git a/src/timegm.c b/src/timegm.c
index 32d2c27c..655d73b4 100644
--- a/src/timegm.c
+++ b/src/timegm.c
@@ -1,71 +1,80 @@
-/* timegm.c - libc replacement function
- * Copyright (C) 2004 Free Software Foundation, Inc.
+/*
+ * aria2 - The high speed download utility
  *
- * This file is part of GnuPG.
+ * Copyright (C) 2012 Tatsuhiro Tsujikawa
  *
- * GnuPG is free software; you can redistribute it and/or modify
+ * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
- * GnuPG is distributed in the hope that it will be useful,
+ * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
- * USA.
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
  */
+/* copyright --> */
+#include "timegm.h"
 
-/*
-  timegm() is a GNU function that might not be available everywhere.
-  It's basically the inverse of gmtime() - you give it a struct tm,
-  and get back a time_t.  It differs from mktime() in that it handles
-  the case where the struct tm is UTC and the local environment isn't.
-
-  Some BSDs don't handle the putenv("foo") case properly, so we use
-  unsetenv if the platform has it to remove environment variables.
-*/
-
-#ifdef HAVE_CONFIG_H
-# include "config.h"
-#endif // HAVE_CONFIG_H
+#include <stdint.h>
 
-#include <time.h>
-#include <stdlib.h>
-#include <string.h>
+/* Counter the number of leap year in the range [0, y). The |y| is the
+   year, including century (e.g., 2012) */
+static int count_leap_year(int y)
+{
+  y -= 1;
+  return y/4-y/100+y/400;
+}
 
-time_t
-timegm(struct tm *tm)
+/* Returns nonzero if the |y| is the leap year. The |y| is the year,
+   including century (e.g., 2012) */
+static int is_leap_year(int y)
 {
-  time_t answer;
-  char *zone;
+  return y%4 == 0 && (y%100 != 0 || y%400 == 0);
+}
 
-  zone=getenv("TZ");
-  putenv("TZ=UTC");
-  tzset();
-  answer=mktime(tm);
-  if(zone)
-    {
-      char *old_zone;
+/* The number of days before ith month begins */
+static int daysum[] = {
+  0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+};
 
-      old_zone=malloc(3+strlen(zone)+1);
-      if(old_zone)
-	{
-	  strcpy(old_zone,"TZ=");
-	  strcat(old_zone,zone);
-	  putenv(old_zone);
-	}
+// Based on the algorithm of Python 2.7 calendar.timegm.
+time_t timegm(struct tm *tm)
+{
+  int days;
+  int num_leap_year;
+  int64_t t;
+  if(tm->tm_mon > 11) {
+    return -1;
+  }
+  num_leap_year = count_leap_year(tm->tm_year + 1900) - count_leap_year(1970);
+  days = (tm->tm_year - 70) * 365 +
+    num_leap_year + daysum[tm->tm_mon] + tm->tm_mday-1;
+  if(tm->tm_mon >= 2 && is_leap_year(tm->tm_year + 1900)) {
+    ++days;
+  }
+  t = ((int64_t)days * 24 + tm->tm_hour) * 3600 + tm->tm_min * 60 + tm->tm_sec;
+  if(sizeof(time_t) == 4) {
+    if(t < INT32_MIN || t > INT32_MAX) {
+      return -1;
     }
-  else
-#ifdef HAVE_UNSETENV
-    unsetenv("TZ");
-#else
-    putenv("TZ=");
-#endif
-
-  tzset();
-  return answer;
+  }
+  return t;
 }