From f81aa515fd91d19f9e670beb45fee83384ce726e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20K=C3=B6hler?= <andi5.py@gmx.net>
Date: Wed, 31 Jan 2007 00:05:23 +0000
Subject: [PATCH] Implement gnc_timegm directly without mktime.

Calculate the seconds since the start of the UNIX epoch directly without
the help of mktime. This also works on Windows. Systems with timegm are
unaffected.


git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@15472 57a11ea4-9604-0410-9ed3-97b8803252fd
---
 src/backend/file/sixtp-utils.c | 49 +++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/src/backend/file/sixtp-utils.c b/src/backend/file/sixtp-utils.c
index 5eca84d04a..4bdd7103b4 100644
--- a/src/backend/file/sixtp-utils.c
+++ b/src/backend/file/sixtp-utils.c
@@ -381,35 +381,36 @@ simple_chars_only_parser_new(sixtp_end_handler end_handler)
 
 #ifdef HAVE_TIMEGM
 #  define gnc_timegm timegm
-#else
+#else /* !HAVE_TIMEGM */
+
+/* This code originates from GLib 2.12, gtimer.c and works until the year 2100
+ * or the system-dependent maximal date that can be represented by a time_t,
+ * whatever comes first.  The old implementation called mktime after setting
+ * the environment variable TZ to UTC.  It did not work on Windows, at least.
+ */
+static const gint days_before[] = {
+  0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+};
+
 static time_t
 gnc_timegm (struct tm *tm)
 {
-  time_t result;
-  char *old_tz;
+  time_t retval;
+  if (tm->tm_mon < 0 || tm->tm_mon > 11)
+    return (time_t) -1;
 
-  old_tz = g_strdup(g_getenv ("TZ"));
-  /* FIXME: there's no way to report this error to the caller. */
-  if (!g_setenv("TZ", "UTC", TRUE))
-    PERR ("couldn't switch the TZ.");
-  result = mktime (tm);
-  if(old_tz)
-  {
-    /* FIXME: there's no way to report this error to the caller. */
-    if (!g_setenv("TZ", old_tz, TRUE))
-      PERR ("couldn't switch the TZ back.");
-    g_free(old_tz);
-  }
-  else
-  {
-    /* FIXME: there's no way to report this error to the caller. */
-    g_unsetenv("TZ");
-    if(errno != 0)
-      PERR ("couldn't restore the TZ to undefined.");
-  }
-  return result;
+  retval = (tm->tm_year - 70) * 365;
+  retval += (tm->tm_year - 68) / 4;
+  retval += days_before[tm->tm_mon] + tm->tm_mday - 1;
+
+  if (tm->tm_year % 4 == 0 && tm->tm_mon < 2)
+    retval -= 1;
+  
+  retval = ((((retval * 24) + tm->tm_hour) * 60) + tm->tm_min) * 60 + tm->tm_sec;
+
+  return retval;
 }
-#endif
+#endif /* HAVE_TIMEGM */
 
 
 /****************************************************************************/