Check for timegm.

2006-03-23  Emmanuele Bassi  <ebassi@cvs.gnome.org>

	* configure.in: Check for timegm.

	* glib/gtimer.h:
	* glib/gtimer.c:
	* glib/glib.symbols:
	* docs/reference/glib/glib-sections.txt: Added g_time_val_to_iso8601
	and g_time_val_from_iso8601, to convert a GTimeVal to and from an
	ISO 8601 encoded date.

	* tests/testglib.c: Added test cases for g_time_val_to_iso8601()
	and g_time_val_from_iso8601() functions.

glib/gtimer.c

@@ -31,6 +31,8 @@
 #include "config.h"
 #include "glibconfig.h"
 
+#include <stdlib.h>
+
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif /* HAVE_UNISTD_H */
@@ -308,5 +310,158 @@ g_time_val_add (GTimeVal *time_, glong microseconds)
     }
 }
 
+/* converts a broken down date representation, relative to UTC, to
+ * a timestamp; it uses timegm() if it's available.
+ */
+static time_t
+mktime_utc (struct tm *tm)
+{
+  time_t retval;
+  
+#ifndef HAVE_TIMEGM
+  static const gint days_before[] =
+  {
+    0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+  };
+#endif
+
+#ifndef HAVE_TIMEGM
+  if (tm->tm_mon < 0 || tm->tm_mon > 11)
+    return (time_t) -1;
+
+  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 == 2 && tm->tm_mon < 2)
+    retval -= 1;
+  
+  retval = ((((retval * 24) + tm->tm_hour) * 60) + tm->tm_min) * 60 + tm->tm_sec;
+#else
+  retval = timegm (tm);
+#endif /* !HAVE_TIMEGM */
+  
+  return retval;
+}
+
+/**
+ * g_time_val_from_iso8601:
+ * @iso_date: a ISO 8601 encoded date string
+ * @time_: a #GTimeVal
+ *
+ * Converts a string containing an ISO 8601 encoded date and time
+ * to a #GTimeVal and puts it into @time_.
+ *
+ * Return value: %TRUE if the conversion was successful.
+ *
+ * Since: 2.10
+ */
+gboolean
+g_time_val_from_iso8601 (const gchar *iso_date,
+			 GTimeVal    *time_)
+{
+  struct tm tm;
+  long val;
+
+  g_return_val_if_fail (iso_date != NULL, FALSE);
+  g_return_val_if_fail (time_ != NULL, FALSE);
+
+  val = strtoul (iso_date, (char **)&iso_date, 10);
+  if (*iso_date == '-')
+    {
+      /* YYYY-MM-DD */
+      tm.tm_year = val - 1900;
+      iso_date++;
+      tm.tm_mon = strtoul (iso_date, (char **)&iso_date, 10) - 1;
+      
+      if (*iso_date++ != '-')
+       	return FALSE;
+      
+      tm.tm_mday = strtoul (iso_date, (char **)&iso_date, 10);
+    }
+  else
+    {
+      /* YYYYMMDD */
+      tm.tm_mday = val % 100;
+      tm.tm_mon = (val % 10000) / 100 - 1;
+      tm.tm_year = val / 10000 - 1900;
+    }
+
+  if (*iso_date++ != 'T')
+    return FALSE;
+  
+  val = strtoul (iso_date, (char **)&iso_date, 10);
+  if (*iso_date == ':')
+    {
+      /* hh:mm:ss */
+      tm.tm_hour = val;
+      iso_date++;
+      tm.tm_min = strtoul (iso_date, (char **)&iso_date, 10);
+      
+      if (*iso_date++ != ':')
+        return FALSE;
+      
+      tm.tm_sec = strtoul (iso_date, (char **)&iso_date, 10);
+    }
+  else
+    {
+      /* hhmmss */
+      tm.tm_sec = val % 100;
+      tm.tm_min = (val % 10000) / 100;
+      tm.tm_hour = val / 10000;
+    }
+
+  time_->tv_sec = mktime_utc (&tm);
+  time_->tv_usec = 1;
+  
+  if (*iso_date == '.')
+    time_->tv_usec = strtoul (iso_date + 1, (char **)&iso_date, 10);
+    
+  if (*iso_date == '+' || *iso_date == '-')
+    {
+      gint sign = (*iso_date == '+') ? -1 : 1;
+      
+      val = 60 * strtoul (iso_date + 1, (char **)&iso_date, 10);
+      
+      if (*iso_date == ':')
+	val = 60 * val + strtoul (iso_date + 1, NULL, 10);
+      else
+        val = 60 * (val / 100) + (val % 100);
+
+      time_->tv_sec += (time_t) (val * sign);
+    }
+
+  return TRUE;
+}
+
+/**
+ * g_time_val_to_iso8601:
+ * @time_: a #GTimeVal
+ * 
+ * Converts @time_ into a ISO 8601 encoded string, relative to the
+ * Coordinated Universal Time (UTC).
+ *
+ * Return value: a newly allocated string containing a ISO 8601 date
+ *
+ * Since: 2.10
+ */
+gchar *
+g_time_val_to_iso8601 (GTimeVal *time_)
+{
+  gchar *retval;
+
+  g_return_val_if_fail (time_->tv_usec >= 0 && time_->tv_usec < G_USEC_PER_SEC, NULL);
+
+#define ISO_8601_LEN 	21
+#define ISO_8601_FORMAT "%Y-%m-%dT%H:%M:%SZ"
+  retval = g_new0 (gchar, ISO_8601_LEN + 1);
+  
+  strftime (retval, ISO_8601_LEN,
+	    ISO_8601_FORMAT,
+	    gmtime (&(time_->tv_sec)));
+  
+  return retval;
+}
+
 #define __G_TIMER_C__
 #include "galiasdef.c"