Change order of system timezone detection

Prefer checking of user's system timezone based on /etc/localtime
content, to get always correct timezone, even when the system doesn't
update config files when timezone is changed. This is fixing timezone
detection in KDE, which doesn't update /etc/sysconfig/clock ZONE key
when user changes local timezone. With the added caching mechanism is
the walk-through zoneinfo directories done only once till the other
change, which usually doesn't happen that often anyway.

diff --git a/calendar/libecal/e-cal-system-timezone.c b/calendar/libecal/e-cal-system-timezone.c
index 8fb108c..66edf13 100644 (file)
--- a/calendar/libecal/e-cal-system-timezone.c
+++ b/calendar/libecal/e-cal-system-timezone.c
@@ -387,6 +387,11 @@ files_are_identical_content (struct stat *a_stat,
 static gchar *
 system_timezone_read_etc_localtime_content (void)
 {
+       static gchar *last_localtime_content = NULL;
+       static gsize last_localtime_content_len = -1;
+       static gchar *last_timezone = NULL;
+       static GStaticRecMutex mutex = G_STATIC_REC_MUTEX_INIT;
+
        struct stat  stat_localtime;
        gchar   *localtime_content = NULL;
        gsize   localtime_content_len = -1;
@@ -404,6 +409,25 @@ system_timezone_read_etc_localtime_content (void)
                                  NULL))
                return NULL;
 
+       g_static_rec_mutex_lock (&mutex);
+
+       if (last_localtime_content) {
+               if (localtime_content_len != last_localtime_content_len
+                   || memcmp (localtime_content, last_localtime_content, localtime_content_len) != 0) {
+                       g_free (last_localtime_content);
+                       g_free (last_timezone);
+                       last_localtime_content = NULL;
+                       last_localtime_content_len = -1;
+                       last_timezone = NULL;
+               } else {
+                       retval = g_strdup (last_timezone);
+                       g_static_rec_mutex_unlock (&mutex);
+
+                       g_free (localtime_content);
+                       return retval;
+               }
+       }
+
        retval = recursive_compare (&stat_localtime,
                                   localtime_content,
                                   localtime_content_len,
@@ -412,13 +436,21 @@ system_timezone_read_etc_localtime_content (void)
                                   0,
                                   &fallback);
 
-       g_free (localtime_content);
-
        if (retval)
                g_free (fallback);
        else
                retval = fallback;
 
+       if (retval) {
+               last_localtime_content = localtime_content;
+               last_localtime_content_len = localtime_content_len;
+               last_timezone = g_strdup (retval);
+       } else {
+               g_free (localtime_content);
+       }
+
+       g_static_rec_mutex_unlock (&mutex);
+
        return retval;
 }
 
@@ -428,6 +460,10 @@ typedef gchar * (*GetSystemTimezone) (void);
 static GetSystemTimezone get_system_timezone_methods[] = {
        /* cheap and "more correct" than data from a config file */
        system_timezone_read_etc_localtime_softlink,
+       /* reading /etc/timezone directly. Expensive since we have to stat
+        * many files, but it returns always correct values, even on KDE */
+       system_timezone_read_etc_localtime_content,
+       system_timezone_read_etc_localtime_hardlink,
        /* reading various config files */
        system_timezone_read_etc_timezone,
        system_timezone_read_etc_sysconfig_clock,
@@ -436,10 +472,6 @@ static GetSystemTimezone get_system_timezone_methods[] = {
        system_timezone_read_etc_rc_conf,
        /* reading deprecated config files */
        system_timezone_read_etc_conf_d_clock,
-       /* reading /etc/timezone directly. Expensive since we have to stat
-        * many files */
-       system_timezone_read_etc_localtime_hardlink,
-       system_timezone_read_etc_localtime_content,
        NULL
 };