[pango] Rework config file reading

[Matthias Clasen <matthiasc src gnome org>]

commit 164c6eb4dc819eb0833d6851f9e16d4994e84e97
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Sep 14 20:09:38 2012 -0400

    Rework config file reading
    
    The code was loading and parsing the system config file
    every single time, and has not correctly handling mixed
    requests for user and system config entries.
    
    This commit reworks the code so that the configuration is
    loaded only once, in threadsafe fashion.
    pango_config_key_get_system is no longer using the same
    hash table, but reloads its data every time - this is
    not a really problem, since this function is only used
    in pango-querymodules.

 pango/pango-utils.c |   75 ++++++++++++++++++++++++++------------------------
 1 files changed, 39 insertions(+), 36 deletions(-)
---
diff --git a/pango/pango-utils.c b/pango/pango-utils.c
index 2595e34..112bc38 100644
--- a/pango/pango-utils.c
+++ b/pango/pango-utils.c
@@ -521,9 +521,6 @@ pango_scan_int (const char **pos, int *out)
   return TRUE;
 }
 
-static GHashTable *config_hash = NULL;
-static gboolean did_read_system_config = FALSE;
-static gboolean did_read_user_config = FALSE;
 
 static void
 read_config_file (const char *filename, gboolean enoent_error, GHashTable *ht)
@@ -595,54 +592,53 @@ read_config_file (const char *filename, gboolean enoent_error, GHashTable *ht)
   g_key_file_free(key_file);
 }
 
-static void
-ensure_config_hash (void)
-{
-  if (!config_hash)
-    config_hash = g_hash_table_new_full (g_str_hash, g_str_equal,
-					 (GDestroyNotify)g_free,
-					 (GDestroyNotify)g_free);
-}
-
-static void
+static GHashTable *
 read_config_system (void)
 {
   char *filename;
+  GHashTable *config_hash;
 
-  if (!did_read_system_config)
-    {
-      did_read_system_config = TRUE;
+  config_hash = g_hash_table_new_full (g_str_hash, g_str_equal,
+                                       (GDestroyNotify)g_free,
+                                       (GDestroyNotify)g_free);
 
-      ensure_config_hash ();
+  filename = g_build_filename (pango_get_sysconf_subdirectory (),
+                               "pangorc",
+			       NULL);
+  read_config_file (filename, FALSE, config_hash);
+  g_free (filename);
 
-      filename = g_build_filename (pango_get_sysconf_subdirectory (),
-                                   "pangorc",
-			           NULL);
-      read_config_file (filename, FALSE, config_hash);
-      g_free (filename);
-    }
+  return config_hash;
 }
 
-static void
+static GHashTable *
 read_config (void)
 {
-  char *filename;
-  const char *envvar;
-
-  read_config_system ();
+  static GHashTable *config_hash = NULL;
 
-  if (!did_read_user_config)
+  if (g_once_init_enter ((gsize*)&config_hash))
     {
-      did_read_user_config = TRUE;
+      GHashTable *tmp_hash;
+      char *filename;
+      const char *envvar;
+
+      tmp_hash = read_config_system ();
 
-      filename = g_build_filename (g_get_user_config_dir (), "pango", "pangorc", NULL);
-      read_config_file (filename, FALSE, config_hash);
+      filename = g_build_filename (g_get_user_config_dir (),
+                                   "pango",
+                                   "pangorc",
+                                   NULL);
+      read_config_file (filename, FALSE, tmp_hash);
       g_free (filename);
 
       envvar = g_getenv ("PANGO_RC_FILE");
       if (envvar)
-        read_config_file (envvar, TRUE, config_hash);
+        read_config_file (envvar, TRUE, tmp_hash);
+
+      g_once_init_leave ((gsize*)&config_hash, (gsize)tmp_hash);
     }
+
+  return config_hash;
 }
 
 /**
@@ -658,11 +654,16 @@ read_config (void)
 char *
 pango_config_key_get_system (const char *key)
 {
+  GHashTable *config_hash;
+  gchar *ret;
+
   g_return_val_if_fail (key != NULL, NULL);
 
-  read_config_system ();
+  config_hash = read_config_system ();
+  ret = g_strdup (g_hash_table_lookup (config_hash, key));
+  g_hash_table_unref (config_hash);
 
-  return g_strdup (g_hash_table_lookup (config_hash, key));
+  return ret;
 }
 
 /**
@@ -679,9 +680,11 @@ pango_config_key_get_system (const char *key)
 char *
 pango_config_key_get (const char *key)
 {
+  GHashTable *config_hash;
+
   g_return_val_if_fail (key != NULL, NULL);
 
-  read_config ();
+  config_hash = read_config ();
 
   return g_strdup (g_hash_table_lookup (config_hash, key));
 }