[evolution-kolab/ek-wip-porting] CamelIMAPXExtdServer: use GOnce in init() for thread safety

[Christian Hilberg <chilberg src gnome org>]

commit 8c2103b56dc208075422d26fa7051ffc42a2250f
Author: Christian Hilberg <hilberg kernelconcepts de>
Date:   Fri Jul 20 16:49:46 2012 +0200

    CamelIMAPXExtdServer: use GOnce in init() for thread safety
    
    * registering of untagged handler functions
      must be done once only, and in a thread-safe
      way

 src/libekolab/camel-imapx-extd-server.c |   41 ++++++++++++++++++++++---------
 1 files changed, 29 insertions(+), 12 deletions(-)
---
diff --git a/src/libekolab/camel-imapx-extd-server.c b/src/libekolab/camel-imapx-extd-server.c
index cae8859..e936d79 100644
--- a/src/libekolab/camel-imapx-extd-server.c
+++ b/src/libekolab/camel-imapx-extd-server.c
@@ -50,6 +50,24 @@ static const CamelIMAPXUntaggedRespHandlerDesc desc = {
 
 /*----------------------------------------------------------------------------*/
 
+static gpointer
+imapx_extd_server_register_untagged_fn (gpointer data)
+{
+	CamelIMAPXServer *is = CAMEL_IMAPX_SERVER (data);
+	const CamelIMAPXUntaggedRespHandlerDesc *prev = NULL;
+
+	prev = camel_imapx_server_register_untagged_handler (is,
+	                                                     IMAPX_IMAP_TOKEN_ANNOTATION,
+	                                                     &desc);
+	/* Make sure we do not have been registered before.
+	 * Returning non-NULL here means that the handler
+	 * has been registered before, which is an error.
+	 * This needs to be checked for all handlers which
+	 * are registered here.
+	 */
+	return (gpointer)prev;
+}
+
 static gboolean
 camel_imapx_extd_server_untagged_annotation (CamelIMAPXServer *is,
                                              GCancellable *cancellable,
@@ -104,24 +122,23 @@ camel_imapx_extd_server_init (CamelIMAPXServer *is,
                               GCancellable *cancellable,
                               GError **err)
 {
-	const CamelIMAPXUntaggedRespHandlerDesc *prev = NULL;
-	static gboolean is_inited = FALSE;
+	static GOnce my_once = G_ONCE_INIT;
 
 	g_assert (CAMEL_IS_IMAPX_SERVER (is));
 	(void)cancellable; /* cancellable may be NULL */
 	g_return_val_if_fail (err == NULL || *err == NULL, FALSE);
 
-	/* TODO change this for a g_once() */
-	if (is_inited)
-		return TRUE;
-
-	prev = camel_imapx_server_register_untagged_handler (is,
-	                                                     IMAPX_IMAP_TOKEN_ANNOTATION,
-	                                                     &desc);
-	/* make sure we do not have been registered before */
-	g_assert (prev == NULL);
+	g_once (&my_once,
+	        imapx_extd_server_register_untagged_fn,
+	        is);
 
-	is_inited = TRUE;
+	if (my_once.retval != NULL) {
+		g_set_error (err,
+		             CAMEL_IMAPX_ERROR,
+		             1, /* define and set a sensible code here */
+		             _("A CamelIMAPXServer extended untagged response handler has been registered twice"));
+		return FALSE;
+	}
 
 	return TRUE;
 }