Fix dictionary usage and use const where possible.

include/belle-sip/dict.h

@@ -127,7 +127,7 @@ BELLESIP_EXPORT void belle_sip_dict_merge( const belle_sip_dict_t* src, belle_si
  * @return 1 if the key exists, 0 otherwise
  * @todo create unit test
  */
-BELLESIP_EXPORT int belle_sip_dict_haskey(belle_sip_dict_t* obj, const char* key);
+BELLESIP_EXPORT int belle_sip_dict_haskey(const belle_sip_dict_t* obj, const char* key);
 
 /**
  * Apply a function for all keys stored in the dictionary

include/belle-sip/object.h

@@ -239,7 +239,7 @@ BELLESIP_EXPORT void* belle_sip_object_data_get( belle_sip_object_t *obj, const
 /**
   * Return 1 if the key exists in the data store, 0 otherwise
   **/
-BELLESIP_EXPORT int belle_sip_object_data_exists( belle_sip_object_t *obj, const char* name );
+BELLESIP_EXPORT int belle_sip_object_data_exists( const belle_sip_object_t *obj, const char* name );
 
 /**
   * Destroys the named data associated by the name provided.

src/belle_sip_dict.c

@@ -113,7 +113,7 @@ void belle_sip_dict_merge( const belle_sip_dict_t* src, belle_sip_dict_t* dst)
 	belle_sip_object_data_merge(BELLE_SIP_OBJECT(src), BELLE_SIP_OBJECT(dst), belle_sip_dict_string_clone);
 }
 
-int belle_sip_dict_haskey(belle_sip_dict_t* obj, const char* key)
+int belle_sip_dict_haskey(const belle_sip_dict_t* obj, const char* key)
 {
 	return belle_sip_object_data_exists(BELLE_SIP_OBJECT(obj), key);
 }

src/belle_sip_object.c

@@ -285,7 +285,7 @@ int belle_sip_object_data_remove( belle_sip_object_t *obj, const char* name)
 	return !(list_entry!= NULL);
 }
 
-int belle_sip_object_data_exists( belle_sip_object_t *obj, const char* name )
+int belle_sip_object_data_exists( const belle_sip_object_t *obj, const char* name )
 {
 	return (belle_sip_list_find_custom(obj->data_store, belle_sip_object_data_find, name) != NULL);
 }
@@ -341,13 +341,14 @@ struct belle_sip_object_foreach_data {
 	void* userdata;
 };
 
-static void belle_sip_object_for_each_cb(void* data, void* userdata)
+static void belle_sip_object_for_each_cb(void* data, void* pvdata)
 {
-	struct belle_sip_object_foreach_data* fd = (struct belle_sip_object_foreach_data*)userdata;
-	struct belle_sip_object_data* it = (struct belle_sip_object_data*)data;
+	struct belle_sip_object_data*         it = (struct belle_sip_object_data*)data;
+	struct belle_sip_object_foreach_data* fd = (struct belle_sip_object_foreach_data*)pvdata;
 
-	if( it && fd->apply_func )
-		fd->apply_func(it->name, it->data, userdata);
+	if( it && fd->apply_func ){
+		fd->apply_func(it->name, it->data, fd->userdata);
+	}
 }
 
 void belle_sip_object_data_foreach( const belle_sip_object_t* obj, void (*apply_func)(const char* key, void* data, void* userdata), void* userdata)