mlt_repository.[hc]: implement the metadata registration and lookup interface

git-svn-id: https://mlt.svn.sourceforge.net/svnroot/mlt/trunk/mlt@1078 d19143bc-622f-0410-bfdd-b5b2a6649095

diff --git a/src/framework/mlt_repository.c b/src/framework/mlt_repository.c
index 1ac8dff470b92de86d1aebc5bb49fb37686afe09..69c89eb45cbf5ebaa03c763c18ec9bee8cc62ba8 100644 (file)
--- a/src/framework/mlt_repository.c
+++ b/src/framework/mlt_repository.c
@@ -2,6 +2,7 @@
  * repository.c -- provides a map between service and shared objects
  * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
  * Author: Charles Yates <charles.yates@pandora.be>
+ * Contributor: Dan Dennedy <dan@dennedy.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -73,7 +74,7 @@ mlt_repository mlt_repository_init( const char *directory )
                if ( object != NULL )
                {
                        // Get the registration function
-                       int ( *symbol_ptr )( mlt_repository ) = dlsym( object, "mlt_register" );
+                       mlt_repository_callback symbol_ptr = dlsym( object, "mlt_register" );
                        
                        // Call the registration function
                        if ( symbol_ptr != NULL )
@@ -90,7 +91,7 @@ mlt_repository mlt_repository_init( const char *directory )
                }
                else if ( strstr( object_name, "libmlt" ) )
                {
-                       fprintf( stderr, "%s:%s: failed to dlopen %s\n", __FILE__, __FUNCTION__, object_name );
+                       fprintf( stderr, "%s, %s: failed to dlopen %s\n", __FILE__, __FUNCTION__, object_name );
                }
        }
        
@@ -108,7 +109,7 @@ static mlt_properties new_service( void *symbol )
     Typically, this is invoked by a module within its mlt_register().
 */
 
-void mlt_repository_register( mlt_repository this, mlt_service_type service_type, const char *service, void *symbol )
+void mlt_repository_register( mlt_repository this, mlt_service_type service_type, const char *service, mlt_register_callback symbol )
 {
        // Add the entry point to the corresponding service list
        switch ( service_type )
@@ -163,8 +164,7 @@ void *mlt_repository_create( mlt_repository this, mlt_profile profile, mlt_servi
        mlt_properties properties = get_service_properties( this, type, service );
        if ( properties != NULL )
        {
-               void *( *symbol_ptr )( mlt_profile, mlt_service_type, const char *, void * ) =
-                       mlt_properties_get_data( properties, "symbol", NULL );
+               mlt_register_callback symbol_ptr = mlt_properties_get_data( properties, "symbol", NULL );
        
                // Construct the service
                return ( symbol_ptr != NULL ) ? symbol_ptr( profile, type, service, input ) : NULL;
@@ -220,17 +220,47 @@ mlt_properties mlt_repository_transitions( mlt_repository self )
 /** Register the metadata for a service
     IMPORTANT: mlt_repository will take responsibility for deallocating the metadata properties that you supply!
 */
-void mlt_repository_register_metadata( mlt_repository self, mlt_service_type type, const char *service, mlt_properties metadata )
+void mlt_repository_register_metadata( mlt_repository self, mlt_service_type type, const char *service, mlt_metadata_callback callback, void *callback_data )
 {
        mlt_properties service_properties = get_service_properties( self, type, service );
-       mlt_properties_set_data( service_properties, "metadata", metadata, 0, ( mlt_destructor )mlt_properties_close, NULL );
+       mlt_properties_set_data( service_properties, "metadata_cb", callback, 0, NULL, NULL );
+       mlt_properties_set_data( service_properties, "metadata_cb_data", callback_data, 0, NULL, NULL );
 }
 
 /** Get the metadata about a service
+    Returns NULL if service or its metadata are unavailable.
 */
 
 mlt_properties mlt_repository_metadata( mlt_repository self, mlt_service_type type, const char *service )
 {
+       mlt_properties metadata = NULL;
        mlt_properties properties = get_service_properties( self, type, service );
-       return mlt_properties_get_data( properties, "metadata", NULL );
+       
+       // If this is a valid service
+       if ( properties )
+       {
+               // Lookup cached metadata
+               metadata = mlt_properties_get_data( properties, "metadata", NULL );
+               if ( ! metadata )
+               {
+                       // Not cached, so get the registered metadata callback function
+                       mlt_metadata_callback callback = mlt_properties_get_data( properties, "metadata_cb", NULL );
+
+                       // If a metadata callback function is registered
+                       if ( callback )
+                       {
+                               // Fetch the callback data arg
+                               void *data = mlt_properties_get_data( properties, "metadata_cb_data", NULL );
+                       
+                               // Fetch the metadata through the callback
+                               metadata = callback( type, service, data );
+                               
+                               // Cache the metadata
+                               if ( metadata )
+                                       // Include dellocation and serialisation
+                                       mlt_properties_set_data( properties, "metadata", metadata, 0, ( mlt_destructor )mlt_properties_close, ( mlt_serialiser )mlt_properties_serialise_yaml );
+                       }
+               }
+       }
+       return metadata;
 }

diff --git a/src/framework/mlt_repository.h b/src/framework/mlt_repository.h
index 651703029a2a5dd427ca1f30d17f90cc81ed73c4..e7b0c67393e81afa52c1a0f9b1c86a47c761179c 100644 (file)
--- a/src/framework/mlt_repository.h
+++ b/src/framework/mlt_repository.h
@@ -2,6 +2,7 @@
  * repository.h -- provides a map between service and shared objects
  * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
  * Author: Charles Yates <charles.yates@pandora.be>
+ * Contributor: Dan Dennedy <dan@dennedy.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -29,25 +30,37 @@
 
 typedef struct mlt_repository_s *mlt_repository;
 
-/** This macro can be used to register services if the function is declared as 
-*   void mlt_register( mlt_repository )
+/** This callback is the main entry point into a module, which must be exported
+    with the symbol "mlt_register".
+    Inside the callback, the module registers the additional callbacks below.
+*/
+
+typedef void ( *mlt_repository_callback )( mlt_repository );
+
+/** These are callback functions that modules implement to construct services
+    and metadata.
+*/
+typedef void *( *mlt_register_callback )( mlt_profile, mlt_service_type, const char * /* service name */, void * /* arg */ );
+typedef mlt_properties ( *mlt_metadata_callback )( mlt_service_type, const char * /* service name */, void * /* callback_data */ );
+
+/** These convenience macros can be used to register services in a more declarative manner.
 */
 #define MLT_REPOSITORY void mlt_register( mlt_repository repository )
-#define MLT_REGISTER( type, service, symbol  ) ( mlt_repository_register( repository, (type), (service), (symbol) ) )
-#define MLT_REGISTER_METADATA( type, service, properties  ) ( mlt_repository_register_metadata( repository, (type), (service), (properties) ) )
+#define MLT_REGISTER( type, service, symbol  ) ( mlt_repository_register( repository, (type), (service), ( mlt_register_callback )(symbol) ) )
+#define MLT_REGISTER_METADATA( type, service, callback, data ) ( mlt_repository_register_metadata( repository, (type), (service), ( mlt_metadata_callback )(callback), (data) ) )
 
 /** Public functions.
 */
 
 extern mlt_repository mlt_repository_init( const char *directory );
-extern void mlt_repository_register( mlt_repository self, mlt_service_type service_type, const char *service, void *symbol );
+extern void mlt_repository_register( mlt_repository self, mlt_service_type service_type, const char *service, mlt_register_callback );
 extern void *mlt_repository_create( mlt_repository self, mlt_profile profile, mlt_service_type type, const char *service, void *arg ); 
 extern void mlt_repository_close( mlt_repository self );
 extern mlt_properties mlt_repository_consumers( mlt_repository self );
 extern mlt_properties mlt_repository_filters( mlt_repository self );
 extern mlt_properties mlt_repository_producers( mlt_repository self );
 extern mlt_properties mlt_repository_transitions( mlt_repository self );
-extern void mlt_repository_register_metadata( mlt_repository self, mlt_service_type type, const char *service, mlt_properties metadata );
+extern void mlt_repository_register_metadata( mlt_repository self, mlt_service_type type, const char *service, mlt_metadata_callback, void *callback_data );
 extern mlt_properties mlt_repository_metadata( mlt_repository self, mlt_service_type type, const char *service );
 
 #endif