db_plugin: add method get_song()

New db_get_song() implementation.

src/database.c

@@ -104,8 +104,7 @@ db_get_song(const char *file)
 	if (db == NULL)
 		return NULL;
 
-	struct directory *music_root = db_get_root();
-	return directory_lookup_song(music_root, file);
+	return db_plugin_get_song(db, file, NULL);
 }
 
 bool

src/db/simple_db_plugin.c

@@ -20,6 +20,7 @@
 #include "config.h"
 #include "simple_db_plugin.h"
 #include "db_internal.h"
+#include "db_error.h"
 #include "db_save.h"
 #include "conf.h"
 #include "glib_compat.h"
@@ -214,12 +215,28 @@ simple_db_close(struct db *_db)
 	directory_free(db->root);
 }
 
+static struct song *
+simple_db_get_song(struct db *_db, const char *uri, GError **error_r)
+{
+	struct simple_db *db = (struct simple_db *)_db;
+
+	assert(db->root != NULL);
+
+	struct song *song = directory_lookup_song(db->root, uri);
+	if (song == NULL)
+		g_set_error(error_r, db_quark(), DB_NOT_FOUND,
+			    "No such song: %s", uri);
+
+	return song;
+}
+
 const struct db_plugin simple_db_plugin = {
 	.name = "simple",
 	.init = simple_db_init,
 	.finish = simple_db_finish,
 	.open = simple_db_open,
 	.close = simple_db_close,
+	.get_song = simple_db_get_song,
 };
 
 struct directory *

src/db_plugin.h

@@ -58,6 +58,15 @@ struct db_plugin {
          * Close the database, free allocated memory.
 	 */
 	void (*close)(struct db *db);
+
+	/**
+         * Look up a song (including tag data) in the database.
+	 *
+	 * @param the URI of the song within the music directory
+	 * (UTF-8)
+	 */
+	struct song *(*get_song)(struct db *db, const char *uri,
+				 GError **error_r);
 };
 
 G_GNUC_MALLOC
@@ -68,6 +77,7 @@ db_plugin_new(const struct db_plugin *plugin, const struct config_param *param,
 	assert(plugin != NULL);
 	assert(plugin->init != NULL);
 	assert(plugin->finish != NULL);
+	assert(plugin->get_song != NULL);
 	assert(error_r == NULL || *error_r == NULL);
 
 	struct db *db = plugin->init(param, error_r);
@@ -108,4 +118,15 @@ db_plugin_close(struct db *db)
 		db->plugin->close(db);
 }
 
+static inline struct song *
+db_plugin_get_song(struct db *db, const char *uri, GError **error_r)
+{
+	assert(db != NULL);
+	assert(db->plugin != NULL);
+	assert(db->plugin->get_song != NULL);
+	assert(uri != NULL);
+
+	return db->plugin->get_song(db, uri, error_r);
+}
+
 #endif