decoder_plugin: added inline wrapper functions

Increase code readability, always use the wrapper functions instead of
calling the plugin method pointers directly.

src/decoder_list.c

@@ -189,7 +189,8 @@ void decoder_plugin_init_all(void)
 {
 	for (unsigned i = 0; i < num_decoder_plugins; ++i) {
 		const struct decoder_plugin *plugin = decoder_plugins[i];
-		if (plugin->init == NULL || decoder_plugins[i]->init())
+
+		if (decoder_plugin_init(plugin))
 			decoder_plugins_enabled[i] = true;
 	}
 }
@@ -198,7 +199,8 @@ void decoder_plugin_deinit_all(void)
 {
 	for (unsigned i = 0; i < num_decoder_plugins; ++i) {
 		const struct decoder_plugin *plugin = decoder_plugins[i];
-		if (decoder_plugins_enabled[i] && plugin->finish != NULL)
+
-			decoder_plugins[i]->finish();
+		if (decoder_plugins_enabled[i])
+			decoder_plugin_finish(plugin);
 	}
 }

src/decoder_plugin.h

@@ -20,6 +20,7 @@
 #define MPD_DECODER_PLUGIN_H
 
 #include <stdbool.h>
+#include <stddef.h>
 
 struct input_stream;
 struct tag;
@@ -77,4 +78,58 @@ struct decoder_plugin {
 	const char *const*mime_types;
 };
 
+/**
+ * Initialize a decoder plugin.
+ *
+ * @return true if the plugin was initialized successfully, false if
+ * the plugin is not available
+ */
+static inline bool
+decoder_plugin_init(const struct decoder_plugin *plugin)
+{
+	return plugin->init != NULL
+		? plugin->init()
+		: true;
+}
+
+/**
+ * Deinitialize a decoder plugin which was initialized successfully.
+ */
+static inline void
+decoder_plugin_finish(const struct decoder_plugin *plugin)
+{
+	if (plugin->finish != NULL)
+		plugin->finish();
+}
+
+/**
+ * Decode a stream.
+ */
+static inline void
+decoder_plugin_stream_decode(const struct decoder_plugin *plugin,
+			     struct decoder *decoder, struct input_stream *is)
+{
+	plugin->stream_decode(decoder, is);
+}
+
+/**
+ * Decode a file.
+ */
+static inline void
+decoder_plugin_file_decode(const struct decoder_plugin *plugin,
+			   struct decoder *decoder, const char *path_fs)
+{
+	plugin->file_decode(decoder, path_fs);
+}
+
+/**
+ * Read the tag of a file.
+ */
+static inline struct tag *
+decoder_plugin_tag_dup(const struct decoder_plugin *plugin,
+		       const char *path_fs)
+{
+	return plugin->tag_dup(path_fs);
+}
+
 #endif

src/decoder_thread.c

@@ -50,7 +50,7 @@ decoder_stream_decode(const struct decoder_plugin *plugin,
 	/* rewind the stream, so each plugin gets a fresh start */
 	input_stream_seek(input_stream, 0, SEEK_SET);
 
-	plugin->stream_decode(decoder, input_stream);
+	decoder_plugin_stream_decode(plugin, decoder, input_stream);
 
 	assert(dc.state == DECODE_STATE_START ||
 	       dc.state == DECODE_STATE_DECODE);
@@ -71,7 +71,7 @@ decoder_file_decode(const struct decoder_plugin *plugin,
 	assert(path[0] == '/');
 	assert(dc.state == DECODE_STATE_START);
 
-	plugin->file_decode(decoder, path);
+	decoder_plugin_file_decode(plugin, decoder, path);
 
 	assert(dc.state == DECODE_STATE_START ||
 	       dc.state == DECODE_STATE_DECODE);