added the encoder API

The new generic encoder API will replace shout's custom encoder API.

src/encoder_plugin.h

@@ -0,0 +1,194 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef MPD_ENCODER_PLUGIN_H
+#define MPD_ENCODER_PLUGIN_H
+
+#include <glib.h>
+
+#include <stdbool.h>
+#include <stddef.h>
+
+struct encoder_plugin;
+struct audio_format;
+struct config_param;
+struct tag;
+
+struct encoder {
+	const struct encoder_plugin *plugin;
+};
+
+struct encoder_plugin {
+	const char *name;
+
+	struct encoder *(*init)(const struct config_param *param,
+				GError **error);
+
+	void (*finish)(struct encoder *encoder);
+
+	bool (*open)(struct encoder *encoder,
+		     struct audio_format *audio_format,
+		     GError **error);
+
+	void (*close)(struct encoder *encoder);
+
+	bool (*flush)(struct encoder *encoder, GError **error);
+
+	bool (*tag)(struct encoder *encoder, const struct tag *tag,
+		    GError **error);
+
+	bool (*write)(struct encoder *encoder,
+		      const void *data, size_t length,
+		      GError **error);
+
+	size_t (*read)(struct encoder *encoder, void *dest, size_t length);
+};
+
+/**
+ * Initializes an encoder object.  This should be used by encoder
+ * plugins to initialize their base class.
+ */
+static inline void
+encoder_struct_init(struct encoder *encoder,
+		    const struct encoder_plugin *plugin)
+{
+	encoder->plugin = plugin;
+}
+
+/**
+ * Creates a new encoder object.
+ *
+ * @param plugin the encoder plugin
+ * @param param optional configuration
+ * @param error location to store the error occuring, or NULL to ignore errors.
+ * @return an encoder object on success, NULL on failure
+ */
+static inline struct encoder *
+encoder_init(const struct encoder_plugin *plugin,
+	     const struct config_param *param, GError **error)
+{
+	return plugin->init(param, error);
+}
+
+/**
+ * Frees an encoder object.
+ *
+ * @param encoder the encoder
+ */
+static inline void
+encoder_finish(struct encoder *encoder)
+{
+	encoder->plugin->finish(encoder);
+}
+
+/**
+ * Opens an encoder object.  You must call this prior to using it.
+ * Before you free it, you must call encoder_close().  You may open
+ * and close (reuse) one encoder any number of times.
+ *
+ * @param encoder the encoder
+ * @param audio_format the encoder's input audio format; the plugin
+ * may modify the struct to adapt it to its abilities
+ * @param error location to store the error occuring, or NULL to ignore errors.
+ * @return true on success
+ */
+static inline bool
+encoder_open(struct encoder *encoder, struct audio_format *audio_format,
+	     GError **error)
+{
+	return encoder->plugin->open(encoder, audio_format, error);
+}
+
+/**
+ * Closes an encoder object.  This disables the encoder, and readies
+ * it for reusal by calling encoder_open() again.
+ *
+ * @param encoder the encoder
+ */
+static inline void
+encoder_close(struct encoder *encoder)
+{
+	if (encoder->plugin->close != NULL)
+		encoder->plugin->close(encoder);
+}
+
+/**
+ * Flushes an encoder object, make everything which might currently be
+ * buffered available by encoder_read().
+ *
+ * @param encoder the encoder
+ * @param error location to store the error occuring, or NULL to ignore errors.
+ * @return true on success
+ */
+static inline bool
+encoder_flush(struct encoder *encoder, GError **error)
+{
+	/* this method is optional */
+	return encoder->plugin->flush != NULL
+		? encoder->plugin->flush(encoder, error)
+		: true;
+}
+
+/**
+ * Sends a tag to the encoder.
+ *
+ * @param encoder the encoder
+ * @param tag the tag object
+ * @param error location to store the error occuring, or NULL to ignore errors.
+ * @return true on success
+ */
+static inline bool
+encoder_tag(struct encoder *encoder, const struct tag *tag, GError **error)
+{
+	/* this method is optional */
+	return encoder->plugin->tag != NULL
+		? encoder->plugin->tag(encoder, tag, error)
+		: true;
+}
+
+/**
+ * Writes raw PCM data to the encoder.
+ *
+ * @param encoder the encoder
+ * @param data the buffer containing PCM samples
+ * @param length the length of the buffer in bytes
+ * @param error location to store the error occuring, or NULL to ignore errors.
+ * @return true on success
+ */
+static inline bool
+encoder_write(struct encoder *encoder, const void *data, size_t length,
+	      GError **error)
+{
+	return encoder->plugin->write(encoder, data, length, error);
+}
+
+/**
+ * Reads encoded data from the encoder.
+ *
+ * @param encoder the encoder
+ * @param dest the destination buffer to copy to
+ * @param length the maximum length of the destination buffer
+ * @return the number of bytes written to #dest
+ */
+static inline size_t
+encoder_read(struct encoder *encoder, void *dest, size_t length)
+{
+	return encoder->plugin->read(encoder, dest, length);
+}
+
+#endif