src/decoder/opus: new decoder plugin for the Opus codec

Using libopus and libogg.

src/decoder/OggUtil.cxx

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2003-2012 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.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "OggUtil.hxx"
+
+extern "C" {
+#include "decoder_api.h"
+}
+
+bool
+OggFeed(ogg_sync_state &oy, struct decoder *decoder,
+	struct input_stream *input_stream, size_t size)
+{
+		char *buffer = ogg_sync_buffer(&oy, size);
+		if (buffer == nullptr)
+			return false;
+
+		size_t nbytes = decoder_read(decoder, input_stream,
+					     buffer, size);
+		if (nbytes == 0)
+			return false;
+
+		ogg_sync_wrote(&oy, nbytes);
+		return true;
+}
+
+bool
+OggExpectPage(ogg_sync_state &oy, ogg_page &page,
+	      struct decoder *decoder, struct input_stream *input_stream)
+{
+	while (true) {
+		int r = ogg_sync_pageout(&oy, &page);
+		if (r != 0)
+			return r > 0;
+
+		if (!OggFeed(oy, decoder, input_stream, 1024))
+			return false;
+	}
+}