decoder/flac: move class FlacMetadataChain to separate source

src/lib/xiph/FlacMetadataChain.cxx

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2003-2018 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 "FlacMetadataChain.hxx"
+#include "FlacMetadataIterator.hxx"
+#include "decoder/plugins/FlacMetadata.hxx"
+
+void
+FlacMetadataChain::Scan(TagHandler &handler) noexcept
+{
+	FlacMetadataIterator iterator(chain);
+
+	do {
+		FLAC__StreamMetadata *block = iterator.GetBlock();
+		if (block == nullptr)
+			break;
+
+		flac_scan_metadata(block, handler);
+	} while (iterator.Next());
+}