decoder/{opus,vorbis}: support embedded pictures (METADATA_BLOCK_PICTURE)

More for https://github.com/MusicPlayerDaemon/MPD/issues/42

src/lib/xiph/VorbisComments.cxx

@@ -18,6 +18,7 @@
  */
 
 #include "VorbisComments.hxx"
+#include "VorbisPicture.hxx"
 #include "XiphTags.hxx"
 #include "tag/Table.hxx"
 #include "tag/Handler.hxx"
@@ -84,6 +85,12 @@ vorbis_copy_comment(StringView comment,
 static void
 vorbis_scan_comment(StringView comment, TagHandler &handler) noexcept
 {
+	const auto picture_b64 = handler.WantPicture()
+		? GetVorbisCommentValue(comment, "METADATA_BLOCK_PICTURE")
+		: nullptr;
+	if (!picture_b64.IsNull())
+		return ScanVorbisPicture(picture_b64, handler);
+
 	if (handler.WantPair()) {
 		const auto split = comment.Split('=');
 		if (!split.first.empty() && !split.second.IsNull())

src/lib/xiph/VorbisPicture.cxx

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2003-2019 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 "VorbisPicture.hxx"
+#include "lib/crypto/Base64.hxx"
+#include "tag/Id3Picture.hxx"
+#include "tag/Handler.hxx"
+#include "util/StringView.hxx"
+#include "util/WritableBuffer.hxx"
+#include "config.h"
+
+#include <memory>
+
+void
+ScanVorbisPicture(StringView value, TagHandler &handler) noexcept
+{
+#ifdef HAVE_BASE64
+	if (value.size > 1024 * 1024)
+		/* ignore image files which are too huge */
+		return;
+
+	size_t debase64_size = CalculateBase64OutputSize(value.size);
+	std::unique_ptr<uint8_t[]> debase64_buffer;
+	debase64_buffer.reset(new uint8_t[debase64_size]);
+
+	try {
+		debase64_size =
+			DecodeBase64({debase64_buffer.get(), debase64_size},
+				     value);
+	} catch (...) {
+		// TODO: log?
+		return;
+	}
+
+	return ScanId3Apic({debase64_buffer.get(), debase64_size}, handler);
+#else
+	(void)value;
+	(void)handler;
+#endif
+}

src/lib/xiph/VorbisPicture.hxx

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2003-2019 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.
+ */
+
+#ifndef MPD_VORBIS_PICTURE_HXX
+#define MPD_VORBIS_PICTURE_HXX
+
+struct StringView;
+class TagHandler;
+
+void
+ScanVorbisPicture(StringView value, TagHandler &handler) noexcept;
+
+#endif

src/lib/xiph/meson.build

@@ -47,6 +47,7 @@ endif
 xiph = static_library(
   'xiph',
   'VorbisComments.cxx',
+  'VorbisPicture.cxx',
   'XiphTags.cxx',
   include_directories: inc,
 )