Split theora::VideoStream into OggDemuxer and TheoraVideoStream

This makes the internal API more modular, but the split also forces a cleaner
implementation. It also means the OggDemuxer is now responsible for the
ogg-specific stuff like seeking and (ogg-specific) type detection.

Backported from the love.video-vpx branch of love-experiments

--HG--
branch : minor

src/modules/video/theora/OggDemuxer.h

@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) 2006-2016 LOVE Development Team
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ **/
+
+#ifndef LOVE_VIDEO_THEORA_OGGDEMUXER_H
+#define LOVE_VIDEO_THEORA_OGGDEMUXER_H
+
+// STL
+#include <functional>
+
+// LOVE
+#include "filesystem/File.h"
+
+// OGG
+#include <ogg/ogg.h>
+
+namespace love
+{
+namespace video
+{
+namespace theora
+{
+
+class OggDemuxer
+{
+public:
+	enum StreamType
+	{
+		TYPE_THEORA,
+		TYPE_UNKNOWN,
+	};
+
+	OggDemuxer(love::filesystem::File *file);
+	~OggDemuxer();
+
+	StreamType findStream();
+	bool readPacket(ogg_packet &packet, bool mustSucceed = false);
+	void resync();
+	bool isEos() const;
+	const std::string &getFilename() const;
+	bool seek(ogg_packet &packet, double target, std::function<double(int64)> getTime);
+
+private:
+	StrongRef<love::filesystem::File> file;
+
+	ogg_sync_state sync;
+	ogg_stream_state stream;
+	ogg_page page;
+
+	bool streamInited;
+	int videoSerial;
+
+	void readPage();
+	StreamType determineType();
+}; // OggDemuxer
+
+} // theora
+} // video
+} // love
+
+#endif // LOVE_VIDEO_THEORA_OGGDEMUXER_H