OggPageSelector.java

/*
 * myLib - https://github.com/taktod/myLib
 * Copyright (c) 2014 ttProject. All rights reserved.
 * 
 * Licensed under The MIT license.
 */
package com.ttProject.container.ogg;

import java.util.HashMap;
import java.util.Map;

import com.ttProject.container.ogg.type.Page;
import com.ttProject.container.ogg.type.StartPage;
import com.ttProject.nio.channels.IReadChannel;
import com.ttProject.unit.ISelector;
import com.ttProject.unit.IUnit;
import com.ttProject.unit.extra.BitLoader;
import com.ttProject.unit.extra.bit.Bit1;
import com.ttProject.unit.extra.bit.Bit5;
import com.ttProject.unit.extra.bit.Bit8;
import com.ttProject.util.BufferUtil;

/**
 * analyze ogg pages.
 * @author taktod
 */
public class OggPageSelector implements ISelector {
	/** logger */
//	private Logger logger = Logger.getLogger(OggPageSelector.class);
	/** startPageMap */
	private Map<Integer, StartPage> startPageMap = new HashMap<Integer, StartPage>();
	/**
	 * {@inheritDoc}
	 */
	@Override
	public IUnit select(IReadChannel channel) throws Exception {
		if(channel.size() == channel.position()) {
			// no more data.
			return null;
		}
		// read first 4 byte check string(OggS)
		String pattern = new String(BufferUtil.safeRead(channel, 4).array());
		if(!OggPage.capturePattern.equals(pattern)) {
			throw new Exception("OggS is not found.");
		}
		Bit8 version = new Bit8();
		Bit1 packetContinurousFlag = new Bit1();
		Bit1 logicStartFlag = new Bit1();
		Bit1 logicEndFlag = new Bit1();
		Bit5 zeroFill = new Bit5();
		BitLoader loader = new BitLoader(channel);
		loader.setLittleEndianFlg(true);
		loader.load(version, packetContinurousFlag,
				logicStartFlag, logicEndFlag, zeroFill
		);
		// make page
		OggPage page = null;
		if(logicStartFlag.get() == 1) {
			page = new StartPage(version, packetContinurousFlag, logicStartFlag, logicEndFlag, zeroFill);
		}
		else {
			page = new Page(version, packetContinurousFlag, logicStartFlag, logicEndFlag, zeroFill);
		}
		page.minimumLoad(channel);
		if(page instanceof StartPage) {
			startPageMap.put(page.getStreamSerialNumber(), (StartPage)page);
		}
		else {
			page.setStartPage(startPageMap.get(page.getStreamSerialNumber()));
		}
		return page;
	}
}