myclass1.jsl

Bitmap 文件的压缩和解压缩

import java.util.ArrayList; 
import java.util.LinkedList; 

	/** This class is only for Lempel-Ziv decompression. */ 
public class LempelZivTable 
{ 

	/* maximum of nodes */ 
	private int maxNodes; 

	/* identity of current node */ 
	private int currentId; 

	/* list of pairs of table, the indices are the ids of nodes */ 
	private ArrayList pairs; 

	/** 
	 * Instantiates the <code>LempelZivTable</code> object. 
	 * @param maxNodes the maximum of nodes. It must be 
	 *        lower than <code>Integer.MAX_VALUE</code>. 
	 */ 
	public LempelZivTable (int maxNodes) 
	{ 

		this.maxNodes = maxNodes; 
		this.currentId = 1; 
		this.pairs = new ArrayList(maxNodes + 1); 

		// to calculate the bit string of a node, 
		// the first two elements must be 'null' 
		this.pairs.add(0, null); 
		this.pairs.add(1, null); 

	} // end of constructor LempelZivTable 

	/** 
	 * Adds to the given <code>restBits</code> the bit string of 
	 * the given complete <code>pair</code>. 
	 * @param pair complete pair. 
	 * @param restBits the buffered bits which could not be saved, 
	 *        because to less bits. 
	 * @return bit string. 
	 */ 
	public LinkedList getBitsOfPair (short pair, LinkedList restBits) 
	{ 

		LinkedList result = new LinkedList(); 
		Pair currentPair = new Pair(pair); 

		if (this.maxNodes > this.currentId) 
		{ 

			this.currentId++; 
			this.pairs.add(this.currentId, currentPair); 
		} 

		do 
		{ 

			result.addFirst(new Boolean(currentPair.bit)); 
			currentPair = (Pair)this.pairs.get(currentPair.predecessorId); 

		} while (currentPair != null); 

		// add the given restBits in front of the pair bit list 
		result.addAll(0, restBits); 

		return result; 

	} // end of getBitsOfPair 

	/** 
	 * Adds to the given <code>restBits</code> the bit string of 
	 * the given <code>nodeId</code> (last pair). 
	 * @param nodeId positive node identity of uncomplete pair. 
	 * @param restBits the buffered bits which could not be saved, 
	 *        because to less bits. 
	 * @return bit string. 
	 */ 
	public LinkedList getBitsOfNode (int nodeId, LinkedList restBits) 
	{ 

		LinkedList result = new LinkedList(); 
		Pair currentPair = (Pair)this.pairs.get(nodeId); 

		while (currentPair != null) 
		{ 

			result.addFirst(new Boolean(currentPair.bit)); 
			currentPair = (Pair)this.pairs.get(currentPair.predecessorId); 
		} 

		// add the given restBits in front of the pair bit list 
		result.addAll(0, restBits); 

		return result; 

	} // end of getBitsOfNode 

	/* Element for ArrayList pair */ 
	private class Pair 
	{ 

		/* the own bit */ 
		private boolean bit; 

		/* the predecessor of this pair */ 
		private int predecessorId; 

		/* instantiates a pair element */ 
		private Pair (short pair) 
		{ 

			this.bit = pair < 0; 

			if (this.bit) 
			{ 
				this.predecessorId = (int)(-pair); 
			} 
			else 
			{ 
				this.predecessorId = (int)pair; 
			} 
		} // end of constructor Pair 
	} // end of private class Pair 
} // end of public class LempelZivTable