compress.java

基于哈夫曼树的压缩解压程序源代码

package logical;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

public class Compress {

	String[] code = new String[256];

	Node[] tree;

	String textName = null; // The name of the file that needs to be compressed

	String fileName = null; // The name of the compressed file

	public Compress(String textName, String fileName) throws IOException {
		this.textName = textName;
		this.fileName = fileName;
		init();
	}

	public void init() throws IOException {

		Reader reader = new Reader(textName); // Read a new file
		this.code = reader.getHuffmanCode(); // Get the huffman code of the
												// file
		this.tree = reader.getHuffmanTree(); // Get the huffman tree of the
												// file
		this.creatCompressedFile(); // Creat the compressed file

	}

	private void creatCompressedFile() throws IOException {
		// Read the file that needs to be compressed
		BufferedInputStream input = new BufferedInputStream(
				new FileInputStream(textName));

		ObjectOutputStream output = new ObjectOutputStream(
				new FileOutputStream(fileName));

		// Read the tree of the file
		output.writeObject(tree);

		int temp; // store the byte that be read from the file
		StringBuffer content = new StringBuffer(); // store the content
		int addLength; // store the length that should be added in the tail

		/** According to the code, translate them into the byte */
		while ((temp = input.read()) != -1) {
			content.append(this.code[temp]);
			int length = content.length() >> 3;
			for (int i = 0; i < length; i++) {
				output.write(B2U(content.substring(0, 8))); // write the bytes
															// into the file
				content.delete(0, 8);
			}
		}
		if (content.length() == 0)
			addLength = 0;

		else {
			// Add 0's at the end of the content
			addLength = 8 - content.length();
			for (int i = 0; i < addLength; i++) {
				content.append('0');
			}
			output.write(B2U(content.substring(0, 8)));
			content.delete(0, 8);

		}

		input.close();
		output.close();
	}

	// Acoording the code, translate them into unsign int
	public int B2U(String s) {
		int value = 0;

		for (int i = 0; i < 8; i++) {
			if (s.charAt(i) == '1') {
				value += 0x1 << (7 - i);
			}
		}
		return value;
	}
}