数据结构哈夫曼树的应用之文件的压缩和解压（java）

数据结构哈夫曼树的应用之文件的压缩和解压（java）

package com.haiyang.datastructure.huffmancode;

import com.sun.org.apache.bcel.internal.generic.NEW;

import java.io.*;
import java.util.*;


public class HuffmanCode {
    //标记最后一个数的位数
    static int lastCode = 8;
    //用于存储哈夫曼编码
    static Map huffmanCodes = new HashMap();
    //用于拼接哈夫曼编码
    static StringBuilder stringBuilder = new StringBuilder();

    public static void main(String[] args) {
        zipFile("C:\Users\haiyang\Pictures\草纸\3.jpg", "C:\Users\haiyang\Pictures\草纸\3.zip");
        unZipFile("C:\Users\haiyang\Pictures\草纸\3.zip", "C:\Users\haiyang\Pictures\草纸\6.jpg");

    }

    
    public static void unZipFile(String zipFile, String dstFile) {
        InputStream is = null;
        OutputStream os = null;
        ObjectInputStream ois = null;
        try {
            is = new FileInputStream(zipFile);//通过输入流读取压缩后文件
            ois = new ObjectInputStream(is);//通过对象流读取压缩后文件和哈夫曼编码两部分
            byte[] huffmanBytes = (byte[]) ois.readObject();
            Map huffmanCodes = (Map) ois.readObject();
            byte[] decode = decode(huffmanCodes, huffmanBytes);//进行解压
            os = new FileOutputStream(dstFile);//通过输出流保存解压后文件
            os.write(decode);//写入解压后文件
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                os.close();
                ois.close();
                is.close();
            } catch (IOException e) {
                System.out.println(e.getMessage());
            }

        }
    }

    
    public static void zipFile(String srcFile, String dstFile) {
        FileInputStream is = null;
        FileOutputStream os = null;
        ObjectOutputStream oos = null;
        try {
            is = new FileInputStream(srcFile);//通过输入流读取文件
            byte[] b = new byte[is.available()];//用于读取文件
            is.read(b);//读取文件到byte[] 中
            byte[] huffmanZip = huffmanZip(b);//进行压缩
            os = new FileOutputStream(dstFile);//输出流保存压缩后文件
            oos = new ObjectOutputStream(os);//因为需保存压缩后文件和哈夫曼编码两部分，使用对象流方便 *** 作
            oos.writeObject(huffmanZip);//写入压缩后文件
            oos.writeObject(huffmanCodes);//写入哈夫曼编码
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
                os.close();
                oos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


    
    public static byte[] decode(Map huffmanCodes, byte[] bytes) {
        //
        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < bytes.length; i++) {
            byte b = bytes[i];
            boolean flag = (i == bytes.length - 1);
            stringBuilder.append(byteToBitString(!flag, b));

        }
        System.out.println(stringBuilder.length());
        //将huffmanCodes 翻转便于比较
        HashMap map = new HashMap<>();
        for (Map.Entry entry : huffmanCodes.entrySet()) {
            map.put(entry.getValue(), entry.getKey());
        }
        //存储比较完成的字符串
        ArrayList list = new ArrayList<>();

        for (int i = 0; i < stringBuilder.length(); ) {
            int count = 1;
            boolean flag = true;
            Byte b = null;
            while (flag) {
                String s = stringBuilder.substring(i, i + count);
                b = map.get(s);
                if (b == null) {
                    count++;
                } else {
                    flag = false;
                }
            }
            list.add(b);
            i += count;

        }
        byte[] bytes1 = new byte[list.size()];
        for (int i = 0; i < list.size(); i++) {
            bytes1[i] = list.get(i);
        }
        return bytes1;
    }

    
    public static String byteToBitString(boolean flag, byte b) {
        int temp = b;//将字节转化为整数类型
        temp |= 256;//整数需要补位       按位与256运算  1 0000 0000 | 0000 0001 => 1 0000 0001

        String str = Integer.toBinaryString(temp);//将整数转化为二进制补码
        if (flag) {
            return str.substring(str.length() - 8);//每个整数占4个字节，32位需取后八位
        } else {
            return str.substring(str.length() - lastCode);//如果字节数组的最后一位位整数，解析时不需要补位
        }
    }

    
    public static byte[] huffmanZip(byte[] bytes) {
        //调用getCodes方法将字节数组转化为结点类型
        List nodes = getNodes(bytes);
        //创建哈夫曼树
        Node huffmanTree = createHuffmanTree(nodes);
        //获取哈夫曼编码
        Map codes = getCodes(huffmanTree);
        byte[] zip = zip(bytes, codes);

        return zip;
    }

    
    public static byte[] zip(byte[] bytes, Map huffmanCodes) {
        //将所有字节的哈夫曼编码拼接
        StringBuilder stringBuilder = new StringBuilder();
        for (byte b : bytes) {
            //遍历字节数组，进行哈夫曼编码拼接
            stringBuilder.append(huffmanCodes.get(b));
        }

//        System.out.println(stringBuilder.toString());

        int len;
        //每8位代表一个字节
        if (stringBuilder.length() % 8 == 0) {
            len = stringBuilder.length() / 8;
        } else {
            lastCode = stringBuilder.length() % 8;
            len = stringBuilder.length() / 8 + 1;
        }


        byte[] bys = new byte[len];
        int index = 0;
        for (int i = 0; i < stringBuilder.length(); i += 8) {
            String strByte;
            if (i + 8 > stringBuilder.length()) {
                strByte = stringBuilder.substring(i);


            } else {
                strByte = stringBuilder.substring(i, i + 8);
            }
            bys[index] = (byte) Integer.parseInt(strByte, 2);
            index++;
        }

        return bys;
    }


    
    public static void getCodes(Node node, String code, StringBuilder stringBuilder) {
        StringBuilder stringBuilder1 = new StringBuilder(stringBuilder);
        stringBuilder1.append(code);
        if (node != null) {
            if (node.data == null) { //代表非叶子结点
                getCodes(node.left, "0", stringBuilder1);
                getCodes(node.right, "1", stringBuilder1);
            } else {
                //如果是叶子结点，代表该字符的编码已拼接完成，加入到Map中
                huffmanCodes.put(node.data, stringBuilder1.toString());

            }
        }
    }

    
    public static Map getCodes(Node root) {
        if (root == null) {
            return null;
        }
        getCodes(root.left, "0", stringBuilder);
        getCodes(root.right, "1", stringBuilder);
        return huffmanCodes;
    }

    public static void preOrder(Node root) {
        if (root != null) {
            root.preOrder();
        } else {
            System.out.println("树为空，无法遍历");
        }
    }

    //将字节数组转化为结点类型
    public static List getNodes(byte[] bytes) {
        ArrayList nodes = new ArrayList<>();//储存结点
        HashMap map = new HashMap<>();//储存每种字节出现的次数
        for (byte b : bytes) {
            //遍历数组记录每种字节出现的次数
            Integer count = map.get(b);
            if (count == null) {
                map.put(b, 1);
            } else {
                map.put(b, count + 1);
            }
        }

        for (Map.Entry entry : map.entrySet()) {
            //遍历Map将每种字节及其出现的次数转化为结点
            nodes.add(new Node(entry.getKey(), entry.getValue()));
        }
        return nodes;
    }

    
    public static Node createHuffmanTree(List nodes) {
        while (nodes.size() > 1) {
            //按weight升序排序
            Collections.sort(nodes);
            //从结点列表nodes中选取两个最小的结点
            Node leftNode = nodes.get(0);
            Node rightNode = nodes.get(1);
            //通过选取的结点构建一棵树,其根节点的weight为两个最小结点的和
            Node parent = new Node(null, leftNode.weight + rightNode.weight);
            parent.left = leftNode;
            parent.right = rightNode;
            //将结点列表中的已选取两个最小的结点移除，并将新构建的树的根节点加入到结点列表中
            nodes.remove(leftNode);
            nodes.remove(rightNode);
            nodes.add(parent);
        }
        return nodes.get(0);
    }
}

class Node implements Comparable {
    //在给定的序列中，每种字符是一个data，weight代表每种字符出现堆得次数
    Byte data;
    int weight;
    Node left;
    Node right;

    public Node(Byte data, int weight) {
        this.data = data;
        this.weight = weight;
    }

    @Override
    public String toString() {
        return "Node{" +
                "data=" + data +
                ", weight=" + weight +
                '}';
    }

    //自定义比较器，通过weight进行升序排序
    @Override
    public int compareTo(Node o) {
        return this.weight - o.weight;
    }

    //先序遍历 用于查看构建的大顶堆是否正确
    public void preOrder() {
        System.out.println(this);
        if (this.left != null) {
            this.left.preOrder();
        }
        if (this.right != null) {
            this.right.preOrder();
        }
    }
}