com.mycomm.itool.compress.huffman.Huffman Maven / Gradle / Ivy
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/*
* Copyright 2020 jw362j.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.mycomm.itool.compress.huffman;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.concurrent.LinkedBlockingQueue;
/**
*
* @author jw362j
*/
class Node {
public Node left, right;
public int source;
public int weight;
public String dest;
public Node(int sour, int wei) {
source = sour;
weight = wei;
left = right = null;
dest = "";
}
}
//写入文件的头信息
class Header implements Serializable {
private static final long serialVersionUID = 1L;
public String[] mp;
public Header(String[] m) {
mp = m;
}
}
public class Huffman {
public String[] mp;
public int[] cnt;
public String path;
public Huffman(String path) {
this.path = path;
mp = new String[256];
cnt = new int[256];
}
//封装了解压的方法
public void unzip() throws FileNotFoundException, IOException, ClassNotFoundException {
ObjectInputStream ins = new ObjectInputStream(new FileInputStream(new File(path)));
FileOutputStream writer = new FileOutputStream(new File(path.substring(0, path.length() - 5)));
Header zipFile = (Header) ins.readObject();
Map mp = new HashMap();
for (int i = 0; i < 256; i++) {
if (zipFile.mp[i] != null) {
mp.put(zipFile.mp[i], (char) i);
}
}
String buff = "";
byte[] bf = null;
while (ins.available() >= 4) {
if (ins.available() == 4) {
bf = new byte[4];
for (int i = 0; i < 4; i++) {
bf[i] = ins.readByte();
}
if (ins.available() == 0) {
break;
}
for (int j = 0; j < 4; j++) {
buff += b2s(bf[j]);
while (buff.length() > 256) {
String s = "";
int cnt = 0;
for (int i = 0; i < buff.length(); i++) {
s += buff.charAt(i);
if (mp.containsKey(s)) {
writer.write(mp.get(s));
cnt += s.length();
s = "";
break;
}
}
writer.flush();
buff = buff.substring(cnt, buff.length());
}
}
}
byte c = ins.readByte();
buff += b2s(c);
while (buff.length() > 256) {
String s = "";
int cnt = 0;
for (int i = 0; i < buff.length(); i++) {
s += buff.charAt(i);
if (mp.containsKey(s)) {
writer.write(mp.get(s));
cnt += s.length();
s = "";
break;
}
}
writer.flush();
buff = buff.substring(cnt, buff.length());
}
}
for (int i = 0; i < 4; i++) {
if (bf[i] == 0) {
buff += "0";
} else if (bf[i] == 1) {
buff += "1";
}
}
String s = "";
for (int i = 0; i < buff.length(); i++) {
s += buff.charAt(i);
if (mp.containsKey(s)) {
writer.write(mp.get(s));
s = "";
}
}
writer.flush();
writer.close();
ins.close();
}
//封装了压缩的方法
public void zip() throws IOException {
readFrequency();
huffmanEncrypt();
FileInputStream ins = new FileInputStream(new File(path));
Header zipFile = new Header(mp);
ObjectOutputStream ous = new ObjectOutputStream(new FileOutputStream(path + ".huff"));
ous.writeObject(zipFile);
String buff = "";
int c;
while ((c = ins.read()) != -1) {
buff += mp[c];
while (buff.length() >= 8) {
ous.writeByte((byte) (s2b(buff.substring(0, 8))));
buff = buff.substring(8, buff.length());
}
}
for (int i = 0; i < 4; i++) {
if (i < buff.length()) {
ous.writeByte(buff.charAt(i) - '0');
} else {
ous.writeByte(255);
}
}
ous.flush();
ous.close();
ins.close();
}
//字节转二进制字符串
public String b2s(byte c) {
int cc = (c + 256) % 256;
String s = "";
while (cc > 0) {
if (cc % 2 == 1) {
s += "1";
} else {
s += "0";
}
cc /= 2;
}
while (s.length() < 8) {
s += "0";
}
return s;
}
//二进制字符串转字节
public byte s2b(String s) {
byte c = 0;
for (int i = 7; i >= 0; i--) {
c *= 2;
if (s.charAt(i) == '1') {
c += 1;
}
}
return c;
}
// 读取文件，并获得每个字符的频数
public void readFrequency() throws IOException {
File file = new File(path);
FileInputStream ins = new FileInputStream(file);
int c;
while ((c = ins.read()) != -1) {
cnt[c] += 1;
}
ins.close();
}
// 读取频数，返回Huffman映射表
public void huffmanEncrypt() {
PriorityQueue pq = new PriorityQueue(256, new Comparator() {
@Override
public int compare(Node o1, Node o2) {
return o1.weight - o2.weight;
}
});
int times = 0;
for (int i = 0; i < 256; i++) {
if (cnt[i] > 0.5) {
pq.add(new Node(i, cnt[i]));
times++;
}
}
for (int i = 0; i < times - 1; i++) {
Node nodeFir, nodeSec;
nodeFir = pq.poll();
nodeSec = pq.poll();
Node newNode = new Node(-1, nodeSec.weight + nodeFir.weight);
newNode.left = nodeSec;
newNode.right = nodeFir;
pq.add(newNode);
}
Node root = pq.poll();
Queue q = new LinkedBlockingQueue();
q.add(root);
while (!q.isEmpty()) {
Node cur = q.poll(); // bfs遍历
if (cur.source == -1) { // 非叶子节点
if (cur.left != null) {
cur.left.dest = cur.dest + "1";
q.add(cur.left);
}
if (cur.right != null) {
cur.right.dest = cur.dest + "0";
q.add(cur.right);
}
} else { // 叶子节点
mp[cur.source] = cur.dest;
}
}
}
public static void main(String[] args) throws IOException, ClassNotFoundException {
Huffman huff = new Huffman("C:\\Users\\Administrator\\Desktop\\in.txt.huff");
huff.unzip();
//Huffman huff = new Huffman("C:\\Users\\Administrator\\Desktop\\in.txt");
//huff.zip();
}
}