113 lines
3.4 KiB
Java
113 lines
3.4 KiB
Java
package com.pdfjet;
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import java.io.*;
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import java.util.*;
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public class LZWEncode {
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private LookupTable table = new LookupTable();
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private int bitBuffer = 0;
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private int bitsInBuffer = 0;
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public LZWEncode(byte[] buffer, OutputStream stream) throws Exception {
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int code1 = 0;
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int code2 = 258;
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int length = 9;
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writeCode(256, length, stream); // Clear Table code
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List<Byte> key = new ArrayList<Byte>();
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int i = 0;
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while (i < buffer.length) {
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key.add(buffer[i]);
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int code = table.at(key, /*put:*/ code2);
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if (code >= 0) {
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code1 = code;
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i += 1;
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if (i < buffer.length) {
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continue;
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}
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writeCode(code1, length, stream);
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}
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else {
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writeCode(code1, length, stream);
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code2 += 1;
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if (code2 == 512) {
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length = 10;
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}
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else if (code2 == 1024) {
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length = 11;
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}
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else if (code2 == 2048) {
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length = 12;
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}
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else if (code2 == 4095) { // EarlyChange is 1
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writeCode(256, length, stream); // Clear Table code
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code2 = 258;
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length = 9;
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table.clear();
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}
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key.clear();
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}
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}
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writeCode(257, length, stream); // EOD
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if (bitsInBuffer > 0) {
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stream.write((bitBuffer << (8 - bitsInBuffer)) & 0xFF);
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}
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}
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private void writeCode(
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int code, int length, OutputStream stream) throws Exception {
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bitBuffer <<= length;
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bitBuffer |= code;
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bitsInBuffer += length;
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while (bitsInBuffer >= 8) {
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stream.write((bitBuffer >>> (bitsInBuffer - 8)) & 0xFF);
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bitsInBuffer -= 8;
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}
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}
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/*
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private static String toBinaryString(
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int value,
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int numOfDigits) {
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StringBuilder buf = new StringBuilder();
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String str = Integer.toBinaryString(value).toUpperCase();
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int len = str.length();
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while (len < numOfDigits) {
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buf.append("0");
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len += 1;
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}
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buf.append(str);
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str = buf.toString();
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if (numOfDigits == 32) {
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buf.setLength(0);
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for (int i = 0; i < str.length(); i++) {
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if (i > 0 && i % 8 == 0) {
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buf.append(" ");
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}
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buf.append(str.charAt(i));
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}
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str = buf.toString();
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}
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return str;
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}
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public static void main(String[] args) throws Exception {
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String fileName = "data/world-communications.txt";
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int fileSize = (int) (new File(fileName)).length();
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BufferedOutputStream stream =
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new BufferedOutputStream(new FileOutputStream("world-commnunications.lzw"));
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FileInputStream fis = new FileInputStream(fileName);
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byte[] buf = new byte[fileSize];
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int len = fis.read(buf, 0, buf.length);
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long time1 = System.currentTimeMillis();
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new LZWEncode(buf, stream);
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long time2 = System.currentTimeMillis();
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System.out.println(time2 - time1);
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fis.close();
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stream.close();
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}
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*/
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}
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