base64util.java

采用JAVA开发

/*
 * Created on 2004-8-3
 *
 * To change the template for this generated file go to
 * Window>Preferences>Java>Code Generation>Code and Comments
 */
package com.gctech.misc.util;

/**
 * <p>Title:</p>
 * <p>Description:</p>
 * <p>Copyright: Copyright (c) Gctech 2004-8-3</p>
 * <p>Company: 吉芙德资讯有限公司</p>
 *
 * @version 1.0
 * @author liyi
 *
 */

import java.util.*;
import java.math.*;

public class Base64Util {
	byte[] bytes;
	HashMap base64Table = new HashMap();
	HashMap base64DecodeTable = new HashMap();

	public Base64Util() {
		setBase64HashMap();
		setBase64DecodeHashMap();
	}

	public String decode(String s) {
		String asciiString = "";
		byte[] mask = new byte[] { 48, 48, 48, 48, 48, 48 };
		ArrayList bin8BitArray = new ArrayList();

		for (int i = 0; i < s.length(); i++) {
			String base64Code = (String) base64DecodeTable.get(s.substring(i, (i + 1)));
			String binString = new BigInteger(base64Code).toString(2);
			byte[] binByte = new BigInteger(base64Code).toString(2).getBytes();

			if (!binString.equals("1000000")) {
				for (int j = (binByte.length - 1), k = mask.length - 1; j > -1; j--, k--) {
					mask[k] = binByte[j];
				}
			}

			binString = new String(mask);
			mask = new byte[] { 48, 48, 48, 48, 48, 48 };
			asciiString = asciiString + binString;
		}

		while (asciiString.endsWith("00000000")) {
			asciiString = asciiString.substring(0, asciiString.length() - 8);
		}

		String bitGroup = "";
		for (int i = 0; i < asciiString.length(); i = i + 8) {
			bitGroup = asciiString.substring(i, i + 8);
			BigInteger bi = new BigInteger(bitGroup, 2);
			Integer asciiValue = new Integer(bi.toString());

			bin8BitArray.add(asciiValue);
		}

		asciiString = "";
		char[] myChars = new char[bin8BitArray.size()];
		for (int i = 0; i < bin8BitArray.size(); i++) {
			Integer myInteger = (Integer) bin8BitArray.get(i);
			myChars[i] = (char) myInteger.intValue();
		}

		asciiString = new String(myChars);

		return (asciiString);
	}

	public String encode(String s) {
		byte[] bytes = s.getBytes();
		byte[] mask = new byte[] { 48, 48, 48, 48, 48, 48, 48, 48 };
		String pad = "00000000";
		String binString = "";
		String base64String = "";
		ArrayList bin6BitArray = new ArrayList();

		for (int i = 0; i < bytes.length; i++) {
			byte[] myByte = new byte[1];
			myByte[0] = bytes[i];
			BigInteger bi = new BigInteger(myByte);
			byte[] binByte = bi.toString(2).getBytes();

			for (int j = (binByte.length - 1), k = mask.length - 1; j > -1; j--, k--) {
				mask[k] = binByte[j];
			}

			String wholeByte = new String(mask);
			mask = new byte[] { 48, 48, 48, 48, 48, 48, 48, 48 };

			binString = binString + wholeByte;
		}

		int sLength = binString.length() / 8;
		int sPad = 3 - (sLength % 3);

		if (sPad == 1)
			binString = binString + pad;
		else if (sPad == 2)
			binString = binString + pad + pad;

		String bitGroup = "";
		for (int i = 0; i < binString.length(); i = i + 6) {
			bitGroup = binString.substring(i, i + 6);
			BigInteger bi = new BigInteger(bitGroup, 2);

			if (bitGroup.equals("000000"))
				bin6BitArray.add("64");
			else
				bin6BitArray.add(bi.toString());
		}

		for (int i = 0; i < bin6BitArray.size(); i++) {
			String base64Code = (String) bin6BitArray.get(i);
			base64String = base64String + (String) base64Table.get(base64Code);
		}

		return (base64String);
	}

	public void setBase64HashMap() {
		char i = 0;

		char increment = 65;
		for (; i < 26; i++) {
			char[] myChars = new char[] {(char) (i + increment)};
			base64Table.put(new Integer(i).toString(), new String(myChars));
		}

		increment = (char) (97 - (i));
		for (; i < 52; i++) {
			char[] myChars = new char[] {(char) (i + increment)};
			base64Table.put(new Integer(i).toString(), new String(myChars));
		}

		increment = (char) (48 - (i));
		for (; i < 62; i++) {
			char[] myChars = new char[] {(char) (i + increment)};
			base64Table.put(new Integer(i).toString(), new String(myChars));
		}

		base64Table.put(new Integer(62).toString(), "+");

		base64Table.put(new Integer(63).toString(), "/");

		base64Table.put(new Integer(64).toString(), "=");
	}

	public void setBase64DecodeHashMap() {
		char i = 0;

		char increment = 65;
		for (; i < 26; i++) {
			char[] myChars = new char[] {(char) (i + increment)};
			base64DecodeTable.put(new String(myChars), new Integer(i).toString());
		}

		increment = (char) (97 - (i));
		for (; i < 52; i++) {
			char[] myChars = new char[] {(char) (i + increment)};
			base64DecodeTable.put(new String(myChars), new Integer(i).toString());
		}

		increment = (char) (48 - (i));
		for (; i < 62; i++) {
			char[] myChars = new char[] {(char) (i + increment)};
			base64DecodeTable.put(new String(myChars), new Integer(i).toString());
		}

		base64DecodeTable.put("+", new Integer(62).toString());

		base64DecodeTable.put("/", new Integer(63).toString());

		base64DecodeTable.put("=", new Integer(64).toString());
	}
	public static void main(String[] args){
		Base64Util util = new Base64Util();
		System.out.println(util.decode("bmV3cwA="));
		System.out.println(util.encode("news"));
	}
}