Base64.java

package czd.lib.encode;

/**
 *
 * @author Chen.Zhidong
 * 2011-12-20
 *
 */

import java.io.ByteArrayOutputStream;

public class Base64 {
	private static final char[] base64EncodeChars = new char[]{
			'A',
			'B',
			'C',
			'D',
			'E',
			'F',
			'G',
			'H',
			'I',
			'J',
			'K',
			'L',
			'M',
			'N',
			'O',
			'P',
			'Q',
			'R',
			'S',
			'T',
			'U',
			'V',
			'W',
			'X',
			'Y',
			'Z',
			'a',
			'b',
			'c',
			'd',
			'e',
			'f',
			'g',
			'h',
			'i',
			'j',
			'k',
			'l',
			'm',
			'n',
			'o',
			'p',
			'q',
			'r',
			's',
			't',
			'u',
			'v',
			'w',
			'x',
			'y',
			'z',
			'0',
			'1',
			'2',
			'3',
			'4',
			'5',
			'6',
			'7',
			'8',
			'9',
			'+',
			'/'
	};

	private static byte[] base64DecodeChars = new byte[]{
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			62,
			-1,
			-1,
			-1,
			63,
			52,
			53,
			54,
			55,
			56,
			57,
			58,
			59,
			60,
			61,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			0,
			1,
			2,
			3,
			4,
			5,
			6,
			7,
			8,
			9,
			10,
			11,
			12,
			13,
			14,
			15,
			16,
			17,
			18,
			19,
			20,
			21,
			22,
			23,
			24,
			25,
			-1,
			-1,
			-1,
			-1,
			-1,
			-1,
			26,
			27,
			28,
			29,
			30,
			31,
			32,
			33,
			34,
			35,
			36,
			37,
			38,
			39,
			40,
			41,
			42,
			43,
			44,
			45,
			46,
			47,
			48,
			49,
			50,
			51,
			-1,
			-1,
			-1,
			-1,
			-1
	};

	public static String encode(byte[] data) {
		StringBuilder sb = new StringBuilder();
		int len = data.length;
		int i = 0;
		int b1, b2, b3;

		while (i < len)
		{
			b1 = data[i++] & 0xff;
			if (i == len)
			{
				sb.append(Base64.base64EncodeChars[b1 >>> 2]);
				sb.append(Base64.base64EncodeChars[(b1 & 0x3) << 4]);
				sb.append("==");
				break;
			}
			b2 = data[i++] & 0xff;
			if (i == len)
			{
				sb.append(Base64.base64EncodeChars[b1 >>> 2]);
				sb.append(Base64.base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
				sb.append(Base64.base64EncodeChars[(b2 & 0x0f) << 2]);
				sb.append("=");
				break;
			}
			b3 = data[i++] & 0xff;
			sb.append(Base64.base64EncodeChars[b1 >>> 2]);
			sb.append(Base64.base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
			sb.append(Base64.base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
			sb.append(Base64.base64EncodeChars[b3 & 0x3f]);
		}
		return sb.toString();
	}

	public static byte[] decode(byte[] data) {
		int len = data.length;
		ByteArrayOutputStream buf = new ByteArrayOutputStream(len);
		int i = 0;
		int b1, b2, b3, b4;

		while (i < len)
		{

			/* b1 */
			do
			{
				b1 = Base64.base64DecodeChars[data[i++]];
			} while (i < len && b1 == -1);
			if (b1 == -1)
			{
				break;
			}

			/* b2 */
			do
			{
				b2 = Base64.base64DecodeChars[data[i++]];
			} while (i < len && b2 == -1);
			if (b2 == -1)
			{
				break;
			}
			buf.write(((b1 << 2) | ((b2 & 0x30) >>> 4)));

			/* b3 */
			do
			{
				b3 = data[i++];
				if (b3 == 61)
				{
					return buf.toByteArray();
				}
				b3 = Base64.base64DecodeChars[b3];
			} while (i < len && b3 == -1);
			if (b3 == -1)
			{
				break;
			}
			buf.write((((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));

			/* b4 */
			do
			{
				b4 = data[i++];
				if (b4 == 61)
				{
					return buf.toByteArray();
				}
				b4 = Base64.base64DecodeChars[b4];
			} while (i < len && b4 == -1);
			if (b4 == -1)
			{
				break;
			}
			buf.write((((b3 & 0x03) << 6) | b4));
		}
		return buf.toByteArray();
	}
}