package com.huawei.insa2.util;

public class Base64 {

	private Base64() {
	}

	public static String encode(byte b[]) {
		int code = 0;
		StringBuffer sb = new StringBuffer((b.length - 1) / 3 << 6);
		for (int i = 0; i < b.length; i++) {
			code |= b[i] << 16 - (i % 3) * 8 & 255 << 16 - (i % 3) * 8;
			if (i % 3 == 2 || i == b.length - 1) {
				sb.append(Base64Code[(code & 0xfc0000) >>> 18]);
				sb.append(Base64Code[(code & 0x3f000) >>> 12]);
				sb.append(Base64Code[(code & 0xfc0) >>> 6]);
				sb.append(Base64Code[code & 0x3f]);
				code = 0;
			}
		}

		if (b.length % 3 > 0)
			sb.setCharAt(sb.length() - 1, '=');
		if (b.length % 3 == 1)
			sb.setCharAt(sb.length() - 2, '=');
		return sb.toString();
	}

	public static byte[] decode(String code) {
		if (code == null)
			return null;
		int len = code.length();
		if (len % 4 != 0)
			throw new IllegalArgumentException(
					"Base64 string length must be 4*n");
		if (code.length() == 0)
			return new byte[0];
		int pad = 0;
		if (code.charAt(len - 1) == '=')
			pad++;
		if (code.charAt(len - 2) == '=')
			pad++;
		int retLen = (len / 4) * 3 - pad;
		byte ret[] = new byte[retLen];
		for (int i = 0; i < len; i += 4) {
			int j = (i / 4) * 3;
			char ch1 = code.charAt(i);
			char ch2 = code.charAt(i + 1);
			char ch3 = code.charAt(i + 2);
			char ch4 = code.charAt(i + 3);
			int tmp = Base64Decode[ch1] << 18 | Base64Decode[ch2] << 12
					| Base64Decode[ch3] << 6 | Base64Decode[ch4];
			ret[j] = (byte) ((tmp & 0xff0000) >> 16);
			if (i < len - 4) {
				ret[j + 1] = (byte) ((tmp & 0xff00) >> 8);
				ret[j + 2] = (byte) (tmp & 0xff);
				continue;
			}
			if (j + 1 < retLen)
				ret[j + 1] = (byte) ((tmp & 0xff00) >> 8);
			if (j + 2 < retLen)
				ret[j + 2] = (byte) (tmp & 0xff);
		}

		return ret;
	}

	private static char Base64Code[] = { '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 Base64Decode[] = { -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, 63, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
			-1, 0, -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 };

}