package wjb.baidu.ai.utils;

/**
 * Base64 工具类
 */
public class Base64Util {
	private static final char last2byte = (char) Integer.parseInt("00000011", 2);
	private static final char last4byte = (char) Integer.parseInt("00001111", 2);
	private static final char last6byte = (char) Integer.parseInt("00111111", 2);
	private static final char lead6byte = (char) Integer.parseInt("11111100", 2);
	private static final char lead4byte = (char) Integer.parseInt("11110000", 2);
	private static final char lead2byte = (char) Integer.parseInt("11000000", 2);
	private static final char[] encodeTable = 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', '+', '/' };

	public Base64Util() {
	}

	public static String encode(byte[] from) {
		StringBuilder to = new StringBuilder((int) ((double) from.length * 1.34D) + 3);
		int num = 0;
		char currentByte = 0;

		int i;
		for (i = 0; i < from.length; ++i) {
			for (num %= 8; num < 8; num += 6) {
				switch (num) {
				case 0:
					currentByte = (char) (from[i] & lead6byte);
					currentByte = (char) (currentByte >>> 2);
				case 1:
				case 3:
				case 5:
				default:
					break;
				case 2:
					currentByte = (char) (from[i] & last6byte);
					break;
				case 4:
					currentByte = (char) (from[i] & last4byte);
					currentByte = (char) (currentByte << 2);
					if (i + 1 < from.length) {
						currentByte = (char) (currentByte | (from[i + 1] & lead2byte) >>> 6);
					}
					break;
				case 6:
					currentByte = (char) (from[i] & last2byte);
					currentByte = (char) (currentByte << 4);
					if (i + 1 < from.length) {
						currentByte = (char) (currentByte | (from[i + 1] & lead4byte) >>> 4);
					}
				}

				to.append(encodeTable[currentByte]);
			}
		}

		if (to.length() % 4 != 0) {
			for (i = 4 - to.length() % 4; i > 0; --i) {
				to.append("=");
			}
		}

		return to.toString();
	}
}