package com.uas.utils;

public final class Hex {
	private static final char[] HEX = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

	public static char[] encode(byte[] bytes) {
		int nBytes = bytes.length;
		char[] result = new char[2 * nBytes];

		int j = 0;
		for (int i = 0; i < nBytes; ++i) {
			result[(j++)] = HEX[((0xF0 & bytes[i]) >>> 4)];

			result[(j++)] = HEX[(0xF & bytes[i])];
		}

		return result;
	}

	public static byte[] decode(CharSequence s) {
		int nChars = s.length();

		if (nChars % 2 != 0) {
			throw new IllegalArgumentException("Hex-encoded string must have an even number of characters");
		}

		byte[] result = new byte[nChars / 2];

		for (int i = 0; i < nChars; i += 2) {
			int msb = Character.digit(s.charAt(i), 16);
			int lsb = Character.digit(s.charAt(i + 1), 16);

			if ((msb < 0) || (lsb < 0)) {
				throw new IllegalArgumentException("Non-hex character in input: " + s);
			}
			result[(i / 2)] = (byte) (msb << 4 | lsb);
		}
		return result;
	}
}