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package spring.turbo.util;

/**
 * HEX相关工具
 *
 * @author 应卓
 * @since 1.0.0
 */
public final class HexUtils {

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

    /**
     * 私有构造方法
     */
    private HexUtils() {
        super();
    }

    public static char[] encode(byte[] bytes) {
        Asserts.notNull(bytes);

        final int nBytes = bytes.length;
        char[] result = new char[2 * nBytes];

        int j = 0;
        for (byte aByte : bytes) {
            // Char for top 4 bits
            result[j++] = HEX[(0xF0 & aByte) >>> 4];
            // Bottom 4
            result[j++] = HEX[(0x0F & aByte)];
        }

        return result;
    }

    public static String encodeToString(byte[] bytes) {
        return new String(encode(bytes));
    }

    public static byte[] decode(CharSequence s) {
        Asserts.notNull(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(
                        "Detected a Non-hex character at " + (i + 1) + " or " + (i + 2) + " position");
            }
            result[i / 2] = (byte) ((msb << 4) | lsb);
        }
        return result;
    }

}