Hex.java

/*
 * Copyright (c) 2014 the original author or authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.werval.util;

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

    public static byte[] decode( CharSequence data )
    {
        return decode( data.toString().toCharArray() );
    }

    public static byte[] decode( char[] data )
    {
        int len = data.length;
        if( ( len & 0x01 ) != 0 )
        {
            throw new IllegalArgumentException( " Odd number of characters in hexadecimal encoded." );
        }
        byte[] out = new byte[ len >> 1 ];
        // two characters form the hex value.
        for( int i = 0, j = 0; j < len; i++ )
        {
            int f = toDigit( data[j], j ) << 4;
            j++;
            f |= toDigit( data[j], j );
            j++;
            out[i] = (byte) ( f & 0xFF );
        }
        return out;
    }

    public static String encode( byte[] data )
    {
        int l = data.length;
        char[] out = new char[ l << 1 ];
        // two characters form the hex value.
        for( int i = 0, j = 0; i < l; i++ )
        {
            out[j++] = HEX_DIGITS[( 0xF0 & data[i] ) >>> 4];
            out[j++] = HEX_DIGITS[ 0x0F & data[i]];
        }
        return new String( out );
    }

    private static int toDigit( char ch, int index )
    {
        int digit = Character.digit( ch, 16 );
        if( digit == -1 )
        {
            throw new IllegalArgumentException( "Illegal hexadecimal character " + ch + " at index " + index );
        }
        return digit;
    }

    private Hex()
    {
    }
}