Decode hex string to a byte array : Byte Array « File « Java Tutorial

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */


/**
 * format validation
 *
 * This class encodes/decodes hexadecimal data
 * 
 * @xerces.internal  
 * 
 * @author Jeffrey Rodriguez
 * @version $Id: HexBin.java 446747 2006-09-15 21:46:20Z mrglavas $
 */
public final class  HexBin {
    static private final int  BASELENGTH   = 128;
    static private final int  LOOKUPLENGTH = 16;
    static final private byte [] hexNumberTable    = new byte[BASELENGTH];
    static final private char [] lookUpHexAlphabet = new char[LOOKUPLENGTH];


    static {
        for (int i = 0; i < BASELENGTH; i++ ) {
            hexNumberTable[i] = -1;
        }
        for ( int i = '9'; i >= '0'; i--) {
            hexNumberTable[i] = (byte) (i-'0');
        }
        for ( int i = 'F'; i>= 'A'; i--) {
            hexNumberTable[i] = (byte) ( i-'A' + 10 );
        }
        for ( int i = 'f'; i>= 'a'; i--) {
           hexNumberTable[i] = (byte) ( i-'a' + 10 );
        }

        for(int i = 0; i<10; i++ ) {
            lookUpHexAlphabet[i] = (char)('0'+i);
        }
        for(int i = 10; i<=15; i++ ) {
            lookUpHexAlphabet[i] = (char)('A'+i -10);
        }
    }

    /**
     * Decode hex string to a byte array
     *
     * @param encoded encoded string
     * @return return array of byte to encode
     */
    static public byte[] decode(String encoded) {
        if (encoded == null)
            return null;
        int lengthData = encoded.length();
        if (lengthData % 2 != 0)
            return null;

        char[] binaryData = encoded.toCharArray();
        int lengthDecode = lengthData / 2;
        byte[] decodedData = new byte[lengthDecode];
        byte temp1, temp2;
        char tempChar;
        for( int i = 0; i<lengthDecode; i++ ){
            tempChar = binaryData[i*2];
            temp1 = (tempChar < BASELENGTH) ? hexNumberTable[tempChar] : -1;
            if (temp1 == -1)
                return null;
            tempChar = binaryData[i*2+1];
            temp2 = (tempChar < BASELENGTH) ? hexNumberTable[tempChar] : -1;
            if (temp2 == -1)
                return null;
            decodedData[i] = (byte)((temp1 << 4) | temp2);
        }
        return decodedData;
    }
}