/*   Copyright 2004 The Apache Software Foundation
 *
 *   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 org.apache.xmlbeans.impl.util;

import java.io.UnsupportedEncodingException;
/**
 * format validation
 *
 * This class encodes/decodes hexadecimal data
 * @author Jeffrey Rodriguez
 * @version $Id$
 */
public final class  HexBin {
    static private final int  BASELENGTH   = 255;
    static private final int  LOOKUPLENGTH = 16;
    static private byte [] hexNumberTable    = new byte[BASELENGTH];
    static private byte [] lookUpHexAlphabet = new byte[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] = (byte) ('0'+i );
        for(int i = 10; i<=15; i++ )
            lookUpHexAlphabet[i] = (byte) ('A'+i -10);
    }

    /**
     * byte to be tested if it is Base64 alphabet
     *
     * @param octect
     * @return
     */
    static boolean isHex(byte octect) {
        return (hexNumberTable[octect] != -1);
    }

    /**
     * Converts bytes to a hex string
     */
    static public String bytesToString(byte[] binaryData)
    {
        if (binaryData == null)
            return null;
        return new String(encode(binaryData));
    }

    /**
     * Converts a hex string to a byte array.
     */
    static public byte[] stringToBytes(String hexEncoded)
    {
        return decode(hexEncoded.getBytes());
    }

    /**
     * array of byte to encode
     *
     * @param binaryData
     * @return return encode binary array
     */
    static public byte[] encode(byte[] binaryData) {
        if (binaryData == null)
            return null;
        int lengthData   = binaryData.length;
        int lengthEncode = lengthData * 2;
        byte[] encodedData = new byte[lengthEncode];
        for( int i = 0; i<lengthData; i++ ){
            encodedData[i*2] = lookUpHexAlphabet[(binaryData[i] >> 4) & 0xf];
            encodedData[i*2+1] = lookUpHexAlphabet[ binaryData[i] & 0xf];
        }
        return encodedData;
    }

    static public byte[] decode(byte[] binaryData) {
        if (binaryData == null)
            return null;
        int lengthData   = binaryData.length;
        if (lengthData % 2 != 0)
            return null;

        int lengthDecode = lengthData / 2;
        byte[] decodedData = new byte[lengthDecode];
        for( int i = 0; i<lengthDecode; i++ ){
            if (!isHex(binaryData[i*2]) || !isHex(binaryData[i*2+1])) {
                return null;
            }
            decodedData[i] = (byte)((hexNumberTable[binaryData[i*2]] << 4) | hexNumberTable[binaryData[i*2+1]]);
        }
        return decodedData;
    }

    /**
     * Decodes Hex data into octects
     *
     * @param binaryData String containing Hex data
     * @return string containing decoded data.
     */
    public static String decode(String binaryData) {
        if (binaryData == null)
            return null;

        byte[] decoded = null;
        try {
          decoded = decode(binaryData.getBytes("utf-8"));
        }
        catch(UnsupportedEncodingException e) {
        }
        return decoded == null ? null : new String(decoded);
    }

    /**
     * Encodes octects (using utf-8) into Hex data
     *
     * @param binaryData String containing Hex data
     * @return string containing decoded data.
     */
    public static String encode(String binaryData) {
        if (binaryData == null)
            return null;

        byte[] encoded = null;
        try {
          encoded = encode(binaryData.getBytes("utf-8"));
        }
        catch(UnsupportedEncodingException e) {}
        return encoded == null ? null : new String(encoded);
    }

}