Mega Code Archive
Decodes Hex data into octects
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/* 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.
*/
//xmlbeans
import java.io.UnsupportedEncodingException;
/**
* format validation
*
* This class encodes/decodes hexadecimal data
* @author Jeffrey Rodriguez
* @version $Id: HexBin.java 125124 2005-01-14 00:23:54Z kkrouse $
*/
public class Main {
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);
}
/**
* 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);
}
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;
}
/**
* byte to be tested if it is Base64 alphabet
*
* @param octect
* @return
*/
static boolean isHex(byte octect) {
return (hexNumberTable[octect] != -1);
}
}
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