Hex encoder and decoder.
/*
* Copyright 2001-2004 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.
*/
/**
* Hex encoder and decoder.
*
* @since 1.1
* @author Apache Software Foundation
* @version $Id: Hex.java,v 1.13 2004/04/18 18:22:33 ggregory Exp $
*/
public class Hex {
/**
* Used building output as Hex
*/
private static final char[] DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a',
'b', 'c', 'd', 'e', 'f' };
/**
* Converts an array of characters representing hexidecimal values into an
* array of bytes of those same values. The returned array will be half the
* length of the passed array, as it takes two characters to represent any
* given byte. An exception is thrown if the passed char array has an odd
* number of elements.
*
* @param data
* An array of characters containing hexidecimal digits
* @return A byte array containing binary data decoded from the supplied char
* array.
* @throws DecoderException
* Thrown if an odd number or illegal of characters is supplied
*/
public static byte[] decodeHex(char[] data) throws RuntimeException {
int len = data.length;
if ((len & 0x01) != 0) {
throw new RuntimeException("Odd number of characters.");
}
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 = f | toDigit(data[j], j);
j++;
out[i] = (byte) (f & 0xFF);
}
return out;
}
/**
* Converts a hexadecimal character to an integer.
*
* @param ch
* A character to convert to an integer digit
* @param index
* The index of the character in the source
* @return An integer
* @throws DecoderException
* Thrown if ch is an illegal hex character
*/
protected static int toDigit(char ch, int index) throws RuntimeException {
int digit = Character.digit(ch, 16);
if (digit == -1) {
throw new RuntimeException("Illegal hexadecimal charcter " + ch + " at index " + index);
}
return digit;
}
/**
* Converts an array of bytes into an array of characters representing the
* hexidecimal values of each byte in order. The returned array will be double
* the length of the passed array, as it takes two characters to represent any
* given byte.
*
* @param data
* a byte[] to convert to Hex characters
* @return A char[] containing hexidecimal characters
*/
public static char[] encodeHex(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++] = DIGITS[(0xF0 & data[i]) >>> 4];
out[j++] = DIGITS[0x0F & data[i]];
}
return out;
}
/**
* Converts an array of character bytes representing hexidecimal values into
* an array of bytes of those same values. The returned array will be half the
* length of the passed array, as it takes two characters to represent any
* given byte. An exception is thrown if the passed char array has an odd
* number of elements.
*
* @param array
* An array of character bytes containing hexidecimal digits
* @return A byte array containing binary data decoded from the supplied byte
* array (representing characters).
* @throws DecoderException
* Thrown if an odd number of characters is supplied to this
* function
* @see #decodeHex(char[])
*/
public byte[] decode(byte[] array) throws RuntimeException {
return decodeHex(new String(array).toCharArray());
}
/**
* Converts a String or an array of character bytes representing hexidecimal
* values into an array of bytes of those same values. The returned array will
* be half the length of the passed String or array, as it takes two
* characters to represent any given byte. An exception is thrown if the
* passed char array has an odd number of elements.
*
* @param object
* A String or, an array of character bytes containing hexidecimal
* digits
* @return A byte array containing binary data decoded from the supplied byte
* array (representing characters).
* @throws DecoderException
* Thrown if an odd number of characters is supplied to this
* function or the object is not a String or char[]
* @see #decodeHex(char[])
*/
public Object decode(Object object) throws RuntimeException {
try {
char[] charArray = object instanceof String ? ((String) object).toCharArray()
: (char[]) object;
return decodeHex(charArray);
} catch (ClassCastException e) {
throw new RuntimeException(e.getMessage());
}
}
/**
* Converts an array of bytes into an array of bytes for the characters
* representing the hexidecimal values of each byte in order. The returned
* array will be double the length of the passed array, as it takes two
* characters to represent any given byte.
*
* @param array
* a byte[] to convert to Hex characters
* @return A byte[] containing the bytes of the hexidecimal characters
* @see #encodeHex(byte[])
*/
public byte[] encode(byte[] array) {
return new String(encodeHex(array)).getBytes();
}
/**
* Converts a String or an array of bytes into an array of characters
* representing the hexidecimal values of each byte in order. The returned
* array will be double the length of the passed String or array, as it takes
* two characters to represent any given byte.
*
* @param object
* a String, or byte[] to convert to Hex characters
* @return A char[] containing hexidecimal characters
* @throws EncoderException
* Thrown if the given object is not a String or byte[]
* @see #encodeHex(byte[])
*/
public Object encode(Object object) throws Exception {
try {
byte[] byteArray = object instanceof String ? ((String) object).getBytes() : (byte[]) object;
return encodeHex(byteArray);
} catch (ClassCastException e) {
throw new RuntimeException(e.getMessage());
}
}
}
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