Java tutorial
/* * 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. */ package org.apache.commons.codec.binary; import java.io.UnsupportedEncodingException; import org.apache.commons.codec.CharEncoding; /** * Converts hexadecimal Strings. The charset used for certain operation can be * set, the default is set in {@link #DEFAULT_CHARSET_NAME} * * @since 1.1 * @author Apache Software Foundation * @version $Id$ */ public class Hex { /** * Default charset name is {@link CharEncoding#UTF_8} * * @since 1.4 */ public static final String DEFAULT_CHARSET_NAME = CharEncoding.UTF_8; /** * Used to build output as Hex */ private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; /** * Used to build output as Hex */ private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' }; /** * Converts an array of characters representing hexadecimal 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 hexadecimal 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 IllegalArgumentException { int len = data.length; if ((len & 0x01) != 0) { throw new IllegalArgumentException("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 an array of bytes into an array of characters representing the * hexadecimal 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 hexadecimal characters */ public static char[] encodeHex(byte[] data) { return encodeHex(data, true); } /** * Converts an array of bytes into an array of characters representing the * hexadecimal 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 * @param toLowerCase * <code>true</code> converts to lowercase, <code>false</code> to * uppercase * @return A char[] containing hexadecimal characters * @since 1.4 */ public static char[] encodeHex(byte[] data, boolean toLowerCase) { return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER); } /** * Converts an array of bytes into an array of characters representing the * hexadecimal 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 * @param toDigits * the output alphabet * @return A char[] containing hexadecimal characters * @since 1.4 */ protected static char[] encodeHex(byte[] data, char[] toDigits) { 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++] = toDigits[(0xF0 & data[i]) >>> 4]; out[j++] = toDigits[0x0F & data[i]]; } return out; } /** * Converts an array of bytes into a String representing the hexadecimal * values of each byte in order. The returned String 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 String containing hexadecimal characters * @since 1.4 */ public static String encodeHexString(byte[] data) { return new String(encodeHex(data)); } /** * 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 IllegalArgumentException { int digit = Character.digit(ch, 16); if (digit == -1) { throw new IllegalArgumentException("Illegal hexadecimal character " + ch + " at index " + index); } return digit; } private final String charsetName; /** * Creates a new codec with the default charset name * {@link #DEFAULT_CHARSET_NAME} */ public Hex() { // use default encoding this.charsetName = DEFAULT_CHARSET_NAME; } /** * Creates a new codec with the given charset name. * * @param csName * the charset name. * @since 1.4 */ public Hex(String csName) { this.charsetName = csName; } /** * Converts an array of character bytes representing hexadecimal 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 hexadecimal 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 UnsupportedEncodingException { return decodeHex(new String(array, getCharsetName()).toCharArray()); } /** * Converts a String or an array of character bytes representing hexadecimal * 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 * hexadecimal 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 ClassCastException { char[] charArray = object instanceof String ? ((String) object).toCharArray() : (char[]) object; return decodeHex(charArray); } /** * Converts an array of bytes into an array of bytes for the characters * representing the hexadecimal 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. * <p> * The conversion from hexadecimal characters to the returned bytes is * performed with the charset named by {@link #getCharsetName()}. * </p> * * @param array * a byte[] to convert to Hex characters * @return A byte[] containing the bytes of the hexadecimal characters * @throws IllegalStateException * if the charsetName is invalid. This API throws * {@link IllegalStateException} instead of * {@link UnsupportedEncodingException} for backward * compatibility. * @see #encodeHex(byte[]) */ public byte[] encode(byte[] array) { return StringUtils.getBytesUnchecked(encodeHexString(array), getCharsetName()); } /** * Converts a String or an array of bytes into an array of characters * representing the hexadecimal 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. * <p> * The conversion from hexadecimal characters to bytes to be encoded to * performed with the charset named by {@link #getCharsetName()}. * </p> * * @param object * a String, or byte[] to convert to Hex characters * @return A char[] containing hexadecimal characters * @throws EncoderException * Thrown if the given object is not a String or byte[] * @see #encodeHex(byte[]) */ public Object encode(Object object) throws ClassCastException, UnsupportedEncodingException { byte[] byteArray = object instanceof String ? ((String) object).getBytes(getCharsetName()) : (byte[]) object; return encodeHex(byteArray); } /** * Gets the charset name. * * @return the charset name. * @since 1.4 */ public String getCharsetName() { return this.charsetName; } /** * Returns a string representation of the object, which includes the charset * name. * * @return a string representation of the object. */ @Override public String toString() { return super.toString() + "[charsetName=" + this.charsetName + "]"; } }