/*
 * 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.nio.ByteBuffer;
import java.nio.charset.Charset;

import org.apache.commons.codec.BinaryDecoder;
import org.apache.commons.codec.BinaryEncoder;
import org.apache.commons.codec.CharEncoding;
import org.apache.commons.codec.Charsets;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.EncoderException;

Converts hexadecimal Strings. The charset used for certain operation can be set, the default is set in DEFAULT_CHARSET_NAME This class is thread-safe. 
Since:
1.1
Version:
$Id$/**
 * Converts hexadecimal Strings. The charset used for certain operation can be set, the default is set in
 * {@link #DEFAULT_CHARSET_NAME}
 *
 * This class is thread-safe.
 *
 * @since 1.1
 * @version $Id$
 */
public class Hex implements BinaryEncoder, BinaryDecoder {

    
Default charset is Charsets.UTF_8 
Since:
1.7/**
     * Default charset is {@link Charsets#UTF_8}
     *
     * @since 1.7
     */
    public static final Charset DEFAULT_CHARSET = Charsets.UTF_8;

    
Default charset name is CharEncoding.UTF_8 
Since:
1.4/**
     * 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
/**
     * 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
/**
     * 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 a String representing hexadecimal values into an array of bytes of those same values. The
returned array will be half the length of the passed String, as it takes two characters to represent any given
byte. An exception is thrown if the passed String has an odd number of elements.
Params:
data – 
           A String containing hexadecimal digits
Throws:
DecoderException – 
            Thrown if an odd number or illegal of characters is supplied
Returns:
A byte array containing binary data decoded from the supplied char array.
Since:
1.11/**
     * Converts a String representing hexadecimal values into an array of bytes of those same values. The
     * returned array will be half the length of the passed String, as it takes two characters to represent any given
     * byte. An exception is thrown if the passed String has an odd number of elements.
     *
     * @param data
     *            A String 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
     * @since 1.11
     */
    public static byte[] decodeHex(final String data) throws DecoderException {
        return decodeHex(data.toCharArray());
    }

    
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.
Params:
data – 
           An array of characters containing hexadecimal digits
Throws:
DecoderException – 
            Thrown if an odd number or illegal of characters is supplied
Returns:
A byte array containing binary data decoded from the supplied char array./**
     * 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(final char[] data) throws DecoderException {

        final int len = data.length;

        if ((len & 0x01) != 0) {
            throw new DecoderException("Odd number of characters.");
        }

        final 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.
Params:
data – 
           a byte[] to convert to Hex characters
Returns:
A char[] containing lower-case hexadecimal characters/**
     * 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 lower-case hexadecimal characters
     */
    public static char[] encodeHex(final byte[] data) {
        return encodeHex(data, true);
    }

    
Converts a byte buffer 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.
Params:
data – 
           a byte buffer to convert to Hex characters
Returns:
A char[] containing lower-case hexadecimal characters
Since:
1.11/**
     * Converts a byte buffer 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 buffer to convert to Hex characters
     * @return A char[] containing lower-case hexadecimal characters
     * @since 1.11
     */
    public static char[] encodeHex(final ByteBuffer 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.
Params:
data – 
           a byte[] to convert to Hex characters
toLowerCase – 
           true converts to lowercase, false to uppercase
Returns:
A char[] containing hexadecimal characters in the selected case
Since:
1.4/**
     * 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 in the selected case
     * @since 1.4
     */
    public static char[] encodeHex(final byte[] data, final boolean toLowerCase) {
        return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
    }

    
Converts a byte buffer 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.
Params:
data – 
           a byte buffer to convert to Hex characters
toLowerCase – 
           true converts to lowercase, false to uppercase
Returns:
A char[] containing hexadecimal characters in the selected case
Since:
1.11/**
     * Converts a byte buffer 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 buffer to convert to Hex characters
     * @param toLowerCase
     *            <code>true</code> converts to lowercase, <code>false</code> to uppercase
     * @return A char[] containing hexadecimal characters in the selected case
     * @since 1.11
     */
    public static char[] encodeHex(final ByteBuffer data, final 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.
Params:
data – 
           a byte[] to convert to Hex characters
toDigits – 
           the output alphabet (must contain at least 16 chars)
Returns:
A char[] containing the appropriate characters from the alphabet
        For best results, this should be either upper- or lower-case hex.
Since:
1.4/**
     * 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 (must contain at least 16 chars)
     * @return A char[] containing the appropriate characters from the alphabet
     *         For best results, this should be either upper- or lower-case hex.
     * @since 1.4
     */
    protected static char[] encodeHex(final byte[] data, final char[] toDigits) {
        final int l = data.length;
        final 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 a byte buffer 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.
Params:
data – 
           a byte buffer to convert to Hex characters
toDigits – 
           the output alphabet (must be at least 16 characters)
Returns:
A char[] containing the appropriate characters from the alphabet
        For best results, this should be either upper- or lower-case hex.
Since:
1.11/**
     * Converts a byte buffer 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 buffer to convert to Hex characters
     * @param toDigits
     *            the output alphabet (must be at least 16 characters)
     * @return A char[] containing the appropriate characters from the alphabet
     *         For best results, this should be either upper- or lower-case hex.
     * @since 1.11
     */
    protected static char[] encodeHex(final ByteBuffer data, final char[] toDigits) {
        return encodeHex(data.array(), toDigits);
    }

    
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.
Params:
data – 
           a byte[] to convert to Hex characters
Returns:
A String containing lower-case hexadecimal characters
Since:
1.4/**
     * 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 lower-case hexadecimal characters
     * @since 1.4
     */
    public static String encodeHexString(final byte[] data) {
        return new String(encodeHex(data));
    }

    
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.
Params:
data – 
           a byte[] to convert to Hex characters
toLowerCase – 
           true converts to lowercase, false to uppercase
Returns:
A String containing lower-case hexadecimal characters
Since:
1.11/**
     * 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
     * @param toLowerCase
     *            <code>true</code> converts to lowercase, <code>false</code> to uppercase
     * @return A String containing lower-case hexadecimal characters
     * @since 1.11
     */
    public static String encodeHexString(final byte[] data, final boolean toLowerCase) {
        return new String(encodeHex(data, toLowerCase));
    }

    
Converts a byte buffer 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.
Params:
data – 
           a byte buffer to convert to Hex characters
Returns:
A String containing lower-case hexadecimal characters
Since:
1.11/**
     * Converts a byte buffer 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 buffer to convert to Hex characters
     * @return A String containing lower-case hexadecimal characters
     * @since 1.11
     */
    public static String encodeHexString(final ByteBuffer data) {
        return new String(encodeHex(data));
    }

    
Converts a byte buffer 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.
Params:
data – 
           a byte buffer to convert to Hex characters
toLowerCase – 
           true converts to lowercase, false to uppercase
Returns:
A String containing lower-case hexadecimal characters
Since:
1.11/**
     * Converts a byte buffer 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 buffer to convert to Hex characters
     * @param toLowerCase
     *            <code>true</code> converts to lowercase, <code>false</code> to uppercase
     * @return A String containing lower-case hexadecimal characters
     * @since 1.11
     */
    public static String encodeHexString(final ByteBuffer data, final boolean toLowerCase) {
        return new String(encodeHex(data, toLowerCase));
    }

    
Converts a hexadecimal character to an integer.
Params:
ch – 
           A character to convert to an integer digit
index – 
           The index of the character in the source
Throws:
DecoderException – 
            Thrown if ch is an illegal hex character
Returns:
An integer/**
     * 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(final char ch, final int index) throws DecoderException {
        final int digit = Character.digit(ch, 16);
        if (digit == -1) {
            throw new DecoderException("Illegal hexadecimal character " + ch + " at index " + index);
        }
        return digit;
    }

    private final Charset charset;

    
Creates a new codec with the default charset name DEFAULT_CHARSET /**
     * Creates a new codec with the default charset name {@link #DEFAULT_CHARSET}
     */
    public Hex() {
        // use default encoding
        this.charset = DEFAULT_CHARSET;
    }

    
Creates a new codec with the given Charset.
Params:
charset – 
           the charset.
Since:
1.7/**
     * Creates a new codec with the given Charset.
     *
     * @param charset
     *            the charset.
     * @since 1.7
     */
    public Hex(final Charset charset) {
        this.charset = charset;
    }

    
Creates a new codec with the given charset name.
Params:
charsetName – 
           the charset name.
Throws:
UnsupportedCharsetException – 
            If the named charset is unavailable
Since:
1.4
Since:
1.7 throws UnsupportedCharsetException if the named charset is unavailable/**
     * Creates a new codec with the given charset name.
     *
     * @param charsetName
     *            the charset name.
     * @throws java.nio.charset.UnsupportedCharsetException
     *             If the named charset is unavailable
     * @since 1.4
     * @since 1.7 throws UnsupportedCharsetException if the named charset is unavailable
     */
    public Hex(final String charsetName) {
        this(Charset.forName(charsetName));
    }

    
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.
Params:
array – 
           An array of character bytes containing hexadecimal digits
Throws:
DecoderException – 
            Thrown if an odd number of characters is supplied to this function
See Also:
decodeHex(char[])
Returns:
A byte array containing binary data decoded from the supplied byte array (representing characters)./**
     * 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[])
     */
    @Override
    public byte[] decode(final byte[] array) throws DecoderException {
        return decodeHex(new String(array, getCharset()).toCharArray());
    }

    
Converts a buffer 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.
Params:
buffer – 
           An array of character bytes containing hexadecimal digits
Throws:
DecoderException – 
            Thrown if an odd number of characters is supplied to this function
See Also:
decodeHex(char[])
Returns:
A byte array containing binary data decoded from the supplied byte array (representing characters).
Since:
1.11/**
     * Converts a buffer 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 buffer
     *            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[])
     * @since 1.11
     */
    public byte[] decode(final ByteBuffer buffer) throws DecoderException {
        return decodeHex(new String(buffer.array(), getCharset()).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.
Params:
object – 
           A String, ByteBuffer, byte[], or an array of character bytes containing hexadecimal digits
Throws:
DecoderException – 
            Thrown if an odd number of characters is supplied to this function or the object is not a String or
            char[]
See Also:
decodeHex(char[])
Returns:
A byte array containing binary data decoded from the supplied byte array (representing characters)./**
     * 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, ByteBuffer, byte[], 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[])
     */
    @Override
    public Object decode(final Object object) throws DecoderException {
        if (object instanceof String) {
            return decode(((String) object).toCharArray());
        } else if (object instanceof byte[]) {
            return decode((byte[]) object);
        } else if (object instanceof ByteBuffer) {
            return decode((ByteBuffer) object);
        } else {
            try {
                return decodeHex((char[]) object);
            } catch (final ClassCastException e) {
                throw new DecoderException(e.getMessage(), e);
            }
        }
    }

    
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.
 The conversion from hexadecimal characters to the returned bytes is performed with the charset named by getCharset(). 
Params:
array – 
           a byte[] to convert to Hex characters
See Also:
encodeHex(byte[])
Returns:
A byte[] containing the bytes of the lower-case hexadecimal characters
Since:
1.7 No longer throws IllegalStateException if the charsetName is invalid./**
     * 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 #getCharset()}.
     * </p>
     *
     * @param array
     *            a byte[] to convert to Hex characters
     * @return A byte[] containing the bytes of the lower-case hexadecimal characters
     * @since 1.7 No longer throws IllegalStateException if the charsetName is invalid.
     * @see #encodeHex(byte[])
     */
    @Override
    public byte[] encode(final byte[] array) {
        return encodeHexString(array).getBytes(this.getCharset());
    }

    
Converts byte buffer 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.
 The conversion from hexadecimal characters to the returned bytes is performed with the charset named by getCharset(). 
Params:
array – 
           a byte buffer to convert to Hex characters
See Also:
encodeHex(byte[])
Returns:
A byte[] containing the bytes of the lower-case hexadecimal characters
Since:
1.11/**
     * Converts byte buffer 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 #getCharset()}.
     * </p>
     *
     * @param array
     *            a byte buffer to convert to Hex characters
     * @return A byte[] containing the bytes of the lower-case hexadecimal characters
     * @see #encodeHex(byte[])
     * @since 1.11
     */
    public byte[] encode(final ByteBuffer array) {
        return encodeHexString(array).getBytes(this.getCharset());
    }

    
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.
 The conversion from hexadecimal characters to bytes to be encoded to performed with the charset named by getCharset(). 
Params:
object – 
           a String, ByteBuffer, or byte[] to convert to Hex characters
Throws:
EncoderException – 
            Thrown if the given object is not a String or byte[]
See Also:
encodeHex(byte[])
Returns:
A char[] containing lower-case hexadecimal characters/**
     * 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 #getCharset()}.
     * </p>
     *
     * @param object
     *            a String, ByteBuffer, or byte[] to convert to Hex characters
     * @return A char[] containing lower-case hexadecimal characters
     * @throws EncoderException
     *             Thrown if the given object is not a String or byte[]
     * @see #encodeHex(byte[])
     */
    @Override
    public Object encode(final Object object) throws EncoderException {
        byte[] byteArray;
        if (object instanceof String) {
            byteArray = ((String) object).getBytes(this.getCharset());
        } else if (object instanceof ByteBuffer) {
            byteArray = ((ByteBuffer) object).array();
        } else {
            try {
                byteArray = (byte[]) object;
            } catch (final ClassCastException e) {
                throw new EncoderException(e.getMessage(), e);
            }
        }
        return encodeHex(byteArray);
    }

    
Gets the charset.
Returns:
the charset.
Since:
1.7/**
     * Gets the charset.
     *
     * @return the charset.
     * @since 1.7
     */
    public Charset getCharset() {
        return this.charset;
    }

    
Gets the charset name.
Returns:
the charset name.
Since:
1.4/**
     * Gets the charset name.
     *
     * @return the charset name.
     * @since 1.4
     */
    public String getCharsetName() {
        return this.charset.name();
    }

    
Returns a string representation of the object, which includes the charset name.
Returns:
a string representation of the object./**
     * 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.charset + "]";
    }
}