    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.codec.binary;
    019
    020import org.apache.commons.codec.BinaryDecoder;
    021import org.apache.commons.codec.BinaryEncoder;
    022import org.apache.commons.codec.DecoderException;
    023import org.apache.commons.codec.EncoderException;
    024
    025/**
    026 * Converts between byte arrays and strings of "0"s and "1"s.
    027 *
    028 * <p>This class is immutable and thread-safe.</p>
    029 *
    030 * TODO: may want to add more bit vector functions like and/or/xor/nand
    031 * TODO: also might be good to generate boolean[] from byte[] et cetera.
    032 *
    033 * @since 1.3
    034 */
    035public class BinaryCodec implements BinaryDecoder, BinaryEncoder {
    036    /*
    037     * tried to avoid using ArrayUtils to minimize dependencies while using these empty arrays - dep is just not worth
    038     * it.
    039     */
    040    /** Empty char array. */
    041    private static final char[] EMPTY_CHAR_ARRAY = {};
    042
    043    /** Empty byte array. */
    044    private static final byte[] EMPTY_BYTE_ARRAY = {};
    045
    046    /** Mask for bit 0 of a byte. */
    047    private static final int BIT_0 = 1;
    048
    049    /** Mask for bit 1 of a byte. */
    050    private static final int BIT_1 = 0x02;
    051
    052    /** Mask for bit 2 of a byte. */
    053    private static final int BIT_2 = 0x04;
    054
    055    /** Mask for bit 3 of a byte. */
    056    private static final int BIT_3 = 0x08;
    057
    058    /** Mask for bit 4 of a byte. */
    059    private static final int BIT_4 = 0x10;
    060
    061    /** Mask for bit 5 of a byte. */
    062    private static final int BIT_5 = 0x20;
    063
    064    /** Mask for bit 6 of a byte. */
    065    private static final int BIT_6 = 0x40;
    066
    067    /** Mask for bit 7 of a byte. */
    068    private static final int BIT_7 = 0x80;
    069
    070    private static final int[] BITS = {BIT_0, BIT_1, BIT_2, BIT_3, BIT_4, BIT_5, BIT_6, BIT_7};
    071
    072    /**
    073     * Decodes a byte array where each byte represents an ASCII '0' or '1'.
    074     *
    075     * @param ascii
    076     *                  each byte represents an ASCII '0' or '1'
    077     * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
    078     */
    079    public static byte[] fromAscii(final byte[] ascii) {
    080        if (isEmpty(ascii)) {
    081            return EMPTY_BYTE_ARRAY;
    082        }
    083        final int asciiLength = ascii.length;
    084        // get length/8 times bytes with 3 bit shifts to the right of the length
    085        final byte[] raw = new byte[asciiLength >> 3];
    086        /*
    087         * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
    088         * loop.
    089         */
    090        for (int ii = 0, jj = asciiLength - 1; ii < raw.length; ii++, jj -= 8) {
    091            for (int bits = 0; bits < BITS.length; ++bits) {
    092                if (ascii[jj - bits] == '1') {
    093                    raw[ii] |= BITS[bits];
    094                }
    095            }
    096        }
    097        return raw;
    098    }
    099
    100    /**
    101     * Decodes a char array where each char represents an ASCII '0' or '1'.
    102     *
    103     * @param ascii
    104     *                  each char represents an ASCII '0' or '1'
    105     * @return the raw encoded binary where each bit corresponds to a char in the char array argument
    106     */
    107    public static byte[] fromAscii(final char[] ascii) {
    108        if (ascii == null || ascii.length == 0) {
    109            return EMPTY_BYTE_ARRAY;
    110        }
    111        final int asciiLength = ascii.length;
    112        // get length/8 times bytes with 3 bit shifts to the right of the length
    113        final byte[] raw = new byte[asciiLength >> 3];
    114        /*
    115         * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
    116         * loop.
    117         */
    118        for (int ii = 0, jj = asciiLength - 1; ii < raw.length; ii++, jj -= 8) {
    119            for (int bits = 0; bits < BITS.length; ++bits) {
    120                if (ascii[jj - bits] == '1') {
    121                    raw[ii] |= BITS[bits];
    122                }
    123            }
    124        }
    125        return raw;
    126    }
    127
    128    /**
    129     * Returns {@code true} if the given array is {@code null} or empty (size 0.)
    130     *
    131     * @param array
    132     *            the source array
    133     * @return {@code true} if the given array is {@code null} or empty (size 0.)
    134     */
    135    static boolean isEmpty(final byte[] array) {
    136        return array == null || array.length == 0;
    137    }
    138
    139    /**
    140     * Converts an array of raw binary data into an array of ASCII 0 and 1 character bytes - each byte is a truncated
    141     * char.
    142     *
    143     * @param raw
    144     *                  the raw binary data to convert
    145     * @return an array of 0 and 1 character bytes for each bit of the argument
    146     * @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
    147     */
    148    public static byte[] toAsciiBytes(final byte[] raw) {
    149        if (isEmpty(raw)) {
    150            return EMPTY_BYTE_ARRAY;
    151        }
    152        final int rawLength = raw.length;
    153        // get 8 times the bytes with 3 bit shifts to the left of the length
    154        final byte[] l_ascii = new byte[rawLength << 3];
    155        /*
    156         * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
    157         * loop.
    158         */
    159        for (int ii = 0, jj = l_ascii.length - 1; ii < rawLength; ii++, jj -= 8) {
    160            for (int bits = 0; bits < BITS.length; ++bits) {
    161                if ((raw[ii] & BITS[bits]) == 0) {
    162                    l_ascii[jj - bits] = '0';
    163                } else {
    164                    l_ascii[jj - bits] = '1';
    165                }
    166            }
    167        }
    168        return l_ascii;
    169    }
    170
    171    /**
    172     * Converts an array of raw binary data into an array of ASCII 0 and 1 characters.
    173     *
    174     * @param raw
    175     *                  the raw binary data to convert
    176     * @return an array of 0 and 1 characters for each bit of the argument
    177     * @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
    178     */
    179    public static char[] toAsciiChars(final byte[] raw) {
    180        if (isEmpty(raw)) {
    181            return EMPTY_CHAR_ARRAY;
    182        }
    183        final int rawLength = raw.length;
    184        // get 8 times the bytes with 3 bit shifts to the left of the length
    185        final char[] l_ascii = new char[rawLength << 3];
    186        /*
    187         * We decr index jj by 8 as we go along to not recompute indices using multiplication every time inside the
    188         * loop.
    189         */
    190        for (int ii = 0, jj = l_ascii.length - 1; ii < rawLength; ii++, jj -= 8) {
    191            for (int bits = 0; bits < BITS.length; ++bits) {
    192                if ((raw[ii] & BITS[bits]) == 0) {
    193                    l_ascii[jj - bits] = '0';
    194                } else {
    195                    l_ascii[jj - bits] = '1';
    196                }
    197            }
    198        }
    199        return l_ascii;
    200    }
    201
    202    /**
    203     * Converts an array of raw binary data into a String of ASCII 0 and 1 characters.
    204     *
    205     * @param raw
    206     *                  the raw binary data to convert
    207     * @return a String of 0 and 1 characters representing the binary data
    208     * @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
    209     */
    210    public static String toAsciiString(final byte[] raw) {
    211        return new String(toAsciiChars(raw));
    212    }
    213
    214    /**
    215     * Decodes a byte array where each byte represents an ASCII '0' or '1'.
    216     *
    217     * @param ascii
    218     *                  each byte represents an ASCII '0' or '1'
    219     * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
    220     * @see org.apache.commons.codec.Decoder#decode(Object)
    221     */
    222    @Override
    223    public byte[] decode(final byte[] ascii) {
    224        return fromAscii(ascii);
    225    }
    226
    227    /**
    228     * Decodes a byte array where each byte represents an ASCII '0' or '1'.
    229     *
    230     * @param ascii
    231     *                  each byte represents an ASCII '0' or '1'
    232     * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
    233     * @throws DecoderException
    234     *                  if argument is not a byte[], char[] or String
    235     * @see org.apache.commons.codec.Decoder#decode(Object)
    236     */
    237    @Override
    238    public Object decode(final Object ascii) throws DecoderException {
    239        if (ascii == null) {
    240            return EMPTY_BYTE_ARRAY;
    241        }
    242        if (ascii instanceof byte[]) {
    243            return fromAscii((byte[]) ascii);
    244        }
    245        if (ascii instanceof char[]) {
    246            return fromAscii((char[]) ascii);
    247        }
    248        if (ascii instanceof String) {
    249            return fromAscii(((String) ascii).toCharArray());
    250        }
    251        throw new DecoderException("argument not a byte array");
    252    }
    253
    254    /**
    255     * Converts an array of raw binary data into an array of ASCII 0 and 1 characters.
    256     *
    257     * @param raw
    258     *                  the raw binary data to convert
    259     * @return 0 and 1 ASCII character bytes one for each bit of the argument
    260     * @see org.apache.commons.codec.BinaryEncoder#encode(byte[])
    261     */
    262    @Override
    263    public byte[] encode(final byte[] raw) {
    264        return toAsciiBytes(raw);
    265    }
    266
    267    /**
    268     * Converts an array of raw binary data into an array of ASCII 0 and 1 chars.
    269     *
    270     * @param raw
    271     *                  the raw binary data to convert
    272     * @return 0 and 1 ASCII character chars one for each bit of the argument
    273     * @throws EncoderException
    274     *                  if the argument is not a byte[]
    275     * @see org.apache.commons.codec.Encoder#encode(Object)
    276     */
    277    @Override
    278    public Object encode(final Object raw) throws EncoderException {
    279        if (!(raw instanceof byte[])) {
    280            throw new EncoderException("argument not a byte array");
    281        }
    282        return toAsciiChars((byte[]) raw);
    283    }
    284
    285    /**
    286     * Decodes a String where each char of the String represents an ASCII '0' or '1'.
    287     *
    288     * @param ascii
    289     *                  String of '0' and '1' characters
    290     * @return the raw encoded binary where each bit corresponds to a byte in the byte array argument
    291     * @see org.apache.commons.codec.Decoder#decode(Object)
    292     */
    293    public byte[] toByteArray(final String ascii) {
    294        if (ascii == null) {
    295            return EMPTY_BYTE_ARRAY;
    296        }
    297        return fromAscii(ascii.toCharArray());
    298    }
    299}