    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 *      https://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 java.util.Arrays;
    021
    022import org.apache.commons.codec.CodecPolicy;
    023
    024/**
    025 * Provides Base16 encoding and decoding as defined by <a href="https://tools.ietf.org/html/rfc4648#section-8">RFC 4648 - 8. Base 16 Encoding</a>.
    026 *
    027 * <p>
    028 * This class is thread-safe.
    029 * </p>
    030 * <p>
    031 * This implementation strictly follows RFC 4648, and as such unlike the {@link Base32} and {@link Base64} implementations, it does not ignore invalid alphabet
    032 * characters or whitespace, neither does it offer chunking or padding characters.
    033 * </p>
    034 * <p>
    035 * The only additional feature above those specified in RFC 4648 is support for working with a lower-case alphabet in addition to the default upper-case
    036 * alphabet.
    037 * </p>
    038 *
    039 * @see Base16InputStream
    040 * @see Base16OutputStream
    041 * @see <a href="https://tools.ietf.org/html/rfc4648#section-8">RFC 4648 - 8. Base 16 Encoding</a>
    042 * @since 1.15
    043 */
    044public class Base16 extends BaseNCodec {
    045
    046    /**
    047     * Builds {@link Base16} instances.
    048     *
    049     * <p>
    050     * To configure a new instance, use a {@link Builder}. For example:
    051     * </p>
    052     *
    053     * <pre>
    054     * Base16 Base16 = Base16.builder()
    055     *   .setDecodingPolicy(DecodingPolicy.LENIENT) // default is lenient
    056     *   .get()
    057     * </pre>
    058     *
    059     * @since 1.20.0
    060     */
    061    public static class Builder extends AbstractBuilder<Base16, Builder> {
    062
    063        /**
    064         * Constructs a new instance.
    065         */
    066        public Builder() {
    067            super(null);
    068            setDecodeTable(UPPER_CASE_DECODE_TABLE);
    069            setEncodeTable(UPPER_CASE_ENCODE_TABLE);
    070            setEncodedBlockSize(BYTES_PER_ENCODED_BLOCK);
    071            setUnencodedBlockSize(BYTES_PER_UNENCODED_BLOCK);
    072            setLineLength(0);
    073            setLineSeparator(EMPTY_BYTE_ARRAY);
    074        }
    075
    076        @Override
    077        public Base16 get() {
    078            return new Base16(this);
    079        }
    080
    081        @Override
    082        public Builder setEncodeTable(final byte... encodeTable) {
    083            super.setDecodeTableRaw(Arrays.equals(encodeTable, LOWER_CASE_ENCODE_TABLE) ? LOWER_CASE_DECODE_TABLE : UPPER_CASE_DECODE_TABLE);
    084            return super.setEncodeTable(encodeTable);
    085        }
    086
    087        /**
    088         * Sets whether to use the the lower-case Base16 alphabet.
    089         *
    090         * @param lowerCase {@code true} to use the lower-case Base16 alphabet.
    091         * @return {@code this} instance.
    092         */
    093        public Builder setLowerCase(final boolean lowerCase) {
    094            setEncodeTableRaw(lowerCase ? LOWER_CASE_ENCODE_TABLE : UPPER_CASE_ENCODE_TABLE);
    095            return asThis();
    096        }
    097
    098    }
    099
    100    /**
    101     * BASE16 characters are 4 bits in length. They are formed by taking an 8-bit group, which is converted into two BASE16 characters.
    102     */
    103    private static final int BITS_PER_ENCODED_BYTE = 4;
    104
    105    private static final int BYTES_PER_ENCODED_BLOCK = 2;
    106
    107    private static final int BYTES_PER_UNENCODED_BLOCK = 1;
    108    /**
    109     * This array is a lookup table that translates Unicode characters drawn from the "Base16 Alphabet" (as specified in Table 5 of RFC 4648) into their 4-bit
    110     * positive integer equivalents. Characters that are not in the Base16 alphabet but fall within the bounds of the array are translated to -1.
    111     */
    112    // @formatter:off
    113    private static final byte[] UPPER_CASE_DECODE_TABLE = {
    114            //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
    115            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
    116            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
    117            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f
    118             0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, // 30-3f 0-9
    119            -1, 10, 11, 12, 13, 14, 15                                      // 40-46 A-F
    120    };
    121    // @formatter:on
    122    /**
    123     * This array is a lookup table that translates 4-bit positive integer index values into their "Base16 Alphabet" equivalents as specified in Table 5 of RFC
    124     * 4648.
    125     */
    126    private static final byte[] UPPER_CASE_ENCODE_TABLE = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
    127
    128    /**
    129     * This array is a lookup table that translates Unicode characters drawn from the a lower-case "Base16 Alphabet" into their 4-bit positive integer
    130     * equivalents. Characters that are not in the Base16 alphabet but fall within the bounds of the array are translated to -1.
    131     */
    132    // @formatter:off
    133    private static final byte[] LOWER_CASE_DECODE_TABLE = {
    134            //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
    135            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
    136            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
    137            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f
    138             0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, // 30-3f 0-9
    139            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 40-4f
    140            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 50-5f
    141            -1, 10, 11, 12, 13, 14, 15                                      // 60-66 a-f
    142    };
    143    // @formatter:on
    144    /**
    145     * This array is a lookup table that translates 4-bit positive integer index values into their "Base16 Alphabet" lower-case equivalents.
    146     */
    147    private static final byte[] LOWER_CASE_ENCODE_TABLE = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
    148
    149    /** Mask used to extract 4 bits, used when decoding character. */
    150    private static final int MASK_4_BITS = 0x0f;
    151
    152    /**
    153     * Constructs a new builder.
    154     *
    155     * @return a new builder.
    156     * @since 1.20.0
    157     */
    158    public static Builder builder() {
    159        return new Builder();
    160    }
    161
    162    /**
    163     * Constructs a Base16 codec used for decoding and encoding.
    164     */
    165    public Base16() {
    166        this(false);
    167    }
    168
    169    /**
    170     * Constructs a Base16 codec used for decoding and encoding.
    171     *
    172     * @param lowerCase {@code true} to use the lower-case Base16 alphabet.
    173     * @deprecated Use {@link #builder()} and {@link Builder}.
    174     */
    175    @Deprecated
    176    public Base16(final boolean lowerCase) {
    177        this(lowerCase, DECODING_POLICY_DEFAULT);
    178    }
    179
    180    /**
    181     * Constructs a Base16 codec used for decoding and encoding.
    182     *
    183     * @param lowerCase      {@code true} to use the lower-case Base16 alphabet.
    184     * @param decodingPolicy Decoding policy.
    185     * @deprecated Use {@link #builder()} and {@link Builder}.
    186     */
    187    @Deprecated
    188    public Base16(final boolean lowerCase, final CodecPolicy decodingPolicy) {
    189        this(builder().setEncodeTable(lowerCase ? LOWER_CASE_ENCODE_TABLE : UPPER_CASE_ENCODE_TABLE).setDecodingPolicy(decodingPolicy));
    190    }
    191
    192    private Base16(final Builder builder) {
    193        super(builder);
    194    }
    195
    196    @Override
    197    void decode(final byte[] data, int offset, final int length, final Context context) {
    198        if (context.eof || length < 0) {
    199            context.eof = true;
    200            if (context.ibitWorkArea != 0) {
    201                validateTrailingCharacter();
    202            }
    203            return;
    204        }
    205        final int dataLen = Math.min(data.length - offset, length);
    206        final int availableChars = (context.ibitWorkArea != 0 ? 1 : 0) + dataLen;
    207        // small optimization to short-cut the rest of this method when it is fed byte-by-byte
    208        if (availableChars == 1 && availableChars == dataLen) {
    209            // store 1/2 byte for next invocation of decode, we offset by +1 as empty-value is 0
    210            context.ibitWorkArea = decodeOctet(data[offset]) + 1;
    211            return;
    212        }
    213        // we must have an even number of chars to decode
    214        final int charsToProcess = availableChars % BYTES_PER_ENCODED_BLOCK == 0 ? availableChars : availableChars - 1;
    215        final int end = offset + dataLen;
    216        final byte[] buffer = ensureBufferSize(charsToProcess / BYTES_PER_ENCODED_BLOCK, context);
    217        int result;
    218        if (dataLen < availableChars) {
    219            // we have 1/2 byte from previous invocation to decode
    220            result = context.ibitWorkArea - 1 << BITS_PER_ENCODED_BYTE;
    221            result |= decodeOctet(data[offset++]);
    222            buffer[context.pos++] = (byte) result;
    223            // reset to empty-value for next invocation!
    224            context.ibitWorkArea = 0;
    225        }
    226        final int loopEnd = end - 1;
    227        while (offset < loopEnd) {
    228            result = decodeOctet(data[offset++]) << BITS_PER_ENCODED_BYTE;
    229            result |= decodeOctet(data[offset++]);
    230            buffer[context.pos++] = (byte) result;
    231        }
    232        // we have one char of a hex-pair left over
    233        if (offset < end) {
    234            // store 1/2 byte for next invocation of decode, we offset by +1 as empty-value is 0
    235            context.ibitWorkArea = decodeOctet(data[offset]) + 1;
    236        }
    237    }
    238
    239    private int decodeOctet(final byte octet) {
    240        int decoded = -1;
    241        if ((octet & 0xff) < decodeTable.length) {
    242            decoded = decodeTable[octet];
    243        }
    244        if (decoded == -1) {
    245            throw new IllegalArgumentException("Invalid octet in encoded value: " + (int) octet);
    246        }
    247        return decoded;
    248    }
    249
    250    @Override
    251    void encode(final byte[] data, final int offset, final int length, final Context context) {
    252        if (context.eof) {
    253            return;
    254        }
    255        if (length < 0) {
    256            context.eof = true;
    257            return;
    258        }
    259        final int size = length * BYTES_PER_ENCODED_BLOCK;
    260        if (size < 0) {
    261            throw new IllegalArgumentException("Input length exceeds maximum size for encoded data: " + length);
    262        }
    263        final byte[] buffer = ensureBufferSize(size, context);
    264        final int end = offset + length;
    265        for (int i = offset; i < end; i++) {
    266            final int value = data[i];
    267            final int high = value >> BITS_PER_ENCODED_BYTE & MASK_4_BITS;
    268            final int low = value & MASK_4_BITS;
    269            buffer[context.pos++] = encodeTable[high];
    270            buffer[context.pos++] = encodeTable[low];
    271        }
    272    }
    273
    274    /**
    275     * Returns whether or not the {@code octet} is in the Base16 alphabet.
    276     *
    277     * @param octet The value to test.
    278     * @return {@code true} if the value is defined in the Base16 alphabet {@code false} otherwise.
    279     */
    280    @Override
    281    public boolean isInAlphabet(final byte octet) {
    282        return (octet & 0xff) < decodeTable.length && decodeTable[octet] != -1;
    283    }
    284
    285    /**
    286     * Validates whether decoding allows an entire final trailing character that cannot be used for a complete byte.
    287     *
    288     * @throws IllegalArgumentException if strict decoding is enabled
    289     */
    290    private void validateTrailingCharacter() {
    291        if (isStrictDecoding()) {
    292            throw new IllegalArgumentException("Strict decoding: Last encoded character is a valid Base 16 alphabet character but not a possible encoding. " +
    293                    "Decoding requires at least two characters to create one byte.");
    294        }
    295    }
    296}