    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;
    021import java.util.Objects;
    022import java.util.function.Supplier;
    023
    024import org.apache.commons.codec.BinaryDecoder;
    025import org.apache.commons.codec.BinaryEncoder;
    026import org.apache.commons.codec.CodecPolicy;
    027import org.apache.commons.codec.DecoderException;
    028import org.apache.commons.codec.EncoderException;
    029
    030/**
    031 * Abstract superclass for Base-N encoders and decoders.
    032 *
    033 * <p>
    034 * This class is thread-safe.
    035 * </p>
    036 * <p>
    037 * You can set the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a valid encoding. These can be bits that are
    038 * unused from the final character or entire characters. The default mode is lenient decoding.
    039 * </p>
    040 * <ul>
    041 * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
    042 * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid encoding. Any unused bits from the final
    043 * character must be zero. Impossible counts of entire final characters are not allowed.
    044 * </ul>
    045 * <p>
    046 * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches the original, i.e. no changes occur on
    047 * the final character. This requires that the input bytes use the same padding and alphabet as the encoder.
    048 * </p>
    049 */
    050public abstract class BaseNCodec implements BinaryEncoder, BinaryDecoder {
    051
    052    /**
    053     * Builds {@link Base64} instances.
    054     *
    055     * @param <T> the codec type to build.
    056     * @param <B> the codec builder subtype.
    057     * @since 1.17.0
    058     */
    059    public abstract static class AbstractBuilder<T, B extends AbstractBuilder<T, B>> implements Supplier<T> {
    060
    061        private int unencodedBlockSize;
    062        private int encodedBlockSize;
    063        private CodecPolicy decodingPolicy = DECODING_POLICY_DEFAULT;
    064        private int lineLength;
    065        private byte[] lineSeparator = CHUNK_SEPARATOR;
    066        private final byte[] defaultEncodeTable;
    067        private byte[] encodeTable;
    068        private byte[] decodeTable;
    069
    070        /** Padding byte. */
    071        private byte padding = PAD_DEFAULT;
    072
    073        AbstractBuilder(final byte[] defaultEncodeTable) {
    074            this.defaultEncodeTable = defaultEncodeTable;
    075            this.encodeTable = defaultEncodeTable;
    076        }
    077
    078        /**
    079         * Returns this instance typed as the subclass type {@code B}.
    080         * <p>
    081         * This is the same as the expression:
    082         * </p>
    083         *
    084         * <pre>
    085         * (B) this
    086         * </pre>
    087         *
    088         * @return {@code this} instance typed as the subclass type {@code B}.
    089         */
    090        @SuppressWarnings("unchecked")
    091        B asThis() {
    092            return (B) this;
    093        }
    094
    095        byte[] getDecodeTable() {
    096            return decodeTable;
    097        }
    098
    099        CodecPolicy getDecodingPolicy() {
    100            return decodingPolicy;
    101        }
    102
    103        int getEncodedBlockSize() {
    104            return encodedBlockSize;
    105        }
    106
    107        byte[] getEncodeTable() {
    108            return encodeTable;
    109        }
    110
    111        int getLineLength() {
    112            return lineLength;
    113        }
    114
    115        byte[] getLineSeparator() {
    116            return lineSeparator;
    117        }
    118
    119        byte getPadding() {
    120            return padding;
    121        }
    122
    123        int getUnencodedBlockSize() {
    124            return unencodedBlockSize;
    125        }
    126
    127        /**
    128         * Sets the decode table.
    129         *
    130         * @param decodeTable the decode table.
    131         * @return {@code this} instance.
    132         * @since 1.20.0
    133         */
    134        public B setDecodeTable(final byte[] decodeTable) {
    135            this.decodeTable = decodeTable != null ? decodeTable.clone() : null;
    136            return asThis();
    137        }
    138
    139        /**
    140         * Sets the decode table.
    141         *
    142         * @param decodeTable the decode table, null resets to the default.
    143         * @return {@code this} instance.
    144         */
    145        B setDecodeTableRaw(final byte[] decodeTable) {
    146            this.decodeTable = decodeTable;
    147            return asThis();
    148        }
    149
    150        /**
    151         * Sets the decoding policy.
    152         *
    153         * @param decodingPolicy the decoding policy, null resets to the default.
    154         * @return {@code this} instance.
    155         */
    156        public B setDecodingPolicy(final CodecPolicy decodingPolicy) {
    157            this.decodingPolicy = decodingPolicy != null ? decodingPolicy : DECODING_POLICY_DEFAULT;
    158            return asThis();
    159        }
    160
    161        /**
    162         * Sets the encoded block size, subclasses normally set this on construction.
    163         *
    164         * @param encodedBlockSize the encoded block size, subclasses normally set this on construction.
    165         * @return {@code this} instance.
    166         */
    167        B setEncodedBlockSize(final int encodedBlockSize) {
    168            this.encodedBlockSize = encodedBlockSize;
    169            return asThis();
    170        }
    171
    172        /**
    173         * Sets the encode table.
    174         *
    175         * @param encodeTable the encode table, null resets to the default.
    176         * @return {@code this} instance.
    177         */
    178        public B setEncodeTable(final byte... encodeTable) {
    179            this.encodeTable = encodeTable != null ? encodeTable.clone() : defaultEncodeTable;
    180            return asThis();
    181        }
    182
    183        /**
    184         * Sets the encode table.
    185         *
    186         * @param encodeTable the encode table, null resets to the default.
    187         * @return {@code this} instance.
    188         */
    189        B setEncodeTableRaw(final byte... encodeTable) {
    190            this.encodeTable = encodeTable != null ? encodeTable : defaultEncodeTable;
    191            return asThis();
    192        }
    193
    194        /**
    195         * Sets the line length.
    196         *
    197         * @param lineLength the line length, less than 0 resets to the default.
    198         * @return {@code this} instance.
    199         */
    200        public B setLineLength(final int lineLength) {
    201            this.lineLength = Math.max(0, lineLength);
    202            return asThis();
    203        }
    204
    205        /**
    206         * Sets the line separator.
    207         *
    208         * @param lineSeparator the line separator, null resets to the default.
    209         * @return {@code this} instance.
    210         */
    211        public B setLineSeparator(final byte... lineSeparator) {
    212            this.lineSeparator = lineSeparator != null ? lineSeparator.clone() : CHUNK_SEPARATOR;
    213            return asThis();
    214        }
    215
    216        /**
    217         * Sets the padding byte.
    218         *
    219         * @param padding the padding byte.
    220         * @return {@code this} instance.
    221         */
    222        public B setPadding(final byte padding) {
    223            this.padding = padding;
    224            return asThis();
    225        }
    226
    227        /**
    228         * Sets the unencoded block size, subclasses normally set this on construction.
    229         *
    230         * @param unencodedBlockSize the unencoded block size, subclasses normally set this on construction.
    231         * @return {@code this} instance.
    232         */
    233        B setUnencodedBlockSize(final int unencodedBlockSize) {
    234            this.unencodedBlockSize = unencodedBlockSize;
    235            return asThis();
    236        }
    237    }
    238
    239    /**
    240     * Holds thread context so classes can be thread-safe.
    241     *
    242     * This class is not itself thread-safe; each thread must allocate its own copy.
    243     */
    244    static class Context {
    245
    246        /**
    247         * Placeholder for the bytes we're dealing with for our based logic. Bitwise operations store and extract the encoding or decoding from this variable.
    248         */
    249        int ibitWorkArea;
    250        /**
    251         * Placeholder for the bytes we're dealing with for our based logic. Bitwise operations store and extract the encoding or decoding from this variable.
    252         */
    253        long lbitWorkArea;
    254        /**
    255         * Buffer for streaming.
    256         */
    257        byte[] buffer;
    258        /**
    259         * Position where next character should be written in the buffer.
    260         */
    261        int pos;
    262        /**
    263         * Position where next character should be read from the buffer.
    264         */
    265        int readPos;
    266        /**
    267         * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless, and must be thrown away.
    268         */
    269        boolean eof;
    270        /**
    271         * Variable tracks how many characters have been written to the current line. Only used when encoding. We use it to make sure each encoded line never
    272         * goes beyond lineLength (if lineLength &gt; 0).
    273         */
    274        int currentLinePos;
    275        /**
    276         * Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This variable helps track that.
    277         */
    278        int modulus;
    279
    280        /**
    281         * Returns a String useful for debugging (especially within a debugger.)
    282         *
    283         * @return a String useful for debugging.
    284         */
    285        @Override
    286        public String toString() {
    287            return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " + "modulus=%s, pos=%s, readPos=%s]",
    288                    this.getClass().getSimpleName(), Arrays.toString(buffer), currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
    289        }
    290    }
    291
    292    /**
    293     * End-of-file marker.
    294     *
    295     * @since 1.7
    296     */
    297    static final int EOF = -1;
    298    /**
    299     * MIME chunk size per RFC 2045 section 6.8.
    300     *
    301     * <p>
    302     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
    303     * </p>
    304     *
    305     * @see <a href="https://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
    306     */
    307    public static final int MIME_CHUNK_SIZE = 76;
    308    /**
    309     * PEM chunk size per RFC 1421 section 4.3.2.4.
    310     *
    311     * <p>
    312     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
    313     * </p>
    314     *
    315     * @see <a href="https://tools.ietf.org/html/rfc1421">RFC 1421 section 4.3.2.4</a>
    316     */
    317    public static final int PEM_CHUNK_SIZE = 64;
    318    private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
    319    /**
    320     * Defines the default buffer size - currently {@value} - must be large enough for at least one encoded block+separator
    321     */
    322    private static final int DEFAULT_BUFFER_SIZE = 8192;
    323    /**
    324     * The maximum size buffer to allocate.
    325     *
    326     * <p>
    327     * This is set to the same size used in the JDK {@link java.util.ArrayList}:
    328     * </p>
    329     * <blockquote> Some VMs reserve some header words in an array. Attempts to allocate larger arrays may result in OutOfMemoryError: Requested array size
    330     * exceeds VM limit. </blockquote>
    331     */
    332    private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
    333    /** Mask used to extract 8 bits, used in decoding bytes */
    334    protected static final int MASK_8BITS = 0xff;
    335    /**
    336     * Byte used to pad output.
    337     */
    338    protected static final byte PAD_DEFAULT = '='; // Allow static access to default
    339    /**
    340     * The default decoding policy.
    341     *
    342     * @since 1.15
    343     */
    344    protected static final CodecPolicy DECODING_POLICY_DEFAULT = CodecPolicy.LENIENT;
    345    /**
    346     * Chunk separator per RFC 2045 section 2.1.
    347     *
    348     * @see <a href="https://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
    349     */
    350    static final byte[] CHUNK_SEPARATOR = { '\r', '\n' };
    351    /**
    352     * The empty byte array.
    353     */
    354    static final byte[] EMPTY_BYTE_ARRAY = {};
    355
    356    /**
    357     * Create a positive capacity at least as large the minimum required capacity. If the minimum capacity is negative then this throws an OutOfMemoryError as
    358     * no array can be allocated.
    359     *
    360     * @param minCapacity the minimum capacity
    361     * @return the capacity
    362     * @throws OutOfMemoryError if the {@code minCapacity} is negative
    363     */
    364    private static int createPositiveCapacity(final int minCapacity) {
    365        if (minCapacity < 0) {
    366            // overflow
    367            throw new OutOfMemoryError("Unable to allocate array size: " + (minCapacity & 0xffffffffL));
    368        }
    369        // This is called when we require buffer expansion to a very big array.
    370        // Use the conservative maximum buffer size if possible, otherwise the biggest required.
    371        //
    372        // Note: In this situation JDK 1.8 java.util.ArrayList returns Integer.MAX_VALUE.
    373        // This excludes some VMs that can exceed MAX_BUFFER_SIZE but not allocate a full
    374        // Integer.MAX_VALUE length array.
    375        // The result is that we may have to allocate an array of this size more than once if
    376        // the capacity must be expanded again.
    377        return Math.max(minCapacity, MAX_BUFFER_SIZE);
    378    }
    379
    380    /**
    381     * Gets a copy of the chunk separator per RFC 2045 section 2.1.
    382     *
    383     * @return the chunk separator
    384     * @see <a href="https://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
    385     * @since 1.15
    386     */
    387    public static byte[] getChunkSeparator() {
    388        return CHUNK_SEPARATOR.clone();
    389    }
    390
    391    /**
    392     * Gets the array length or 0 if null.
    393     *
    394     * @param array the array or null.
    395     * @return the array length or 0 if null.
    396     */
    397    static int getLength(final byte[] array) {
    398        return array == null ? 0 : array.length;
    399    }
    400
    401    /**
    402     * Checks if a byte value is whitespace or not.
    403     *
    404     * @param byteToCheck the byte to check
    405     * @return true if byte is whitespace, false otherwise
    406     * @see Character#isWhitespace(int)
    407     * @deprecated Use {@link Character#isWhitespace(int)}.
    408     */
    409    @Deprecated
    410    protected static boolean isWhiteSpace(final byte byteToCheck) {
    411        return Character.isWhitespace(byteToCheck);
    412    }
    413
    414    /**
    415     * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
    416     *
    417     * @param context     the context to be used
    418     * @param minCapacity the minimum required capacity
    419     * @return the resized byte[] buffer
    420     * @throws OutOfMemoryError if the {@code minCapacity} is negative
    421     */
    422    private static byte[] resizeBuffer(final Context context, final int minCapacity) {
    423        // Overflow-conscious code treats the min and new capacity as unsigned.
    424        final int oldCapacity = context.buffer.length;
    425        int newCapacity = oldCapacity * DEFAULT_BUFFER_RESIZE_FACTOR;
    426        if (Integer.compareUnsigned(newCapacity, minCapacity) < 0) {
    427            newCapacity = minCapacity;
    428        }
    429        if (Integer.compareUnsigned(newCapacity, MAX_BUFFER_SIZE) > 0) {
    430            newCapacity = createPositiveCapacity(minCapacity);
    431        }
    432        final byte[] b = Arrays.copyOf(context.buffer, newCapacity);
    433        context.buffer = b;
    434        return b;
    435    }
    436
    437    /**
    438     * Deprecated: Will be removed in 2.0.
    439     * <p>
    440     * Instance variable just in case it needs to vary later
    441     * </p>
    442     *
    443     * @deprecated Use {@link #pad}. Will be removed in 2.0.
    444     */
    445    @Deprecated
    446    protected final byte PAD = PAD_DEFAULT;
    447    /** Pad byte. Instance variable just in case it needs to vary later. */
    448    protected final byte pad;
    449    /** Number of bytes in each full block of unencoded data, for example 4 for Base64 and 5 for Base32 */
    450    private final int unencodedBlockSize;
    451    /** Number of bytes in each full block of encoded data, for example 3 for Base64 and 8 for Base32 */
    452    private final int encodedBlockSize;
    453    /**
    454     * Chunksize for encoding. Not used when decoding. A value of zero or less implies no chunking of the encoded data. Rounded down to the nearest multiple of
    455     * encodedBlockSize.
    456     */
    457    protected final int lineLength;
    458    /**
    459     * Size of chunk separator. Not used unless {@link #lineLength} &gt; 0.
    460     */
    461    private final int chunkSeparatorLength;
    462    /**
    463     * Defines the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a valid encoding. These can be bits that are
    464     * unused from the final character or entire characters. The default mode is lenient decoding. Set this to {@code true} to enable strict decoding.
    465     * <ul>
    466     * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
    467     * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid encoding. Any unused bits from the final
    468     * character must be zero. Impossible counts of entire final characters are not allowed.
    469     * </ul>
    470     * <p>
    471     * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches the original, i.e. no changes occur
    472     * on the final character. This requires that the input bytes use the same padding and alphabet as the encoder.
    473     * </p>
    474     */
    475    private final CodecPolicy decodingPolicy;
    476
    477    /**
    478     * Decode table to use.
    479     */
    480    final byte[] decodeTable;
    481
    482    /**
    483     * Encode table.
    484     */
    485    final byte[] encodeTable;
    486
    487    /**
    488     * Constructs a new instance for a subclass.
    489     *
    490     * @param builder How to build this portion of the instance.
    491     * @since 1.20.0
    492     */
    493    protected BaseNCodec(final AbstractBuilder<?, ?> builder) {
    494        this.unencodedBlockSize = builder.unencodedBlockSize;
    495        this.encodedBlockSize = builder.encodedBlockSize;
    496        final boolean useChunking = builder.lineLength > 0 && builder.lineSeparator.length > 0;
    497        this.lineLength = useChunking ? builder.lineLength / builder.encodedBlockSize * builder.encodedBlockSize : 0;
    498        this.chunkSeparatorLength = builder.lineSeparator.length;
    499        this.pad = builder.padding;
    500        this.decodingPolicy = Objects.requireNonNull(builder.decodingPolicy, "codecPolicy");
    501        this.encodeTable = Objects.requireNonNull(builder.getEncodeTable(), "builder.getEncodeTable()");
    502        this.decodeTable = builder.getDecodeTable();
    503    }
    504
    505    /**
    506     * Constructs a new instance.
    507     * <p>
    508     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size. If {@code chunkSeparatorLength} is zero, then chunking is
    509     * disabled.
    510     * </p>
    511     *
    512     * @param unencodedBlockSize   the size of an unencoded block (for example Base64 = 3).
    513     * @param encodedBlockSize     the size of an encoded block (for example Base64 = 4).
    514     * @param lineLength           if &gt; 0, use chunking with a length {@code lineLength}.
    515     * @param chunkSeparatorLength the chunk separator length, if relevant.
    516     * @deprecated Use {@link BaseNCodec#BaseNCodec(AbstractBuilder)}.
    517     */
    518    @Deprecated
    519    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength) {
    520        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
    521    }
    522
    523    /**
    524     * Constructs a new instance.
    525     * <p>
    526     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size. If {@code chunkSeparatorLength} is zero, then chunking is
    527     * disabled.
    528     * </p>
    529     *
    530     * @param unencodedBlockSize   the size of an unencoded block (for example Base64 = 3).
    531     * @param encodedBlockSize     the size of an encoded block (for example Base64 = 4).
    532     * @param lineLength           if &gt; 0, use chunking with a length {@code lineLength}.
    533     * @param chunkSeparatorLength the chunk separator length, if relevant.
    534     * @param pad                  byte used as padding byte.
    535     * @deprecated Use {@link BaseNCodec#BaseNCodec(AbstractBuilder)}.
    536     */
    537    @Deprecated
    538    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad) {
    539        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, pad, DECODING_POLICY_DEFAULT);
    540    }
    541
    542    /**
    543     * Constructs a new instance.
    544     * <p>
    545     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size. If {@code chunkSeparatorLength} is zero, then chunking is
    546     * disabled.
    547     * </p>
    548     *
    549     * @param unencodedBlockSize   the size of an unencoded block (for example Base64 = 3).
    550     * @param encodedBlockSize     the size of an encoded block (for example Base64 = 4).
    551     * @param lineLength           if &gt; 0, use chunking with a length {@code lineLength}.
    552     * @param chunkSeparatorLength the chunk separator length, if relevant.
    553     * @param pad                  byte used as padding byte.
    554     * @param decodingPolicy       Decoding policy.
    555     * @since 1.15
    556     * @deprecated Use {@link BaseNCodec#BaseNCodec(AbstractBuilder)}.
    557     */
    558    @Deprecated
    559    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad,
    560            final CodecPolicy decodingPolicy) {
    561        this.unencodedBlockSize = unencodedBlockSize;
    562        this.encodedBlockSize = encodedBlockSize;
    563        final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
    564        this.lineLength = useChunking ? lineLength / encodedBlockSize * encodedBlockSize : 0;
    565        this.chunkSeparatorLength = chunkSeparatorLength;
    566        this.pad = pad;
    567        this.decodingPolicy = Objects.requireNonNull(decodingPolicy, "codecPolicy");
    568        this.encodeTable = null;
    569        this.decodeTable = null;
    570    }
    571
    572    /**
    573     * Returns the amount of buffered data available for reading.
    574     *
    575     * @param context the context to be used.
    576     * @return The amount of buffered data available for reading.
    577     */
    578    int available(final Context context) { // package protected for access from I/O streams
    579        return hasData(context) ? context.pos - context.readPos : 0;
    580    }
    581
    582    /**
    583     * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
    584     *
    585     * Intended for use in checking line-ending arrays.
    586     *
    587     * @param arrayOctet byte array to test.
    588     * @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise.
    589     */
    590    protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
    591        if (arrayOctet != null) {
    592            for (final byte element : arrayOctet) {
    593                if (pad == element || isInAlphabet(element)) {
    594                    return true;
    595                }
    596            }
    597        }
    598        return false;
    599    }
    600
    601    /**
    602     * Decodes a byte[] containing characters in the Base-N alphabet.
    603     *
    604     * @param array A byte array containing Base-N character data.
    605     * @return a byte array containing binary data.
    606     */
    607    @Override
    608    public byte[] decode(final byte[] array) {
    609        if (BinaryCodec.isEmpty(array)) {
    610            return array;
    611        }
    612        final Context context = new Context();
    613        decode(array, 0, array.length, context);
    614        decode(array, 0, EOF, context); // Notify decoder of EOF.
    615        final byte[] result = new byte[context.pos];
    616        readResults(result, 0, result.length, context);
    617        return result;
    618    }
    619
    620    // package protected for access from I/O streams
    621    abstract void decode(byte[] array, int i, int length, Context context);
    622
    623    /**
    624     * Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of the Decoder interface, and will throw a
    625     * DecoderException if the supplied object is not of type byte[] or String.
    626     *
    627     * @param obj Object to decode.
    628     * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String supplied.
    629     * @throws DecoderException if the parameter supplied is not of type byte[].
    630     */
    631    @Override
    632    public Object decode(final Object obj) throws DecoderException {
    633        if (obj instanceof byte[]) {
    634            return decode((byte[]) obj);
    635        }
    636        if (obj instanceof String) {
    637            return decode((String) obj);
    638        }
    639        throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
    640    }
    641
    642    /**
    643     * Decodes a String containing characters in the Base-N alphabet.
    644     *
    645     * @param array A String containing Base-N character data.
    646     * @return a byte array containing binary data.
    647     */
    648    public byte[] decode(final String array) {
    649        return decode(StringUtils.getBytesUtf8(array));
    650    }
    651
    652    /**
    653     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    654     *
    655     * @param array a byte array containing binary data.
    656     * @return A byte array containing only the base N alphabetic character data.
    657     */
    658    @Override
    659    public byte[] encode(final byte[] array) {
    660        if (BinaryCodec.isEmpty(array)) {
    661            return array;
    662        }
    663        return encode(array, 0, array.length);
    664    }
    665
    666    /**
    667     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    668     *
    669     * @param array  a byte array containing binary data.
    670     * @param offset initial offset of the subarray.
    671     * @param length length of the subarray.
    672     * @return A byte array containing only the base N alphabetic character data.
    673     * @since 1.11
    674     */
    675    public byte[] encode(final byte[] array, final int offset, final int length) {
    676        if (BinaryCodec.isEmpty(array)) {
    677            return array;
    678        }
    679        final Context context = new Context();
    680        encode(array, offset, length, context);
    681        encode(array, offset, EOF, context); // Notify encoder of EOF.
    682        final byte[] buf = new byte[context.pos - context.readPos];
    683        readResults(buf, 0, buf.length, context);
    684        return buf;
    685    }
    686
    687    // package protected for access from I/O streams
    688    abstract void encode(byte[] array, int i, int length, Context context);
    689
    690    /**
    691     * Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of the Encoder interface, and will throw an
    692     * EncoderException if the supplied object is not of type byte[].
    693     *
    694     * @param obj Object to encode.
    695     * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
    696     * @throws EncoderException if the parameter supplied is not of type byte[].
    697     */
    698    @Override
    699    public Object encode(final Object obj) throws EncoderException {
    700        if (!(obj instanceof byte[])) {
    701            throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
    702        }
    703        return encode((byte[]) obj);
    704    }
    705
    706    /**
    707     * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet. Uses UTF8 encoding.
    708     * <p>
    709     * This is a duplicate of {@link #encodeToString(byte[])}; it was merged during refactoring.
    710     * </p>
    711     *
    712     * @param array a byte array containing binary data.
    713     * @return String containing only character data in the appropriate alphabet.
    714     * @since 1.5
    715     */
    716    public String encodeAsString(final byte[] array) {
    717        return StringUtils.newStringUtf8(encode(array));
    718    }
    719
    720    /**
    721     * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet. Uses UTF8 encoding.
    722     *
    723     * @param array a byte array containing binary data.
    724     * @return A String containing only Base-N character data.
    725     */
    726    public String encodeToString(final byte[] array) {
    727        return StringUtils.newStringUtf8(encode(array));
    728    }
    729
    730    /**
    731     * Ensures that the buffer has room for {@code size} bytes
    732     *
    733     * @param size    minimum spare space required.
    734     * @param context the context to be used.
    735     * @return the buffer
    736     */
    737    protected byte[] ensureBufferSize(final int size, final Context context) {
    738        if (context.buffer == null) {
    739            context.buffer = new byte[Math.max(size, getDefaultBufferSize())];
    740            context.pos = 0;
    741            context.readPos = 0;
    742            // Overflow-conscious:
    743            // x + y > z == x + y - z > 0
    744        } else if (context.pos + size - context.buffer.length > 0) {
    745            return resizeBuffer(context, context.pos + size);
    746        }
    747        return context.buffer;
    748    }
    749
    750    /**
    751     * Gets the decoding behavior policy.
    752     *
    753     * <p>
    754     * The default is lenient. If the decoding policy is strict, then decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a
    755     * valid encoding. Decoding will compose trailing bits into 8-bit bytes and discard the remainder.
    756     * </p>
    757     *
    758     * @return true if using strict decoding.
    759     * @since 1.15
    760     */
    761    public CodecPolicy getCodecPolicy() {
    762        return decodingPolicy;
    763    }
    764
    765    /**
    766     * Gets the default buffer size. Can be overridden.
    767     *
    768     * @return the default buffer size.
    769     */
    770    protected int getDefaultBufferSize() {
    771        return DEFAULT_BUFFER_SIZE;
    772    }
    773
    774    /**
    775     * Gets the amount of space needed to encode the supplied array.
    776     *
    777     * @param array byte[] array which will later be encoded.
    778     * @return amount of space needed to encode the supplied array. Returns a long since a max-len array will require &gt; Integer.MAX_VALUE.
    779     */
    780    public long getEncodedLength(final byte[] array) {
    781        // Calculate non-chunked size - rounded up to allow for padding
    782        // cast to long is needed to avoid possibility of overflow
    783        long len = (array.length + unencodedBlockSize - 1) / unencodedBlockSize * (long) encodedBlockSize;
    784        if (lineLength > 0) { // We're using chunking
    785            // Round up to nearest multiple
    786            len += (len + lineLength - 1) / lineLength * chunkSeparatorLength;
    787        }
    788        return len;
    789    }
    790
    791    /**
    792     * Tests whether this object has buffered data for reading.
    793     *
    794     * @param context the context to be used.
    795     * @return true if there is data still available for reading.
    796     */
    797    boolean hasData(final Context context) { // package protected for access from I/O streams
    798        return context.pos > context.readPos;
    799    }
    800
    801    /**
    802     * Tests whether or not the {@code octet} is in the current alphabet. Does not allow whitespace or pad.
    803     *
    804     * @param value The value to test.
    805     * @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
    806     */
    807    protected abstract boolean isInAlphabet(byte value);
    808
    809    /**
    810     * Tests a given byte array to see if it contains only valid characters within the alphabet. The method optionally treats whitespace and pad as valid.
    811     *
    812     * @param arrayOctet byte array to test.
    813     * @param allowWSPad if {@code true}, then whitespace and PAD are also allowed.
    814     * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty; {@code false}, otherwise.
    815     */
    816    public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
    817        for (final byte octet : arrayOctet) {
    818            if (!isInAlphabet(octet) && (!allowWSPad || octet != pad && !Character.isWhitespace(octet))) {
    819                return false;
    820            }
    821        }
    822        return true;
    823    }
    824
    825    /**
    826     * Tests a given String to see if it contains only valid characters within the alphabet. The method treats whitespace and PAD as valid.
    827     *
    828     * @param basen String to test.
    829     * @return {@code true} if all characters in the String are valid characters in the alphabet or if the String is empty; {@code false}, otherwise.
    830     * @see #isInAlphabet(byte[], boolean)
    831     */
    832    public boolean isInAlphabet(final String basen) {
    833        return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
    834    }
    835
    836    /**
    837     * Tests true if decoding behavior is strict. Decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid encoding.
    838     *
    839     * <p>
    840     * The default is false for lenient decoding. Decoding will compose trailing bits into 8-bit bytes and discard the remainder.
    841     * </p>
    842     *
    843     * @return true if using strict decoding.
    844     * @since 1.15
    845     */
    846    public boolean isStrictDecoding() {
    847        return decodingPolicy == CodecPolicy.STRICT;
    848    }
    849
    850    /**
    851     * Reads buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail bytes. Returns how many bytes were actually
    852     * extracted.
    853     * <p>
    854     * Package private for access from I/O streams.
    855     * </p>
    856     *
    857     * @param b       byte[] array to extract the buffered data into.
    858     * @param bPos    position in byte[] array to start extraction at.
    859     * @param bAvail  amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
    860     * @param context the context to be used.
    861     * @return The number of bytes successfully extracted into the provided byte[] array.
    862     */
    863    int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
    864        if (hasData(context)) {
    865            final int len = Math.min(available(context), bAvail);
    866            System.arraycopy(context.buffer, context.readPos, b, bPos, len);
    867            context.readPos += len;
    868            if (!hasData(context)) {
    869                // All data read.
    870                // Reset position markers but do not set buffer to null to allow its reuse.
    871                // hasData(context) will still return false, and this method will return 0 until
    872                // more data is available, or -1 if EOF.
    873                context.pos = context.readPos = 0;
    874            }
    875            return len;
    876        }
    877        return context.eof ? EOF : 0;
    878    }
    879}