    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.</li>
    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.</li>
    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        /**
    252         * Placeholder for the bytes we're dealing with for our based logic. Bitwise operations store and extract the encoding or decoding from this variable.
    253         */
    254        long lbitWorkArea;
    255
    256        /**
    257         * Buffer for streaming.
    258         */
    259        byte[] buffer;
    260
    261        /**
    262         * Position where next character should be written in the buffer.
    263         */
    264        int pos;
    265
    266        /**
    267         * Position where next character should be read from the buffer.
    268         */
    269        int readPos;
    270
    271        /**
    272         * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless, and must be thrown away.
    273         */
    274        boolean eof;
    275
    276        /**
    277         * 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
    278         * goes beyond lineLength (if lineLength &gt; 0).
    279         */
    280        int currentLinePos;
    281
    282        /**
    283         * 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.
    284         */
    285        int modulus;
    286
    287        /**
    288         * Returns a String useful for debugging (especially within a debugger.)
    289         *
    290         * @return a String useful for debugging.
    291         */
    292        @Override
    293        public String toString() {
    294            return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " + "modulus=%s, pos=%s, readPos=%s]",
    295                    this.getClass().getSimpleName(), Arrays.toString(buffer), currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
    296        }
    297    }
    298
    299    /**
    300     * End-of-file marker.
    301     *
    302     * @since 1.7
    303     */
    304    static final int EOF = -1;
    305
    306    /**
    307     * MIME chunk size per RFC 2045 section 6.8.
    308     *
    309     * <p>
    310     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
    311     * </p>
    312     *
    313     * @see <a href="https://www.ietf.org/rfc/rfc2045">RFC 2045 section 6.8</a>
    314     */
    315    public static final int MIME_CHUNK_SIZE = 76;
    316
    317    /**
    318     * PEM chunk size per RFC 1421 section 4.3.2.4.
    319     *
    320     * <p>
    321     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
    322     * </p>
    323     *
    324     * @see <a href="https://tools.ietf.org/html/rfc1421">RFC 1421 section 4.3.2.4</a>
    325     */
    326    public static final int PEM_CHUNK_SIZE = 64;
    327    private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
    328
    329    /**
    330     * Defines the default buffer size - currently {@value} - must be large enough for at least one encoded block+separator
    331     */
    332    private static final int DEFAULT_BUFFER_SIZE = 8192;
    333
    334    /**
    335     * The maximum size buffer to allocate.
    336     *
    337     * <p>
    338     * This is set to the same size used in the JDK {@link java.util.ArrayList}:
    339     * </p>
    340     * <blockquote> Some VMs reserve some header words in an array. Attempts to allocate larger arrays may result in OutOfMemoryError: Requested array size
    341     * exceeds VM limit. </blockquote>
    342     */
    343    private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
    344
    345    /** Mask used to extract 8 bits, used in decoding bytes */
    346    protected static final int MASK_8BITS = 0xff;
    347
    348    /**
    349     * Byte used to pad output.
    350     */
    351    protected static final byte PAD_DEFAULT = '='; // Allow static access to default
    352
    353    /**
    354     * The default decoding policy.
    355     *
    356     * @since 1.15
    357     */
    358    protected static final CodecPolicy DECODING_POLICY_DEFAULT = CodecPolicy.LENIENT;
    359
    360    /**
    361     * Chunk separator per RFC 2045 section 2.1.
    362     *
    363     * @see <a href="https://www.ietf.org/rfc/rfc2045">RFC 2045 section 2.1</a>
    364     */
    365    static final byte[] CHUNK_SEPARATOR = { '\r', '\n' };
    366
    367    /**
    368     * The empty byte array.
    369     */
    370    static final byte[] EMPTY_BYTE_ARRAY = {};
    371
    372    /**
    373     * Create a positive capacity at least as large the minimum required capacity. If the minimum capacity is negative then this throws an OutOfMemoryError as
    374     * no array can be allocated.
    375     *
    376     * @param minCapacity the minimum capacity.
    377     * @return the capacity.
    378     * @throws OutOfMemoryError if the {@code minCapacity} is negative.
    379     */
    380    private static int createPositiveCapacity(final int minCapacity) {
    381        if (minCapacity < 0) {
    382            // overflow
    383            throw new OutOfMemoryError("Unable to allocate array size: " + (minCapacity & 0xffffffffL));
    384        }
    385        // This is called when we require buffer expansion to a very big array.
    386        // Use the conservative maximum buffer size if possible, otherwise the biggest required.
    387        //
    388        // Note: In this situation JDK 1.8 java.util.ArrayList returns Integer.MAX_VALUE.
    389        // This excludes some VMs that can exceed MAX_BUFFER_SIZE but not allocate a full
    390        // Integer.MAX_VALUE length array.
    391        // The result is that we may have to allocate an array of this size more than once if
    392        // the capacity must be expanded again.
    393        return Math.max(minCapacity, MAX_BUFFER_SIZE);
    394    }
    395
    396    /**
    397     * Gets a copy of the chunk separator per RFC 2045 section 2.1.
    398     *
    399     * @return the chunk separator.
    400     * @see <a href="https://www.ietf.org/rfc/rfc2045">RFC 2045 section 2.1</a>
    401     * @since 1.15
    402     */
    403    public static byte[] getChunkSeparator() {
    404        return CHUNK_SEPARATOR.clone();
    405    }
    406
    407    /**
    408     * Gets the array length or 0 if null.
    409     *
    410     * @param array the array or null.
    411     * @return the array length or 0 if null.
    412     */
    413    static int getLength(final byte[] array) {
    414        return array == null ? 0 : array.length;
    415    }
    416
    417    /**
    418     * Checks if a byte value is whitespace or not.
    419     *
    420     * @param byteToCheck the byte to check.
    421     * @return true if byte is whitespace, false otherwise.
    422     * @see Character#isWhitespace(int)
    423     * @deprecated Use {@link Character#isWhitespace(int)}.
    424     */
    425    @Deprecated
    426    protected static boolean isWhiteSpace(final byte byteToCheck) {
    427        return Character.isWhitespace(byteToCheck);
    428    }
    429
    430    /**
    431     * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
    432     *
    433     * @param context     the context to be used.
    434     * @param minCapacity the minimum required capacity.
    435     * @return the resized byte[] buffer.
    436     * @throws OutOfMemoryError if the {@code minCapacity} is negative.
    437     */
    438    private static byte[] resizeBuffer(final Context context, final int minCapacity) {
    439        // Overflow-conscious code treats the min and new capacity as unsigned.
    440        final int oldCapacity = context.buffer.length;
    441        int newCapacity = oldCapacity * DEFAULT_BUFFER_RESIZE_FACTOR;
    442        if (Integer.compareUnsigned(newCapacity, minCapacity) < 0) {
    443            newCapacity = minCapacity;
    444        }
    445        if (Integer.compareUnsigned(newCapacity, MAX_BUFFER_SIZE) > 0) {
    446            newCapacity = createPositiveCapacity(minCapacity);
    447        }
    448        final byte[] b = Arrays.copyOf(context.buffer, newCapacity);
    449        context.buffer = b;
    450        return b;
    451    }
    452
    453    /**
    454     * Deprecated: Will be removed in 2.0.
    455     * <p>
    456     * Instance variable just in case it needs to vary later
    457     * </p>
    458     *
    459     * @deprecated Use {@link #pad}. Will be removed in 2.0.
    460     */
    461    @Deprecated
    462    protected final byte PAD = PAD_DEFAULT;
    463
    464    /** Pad byte. Instance variable just in case it needs to vary later. */
    465    protected final byte pad;
    466
    467    /** Number of bytes in each full block of unencoded data, for example 4 for Base64 and 5 for Base32 */
    468    private final int unencodedBlockSize;
    469
    470    /** Number of bytes in each full block of encoded data, for example 3 for Base64 and 8 for Base32 */
    471    private final int encodedBlockSize;
    472
    473    /**
    474     * 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
    475     * encodedBlockSize.
    476     */
    477    protected final int lineLength;
    478
    479    /**
    480     * Size of chunk separator. Not used unless {@link #lineLength} &gt; 0.
    481     */
    482    private final int chunkSeparatorLength;
    483
    484    /**
    485     * 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
    486     * unused from the final character or entire characters. The default mode is lenient decoding. Set this to {@code true} to enable strict decoding.
    487     * <ul>
    488     * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.</li>
    489     * <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
    490     * character must be zero. Impossible counts of entire final characters are not allowed.</li>
    491     * </ul>
    492     * <p>
    493     * 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
    494     * on the final character. This requires that the input bytes use the same padding and alphabet as the encoder.
    495     * </p>
    496     */
    497    private final CodecPolicy decodingPolicy;
    498
    499    /**
    500     * Decode table to use.
    501     */
    502    final byte[] decodeTable;
    503
    504    /**
    505     * Encode table.
    506     */
    507    final byte[] encodeTable;
    508
    509    /**
    510     * Constructs a new instance for a subclass.
    511     *
    512     * @param builder How to build this portion of the instance.
    513     * @since 1.20.0
    514     */
    515    protected BaseNCodec(final AbstractBuilder<?, ?> builder) {
    516        this.unencodedBlockSize = builder.unencodedBlockSize;
    517        this.encodedBlockSize = builder.encodedBlockSize;
    518        final boolean useChunking = builder.lineLength > 0 && builder.lineSeparator.length > 0;
    519        this.lineLength = useChunking ? builder.lineLength / builder.encodedBlockSize * builder.encodedBlockSize : 0;
    520        this.chunkSeparatorLength = builder.lineSeparator.length;
    521        this.pad = builder.padding;
    522        this.decodingPolicy = Objects.requireNonNull(builder.decodingPolicy, "codecPolicy");
    523        this.encodeTable = Objects.requireNonNull(builder.getEncodeTable(), "builder.getEncodeTable()");
    524        this.decodeTable = builder.getDecodeTable();
    525    }
    526
    527    /**
    528     * Constructs a new instance.
    529     * <p>
    530     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size. If {@code chunkSeparatorLength} is zero, then chunking is
    531     * disabled.
    532     * </p>
    533     *
    534     * @param unencodedBlockSize   the size of an unencoded block (for example Base64 = 3).
    535     * @param encodedBlockSize     the size of an encoded block (for example Base64 = 4).
    536     * @param lineLength           if &gt; 0, use chunking with a length {@code lineLength}.
    537     * @param chunkSeparatorLength the chunk separator length, if relevant.
    538     * @deprecated Use {@link BaseNCodec#BaseNCodec(AbstractBuilder)}.
    539     */
    540    @Deprecated
    541    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength) {
    542        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
    543    }
    544
    545    /**
    546     * Constructs a new instance.
    547     * <p>
    548     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size. If {@code chunkSeparatorLength} is zero, then chunking is
    549     * disabled.
    550     * </p>
    551     *
    552     * @param unencodedBlockSize   the size of an unencoded block (for example Base64 = 3).
    553     * @param encodedBlockSize     the size of an encoded block (for example Base64 = 4).
    554     * @param lineLength           if &gt; 0, use chunking with a length {@code lineLength}.
    555     * @param chunkSeparatorLength the chunk separator length, if relevant.
    556     * @param pad                  byte used as padding byte.
    557     * @deprecated Use {@link BaseNCodec#BaseNCodec(AbstractBuilder)}.
    558     */
    559    @Deprecated
    560    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad) {
    561        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, pad, DECODING_POLICY_DEFAULT);
    562    }
    563
    564    /**
    565     * Constructs a new instance.
    566     * <p>
    567     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size. If {@code chunkSeparatorLength} is zero, then chunking is
    568     * disabled.
    569     * </p>
    570     *
    571     * @param unencodedBlockSize   the size of an unencoded block (for example Base64 = 3).
    572     * @param encodedBlockSize     the size of an encoded block (for example Base64 = 4).
    573     * @param lineLength           if &gt; 0, use chunking with a length {@code lineLength}.
    574     * @param chunkSeparatorLength the chunk separator length, if relevant.
    575     * @param pad                  byte used as padding byte.
    576     * @param decodingPolicy       Decoding policy.
    577     * @since 1.15
    578     * @deprecated Use {@link BaseNCodec#BaseNCodec(AbstractBuilder)}.
    579     */
    580    @Deprecated
    581    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad,
    582            final CodecPolicy decodingPolicy) {
    583        this.unencodedBlockSize = unencodedBlockSize;
    584        this.encodedBlockSize = encodedBlockSize;
    585        final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
    586        this.lineLength = useChunking ? lineLength / encodedBlockSize * encodedBlockSize : 0;
    587        this.chunkSeparatorLength = chunkSeparatorLength;
    588        this.pad = pad;
    589        this.decodingPolicy = Objects.requireNonNull(decodingPolicy, "codecPolicy");
    590        this.encodeTable = null;
    591        this.decodeTable = null;
    592    }
    593
    594    /**
    595     * Returns the amount of buffered data available for reading.
    596     *
    597     * @param context the context to be used.
    598     * @return The amount of buffered data available for reading.
    599     */
    600    int available(final Context context) { // package protected for access from I/O streams
    601        return hasData(context) ? context.pos - context.readPos : 0;
    602    }
    603
    604    /**
    605     * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
    606     *
    607     * Intended for use in checking line-ending arrays.
    608     *
    609     * @param arrayOctet byte array to test.
    610     * @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise.
    611     */
    612    protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
    613        if (arrayOctet != null) {
    614            for (final byte element : arrayOctet) {
    615                if (pad == element || isInAlphabet(element)) {
    616                    return true;
    617                }
    618            }
    619        }
    620        return false;
    621    }
    622
    623    /**
    624     * Decodes a byte[] containing characters in the Base-N alphabet.
    625     *
    626     * @param array A byte array containing Base-N character data.
    627     * @return a byte array containing binary data.
    628     */
    629    @Override
    630    public byte[] decode(final byte[] array) {
    631        if (BinaryCodec.isEmpty(array)) {
    632            return array;
    633        }
    634        final Context context = new Context();
    635        decode(array, 0, array.length, context);
    636        decode(array, 0, EOF, context); // Notify decoder of EOF.
    637        final byte[] result = new byte[context.pos];
    638        readResults(result, 0, result.length, context);
    639        return result;
    640    }
    641
    642    // package protected for access from I/O streams
    643    abstract void decode(byte[] array, int i, int length, Context context);
    644
    645    /**
    646     * 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
    647     * DecoderException if the supplied object is not of type byte[] or String.
    648     *
    649     * @param obj Object to decode.
    650     * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String supplied.
    651     * @throws DecoderException if the parameter supplied is not of type byte[].
    652     */
    653    @Override
    654    public Object decode(final Object obj) throws DecoderException {
    655        if (obj instanceof byte[]) {
    656            return decode((byte[]) obj);
    657        }
    658        if (obj instanceof String) {
    659            return decode((String) obj);
    660        }
    661        throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
    662    }
    663
    664    /**
    665     * Decodes a String containing characters in the Base-N alphabet.
    666     *
    667     * @param array A String containing Base-N character data.
    668     * @return a byte array containing binary data.
    669     */
    670    public byte[] decode(final String array) {
    671        return decode(StringUtils.getBytesUtf8(array));
    672    }
    673
    674    /**
    675     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    676     *
    677     * @param array a byte array containing binary data.
    678     * @return A byte array containing only the base N alphabetic character data.
    679     */
    680    @Override
    681    public byte[] encode(final byte[] array) {
    682        if (BinaryCodec.isEmpty(array)) {
    683            return array;
    684        }
    685        return encode(array, 0, array.length);
    686    }
    687
    688    /**
    689     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    690     *
    691     * @param array  a byte array containing binary data.
    692     * @param offset initial offset of the subarray.
    693     * @param length length of the subarray.
    694     * @return A byte array containing only the base N alphabetic character data.
    695     * @since 1.11
    696     */
    697    public byte[] encode(final byte[] array, final int offset, final int length) {
    698        if (BinaryCodec.isEmpty(array)) {
    699            return array;
    700        }
    701        final Context context = new Context();
    702        encode(array, offset, length, context);
    703        encode(array, offset, EOF, context); // Notify encoder of EOF.
    704        final byte[] buf = new byte[context.pos - context.readPos];
    705        readResults(buf, 0, buf.length, context);
    706        return buf;
    707    }
    708
    709    // package protected for access from I/O streams
    710    abstract void encode(byte[] array, int i, int length, Context context);
    711
    712    /**
    713     * 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
    714     * EncoderException if the supplied object is not of type byte[].
    715     *
    716     * @param obj Object to encode.
    717     * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
    718     * @throws EncoderException if the parameter supplied is not of type byte[].
    719     */
    720    @Override
    721    public Object encode(final Object obj) throws EncoderException {
    722        if (!(obj instanceof byte[])) {
    723            throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
    724        }
    725        return encode((byte[]) obj);
    726    }
    727
    728    /**
    729     * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet. Uses UTF8 encoding.
    730     * <p>
    731     * This is a duplicate of {@link #encodeToString(byte[])}; it was merged during refactoring.
    732     * </p>
    733     *
    734     * @param array a byte array containing binary data.
    735     * @return String containing only character data in the appropriate alphabet.
    736     * @since 1.5
    737     */
    738    public String encodeAsString(final byte[] array) {
    739        return StringUtils.newStringUtf8(encode(array));
    740    }
    741
    742    /**
    743     * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet. Uses UTF8 encoding.
    744     *
    745     * @param array a byte array containing binary data.
    746     * @return A String containing only Base-N character data.
    747     */
    748    public String encodeToString(final byte[] array) {
    749        return StringUtils.newStringUtf8(encode(array));
    750    }
    751
    752    /**
    753     * Ensures that the buffer has room for {@code size} bytes
    754     *
    755     * @param size    minimum spare space required.
    756     * @param context the context to be used.
    757     * @return the buffer.
    758     */
    759    protected byte[] ensureBufferSize(final int size, final Context context) {
    760        if (context.buffer == null) {
    761            context.buffer = new byte[Math.max(size, getDefaultBufferSize())];
    762            context.pos = 0;
    763            context.readPos = 0;
    764            // Overflow-conscious:
    765            // x + y > z == x + y - z > 0
    766        } else if (context.pos + size - context.buffer.length > 0) {
    767            return resizeBuffer(context, context.pos + size);
    768        }
    769        return context.buffer;
    770    }
    771
    772    /**
    773     * Gets the decoding behavior policy.
    774     *
    775     * <p>
    776     * 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
    777     * valid encoding. Decoding will compose trailing bits into 8-bit bytes and discard the remainder.
    778     * </p>
    779     *
    780     * @return true if using strict decoding.
    781     * @since 1.15
    782     */
    783    public CodecPolicy getCodecPolicy() {
    784        return decodingPolicy;
    785    }
    786
    787    /**
    788     * Gets the default buffer size. Can be overridden.
    789     *
    790     * @return the default buffer size.
    791     */
    792    protected int getDefaultBufferSize() {
    793        return DEFAULT_BUFFER_SIZE;
    794    }
    795
    796    /**
    797     * Gets the amount of space needed to encode the supplied array.
    798     *
    799     * @param array byte[] array which will later be encoded.
    800     * @return amount of space needed to encode the supplied array. Returns a long since a max-len array will require &gt; Integer.MAX_VALUE.
    801     */
    802    public long getEncodedLength(final byte[] array) {
    803        // Calculate non-chunked size - rounded up to allow for padding
    804        // cast to long is needed to avoid possibility of overflow
    805        long len = (array.length + unencodedBlockSize - 1) / unencodedBlockSize * (long) encodedBlockSize;
    806        if (lineLength > 0) { // We're using chunking
    807            // Round up to nearest multiple
    808            len += (len + lineLength - 1) / lineLength * chunkSeparatorLength;
    809        }
    810        return len;
    811    }
    812
    813    /**
    814     * Tests whether this object has buffered data for reading.
    815     *
    816     * @param context the context to be used.
    817     * @return true if there is data still available for reading.
    818     */
    819    boolean hasData(final Context context) { // package protected for access from I/O streams
    820        return context.pos > context.readPos;
    821    }
    822
    823    /**
    824     * Tests whether or not the {@code octet} is in the current alphabet. Does not allow whitespace or pad.
    825     *
    826     * @param value The value to test.
    827     * @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
    828     */
    829    protected abstract boolean isInAlphabet(byte value);
    830
    831    /**
    832     * 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.
    833     *
    834     * @param arrayOctet byte array to test.
    835     * @param allowWSPad if {@code true}, then whitespace and PAD are also allowed.
    836     * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty; {@code false}, otherwise.
    837     */
    838    public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
    839        for (final byte octet : arrayOctet) {
    840            if (!isInAlphabet(octet) && (!allowWSPad || octet != pad && !Character.isWhitespace(octet))) {
    841                return false;
    842            }
    843        }
    844        return true;
    845    }
    846
    847    /**
    848     * Tests a given String to see if it contains only valid characters within the alphabet. The method treats whitespace and PAD as valid.
    849     *
    850     * @param basen String to test.
    851     * @return {@code true} if all characters in the String are valid characters in the alphabet or if the String is empty; {@code false}, otherwise.
    852     * @see #isInAlphabet(byte[], boolean)
    853     */
    854    public boolean isInAlphabet(final String basen) {
    855        return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
    856    }
    857
    858    /**
    859     * Tests true if decoding behavior is strict. Decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid encoding.
    860     *
    861     * <p>
    862     * The default is false for lenient decoding. Decoding will compose trailing bits into 8-bit bytes and discard the remainder.
    863     * </p>
    864     *
    865     * @return true if using strict decoding.
    866     * @since 1.15
    867     */
    868    public boolean isStrictDecoding() {
    869        return decodingPolicy == CodecPolicy.STRICT;
    870    }
    871
    872    /**
    873     * 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
    874     * extracted.
    875     * <p>
    876     * Package private for access from I/O streams.
    877     * </p>
    878     *
    879     * @param b       byte[] array to extract the buffered data into.
    880     * @param bPos    position in byte[] array to start extraction at.
    881     * @param bAvail  amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
    882     * @param context the context to be used.
    883     * @return The number of bytes successfully extracted into the provided byte[] array.
    884     */
    885    int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
    886        if (hasData(context)) {
    887            final int len = Math.min(available(context), bAvail);
    888            System.arraycopy(context.buffer, context.readPos, b, bPos, len);
    889            context.readPos += len;
    890            if (!hasData(context)) {
    891                // All data read.
    892                // Reset position markers but do not set buffer to null to allow its reuse.
    893                // hasData(context) will still return false, and this method will return 0 until
    894                // more data is available, or -1 if EOF.
    895                context.pos = context.readPos = 0;
    896            }
    897            return len;
    898        }
    899        return context.eof ? EOF : 0;
    900    }
    901}