    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.codec.binary;
    019
    020import 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
    038 * valid encoding. These can be bits that are unused from the final character or entire characters. The default mode is
    039 * lenient decoding.
    040 * </p>
    041 * <ul>
    042 * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
    043 * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid
    044 * encoding. Any unused bits from the final character must be zero. Impossible counts of entire final characters are not
    045 * allowed.
    046 * </ul>
    047 * <p>
    048 * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches
    049 * the original, i.e. no changes occur on the final character. This requires that the input bytes use the same padding
    050 * and alphabet as the encoder.
    051 * </p>
    052 */
    053public abstract class BaseNCodec implements BinaryEncoder, BinaryDecoder {
    054
    055    /**
    056     * Builds {@link Base64} instances.
    057     *
    058     * @param <T> the codec type to build.
    059     * @param <B> the codec builder subtype.
    060     * @since 1.17.0
    061     */
    062    public abstract static class AbstractBuilder<T, B extends AbstractBuilder<T, B>> implements Supplier<T> {
    063
    064        private CodecPolicy decodingPolicy = DECODING_POLICY_DEFAULT;
    065        private int lineLength;
    066        private byte[] lineSeparator = CHUNK_SEPARATOR;
    067        private final byte[] defaultEncodeTable;
    068        private byte[] encodeTable;
    069        /** Padding byte. */
    070        private byte padding = PAD_DEFAULT;
    071
    072        AbstractBuilder(final byte[] defaultEncodeTable) {
    073            this.defaultEncodeTable = defaultEncodeTable;
    074            this.encodeTable = defaultEncodeTable;
    075        }
    076
    077        @SuppressWarnings("unchecked")
    078        B asThis() {
    079            return (B) this;
    080        }
    081
    082        CodecPolicy getDecodingPolicy() {
    083            return decodingPolicy;
    084        }
    085
    086        byte[] getEncodeTable() {
    087            return encodeTable;
    088        }
    089
    090        int getLineLength() {
    091            return lineLength;
    092        }
    093
    094        byte[] getLineSeparator() {
    095            return lineSeparator;
    096        }
    097
    098        byte getPadding() {
    099            return padding;
    100        }
    101
    102        /**
    103         * Sets the decoding policy.
    104         *
    105         * @param decodingPolicy the decoding policy, null resets to the default.
    106         * @return this.
    107         */
    108        public B setDecodingPolicy(final CodecPolicy decodingPolicy) {
    109            this.decodingPolicy = decodingPolicy != null ? decodingPolicy : DECODING_POLICY_DEFAULT;
    110            return asThis();
    111        }
    112
    113        /**
    114         * Sets the encode table.
    115         *
    116         * @param encodeTable the encode table, null resets to the default.
    117         * @return this.
    118         */
    119        public B setEncodeTable(final byte... encodeTable) {
    120            this.encodeTable = encodeTable != null ? encodeTable : defaultEncodeTable;
    121            return asThis();
    122        }
    123
    124        /**
    125         * Sets the line length.
    126         *
    127         * @param lineLength the line length, less than 0 resets to the default.
    128         * @return this.
    129         */
    130        public B setLineLength(final int lineLength) {
    131            this.lineLength = Math.max(0, lineLength);
    132            return asThis();
    133        }
    134
    135        /**
    136         * Sets the line separator.
    137         *
    138         * @param lineSeparator the line separator, null resets to the default.
    139         * @return this.
    140         */
    141        public B setLineSeparator(final byte... lineSeparator) {
    142            this.lineSeparator = lineSeparator != null ? lineSeparator : CHUNK_SEPARATOR;
    143            return asThis();
    144        }
    145
    146        /**
    147         * Sets the padding byte.
    148         *
    149         * @param padding the padding byte.
    150         * @return this.
    151         */
    152        public B setPadding(final byte padding) {
    153            this.padding = padding;
    154            return asThis();
    155        }
    156
    157    }
    158
    159    /**
    160     * Holds thread context so classes can be thread-safe.
    161     *
    162     * This class is not itself thread-safe; each thread must allocate its own copy.
    163     */
    164    static class Context {
    165
    166        /**
    167         * Placeholder for the bytes we're dealing with for our based logic.
    168         * Bitwise operations store and extract the encoding or decoding from this variable.
    169         */
    170        int ibitWorkArea;
    171
    172        /**
    173         * Placeholder for the bytes we're dealing with for our based logic.
    174         * Bitwise operations store and extract the encoding or decoding from this variable.
    175         */
    176        long lbitWorkArea;
    177
    178        /**
    179         * Buffer for streaming.
    180         */
    181        byte[] buffer;
    182
    183        /**
    184         * Position where next character should be written in the buffer.
    185         */
    186        int pos;
    187
    188        /**
    189         * Position where next character should be read from the buffer.
    190         */
    191        int readPos;
    192
    193        /**
    194         * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless,
    195         * and must be thrown away.
    196         */
    197        boolean eof;
    198
    199        /**
    200         * Variable tracks how many characters have been written to the current line. Only used when encoding. We use
    201         * it to make sure each encoded line never goes beyond lineLength (if lineLength &gt; 0).
    202         */
    203        int currentLinePos;
    204
    205        /**
    206         * Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This
    207         * variable helps track that.
    208         */
    209        int modulus;
    210
    211        /**
    212         * Returns a String useful for debugging (especially within a debugger.)
    213         *
    214         * @return a String useful for debugging.
    215         */
    216        @Override
    217        public String toString() {
    218            return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
    219                    "modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
    220                    currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
    221        }
    222    }
    223
    224    /**
    225     * EOF
    226     *
    227     * @since 1.7
    228     */
    229    static final int EOF = -1;
    230
    231    /**
    232     *  MIME chunk size per RFC 2045 section 6.8.
    233     *
    234     * <p>
    235     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
    236     * equal signs.
    237     * </p>
    238     *
    239     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
    240     */
    241    public static final int MIME_CHUNK_SIZE = 76;
    242
    243    /**
    244     * PEM chunk size per RFC 1421 section 4.3.2.4.
    245     *
    246     * <p>
    247     * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
    248     * equal signs.
    249     * </p>
    250     *
    251     * @see <a href="https://tools.ietf.org/html/rfc1421">RFC 1421 section 4.3.2.4</a>
    252     */
    253    public static final int PEM_CHUNK_SIZE = 64;
    254
    255    private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
    256
    257    /**
    258     * Defines the default buffer size - currently {@value}
    259     * - must be large enough for at least one encoded block+separator
    260     */
    261    private static final int DEFAULT_BUFFER_SIZE = 8192;
    262
    263    /**
    264     * The maximum size buffer to allocate.
    265     *
    266     * <p>This is set to the same size used in the JDK {@link java.util.ArrayList}:</p>
    267     * <blockquote>
    268     * Some VMs reserve some header words in an array.
    269     * Attempts to allocate larger arrays may result in
    270     * OutOfMemoryError: Requested array size exceeds VM limit.
    271     * </blockquote>
    272     */
    273    private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
    274
    275    /** Mask used to extract 8 bits, used in decoding bytes */
    276    protected static final int MASK_8BITS = 0xff;
    277
    278    /**
    279     * Byte used to pad output.
    280     */
    281    protected static final byte PAD_DEFAULT = '='; // Allow static access to default
    282
    283    /**
    284     * The default decoding policy.
    285     * @since 1.15
    286     */
    287    protected static final CodecPolicy DECODING_POLICY_DEFAULT = CodecPolicy.LENIENT;
    288
    289    /**
    290     * Chunk separator per RFC 2045 section 2.1.
    291     *
    292     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
    293     */
    294    static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
    295
    296    /**
    297     * Create a positive capacity at least as large the minimum required capacity.
    298     * If the minimum capacity is negative then this throws an OutOfMemoryError as no array
    299     * can be allocated.
    300     *
    301     * @param minCapacity the minimum capacity
    302     * @return the capacity
    303     * @throws OutOfMemoryError if the {@code minCapacity} is negative
    304     */
    305    private static int createPositiveCapacity(final int minCapacity) {
    306        if (minCapacity < 0) {
    307            // overflow
    308            throw new OutOfMemoryError("Unable to allocate array size: " + (minCapacity & 0xffffffffL));
    309        }
    310        // This is called when we require buffer expansion to a very big array.
    311        // Use the conservative maximum buffer size if possible, otherwise the biggest required.
    312        //
    313        // Note: In this situation JDK 1.8 java.util.ArrayList returns Integer.MAX_VALUE.
    314        // This excludes some VMs that can exceed MAX_BUFFER_SIZE but not allocate a full
    315        // Integer.MAX_VALUE length array.
    316        // The result is that we may have to allocate an array of this size more than once if
    317        // the capacity must be expanded again.
    318        return Math.max(minCapacity, MAX_BUFFER_SIZE);
    319    }
    320
    321    /**
    322     * Gets a copy of the chunk separator per RFC 2045 section 2.1.
    323     *
    324     * @return the chunk separator
    325     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
    326     * @since 1.15
    327     */
    328    public static byte[] getChunkSeparator() {
    329        return CHUNK_SEPARATOR.clone();
    330    }
    331
    332    /**
    333     * Checks if a byte value is whitespace or not.
    334     * @param byteToCheck
    335     *            the byte to check
    336     * @return true if byte is whitespace, false otherwise
    337     * @see Character#isWhitespace(int)
    338     * @deprecated Use {@link Character#isWhitespace(int)}.
    339     */
    340    @Deprecated
    341    protected static boolean isWhiteSpace(final byte byteToCheck) {
    342        return Character.isWhitespace(byteToCheck);
    343    }
    344
    345    /**
    346     * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
    347     * @param context the context to be used
    348     * @param minCapacity the minimum required capacity
    349     * @return the resized byte[] buffer
    350     * @throws OutOfMemoryError if the {@code minCapacity} is negative
    351     */
    352    private static byte[] resizeBuffer(final Context context, final int minCapacity) {
    353        // Overflow-conscious code treats the min and new capacity as unsigned.
    354        final int oldCapacity = context.buffer.length;
    355        int newCapacity = oldCapacity * DEFAULT_BUFFER_RESIZE_FACTOR;
    356        if (Integer.compareUnsigned(newCapacity, minCapacity) < 0) {
    357            newCapacity = minCapacity;
    358        }
    359        if (Integer.compareUnsigned(newCapacity, MAX_BUFFER_SIZE) > 0) {
    360            newCapacity = createPositiveCapacity(minCapacity);
    361        }
    362        final byte[] b = Arrays.copyOf(context.buffer, newCapacity);
    363        context.buffer = b;
    364        return b;
    365    }
    366
    367    /**
    368     * Gets the array length or 0 if null.
    369     *
    370     * @param array the array or null.
    371     * @return the array length or 0 if null.
    372     */
    373    static int toLength(final byte[] array) {
    374        return array == null ? 0 : array.length;
    375    }
    376
    377    /**
    378     * @deprecated Use {@link #pad}. Will be removed in 2.0.
    379     */
    380    @Deprecated
    381    protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
    382
    383    /** Pad byte. Instance variable just in case it needs to vary later. */
    384    protected final byte pad;
    385
    386    /** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
    387    private final int unencodedBlockSize;
    388
    389    /** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
    390    private final int encodedBlockSize;
    391
    392    /**
    393     * Chunksize for encoding. Not used when decoding.
    394     * A value of zero or less implies no chunking of the encoded data.
    395     * Rounded down to the nearest multiple of encodedBlockSize.
    396     */
    397    protected final int lineLength;
    398
    399    /**
    400     * Size of chunk separator. Not used unless {@link #lineLength} &gt; 0.
    401     */
    402    private final int chunkSeparatorLength;
    403
    404    /**
    405     * Defines the decoding behavior when the input bytes contain leftover trailing bits that
    406     * cannot be created by a valid encoding. These can be bits that are unused from the final
    407     * character or entire characters. The default mode is lenient decoding. Set this to
    408     * {@code true} to enable strict decoding.
    409     * <ul>
    410     * <li>Lenient: Any trailing bits are composed into 8-bit bytes where possible.
    411     *     The remainder are discarded.
    412     * <li>Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits
    413     *     are not part of a valid encoding. Any unused bits from the final character must
    414     *     be zero. Impossible counts of entire final characters are not allowed.
    415     * </ul>
    416     * <p>
    417     * When strict decoding is enabled it is expected that the decoded bytes will be re-encoded
    418     * to a byte array that matches the original, i.e. no changes occur on the final
    419     * character. This requires that the input bytes use the same padding and alphabet
    420     * as the encoder.
    421     * </p>
    422     */
    423    private final CodecPolicy decodingPolicy;
    424
    425    /**
    426     * Constructs a new instance.
    427     * <p>
    428     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size.
    429     * If {@code chunkSeparatorLength} is zero, then chunking is disabled.
    430     * </p>
    431     *
    432     * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
    433     * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
    434     * @param lineLength if &gt; 0, use chunking with a length {@code lineLength}
    435     * @param chunkSeparatorLength the chunk separator length, if relevant
    436     */
    437    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength) {
    438        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
    439    }
    440
    441    /**
    442     * Constructs a new instance.
    443     * <p>
    444     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size.
    445     * If {@code chunkSeparatorLength} is zero, then chunking is disabled.
    446     * </p>
    447     *
    448     * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
    449     * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
    450     * @param lineLength if &gt; 0, use chunking with a length {@code lineLength}
    451     * @param chunkSeparatorLength the chunk separator length, if relevant
    452     * @param pad byte used as padding byte.
    453     */
    454    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad) {
    455        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, pad, DECODING_POLICY_DEFAULT);
    456    }
    457
    458    /**
    459     * Constructs a new instance.
    460     * <p>
    461     * Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size.
    462     * If {@code chunkSeparatorLength} is zero, then chunking is disabled.
    463     * </p>
    464     *
    465     * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
    466     * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
    467     * @param lineLength if &gt; 0, use chunking with a length {@code lineLength}
    468     * @param chunkSeparatorLength the chunk separator length, if relevant
    469     * @param pad byte used as padding byte.
    470     * @param decodingPolicy Decoding policy.
    471     * @since 1.15
    472     */
    473    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad,
    474            final CodecPolicy decodingPolicy) {
    475        this.unencodedBlockSize = unencodedBlockSize;
    476        this.encodedBlockSize = encodedBlockSize;
    477        final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
    478        this.lineLength = useChunking ? lineLength / encodedBlockSize * encodedBlockSize : 0;
    479        this.chunkSeparatorLength = chunkSeparatorLength;
    480        this.pad = pad;
    481        this.decodingPolicy = Objects.requireNonNull(decodingPolicy, "codecPolicy");
    482    }
    483
    484    /**
    485     * Returns the amount of buffered data available for reading.
    486     *
    487     * @param context the context to be used
    488     * @return The amount of buffered data available for reading.
    489     */
    490    int available(final Context context) {  // package protected for access from I/O streams
    491        return hasData(context) ? context.pos - context.readPos : 0;
    492    }
    493
    494    /**
    495     * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
    496     *
    497     * Intended for use in checking line-ending arrays
    498     *
    499     * @param arrayOctet
    500     *            byte array to test
    501     * @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise
    502     */
    503    protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
    504        if (arrayOctet != null) {
    505            for (final byte element : arrayOctet) {
    506                if (pad == element || isInAlphabet(element)) {
    507                    return true;
    508                }
    509            }
    510        }
    511        return false;
    512    }
    513
    514    /**
    515     * Decodes a byte[] containing characters in the Base-N alphabet.
    516     *
    517     * @param pArray
    518     *            A byte array containing Base-N character data
    519     * @return a byte array containing binary data
    520     */
    521    @Override
    522    public byte[] decode(final byte[] pArray) {
    523        if (BinaryCodec.isEmpty(pArray)) {
    524            return pArray;
    525        }
    526        final Context context = new Context();
    527        decode(pArray, 0, pArray.length, context);
    528        decode(pArray, 0, EOF, context); // Notify decoder of EOF.
    529        final byte[] result = new byte[context.pos];
    530        readResults(result, 0, result.length, context);
    531        return result;
    532    }
    533
    534    // package protected for access from I/O streams
    535    abstract void decode(byte[] pArray, int i, int length, Context context);
    536
    537    /**
    538     * Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
    539     * the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
    540     *
    541     * @param obj
    542     *            Object to decode
    543     * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
    544     *         supplied.
    545     * @throws DecoderException
    546     *             if the parameter supplied is not of type byte[]
    547     */
    548    @Override
    549    public Object decode(final Object obj) throws DecoderException {
    550        if (obj instanceof byte[]) {
    551            return decode((byte[]) obj);
    552        }
    553        if (obj instanceof String) {
    554            return decode((String) obj);
    555        }
    556        throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
    557    }
    558
    559    /**
    560     * Decodes a String containing characters in the Base-N alphabet.
    561     *
    562     * @param pArray
    563     *            A String containing Base-N character data
    564     * @return a byte array containing binary data
    565     */
    566    public byte[] decode(final String pArray) {
    567        return decode(StringUtils.getBytesUtf8(pArray));
    568    }
    569
    570    /**
    571     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    572     *
    573     * @param pArray
    574     *            a byte array containing binary data
    575     * @return A byte array containing only the base N alphabetic character data
    576     */
    577    @Override
    578    public byte[] encode(final byte[] pArray) {
    579        if (BinaryCodec.isEmpty(pArray)) {
    580            return pArray;
    581        }
    582        return encode(pArray, 0, pArray.length);
    583    }
    584
    585    /**
    586     * Encodes a byte[] containing binary data, into a byte[] containing
    587     * characters in the alphabet.
    588     *
    589     * @param pArray
    590     *            a byte array containing binary data
    591     * @param offset
    592     *            initial offset of the subarray.
    593     * @param length
    594     *            length of the subarray.
    595     * @return A byte array containing only the base N alphabetic character data
    596     * @since 1.11
    597     */
    598    public byte[] encode(final byte[] pArray, final int offset, final int length) {
    599        if (BinaryCodec.isEmpty(pArray)) {
    600            return pArray;
    601        }
    602        final Context context = new Context();
    603        encode(pArray, offset, length, context);
    604        encode(pArray, offset, EOF, context); // Notify encoder of EOF.
    605        final byte[] buf = new byte[context.pos - context.readPos];
    606        readResults(buf, 0, buf.length, context);
    607        return buf;
    608    }
    609
    610    // package protected for access from I/O streams
    611    abstract void encode(byte[] pArray, int i, int length, Context context);
    612
    613    /**
    614     * Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
    615     * the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
    616     *
    617     * @param obj
    618     *            Object to encode
    619     * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
    620     * @throws EncoderException
    621     *             if the parameter supplied is not of type byte[]
    622     */
    623    @Override
    624    public Object encode(final Object obj) throws EncoderException {
    625        if (!(obj instanceof byte[])) {
    626            throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
    627        }
    628        return encode((byte[]) obj);
    629    }
    630
    631    /**
    632     * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
    633     * Uses UTF8 encoding.
    634     * <p>
    635     * This is a duplicate of {@link #encodeToString(byte[])}; it was merged during refactoring.
    636     * </p>
    637     *
    638     * @param pArray a byte array containing binary data
    639     * @return String containing only character data in the appropriate alphabet.
    640     * @since 1.5
    641    */
    642    public String encodeAsString(final byte[] pArray) {
    643        return StringUtils.newStringUtf8(encode(pArray));
    644    }
    645
    646    /**
    647     * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
    648     * Uses UTF8 encoding.
    649     *
    650     * @param pArray
    651     *            a byte array containing binary data
    652     * @return A String containing only Base-N character data
    653     */
    654    public String encodeToString(final byte[] pArray) {
    655        return StringUtils.newStringUtf8(encode(pArray));
    656    }
    657
    658    /**
    659     * Ensure that the buffer has room for {@code size} bytes
    660     *
    661     * @param size minimum spare space required
    662     * @param context the context to be used
    663     * @return the buffer
    664     */
    665    protected byte[] ensureBufferSize(final int size, final Context context) {
    666        if (context.buffer == null) {
    667            context.buffer = new byte[Math.max(size, getDefaultBufferSize())];
    668            context.pos = 0;
    669            context.readPos = 0;
    670            // Overflow-conscious:
    671            // x + y > z == x + y - z > 0
    672        } else if (context.pos + size - context.buffer.length > 0) {
    673            return resizeBuffer(context, context.pos + size);
    674        }
    675        return context.buffer;
    676    }
    677
    678    /**
    679     * Returns the decoding behavior policy.
    680     *
    681     * <p>
    682     * The default is lenient. If the decoding policy is strict, then decoding will raise an
    683     * {@link IllegalArgumentException} if trailing bits are not part of a valid encoding. Decoding will compose
    684     * trailing bits into 8-bit bytes and discard the remainder.
    685     * </p>
    686     *
    687     * @return true if using strict decoding
    688     * @since 1.15
    689     */
    690    public CodecPolicy getCodecPolicy() {
    691        return decodingPolicy;
    692    }
    693
    694    /**
    695     * Gets the default buffer size. Can be overridden.
    696     *
    697     * @return the default buffer size.
    698     */
    699    protected int getDefaultBufferSize() {
    700        return DEFAULT_BUFFER_SIZE;
    701    }
    702
    703    /**
    704     * Calculates the amount of space needed to encode the supplied array.
    705     *
    706     * @param pArray byte[] array which will later be encoded
    707     *
    708     * @return amount of space needed to encode the supplied array.
    709     * Returns a long since a max-len array will require &gt; Integer.MAX_VALUE
    710     */
    711    public long getEncodedLength(final byte[] pArray) {
    712        // Calculate non-chunked size - rounded up to allow for padding
    713        // cast to long is needed to avoid possibility of overflow
    714        long len = (pArray.length + unencodedBlockSize - 1) / unencodedBlockSize * (long) encodedBlockSize;
    715        if (lineLength > 0) { // We're using chunking
    716            // Round up to nearest multiple
    717            len += (len + lineLength - 1) / lineLength * chunkSeparatorLength;
    718        }
    719        return len;
    720    }
    721
    722    /**
    723     * Returns true if this object has buffered data for reading.
    724     *
    725     * @param context the context to be used
    726     * @return true if there is data still available for reading.
    727     */
    728    boolean hasData(final Context context) {  // package protected for access from I/O streams
    729        return context.pos > context.readPos;
    730    }
    731
    732    /**
    733     * Returns whether or not the {@code octet} is in the current alphabet.
    734     * Does not allow whitespace or pad.
    735     *
    736     * @param value The value to test
    737     *
    738     * @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
    739     */
    740    protected abstract boolean isInAlphabet(byte value);
    741
    742    /**
    743     * Tests a given byte array to see if it contains only valid characters within the alphabet.
    744     * The method optionally treats whitespace and pad as valid.
    745     *
    746     * @param arrayOctet byte array to test
    747     * @param allowWSPad if {@code true}, then whitespace and PAD are also allowed
    748     *
    749     * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty;
    750     *         {@code false}, otherwise
    751     */
    752    public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
    753        for (final byte octet : arrayOctet) {
    754            if (!isInAlphabet(octet) && (!allowWSPad || octet != pad && !Character.isWhitespace(octet))) {
    755                return false;
    756            }
    757        }
    758        return true;
    759    }
    760
    761    /**
    762     * Tests a given String to see if it contains only valid characters within the alphabet.
    763     * The method treats whitespace and PAD as valid.
    764     *
    765     * @param basen String to test
    766     * @return {@code true} if all characters in the String are valid characters in the alphabet or if
    767     *         the String is empty; {@code false}, otherwise
    768     * @see #isInAlphabet(byte[], boolean)
    769     */
    770    public boolean isInAlphabet(final String basen) {
    771        return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
    772    }
    773
    774    /**
    775     * Returns true if decoding behavior is strict. Decoding will raise an {@link IllegalArgumentException} if trailing
    776     * bits are not part of a valid encoding.
    777     *
    778     * <p>
    779     * The default is false for lenient decoding. Decoding will compose trailing bits into 8-bit bytes and discard the
    780     * remainder.
    781     * </p>
    782     *
    783     * @return true if using strict decoding
    784     * @since 1.15
    785     */
    786    public boolean isStrictDecoding() {
    787        return decodingPolicy == CodecPolicy.STRICT;
    788    }
    789
    790    /**
    791     * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
    792     * bytes. Returns how many bytes were actually extracted.
    793     * <p>
    794     * Package private for access from I/O streams.
    795     * </p>
    796     *
    797     * @param b
    798     *            byte[] array to extract the buffered data into.
    799     * @param bPos
    800     *            position in byte[] array to start extraction at.
    801     * @param bAvail
    802     *            amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
    803     * @param context
    804     *            the context to be used
    805     * @return The number of bytes successfully extracted into the provided byte[] array.
    806     */
    807    int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
    808        if (hasData(context)) {
    809            final int len = Math.min(available(context), bAvail);
    810            System.arraycopy(context.buffer, context.readPos, b, bPos, len);
    811            context.readPos += len;
    812            if (!hasData(context)) {
    813                // All data read.
    814                // Reset position markers but do not set buffer to null to allow its reuse.
    815                // hasData(context) will still return false, and this method will return 0 until
    816                // more data is available, or -1 if EOF.
    817                context.pos = context.readPos = 0;
    818            }
    819            return len;
    820        }
    821        return context.eof ? EOF : 0;
    822    }
    823}