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 {@code this} instance.
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 {@code this} instance.
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 {@code this} instance.
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 {@code this} instance.
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 {@code this} instance.
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}