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