    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
    018    package org.apache.commons.codec.binary;
    019
    020    import java.util.Arrays;
    021
    022    import org.apache.commons.codec.BinaryDecoder;
    023    import org.apache.commons.codec.BinaryEncoder;
    024    import org.apache.commons.codec.DecoderException;
    025    import org.apache.commons.codec.EncoderException;
    026
    027    /**
    028     * Abstract superclass for Base-N encoders and decoders.
    029     *
    030     * <p>
    031     * This class is thread-safe.
    032     * </p>
    033     *
    034     * @version $Id: BaseNCodec.java 1465182 2013-04-06 04:03:12Z ggregory $
    035     */
    036    public abstract class BaseNCodec implements BinaryEncoder, BinaryDecoder {
    037
    038        /**
    039         * Holds thread context so classes can be thread-safe.
    040         *
    041         * This class is not itself thread-safe; each thread must allocate its own copy.
    042         *
    043         * @since 1.7
    044         */
    045        static class Context {
    046
    047            /**
    048             * Place holder for the bytes we're dealing with for our based logic.
    049             * Bitwise operations store and extract the encoding or decoding from this variable.
    050             */
    051            int ibitWorkArea;
    052
    053            /**
    054             * Place holder for the bytes we're dealing with for our based logic.
    055             * Bitwise operations store and extract the encoding or decoding from this variable.
    056             */
    057            long lbitWorkArea;
    058
    059            /**
    060             * Buffer for streaming.
    061             */
    062            byte[] buffer;
    063
    064            /**
    065             * Position where next character should be written in the buffer.
    066             */
    067            int pos;
    068
    069            /**
    070             * Position where next character should be read from the buffer.
    071             */
    072            int readPos;
    073
    074            /**
    075             * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless,
    076             * and must be thrown away.
    077             */
    078            boolean eof;
    079
    080            /**
    081             * Variable tracks how many characters have been written to the current line. Only used when encoding. We use
    082             * it to make sure each encoded line never goes beyond lineLength (if lineLength > 0).
    083             */
    084            int currentLinePos;
    085
    086            /**
    087             * Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This
    088             * variable helps track that.
    089             */
    090            int modulus;
    091
    092            Context() {
    093            }
    094
    095            /**
    096             * Returns a String useful for debugging (especially within a debugger.)
    097             *
    098             * @return a String useful for debugging.
    099             */
    100            @SuppressWarnings("boxing") // OK to ignore boxing here
    101            @Override
    102            public String toString() {
    103                return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
    104                        "modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
    105                        currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
    106            }
    107        }
    108
    109        /**
    110         * EOF
    111         *
    112         * @since 1.7
    113         */
    114        static final int EOF = -1;
    115
    116        /**
    117         *  MIME chunk size per RFC 2045 section 6.8.
    118         *
    119         * <p>
    120         * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
    121         * equal signs.
    122         * </p>
    123         *
    124         * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
    125         */
    126        public static final int MIME_CHUNK_SIZE = 76;
    127
    128        /**
    129         * PEM chunk size per RFC 1421 section 4.3.2.4.
    130         *
    131         * <p>
    132         * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
    133         * equal signs.
    134         * </p>
    135         *
    136         * @see <a href="http://tools.ietf.org/html/rfc1421">RFC 1421 section 4.3.2.4</a>
    137         */
    138        public static final int PEM_CHUNK_SIZE = 64;
    139
    140        private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
    141
    142        /**
    143         * Defines the default buffer size - currently {@value}
    144         * - must be large enough for at least one encoded block+separator
    145         */
    146        private static final int DEFAULT_BUFFER_SIZE = 8192;
    147
    148        /** Mask used to extract 8 bits, used in decoding bytes */
    149        protected static final int MASK_8BITS = 0xff;
    150
    151        /**
    152         * Byte used to pad output.
    153         */
    154        protected static final byte PAD_DEFAULT = '='; // Allow static access to default
    155
    156        protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
    157
    158        /** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
    159        private final int unencodedBlockSize;
    160
    161        /** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
    162        private final int encodedBlockSize;
    163
    164        /**
    165         * Chunksize for encoding. Not used when decoding.
    166         * A value of zero or less implies no chunking of the encoded data.
    167         * Rounded down to nearest multiple of encodedBlockSize.
    168         */
    169        protected final int lineLength;
    170
    171        /**
    172         * Size of chunk separator. Not used unless {@link #lineLength} > 0.
    173         */
    174        private final int chunkSeparatorLength;
    175
    176        /**
    177         * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
    178         * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
    179         * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
    180         * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
    181         * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
    182         * @param chunkSeparatorLength the chunk separator length, if relevant
    183         */
    184        protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
    185                             final int lineLength, final int chunkSeparatorLength) {
    186            this.unencodedBlockSize = unencodedBlockSize;
    187            this.encodedBlockSize = encodedBlockSize;
    188            final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
    189            this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
    190            this.chunkSeparatorLength = chunkSeparatorLength;
    191        }
    192
    193        /**
    194         * Returns true if this object has buffered data for reading.
    195         *
    196         * @param context the context to be used
    197         * @return true if there is data still available for reading.
    198         */
    199        boolean hasData(final Context context) {  // package protected for access from I/O streams
    200            return context.buffer != null;
    201        }
    202
    203        /**
    204         * Returns the amount of buffered data available for reading.
    205         *
    206         * @param context the context to be used
    207         * @return The amount of buffered data available for reading.
    208         */
    209        int available(final Context context) {  // package protected for access from I/O streams
    210            return context.buffer != null ? context.pos - context.readPos : 0;
    211        }
    212
    213        /**
    214         * Get the default buffer size. Can be overridden.
    215         *
    216         * @return {@link #DEFAULT_BUFFER_SIZE}
    217         */
    218        protected int getDefaultBufferSize() {
    219            return DEFAULT_BUFFER_SIZE;
    220        }
    221
    222        /**
    223         * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
    224         * @param context the context to be used
    225         */
    226        private byte[] resizeBuffer(final Context context) {
    227            if (context.buffer == null) {
    228                context.buffer = new byte[getDefaultBufferSize()];
    229                context.pos = 0;
    230                context.readPos = 0;
    231            } else {
    232                final byte[] b = new byte[context.buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
    233                System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
    234                context.buffer = b;
    235            }
    236            return context.buffer;
    237        }
    238
    239        /**
    240         * Ensure that the buffer has room for <code>size</code> bytes
    241         *
    242         * @param size minimum spare space required
    243         * @param context the context to be used
    244         */
    245        protected byte[] ensureBufferSize(final int size, final Context context){
    246            if ((context.buffer == null) || (context.buffer.length < context.pos + size)){
    247                return resizeBuffer(context);
    248            }
    249            return context.buffer;
    250        }
    251
    252        /**
    253         * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
    254         * bytes. Returns how many bytes were actually extracted.
    255         * <p>
    256         * Package protected for access from I/O streams.
    257         *
    258         * @param b
    259         *            byte[] array to extract the buffered data into.
    260         * @param bPos
    261         *            position in byte[] array to start extraction at.
    262         * @param bAvail
    263         *            amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
    264         * @param context
    265         *            the context to be used
    266         * @return The number of bytes successfully extracted into the provided byte[] array.
    267         */
    268        int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
    269            if (context.buffer != null) {
    270                final int len = Math.min(available(context), bAvail);
    271                System.arraycopy(context.buffer, context.readPos, b, bPos, len);
    272                context.readPos += len;
    273                if (context.readPos >= context.pos) {
    274                    context.buffer = null; // so hasData() will return false, and this method can return -1
    275                }
    276                return len;
    277            }
    278            return context.eof ? EOF : 0;
    279        }
    280
    281        /**
    282         * Checks if a byte value is whitespace or not.
    283         * Whitespace is taken to mean: space, tab, CR, LF
    284         * @param byteToCheck
    285         *            the byte to check
    286         * @return true if byte is whitespace, false otherwise
    287         */
    288        protected static boolean isWhiteSpace(final byte byteToCheck) {
    289            switch (byteToCheck) {
    290                case ' ' :
    291                case '\n' :
    292                case '\r' :
    293                case '\t' :
    294                    return true;
    295                default :
    296                    return false;
    297            }
    298        }
    299
    300        /**
    301         * Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
    302         * the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
    303         *
    304         * @param obj
    305         *            Object to encode
    306         * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
    307         * @throws EncoderException
    308         *             if the parameter supplied is not of type byte[]
    309         */
    310        @Override
    311        public Object encode(final Object obj) throws EncoderException {
    312            if (!(obj instanceof byte[])) {
    313                throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
    314            }
    315            return encode((byte[]) obj);
    316        }
    317
    318        /**
    319         * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
    320         * Uses UTF8 encoding.
    321         *
    322         * @param pArray
    323         *            a byte array containing binary data
    324         * @return A String containing only Base-N character data
    325         */
    326        public String encodeToString(final byte[] pArray) {
    327            return StringUtils.newStringUtf8(encode(pArray));
    328        }
    329
    330        /**
    331         * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
    332         * Uses UTF8 encoding.
    333         *
    334         * @param pArray a byte array containing binary data
    335         * @return String containing only character data in the appropriate alphabet.
    336        */
    337        public String encodeAsString(final byte[] pArray){
    338            return StringUtils.newStringUtf8(encode(pArray));
    339        }
    340
    341        /**
    342         * Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
    343         * the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
    344         *
    345         * @param obj
    346         *            Object to decode
    347         * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
    348         *         supplied.
    349         * @throws DecoderException
    350         *             if the parameter supplied is not of type byte[]
    351         */
    352        @Override
    353        public Object decode(final Object obj) throws DecoderException {
    354            if (obj instanceof byte[]) {
    355                return decode((byte[]) obj);
    356            } else if (obj instanceof String) {
    357                return decode((String) obj);
    358            } else {
    359                throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
    360            }
    361        }
    362
    363        /**
    364         * Decodes a String containing characters in the Base-N alphabet.
    365         *
    366         * @param pArray
    367         *            A String containing Base-N character data
    368         * @return a byte array containing binary data
    369         */
    370        public byte[] decode(final String pArray) {
    371            return decode(StringUtils.getBytesUtf8(pArray));
    372        }
    373
    374        /**
    375         * Decodes a byte[] containing characters in the Base-N alphabet.
    376         *
    377         * @param pArray
    378         *            A byte array containing Base-N character data
    379         * @return a byte array containing binary data
    380         */
    381        @Override
    382        public byte[] decode(final byte[] pArray) {
    383            if (pArray == null || pArray.length == 0) {
    384                return pArray;
    385            }
    386            final Context context = new Context();
    387            decode(pArray, 0, pArray.length, context);
    388            decode(pArray, 0, EOF, context); // Notify decoder of EOF.
    389            final byte[] result = new byte[context.pos];
    390            readResults(result, 0, result.length, context);
    391            return result;
    392        }
    393
    394        /**
    395         * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    396         *
    397         * @param pArray
    398         *            a byte array containing binary data
    399         * @return A byte array containing only the basen alphabetic character data
    400         */
    401        @Override
    402        public byte[] encode(final byte[] pArray) {
    403            if (pArray == null || pArray.length == 0) {
    404                return pArray;
    405            }
    406            final Context context = new Context();
    407            encode(pArray, 0, pArray.length, context);
    408            encode(pArray, 0, EOF, context); // Notify encoder of EOF.
    409            final byte[] buf = new byte[context.pos - context.readPos];
    410            readResults(buf, 0, buf.length, context);
    411            return buf;
    412        }
    413
    414        // package protected for access from I/O streams
    415        abstract void encode(byte[] pArray, int i, int length, Context context);
    416
    417        // package protected for access from I/O streams
    418        abstract void decode(byte[] pArray, int i, int length, Context context);
    419
    420        /**
    421         * Returns whether or not the <code>octet</code> is in the current alphabet.
    422         * Does not allow whitespace or pad.
    423         *
    424         * @param value The value to test
    425         *
    426         * @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
    427         */
    428        protected abstract boolean isInAlphabet(byte value);
    429
    430        /**
    431         * Tests a given byte array to see if it contains only valid characters within the alphabet.
    432         * The method optionally treats whitespace and pad as valid.
    433         *
    434         * @param arrayOctet byte array to test
    435         * @param allowWSPad if {@code true}, then whitespace and PAD are also allowed
    436         *
    437         * @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty;
    438         *         {@code false}, otherwise
    439         */
    440        public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
    441            for (int i = 0; i < arrayOctet.length; i++) {
    442                if (!isInAlphabet(arrayOctet[i]) &&
    443                        (!allowWSPad || (arrayOctet[i] != PAD) && !isWhiteSpace(arrayOctet[i]))) {
    444                    return false;
    445                }
    446            }
    447            return true;
    448        }
    449
    450        /**
    451         * Tests a given String to see if it contains only valid characters within the alphabet.
    452         * The method treats whitespace and PAD as valid.
    453         *
    454         * @param basen String to test
    455         * @return {@code true} if all characters in the String are valid characters in the alphabet or if
    456         *         the String is empty; {@code false}, otherwise
    457         * @see #isInAlphabet(byte[], boolean)
    458         */
    459        public boolean isInAlphabet(final String basen) {
    460            return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
    461        }
    462
    463        /**
    464         * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
    465         *
    466         * Intended for use in checking line-ending arrays
    467         *
    468         * @param arrayOctet
    469         *            byte array to test
    470         * @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise
    471         */
    472        protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
    473            if (arrayOctet == null) {
    474                return false;
    475            }
    476            for (final byte element : arrayOctet) {
    477                if (PAD == element || isInAlphabet(element)) {
    478                    return true;
    479                }
    480            }
    481            return false;
    482        }
    483
    484        /**
    485         * Calculates the amount of space needed to encode the supplied array.
    486         *
    487         * @param pArray byte[] array which will later be encoded
    488         *
    489         * @return amount of space needed to encoded the supplied array.
    490         * Returns a long since a max-len array will require > Integer.MAX_VALUE
    491         */
    492        public long getEncodedLength(final byte[] pArray) {
    493            // Calculate non-chunked size - rounded up to allow for padding
    494            // cast to long is needed to avoid possibility of overflow
    495            long len = ((pArray.length + unencodedBlockSize-1)  / unencodedBlockSize) * (long) encodedBlockSize;
    496            if (lineLength > 0) { // We're using chunking
    497                // Round up to nearest multiple
    498                len += ((len + lineLength-1) / lineLength) * chunkSeparatorLength;
    499            }
    500            return len;
    501        }
    502    }