    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;
    021
    022import org.apache.commons.codec.BinaryDecoder;
    023import org.apache.commons.codec.BinaryEncoder;
    024import org.apache.commons.codec.DecoderException;
    025import 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 $Id$
    035 */
    036public 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 &gt; 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    /**
    157     * @deprecated Use {@link #pad}. Will be removed in 2.0.
    158     */
    159    @Deprecated
    160    protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
    161
    162    protected final byte pad; // instance variable just in case it needs to vary later
    163
    164    /** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
    165    private final int unencodedBlockSize;
    166
    167    /** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
    168    private final int encodedBlockSize;
    169
    170    /**
    171     * Chunksize for encoding. Not used when decoding.
    172     * A value of zero or less implies no chunking of the encoded data.
    173     * Rounded down to nearest multiple of encodedBlockSize.
    174     */
    175    protected final int lineLength;
    176
    177    /**
    178     * Size of chunk separator. Not used unless {@link #lineLength} &gt; 0.
    179     */
    180    private final int chunkSeparatorLength;
    181
    182    /**
    183     * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
    184     * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
    185     * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
    186     * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
    187     * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
    188     * @param chunkSeparatorLength the chunk separator length, if relevant
    189     */
    190    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
    191                         final int lineLength, final int chunkSeparatorLength) {
    192        this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
    193    }
    194
    195    /**
    196     * Note <code>lineLength</code> is rounded down to the nearest multiple of {@link #encodedBlockSize}
    197     * If <code>chunkSeparatorLength</code> is zero, then chunking is disabled.
    198     * @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
    199     * @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
    200     * @param lineLength if &gt; 0, use chunking with a length <code>lineLength</code>
    201     * @param chunkSeparatorLength the chunk separator length, if relevant
    202     * @param pad byte used as padding byte.
    203     */
    204    protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize,
    205                         final int lineLength, final int chunkSeparatorLength, final byte pad) {
    206        this.unencodedBlockSize = unencodedBlockSize;
    207        this.encodedBlockSize = encodedBlockSize;
    208        final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
    209        this.lineLength = useChunking ? (lineLength / encodedBlockSize) * encodedBlockSize : 0;
    210        this.chunkSeparatorLength = chunkSeparatorLength;
    211
    212        this.pad = pad;
    213    }
    214
    215    /**
    216     * Returns true if this object has buffered data for reading.
    217     *
    218     * @param context the context to be used
    219     * @return true if there is data still available for reading.
    220     */
    221    boolean hasData(final Context context) {  // package protected for access from I/O streams
    222        return context.buffer != null;
    223    }
    224
    225    /**
    226     * Returns the amount of buffered data available for reading.
    227     *
    228     * @param context the context to be used
    229     * @return The amount of buffered data available for reading.
    230     */
    231    int available(final Context context) {  // package protected for access from I/O streams
    232        return context.buffer != null ? context.pos - context.readPos : 0;
    233    }
    234
    235    /**
    236     * Get the default buffer size. Can be overridden.
    237     *
    238     * @return {@link #DEFAULT_BUFFER_SIZE}
    239     */
    240    protected int getDefaultBufferSize() {
    241        return DEFAULT_BUFFER_SIZE;
    242    }
    243
    244    /**
    245     * Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
    246     * @param context the context to be used
    247     */
    248    private byte[] resizeBuffer(final Context context) {
    249        if (context.buffer == null) {
    250            context.buffer = new byte[getDefaultBufferSize()];
    251            context.pos = 0;
    252            context.readPos = 0;
    253        } else {
    254            final byte[] b = new byte[context.buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
    255            System.arraycopy(context.buffer, 0, b, 0, context.buffer.length);
    256            context.buffer = b;
    257        }
    258        return context.buffer;
    259    }
    260
    261    /**
    262     * Ensure that the buffer has room for <code>size</code> bytes
    263     *
    264     * @param size minimum spare space required
    265     * @param context the context to be used
    266     * @return the buffer
    267     */
    268    protected byte[] ensureBufferSize(final int size, final Context context){
    269        if ((context.buffer == null) || (context.buffer.length < context.pos + size)){
    270            return resizeBuffer(context);
    271        }
    272        return context.buffer;
    273    }
    274
    275    /**
    276     * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
    277     * bytes. Returns how many bytes were actually extracted.
    278     * <p>
    279     * Package protected for access from I/O streams.
    280     *
    281     * @param b
    282     *            byte[] array to extract the buffered data into.
    283     * @param bPos
    284     *            position in byte[] array to start extraction at.
    285     * @param bAvail
    286     *            amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
    287     * @param context
    288     *            the context to be used
    289     * @return The number of bytes successfully extracted into the provided byte[] array.
    290     */
    291    int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
    292        if (context.buffer != null) {
    293            final int len = Math.min(available(context), bAvail);
    294            System.arraycopy(context.buffer, context.readPos, b, bPos, len);
    295            context.readPos += len;
    296            if (context.readPos >= context.pos) {
    297                context.buffer = null; // so hasData() will return false, and this method can return -1
    298            }
    299            return len;
    300        }
    301        return context.eof ? EOF : 0;
    302    }
    303
    304    /**
    305     * Checks if a byte value is whitespace or not.
    306     * Whitespace is taken to mean: space, tab, CR, LF
    307     * @param byteToCheck
    308     *            the byte to check
    309     * @return true if byte is whitespace, false otherwise
    310     */
    311    protected static boolean isWhiteSpace(final byte byteToCheck) {
    312        switch (byteToCheck) {
    313            case ' ' :
    314            case '\n' :
    315            case '\r' :
    316            case '\t' :
    317                return true;
    318            default :
    319                return false;
    320        }
    321    }
    322
    323    /**
    324     * Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
    325     * the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
    326     *
    327     * @param obj
    328     *            Object to encode
    329     * @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
    330     * @throws EncoderException
    331     *             if the parameter supplied is not of type byte[]
    332     */
    333    @Override
    334    public Object encode(final Object obj) throws EncoderException {
    335        if (!(obj instanceof byte[])) {
    336            throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
    337        }
    338        return encode((byte[]) obj);
    339    }
    340
    341    /**
    342     * Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
    343     * Uses UTF8 encoding.
    344     *
    345     * @param pArray
    346     *            a byte array containing binary data
    347     * @return A String containing only Base-N character data
    348     */
    349    public String encodeToString(final byte[] pArray) {
    350        return StringUtils.newStringUtf8(encode(pArray));
    351    }
    352
    353    /**
    354     * Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
    355     * Uses UTF8 encoding.
    356     *
    357     * @param pArray a byte array containing binary data
    358     * @return String containing only character data in the appropriate alphabet.
    359     * @since 1.5
    360     * This is a duplicate of {@link #encodeToString(byte[])}; it was merged during refactoring.
    361    */
    362    public String encodeAsString(final byte[] pArray){
    363        return StringUtils.newStringUtf8(encode(pArray));
    364    }
    365
    366    /**
    367     * Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
    368     * the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
    369     *
    370     * @param obj
    371     *            Object to decode
    372     * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
    373     *         supplied.
    374     * @throws DecoderException
    375     *             if the parameter supplied is not of type byte[]
    376     */
    377    @Override
    378    public Object decode(final Object obj) throws DecoderException {
    379        if (obj instanceof byte[]) {
    380            return decode((byte[]) obj);
    381        } else if (obj instanceof String) {
    382            return decode((String) obj);
    383        } else {
    384            throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
    385        }
    386    }
    387
    388    /**
    389     * Decodes a String containing characters in the Base-N alphabet.
    390     *
    391     * @param pArray
    392     *            A String containing Base-N character data
    393     * @return a byte array containing binary data
    394     */
    395    public byte[] decode(final String pArray) {
    396        return decode(StringUtils.getBytesUtf8(pArray));
    397    }
    398
    399    /**
    400     * Decodes a byte[] containing characters in the Base-N alphabet.
    401     *
    402     * @param pArray
    403     *            A byte array containing Base-N character data
    404     * @return a byte array containing binary data
    405     */
    406    @Override
    407    public byte[] decode(final byte[] pArray) {
    408        if (pArray == null || pArray.length == 0) {
    409            return pArray;
    410        }
    411        final Context context = new Context();
    412        decode(pArray, 0, pArray.length, context);
    413        decode(pArray, 0, EOF, context); // Notify decoder of EOF.
    414        final byte[] result = new byte[context.pos];
    415        readResults(result, 0, result.length, context);
    416        return result;
    417    }
    418
    419    /**
    420     * Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    421     *
    422     * @param pArray
    423     *            a byte array containing binary data
    424     * @return A byte array containing only the base N alphabetic character data
    425     */
    426    @Override
    427    public byte[] encode(final byte[] pArray) {
    428        if (pArray == null || pArray.length == 0) {
    429            return pArray;
    430        }
    431        return encode(pArray, 0, pArray.length);
    432    }
    433
    434    /**
    435     * Encodes a byte[] containing binary data, into a byte[] containing
    436     * characters in the alphabet.
    437     *
    438     * @param pArray
    439     *            a byte array containing binary data
    440     * @param offset
    441     *            initial offset of the subarray.
    442     * @param length
    443     *            length of the subarray.
    444     * @return A byte array containing only the base N alphabetic character data
    445     * @since 1.11
    446     */
    447    public byte[] encode(final byte[] pArray, final int offset, final int length) {
    448        if (pArray == null || pArray.length == 0) {
    449            return pArray;
    450        }
    451        final Context context = new Context();
    452        encode(pArray, offset, length, context);
    453        encode(pArray, offset, EOF, context); // Notify encoder of EOF.
    454        final byte[] buf = new byte[context.pos - context.readPos];
    455        readResults(buf, 0, buf.length, context);
    456        return buf;
    457    }
    458
    459    // package protected for access from I/O streams
    460    abstract void encode(byte[] pArray, int i, int length, Context context);
    461
    462    // package protected for access from I/O streams
    463    abstract void decode(byte[] pArray, int i, int length, Context context);
    464
    465    /**
    466     * Returns whether or not the <code>octet</code> is in the current alphabet.
    467     * Does not allow whitespace or pad.
    468     *
    469     * @param value The value to test
    470     *
    471     * @return <code>true</code> if the value is defined in the current alphabet, <code>false</code> otherwise.
    472     */
    473    protected abstract boolean isInAlphabet(byte value);
    474
    475    /**
    476     * Tests a given byte array to see if it contains only valid characters within the alphabet.
    477     * The method optionally treats whitespace and pad as valid.
    478     *
    479     * @param arrayOctet byte array to test
    480     * @param allowWSPad if <code>true</code>, then whitespace and PAD are also allowed
    481     *
    482     * @return <code>true</code> if all bytes are valid characters in the alphabet or if the byte array is empty;
    483     *         <code>false</code>, otherwise
    484     */
    485    public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
    486        for (final byte octet : arrayOctet) {
    487            if (!isInAlphabet(octet) &&
    488                    (!allowWSPad || (octet != pad) && !isWhiteSpace(octet))) {
    489                return false;
    490            }
    491        }
    492        return true;
    493    }
    494
    495    /**
    496     * Tests a given String to see if it contains only valid characters within the alphabet.
    497     * The method treats whitespace and PAD as valid.
    498     *
    499     * @param basen String to test
    500     * @return <code>true</code> if all characters in the String are valid characters in the alphabet or if
    501     *         the String is empty; <code>false</code>, otherwise
    502     * @see #isInAlphabet(byte[], boolean)
    503     */
    504    public boolean isInAlphabet(final String basen) {
    505        return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
    506    }
    507
    508    /**
    509     * Tests a given byte array to see if it contains any characters within the alphabet or PAD.
    510     *
    511     * Intended for use in checking line-ending arrays
    512     *
    513     * @param arrayOctet
    514     *            byte array to test
    515     * @return <code>true</code> if any byte is a valid character in the alphabet or PAD; <code>false</code> otherwise
    516     */
    517    protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
    518        if (arrayOctet == null) {
    519            return false;
    520        }
    521        for (final byte element : arrayOctet) {
    522            if (pad == element || isInAlphabet(element)) {
    523                return true;
    524            }
    525        }
    526        return false;
    527    }
    528
    529    /**
    530     * Calculates the amount of space needed to encode the supplied array.
    531     *
    532     * @param pArray byte[] array which will later be encoded
    533     *
    534     * @return amount of space needed to encoded the supplied array.
    535     * Returns a long since a max-len array will require &gt; Integer.MAX_VALUE
    536     */
    537    public long getEncodedLength(final byte[] pArray) {
    538        // Calculate non-chunked size - rounded up to allow for padding
    539        // cast to long is needed to avoid possibility of overflow
    540        long len = ((pArray.length + unencodedBlockSize-1)  / unencodedBlockSize) * (long) encodedBlockSize;
    541        if (lineLength > 0) { // We're using chunking
    542            // Round up to nearest multiple
    543            len += ((len + lineLength-1) / lineLength) * chunkSeparatorLength;
    544        }
    545        return len;
    546    }
    547}