Apache Commons Codec Source Code

Apache Commons Codec library provides implementations of common encoders and decoders such as Base64, Hex, Phonetic and URLs.

Apache Commons Codec Source Code files are provided in both binary packge (commons-codec-3.15-bin.zip) and source package (commons-codec-3.15-src.zip). You can download them at Apache Commons Codec Website.

Apache Commons Codec Source Code has no dependencies. You can compile it to generate your own version of Apache Commons Codec JAR file.

The source code of Apache Commons Codec 1.15 is provided below:

✍: FYIcenter

org/apache/commons/codec/binary/Base32.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.codec.binary;

import org.apache.commons.codec.CodecPolicy;

/**
 * Provides Base32 encoding and decoding as defined by <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>.
 *
 * <p>
 * The class can be parameterized in the following manner with various constructors:
 * </p>
 * <ul>
 * <li>Whether to use the "base32hex" variant instead of the default "base32"</li>
 * <li>Line length: Default 76. Line length that aren't multiples of 8 will still essentially end up being multiples of
 * 8 in the encoded data.
 * <li>Line separator: Default is CRLF ("\r\n")</li>
 * </ul>
 * <p>
 * This class operates directly on byte streams, and not character streams.
 * </p>
 * <p>
 * This class is thread-safe.
 * </p>
 *
 * @see <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>
 *
 * @since 1.5
 */
public class Base32 extends BaseNCodec {

    /**
     * BASE32 characters are 5 bits in length.
     * They are formed by taking a block of five octets to form a 40-bit string,
     * which is converted into eight BASE32 characters.
     */
    private static final int BITS_PER_ENCODED_BYTE = 5;
    private static final int BYTES_PER_ENCODED_BLOCK = 8;
    private static final int BYTES_PER_UNENCODED_BLOCK = 5;

    /**
     * This array is a lookup table that translates Unicode characters drawn from the "Base32 Alphabet" (as specified
     * in Table 3 of RFC 4648) into their 5-bit positive integer equivalents. Characters that are not in the Base32
     * alphabet but fall within the bounds of the array are translated to -1.
     */
    private static final byte[] DECODE_TABLE = {
         //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f
            -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, // 30-3f 2-7
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, // 40-4f A-O
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,                     // 50-5a P-Z
                                                        -1, -1, -1, -1, -1, // 5b-5f
            -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, // 60-6f a-o
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,                     // 70-7a p-z
    };

    /**
     * This array is a lookup table that translates 5-bit positive integer index values into their "Base32 Alphabet"
     * equivalents as specified in Table 3 of RFC 4648.
     */
    private static final byte[] ENCODE_TABLE = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            '2', '3', '4', '5', '6', '7',
    };

    /**
     * This array is a lookup table that translates Unicode characters drawn from the "Base32 Hex Alphabet" (as
     * specified in Table 4 of RFC 4648) into their 5-bit positive integer equivalents. Characters that are not in the
     * Base32 Hex alphabet but fall within the bounds of the array are translated to -1.
     */
    private static final byte[] HEX_DECODE_TABLE = {
         //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f
             0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, // 30-3f 0-9
            -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 40-4f A-O
            25, 26, 27, 28, 29, 30, 31,                                     // 50-56 P-V
                                        -1, -1, -1, -1, -1, -1, -1, -1, -1, // 57-5f 
            -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 60-6f a-o
            25, 26, 27, 28, 29, 30, 31                                      // 70-76 p-v
    };

    /**
     * This array is a lookup table that translates 5-bit positive integer index values into their
     * "Base32 Hex Alphabet" equivalents as specified in Table 4 of RFC 4648.
     */
    private static final byte[] HEX_ENCODE_TABLE = {
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
    };

    /** Mask used to extract 5 bits, used when encoding Base32 bytes */
    private static final int MASK_5BITS = 0x1f;
    /** Mask used to extract 4 bits, used when decoding final trailing character. */
    private static final long MASK_4BITS = 0x0fL;
    /** Mask used to extract 3 bits, used when decoding final trailing character. */
    private static final long MASK_3BITS = 0x07L;
    /** Mask used to extract 2 bits, used when decoding final trailing character. */
    private static final long MASK_2BITS = 0x03L;
    /** Mask used to extract 1 bits, used when decoding final trailing character. */
    private static final long MASK_1BITS = 0x01L;

    // The static final fields above are used for the original static byte[] methods on Base32.
    // The private member fields below are used with the new streaming approach, which requires
    // some state be preserved between calls of encode() and decode().

    /**
     * Place holder for the bytes we're dealing with for our based logic.
     * Bitwise operations store and extract the encoding or decoding from this variable.
     */

    /**
     * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
     * {@code decodeSize = {@link #BYTES_PER_ENCODED_BLOCK} - 1 + lineSeparator.length;}
     */
    private final int decodeSize;

    /**
     * Decode table to use.
     */
    private final byte[] decodeTable;

    /**
     * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
     * {@code encodeSize = {@link #BYTES_PER_ENCODED_BLOCK} + lineSeparator.length;}
     */
    private final int encodeSize;

    /**
     * Encode table to use.
     */
    private final byte[] encodeTable;

    /**
     * Line separator for encoding. Not used when decoding. Only used if lineLength &gt; 0.
     */
    private final byte[] lineSeparator;

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is 0 (no chunking).
     * </p>
     *
     */
    public Base32() {
        this(false);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is 0 (no chunking).
     * </p>
     * @param useHex if {@code true} then use Base32 Hex alphabet
     */
    public Base32(final boolean useHex) {
        this(0, null, useHex, PAD_DEFAULT);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is 0 (no chunking).
     * </p>
     * @param useHex if {@code true} then use Base32 Hex alphabet
     * @param padding byte used as padding byte.
     */
    public Base32(final boolean useHex, final byte padding) {
        this(0, null, useHex, padding);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is 0 (no chunking).
     * </p>
     * @param pad byte used as padding byte.
     */
    public Base32(final byte pad) {
        this(false, pad);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length is given in the constructor, the line separator is CRLF.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
     *            8). If lineLength &lt;= 0, then the output will not be divided into lines (chunks). Ignored when
     *            decoding.
     */
    public Base32(final int lineLength) {
        this(lineLength, CHUNK_SEPARATOR);
    }

    /**
     * Creates a Base32 codec used for decoding and encoding.
     * <p>
     * When encoding the line length and line separator are given in the constructor.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
     *            8). If lineLength &lt;= 0, then the output will not be divided into lines (chunks). Ignored when
     *            decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @throws IllegalArgumentException
     *             Thrown when the {@code lineSeparator} contains Base32 characters.
     */
    public Base32(final int lineLength, final byte[] lineSeparator) {
        this(lineLength, lineSeparator, false, PAD_DEFAULT);
    }

    /**
     * Creates a Base32 / Base32 Hex codec used for decoding and encoding.
     * <p>
     * When encoding the line length and line separator are given in the constructor.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
     *            8). If lineLength &lt;= 0, then the output will not be divided into lines (chunks). Ignored when
     *            decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @param useHex
     *            if {@code true}, then use Base32 Hex alphabet, otherwise use Base32 alphabet
     * @throws IllegalArgumentException
     *             Thrown when the {@code lineSeparator} contains Base32 characters. Or the
     *             lineLength &gt; 0 and lineSeparator is null.
     */
    public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex) {
        this(lineLength, lineSeparator, useHex, PAD_DEFAULT);
    }

    /**
     * Creates a Base32 / Base32 Hex codec used for decoding and encoding.
     * <p>
     * When encoding the line length and line separator are given in the constructor.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
     *            8). If lineLength &lt;= 0, then the output will not be divided into lines (chunks). Ignored when
     *            decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @param useHex
     *            if {@code true}, then use Base32 Hex alphabet, otherwise use Base32 alphabet
     * @param padding byte used as padding byte.
     * @throws IllegalArgumentException
     *             Thrown when the {@code lineSeparator} contains Base32 characters. Or the
     *             lineLength &gt; 0 and lineSeparator is null.
     */
    public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex, final byte padding) {
        this(lineLength, lineSeparator, useHex, padding, DECODING_POLICY_DEFAULT);
    }

    /**
     * Creates a Base32 / Base32 Hex codec used for decoding and encoding.
     * <p>
     * When encoding the line length and line separator are given in the constructor.
     * </p>
     * <p>
     * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
     * </p>
     *
     * @param lineLength
     *            Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
     *            8). If lineLength &lt;= 0, then the output will not be divided into lines (chunks). Ignored when
     *            decoding.
     * @param lineSeparator
     *            Each line of encoded data will end with this sequence of bytes.
     * @param useHex
     *            if {@code true}, then use Base32 Hex alphabet, otherwise use Base32 alphabet
     * @param padding byte used as padding byte.
     * @param decodingPolicy The decoding policy.
     * @throws IllegalArgumentException
     *             Thrown when the {@code lineSeparator} contains Base32 characters. Or the
     *             lineLength &gt; 0 and lineSeparator is null.
     * @since 1.15
     */
    public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex, final byte padding, CodecPolicy decodingPolicy) {
        super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, lineLength,
                lineSeparator == null ? 0 : lineSeparator.length, padding, decodingPolicy);
        if (useHex) {
            this.encodeTable = HEX_ENCODE_TABLE;
            this.decodeTable = HEX_DECODE_TABLE;
        } else {
            this.encodeTable = ENCODE_TABLE;
            this.decodeTable = DECODE_TABLE;
        }
        if (lineLength > 0) {
            if (lineSeparator == null) {
                throw new IllegalArgumentException("lineLength " + lineLength + " > 0, but lineSeparator is null");
            }
            // Must be done after initializing the tables
            if (containsAlphabetOrPad(lineSeparator)) {
                final String sep = StringUtils.newStringUtf8(lineSeparator);
                throw new IllegalArgumentException("lineSeparator must not contain Base32 characters: [" + sep + "]");
            }
            this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
            this.lineSeparator = new byte[lineSeparator.length];
            System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
        } else {
            this.encodeSize = BYTES_PER_ENCODED_BLOCK;
            this.lineSeparator = null;
        }
        this.decodeSize = this.encodeSize - 1;

        if (isInAlphabet(padding) || isWhiteSpace(padding)) {
            throw new IllegalArgumentException("pad must not be in alphabet or whitespace");
        }
    }

    /**
     * <p>
     * Decodes all of the provided data, starting at inPos, for inAvail bytes. Should be called at least twice: once
     * with the data to decode, and once with inAvail set to "-1" to alert decoder that EOF has been reached. The "-1"
     * call is not necessary when decoding, but it doesn't hurt, either.
     * </p>
     * <p>
     * Ignores all non-Base32 characters. This is how chunked (e.g. 76 character) data is handled, since CR and LF are
     * silently ignored, but has implications for other bytes, too. This method subscribes to the garbage-in,
     * garbage-out philosophy: it will not check the provided data for validity.
     * </p>
     * <p>
     * Output is written to {@link org.apache.commons.codec.binary.BaseNCodec.Context#buffer Context#buffer} as 8-bit
     * octets, using {@link org.apache.commons.codec.binary.BaseNCodec.Context#pos Context#pos} as the buffer position
     * </p>
     *
     * @param input byte[] array of ascii data to Base32 decode.
     * @param inPos Position to start reading data from.
     * @param inAvail Amount of bytes available from input for decoding.
     * @param context the context to be used
     */
    @Override
    void decode(final byte[] input, int inPos, final int inAvail, final Context context) {
        // package protected for access from I/O streams

        if (context.eof) {
            return;
        }
        if (inAvail < 0) {
            context.eof = true;
        }
        for (int i = 0; i < inAvail; i++) {
            final byte b = input[inPos++];
            if (b == pad) {
                // We're done.
                context.eof = true;
                break;
            }
            final byte[] buffer = ensureBufferSize(decodeSize, context);
            if (b >= 0 && b < this.decodeTable.length) {
                final int result = this.decodeTable[b];
                if (result >= 0) {
                    context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
                    // collect decoded bytes
                    context.lbitWorkArea = (context.lbitWorkArea << BITS_PER_ENCODED_BYTE) + result;
                    if (context.modulus == 0) { // we can output the 5 bytes
                        buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 32) & MASK_8BITS);
                        buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 24) & MASK_8BITS);
                        buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
                        buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
                        buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
                    }
                }
            }
        }

        // Two forms of EOF as far as Base32 decoder is concerned: actual
        // EOF (-1) and first time '=' character is encountered in stream.
        // This approach makes the '=' padding characters completely optional.
        if (context.eof && context.modulus > 0) { // if modulus == 0, nothing to do
            final byte[] buffer = ensureBufferSize(decodeSize, context);

            // We ignore partial bytes, i.e. only multiples of 8 count.
            // Any combination not part of a valid encoding is either partially decoded
            // or will raise an exception. Possible trailing characters are 2, 4, 5, 7.
            // It is not possible to encode with 1, 3, 6 trailing characters.
            // For backwards compatibility 3 & 6 chars are decoded anyway rather than discarded.
            // See the encode(byte[]) method EOF section.
            switch (context.modulus) {
//              case 0 : // impossible, as excluded above
                case 1 : // 5 bits - either ignore entirely, or raise an exception
                    validateTrailingCharacters();
                case 2 : // 10 bits, drop 2 and output one byte
                    validateCharacter(MASK_2BITS, context);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 2) & MASK_8BITS);
                    break;
                case 3 : // 15 bits, drop 7 and output 1 byte, or raise an exception
                    validateTrailingCharacters();
                    // Not possible from a valid encoding but decode anyway
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 7) & MASK_8BITS);
                    break;
                case 4 : // 20 bits = 2*8 + 4
                    validateCharacter(MASK_4BITS, context);
                    context.lbitWorkArea = context.lbitWorkArea >> 4; // drop 4 bits
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
                    break;
                case 5 : // 25 bits = 3*8 + 1
                    validateCharacter(MASK_1BITS, context);
                    context.lbitWorkArea = context.lbitWorkArea >> 1;
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
                    break;
                case 6 : // 30 bits = 3*8 + 6, or raise an exception
                    validateTrailingCharacters();
                    // Not possible from a valid encoding but decode anyway
                    context.lbitWorkArea = context.lbitWorkArea >> 6;
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
                    break;
                case 7 : // 35 bits = 4*8 +3
                    validateCharacter(MASK_3BITS, context);
                    context.lbitWorkArea = context.lbitWorkArea >> 3;
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 24) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
                    break;
                default:
                    // modulus can be 0-7, and we excluded 0,1 already
                    throw new IllegalStateException("Impossible modulus " + context.modulus);
            }
        }
    }

    /**
     * <p>
     * Encodes all of the provided data, starting at inPos, for inAvail bytes. Must be called at least twice: once with
     * the data to encode, and once with inAvail set to "-1" to alert encoder that EOF has been reached, so flush last
     * remaining bytes (if not multiple of 5).
     * </p>
     *
     * @param input
     *            byte[] array of binary data to Base32 encode.
     * @param inPos
     *            Position to start reading data from.
     * @param inAvail
     *            Amount of bytes available from input for encoding.
     * @param context the context to be used
     */
    @Override
    void encode(final byte[] input, int inPos, final int inAvail, final Context context) {
        // package protected for access from I/O streams

        if (context.eof) {
            return;
        }
        // inAvail < 0 is how we're informed of EOF in the underlying data we're
        // encoding.
        if (inAvail < 0) {
            context.eof = true;
            if (0 == context.modulus && lineLength == 0) {
                return; // no leftovers to process and not using chunking
            }
            final byte[] buffer = ensureBufferSize(encodeSize, context);
            final int savedPos = context.pos;
            switch (context.modulus) { // % 5
                case 0 :
                    break;
                case 1 : // Only 1 octet; take top 5 bits then remainder
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 3) & MASK_5BITS]; // 8-1*5 = 3
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea << 2) & MASK_5BITS]; // 5-3=2
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    break;
                case 2 : // 2 octets = 16 bits to use
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 11) & MASK_5BITS]; // 16-1*5 = 11
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >>  6) & MASK_5BITS]; // 16-2*5 = 6
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >>  1) & MASK_5BITS]; // 16-3*5 = 1
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea <<  4) & MASK_5BITS]; // 5-1 = 4
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    break;
                case 3 : // 3 octets = 24 bits to use
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 19) & MASK_5BITS]; // 24-1*5 = 19
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 14) & MASK_5BITS]; // 24-2*5 = 14
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >>  9) & MASK_5BITS]; // 24-3*5 = 9
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >>  4) & MASK_5BITS]; // 24-4*5 = 4
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea <<  1) & MASK_5BITS]; // 5-4 = 1
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    buffer[context.pos++] = pad;
                    break;
                case 4 : // 4 octets = 32 bits to use
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 27) & MASK_5BITS]; // 32-1*5 = 27
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 22) & MASK_5BITS]; // 32-2*5 = 22
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 17) & MASK_5BITS]; // 32-3*5 = 17
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 12) & MASK_5BITS]; // 32-4*5 = 12
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >>  7) & MASK_5BITS]; // 32-5*5 =  7
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >>  2) & MASK_5BITS]; // 32-6*5 =  2
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea <<  3) & MASK_5BITS]; // 5-2 = 3
                    buffer[context.pos++] = pad;
                    break;
                default:
                    throw new IllegalStateException("Impossible modulus " + context.modulus);
            }
            context.currentLinePos += context.pos - savedPos; // keep track of current line position
            // if currentPos == 0 we are at the start of a line, so don't add CRLF
            if (lineLength > 0 && context.currentLinePos > 0){ // add chunk separator if required
                System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
                context.pos += lineSeparator.length;
            }
        } else {
            for (int i = 0; i < inAvail; i++) {
                final byte[] buffer = ensureBufferSize(encodeSize, context);
                context.modulus = (context.modulus+1) % BYTES_PER_UNENCODED_BLOCK;
                int b = input[inPos++];
                if (b < 0) {
                    b += 256;
                }
                context.lbitWorkArea = (context.lbitWorkArea << 8) + b; // BITS_PER_BYTE
                if (0 == context.modulus) { // we have enough bytes to create our output
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 35) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 30) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 25) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 20) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 15) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 10) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 5) & MASK_5BITS];
                    buffer[context.pos++] = encodeTable[(int)context.lbitWorkArea & MASK_5BITS];
                    context.currentLinePos += BYTES_PER_ENCODED_BLOCK;
                    if (lineLength > 0 && lineLength <= context.currentLinePos) {
                        System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
                        context.pos += lineSeparator.length;
                        context.currentLinePos = 0;
                    }
                }
            }
        }
    }

    /**
     * Returns whether or not the {@code octet} is in the Base32 alphabet.
     *
     * @param octet
     *            The value to test
     * @return {@code true} if the value is defined in the the Base32 alphabet {@code false} otherwise.
     */
    @Override
    public boolean isInAlphabet(final byte octet) {
        return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
    }

    /**
     * Validates whether decoding the final trailing character is possible in the context
     * of the set of possible base 32 values.
     *
     * <p>The character is valid if the lower bits within the provided mask are zero. This
     * is used to test the final trailing base-32 digit is zero in the bits that will be discarded.
     *
     * @param emptyBitsMask The mask of the lower bits that should be empty
     * @param context the context to be used
     *
     * @throws IllegalArgumentException if the bits being checked contain any non-zero value
     */
    private void validateCharacter(final long emptyBitsMask, final Context context) {
        // Use the long bit work area
        if (isStrictDecoding() && (context.lbitWorkArea & emptyBitsMask) != 0) {
            throw new IllegalArgumentException(
                "Strict decoding: Last encoded character (before the paddings if any) is a valid base 32 alphabet but not a possible encoding. " +
                "Expected the discarded bits from the character to be zero.");
        }
    }

    /**
     * Validates whether decoding allows final trailing characters that cannot be
     * created during encoding.
     *
     * @throws IllegalArgumentException if strict decoding is enabled
     */
    private void validateTrailingCharacters() {
        if (isStrictDecoding()) {
            throw new IllegalArgumentException(
                "Strict decoding: Last encoded character(s) (before the paddings if any) are valid base 32 alphabet but not a possible encoding. " +
                "Decoding requires either 2, 4, 5, or 7 trailing 5-bit characters to create bytes.");
        }
    }
}

org/apache/commons/codec/binary/Base32.java

 

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