/*
 * 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;

Provides Base32 encoding and decoding as defined by RFC 4648.

The class can be parameterized in the following manner with various constructors:


Whether to use the "base32hex" variant instead of the default "base32"
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.
Line separator: Default is CRLF ("\r\n")


This class operates directly on byte streams, and not character streams.


This class is thread-safe.

See Also:
RFC 4648
Since:
1.5
Version:
$Id$/**
 * 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
 * @version $Id$
 */
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.
/**
     * 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;

    
Chunk separator per RFC 2045 section 2.1.
See Also:
RFC 2045 section 2.1/**
     * Chunk separator per RFC 2045 section 2.1.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
     */
    private static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};

    
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.
/**
     * 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.
/**
     * 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.
/**
     * 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 2-7
            -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 Z-_
            -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 60-6f `-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.
/**
     * 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 /** Mask used to extract 5 bits, used when encoding Base32 bytes */
    private static final int MASK_5BITS = 0x1f;

    // 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.
decodeSize = BYTES_PER_ENCODED_BLOCK - 1 + lineSeparator.length;
/**
     * 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;</code>
     */
    private final int decodeSize;

    
Decode table to use.
/**
     * 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.
encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparator.length;
/**
     * 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;</code>
     */
    private final int encodeSize;

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

    
Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
/**
     * 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.

When encoding the line length is 0 (no chunking).

/**
     * 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.

When encoding the line length is 0 (no chunking).

Params:
pad – byte used as padding byte./**
     * 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.

When encoding the line length is 0 (no chunking).

Params:
useHex – if true then use Base32 Hex alphabet/**
     * 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.

When encoding the line length is 0 (no chunking).

Params:
useHex – if true then use Base32 Hex alphabet
pad – byte used as padding byte./**
     * 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 pad byte used as padding byte.
     */
    public Base32(final boolean useHex, final byte pad) {
        this(0, null, useHex, pad);
    }

    
Creates a Base32 codec used for decoding and encoding.

When encoding the line length is given in the constructor, the line separator is CRLF.

Params:
lineLength – 
           Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
           8). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when
           decoding./**
     * 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.

When encoding the line length and line separator are given in the constructor.


Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.

Params:
lineLength – 
           Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
           8). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when
           decoding.
lineSeparator – 
           Each line of encoded data will end with this sequence of bytes.
Throws:
IllegalArgumentException – 
            The provided lineSeparator included some Base32 characters. That's not going to work!/**
     * 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
     *             The provided lineSeparator included some Base32 characters. That's not going to work!
     */
    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.

When encoding the line length and line separator are given in the constructor.


Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.

Params:
lineLength – 
           Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
           8). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when
           decoding.
lineSeparator – 
           Each line of encoded data will end with this sequence of bytes.
useHex –  if true, then use Base32 Hex alphabet, otherwise use Base32 alphabet
Throws:
IllegalArgumentException – 
            The provided lineSeparator included some Base32 characters. That's not going to work! Or the
            lineLength > 0 and lineSeparator is null./**
     * 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
     *             The provided lineSeparator included some Base32 characters. That's not going to work! 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.

When encoding the line length and line separator are given in the constructor.


Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.

Params:
lineLength – 
           Each line of encoded data will be at most of the given length (rounded down to nearest multiple of
           8). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when
           decoding.
lineSeparator – 
           Each line of encoded data will end with this sequence of bytes.
useHex –  if true, then use Base32 Hex alphabet, otherwise use Base32 alphabet
pad – byte used as padding byte.
Throws:
IllegalArgumentException – 
            The provided lineSeparator included some Base32 characters. That's not going to work! Or the
            lineLength > 0 and lineSeparator is null./**
     * 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 pad byte used as padding byte.
     * @throws IllegalArgumentException
     *             The provided lineSeparator included some Base32 characters. That's not going to work! Or the
     *             lineLength &gt; 0 and lineSeparator is null.
     */
    public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex, final byte pad) {
        super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, lineLength,
                lineSeparator == null ? 0 : lineSeparator.length, pad);
        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(pad) || isWhiteSpace(pad)) {
            throw new IllegalArgumentException("pad must not be in alphabet or whitespace");
        }
    }

    

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.


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.

Params:
in – 
           byte[] array of ascii data to Base32 decode.
inPos – 
           Position to start reading data from.
inAvail – 
           Amount of bytes available from input for encoding.
context – the context to be used Output is written to Context.buffer as 8-bit octets, using Context.pos as the buffer position/**
     * <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>
     *
     * @param in
     *            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 encoding.
     * @param context the context to be used
     *
     * Output is written to {@link Context#buffer} as 8-bit octets, using {@link Context#pos} as the buffer position
     */
    @Override
    void decode(final byte[] in, 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 = in[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 >= 2) { // if modulus < 2, nothing to do
            final byte[] buffer = ensureBufferSize(decodeSize, context);

            //  we ignore partial bytes, i.e. only multiples of 8 count
            switch (context.modulus) {
                case 2 : // 10 bits, drop 2 and output one byte
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 2) & MASK_8BITS);
                    break;
                case 3 : // 15 bits, drop 7 and output 1 byte
                    buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 7) & MASK_8BITS);
                    break;
                case 4 : // 20 bits = 2*8 + 4
                    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 : // 25bits = 3*8 + 1
                    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 : // 30bits = 3*8 + 6
                    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 = 4*8 +3
                    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);
            }
        }
    }

    

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).

Params:
in – 
           byte[] array of binary data to Base32 encode.
inPos – 
           Position to start reading data from.
inAvail – 
           Amount of bytes available from input for encoding.
context – the context to be used/**
     * <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 in
     *            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[] in, 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 = in[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 octet is in the Base32 alphabet. 
Params:
octet – 
           The value to test
Returns:
true if the value is defined in the the Base32 alphabet false otherwise./**
     * 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;
    }
}