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 io.multibase.binary;

/**
 * Provides Base32 encoding and decoding as defined by <a
 * href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>.
 *
 * <p>From https://commons.apache.org/proper/commons-codec/
 *
 * <p>The class can be parameterized in the following manner with various constructors:
 *
 * <ul>
 *   <li>Whether to use the "base32hex" variant instead of the default "base32"
 *   <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")
 * </ul>
 *
 * <p>This class operates directly on byte streams, and not character streams.
 *
 * <p>This class is thread-safe.
 *
 * @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.
   */
  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 <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.
   */
  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 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.
   */
  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;

  // 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;
   * </code>
   */
  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;</code>
   */
  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).
   */
  public Base32() {
    this(false);
  }

  /**
   * Creates a Base32 codec used for decoding and encoding.
   *
   * <p>When encoding the line length is 0 (no chunking).
   *
   * @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 0 (no chunking).
   *
   * @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).
   *
   * @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.
   *
   * <p>When encoding the line length is given in the constructor, the line separator is CRLF.
   *
   * @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>Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8
   * in the encoded data.
   *
   * @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.
   *
   * <p>When encoding the line length and line separator are given in the constructor.
   *
   * <p>Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8
   * in the encoded data.
   *
   * @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.
   *
   * <p>When encoding the line length and line separator are given in the constructor.
   *
   * <p>Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8
   * in the encoded data.
   *
   * @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.
   *
   * <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.
   *
   * @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
   *     <p>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).
   *
   * @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 {@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;
  }
}