Base32.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *      https://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */

  18. package org.apache.commons.codec.binary;

  20. import java.util.Objects;

  22. import org.apache.commons.codec.CodecPolicy;

  24. /**
  25.  * Provides Base32 encoding and decoding as defined by <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>.
  26.  *
  27.  * <p>
  28.  * The class can be parameterized in the following manner with various constructors:
  29.  * </p>
  30.  * <ul>
  31.  * <li>Whether to use the "base32hex" variant instead of the default "base32"</li>
  32.  * <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.
  33.  * <li>Line separator: Default is CRLF ("\r\n")</li>
  34.  * </ul>
  35.  * <p>
  36.  * This class operates directly on byte streams, and not character streams.
  37.  * </p>
  38.  * <p>
  39.  * This class is thread-safe.
  40.  * </p>
  41.  * <p>
  42.  * You can configure instances with the {@link Builder}.
  43.  * </p>
  44.  * <pre>
  45.  * Base32 base32 = Base32.builder()
  46.  *   .setDecodingPolicy(DecodingPolicy.LENIENT) // default is lenient
  47.  *   .setEncodeTable(customEncodeTable)
  48.  *   .setLineLength(0)                          // default is none
  49.  *   .setLineSeparator('\r', '\n')              // default is CR LF
  50.  *   .setPadding('=')                           // default is =
  51.  *   .get()
  52.  * </pre>
  53.  *
  54.  * @see <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a>
  55.  * @since 1.5
  56.  */
  57. public class Base32 extends BaseNCodec {

  59.     /**
  60.      * Builds {@link Base32} instances.
  61.      *
  62.      * @since 1.17.0
  63.      */
  64.     public static class Builder extends AbstractBuilder<Base32, Builder> {

  66.         /**
  67.          * Constructs a new instance.
  68.          */
  69.         public Builder() {
  70.             super(ENCODE_TABLE);
  71.         }

  73.         @Override
  74.         public Base32 get() {
  75.             return new Base32(getLineLength(), getLineSeparator(), getEncodeTable(), getPadding(), getDecodingPolicy());
  76.         }

  78.         /**
  79.          * Sets the decode table to use Base32 hexadecimal if {@code true}, otherwise use the Base32 alphabet.
  80.          * <p>
  81.          * This overrides a value previously set with {@link #setEncodeTable(byte...)}.
  82.          * </p>
  83.          *
  84.          * @param useHex use Base32 hexadecimal if {@code true}, otherwise use the Base32 alphabet.
  85.          * @return this instance.
  86.          * @since 1.18.0
  87.          */
  88.         public Builder setHexDecodeTable(final boolean useHex) {
  89.             return setEncodeTable(decodeTable(useHex));
  90.         }

  92.         /**
  93.          * Sets the encode table to use Base32 hexadecimal if {@code true}, otherwise use the Base32 alphabet.
  94.          * <p>
  95.          * This overrides a value previously set with {@link #setEncodeTable(byte...)}.
  96.          * </p>
  97.          *
  98.          * @param useHex use Base32 hexadecimal if {@code true}, otherwise use the Base32 alphabet.
  99.          * @return this instance.
  100.          * @since 1.18.0
  101.          */
  102.         public Builder setHexEncodeTable(final boolean useHex) {
  103.             return setEncodeTable(encodeTable(useHex));
  104.         }
  105.     }

  107.     /**
  108.      * 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
  109.      * characters.
  110.      */
  111.     private static final int BITS_PER_ENCODED_BYTE = 5;

  113.     private static final int BYTES_PER_ENCODED_BLOCK = 8;
  114.     private static final int BYTES_PER_UNENCODED_BLOCK = 5;
  115.     /**
  116.      * 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
  117.      * positive integer equivalents. Characters that are not in the Base32 alphabet but fall within the bounds of the array are translated to -1.
  118.      */
  119.     // @formatter:off
  120.     private static final byte[] DECODE_TABLE = {
  121.          //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
  122.             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
  123.             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
  124.             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f
  125.             -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, // 30-3f 2-7
  126.             -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, // 40-4f A-O
  127.             15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,                     // 50-5a P-Z
  128.                                                         -1, -1, -1, -1, -1, // 5b-5f
  129.             -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, // 60-6f a-o
  130.             15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,                     // 70-7a p-z
  131.     };
  132.     // @formatter:on

  134.     /**
  135.      * 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
  136.      * 4648.
  137.      */
  138.     // @formatter:off
  139.     private static final byte[] ENCODE_TABLE = {
  140.             'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
  141.             'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
  142.             '2', '3', '4', '5', '6', '7',
  143.     };
  144.     // @formatter:on

  146.     /**
  147.      * 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
  148.      * 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.
  149.      */
  150.     // @formatter:off
  151.     private static final byte[] HEX_DECODE_TABLE = {
  152.          //  0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
  153.             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
  154.             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
  155.             -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 20-2f
  156.              0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, // 30-3f 0-9
  157.             -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 40-4f A-O
  158.             25, 26, 27, 28, 29, 30, 31,                                     // 50-56 P-V
  159.                                         -1, -1, -1, -1, -1, -1, -1, -1, -1, // 57-5f
  160.             -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 60-6f a-o
  161.             25, 26, 27, 28, 29, 30, 31                                      // 70-76 p-v
  162.     };
  163.     // @formatter:on

  165.     /**
  166.      * 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
  167.      * RFC 4648.
  168.      */
  169.     // @formatter:off
  170.     private static final byte[] HEX_ENCODE_TABLE = {
  171.             '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
  172.             'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
  173.             'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
  174.     };
  175.     // @formatter:on

  177.     /** Mask used to extract 5 bits, used when encoding Base32 bytes */
  178.     private static final int MASK_5BITS = 0x1f;

  180.     /** Mask used to extract 4 bits, used when decoding final trailing character. */
  181.     private static final long MASK_4BITS = 0x0fL;

  183.     /** Mask used to extract 3 bits, used when decoding final trailing character. */
  184.     private static final long MASK_3BITS = 0x07L;

  186.     /** Mask used to extract 2 bits, used when decoding final trailing character. */
  187.     private static final long MASK_2BITS = 0x03L;

  189.     /** Mask used to extract 1 bits, used when decoding final trailing character. */
  190.     private static final long MASK_1BITS = 0x01L;

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

  196.     /**
  197.      * Creates a new Builder.
  198.      *
  199.      * @return a new Builder.
  200.      * @since 1.17.0
  201.      */
  202.     public static Builder builder() {
  203.         return new Builder();
  204.     }

  206.     private static byte[] decodeTable(final boolean useHex) {
  207.         return useHex ? HEX_DECODE_TABLE : DECODE_TABLE;
  208.     }

  210.     private static byte[] encodeTable(final boolean useHex) {
  211.         return useHex ? HEX_ENCODE_TABLE : ENCODE_TABLE;
  212.     }

  214.     /**
  215.      * Decode table to use.
  216.      */
  217.     private final byte[] decodeTable;

  219.     /**
  220.      * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing. {@code encodeSize = {@link
  221.      * #BYTES_PER_ENCODED_BLOCK} + lineSeparator.length;}
  222.      */
  223.     private final int encodeSize;

  225.     /**
  226.      * Encode table to use.
  227.      */
  228.     private final byte[] encodeTable;

  230.     /**
  231.      * Line separator for encoding. Not used when decoding. Only used if lineLength &gt; 0.
  232.      */
  233.     private final byte[] lineSeparator;

  235.     /**
  236.      * Constructs a Base32 codec used for decoding and encoding.
  237.      * <p>
  238.      * When encoding the line length is 0 (no chunking).
  239.      * </p>
  240.      */
  241.     public Base32() {
  242.         this(false);
  243.     }

  245.     /**
  246.      * Constructs a Base32 codec used for decoding and encoding.
  247.      * <p>
  248.      * When encoding the line length is 0 (no chunking).
  249.      * </p>
  250.      *
  251.      * @param useHex if {@code true} then use Base32 Hex alphabet
  252.      */
  253.     public Base32(final boolean useHex) {
  254.         this(0, null, useHex, PAD_DEFAULT);
  255.     }

  257.     /**
  258.      * Constructs a Base32 codec used for decoding and encoding.
  259.      * <p>
  260.      * When encoding the line length is 0 (no chunking).
  261.      * </p>
  262.      *
  263.      * @param useHex  if {@code true} then use Base32 Hex alphabet
  264.      * @param padding byte used as padding byte.
  265.      */
  266.     public Base32(final boolean useHex, final byte padding) {
  267.         this(0, null, useHex, padding);
  268.     }

  270.     /**
  271.      * Constructs a Base32 codec used for decoding and encoding.
  272.      * <p>
  273.      * When encoding the line length is 0 (no chunking).
  274.      * </p>
  275.      *
  276.      * @param pad byte used as padding byte.
  277.      */
  278.     public Base32(final byte pad) {
  279.         this(false, pad);
  280.     }

  282.     /**
  283.      * Constructs a Base32 codec used for decoding and encoding.
  284.      * <p>
  285.      * When encoding the line length is given in the constructor, the line separator is CRLF.
  286.      * </p>
  287.      *
  288.      * @param lineLength Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 8). If lineLength &lt;= 0, then
  289.      *                   the output will not be divided into lines (chunks). Ignored when decoding.
  290.      */
  291.     public Base32(final int lineLength) {
  292.         this(lineLength, CHUNK_SEPARATOR);
  293.     }

  295.     /**
  296.      * Constructs a Base32 codec used for decoding and encoding.
  297.      * <p>
  298.      * When encoding the line length and line separator are given in the constructor.
  299.      * </p>
  300.      * <p>
  301.      * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
  302.      * </p>
  303.      *
  304.      * @param lineLength    Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 8). If lineLength &lt;= 0,
  305.      *                      then the output will not be divided into lines (chunks). Ignored when decoding.
  306.      * @param lineSeparator Each line of encoded data will end with this sequence of bytes.
  307.      * @throws IllegalArgumentException Thrown when the {@code lineSeparator} contains Base32 characters.
  308.      */
  309.     public Base32(final int lineLength, final byte[] lineSeparator) {
  310.         this(lineLength, lineSeparator, false, PAD_DEFAULT);
  311.     }

  313.     /**
  314.      * Constructs a Base32 / Base32 Hex codec used for decoding and encoding.
  315.      * <p>
  316.      * When encoding the line length and line separator are given in the constructor.
  317.      * </p>
  318.      * <p>
  319.      * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
  320.      * </p>
  321.      *
  322.      * @param lineLength    Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 8). If lineLength &lt;= 0,
  323.      *                      then the output will not be divided into lines (chunks). Ignored when decoding.
  324.      * @param lineSeparator Each line of encoded data will end with this sequence of bytes.
  325.      * @param useHex        if {@code true}, then use Base32 Hex alphabet, otherwise use Base32 alphabet
  326.      * @throws IllegalArgumentException Thrown when the {@code lineSeparator} contains Base32 characters. Or the lineLength &gt; 0 and lineSeparator is null.
  327.      */
  328.     public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex) {
  329.         this(lineLength, lineSeparator, useHex, PAD_DEFAULT);
  330.     }

  332.     /**
  333.      * Constructs a Base32 / Base32 Hex codec used for decoding and encoding.
  334.      * <p>
  335.      * When encoding the line length and line separator are given in the constructor.
  336.      * </p>
  337.      * <p>
  338.      * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
  339.      * </p>
  340.      *
  341.      * @param lineLength    Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 8). If lineLength &lt;= 0,
  342.      *                      then the output will not be divided into lines (chunks). Ignored when decoding.
  343.      * @param lineSeparator Each line of encoded data will end with this sequence of bytes.
  344.      * @param useHex        if {@code true}, then use Base32 Hex alphabet, otherwise use Base32 alphabet
  345.      * @param padding       padding byte.
  346.      * @throws IllegalArgumentException Thrown when the {@code lineSeparator} contains Base32 characters. Or the lineLength &gt; 0 and lineSeparator is null.
  347.      */
  348.     public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex, final byte padding) {
  349.         this(lineLength, lineSeparator, useHex, padding, DECODING_POLICY_DEFAULT);
  350.     }

  352.     /**
  353.      * Constructs a Base32 / Base32 Hex codec used for decoding and encoding.
  354.      * <p>
  355.      * When encoding the line length and line separator are given in the constructor.
  356.      * </p>
  357.      * <p>
  358.      * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
  359.      * </p>
  360.      *
  361.      * @param lineLength     Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 8). If lineLength &lt;= 0,
  362.      *                       then the output will not be divided into lines (chunks). Ignored when decoding.
  363.      * @param lineSeparator  Each line of encoded data will end with this sequence of bytes.
  364.      * @param useHex         use Base32 hexadecimal if {@code true}, otherwise use the Base32 alphabet.
  365.      * @param padding        padding byte.
  366.      * @param decodingPolicy The decoding policy.
  367.      * @throws IllegalArgumentException Thrown when the {@code lineSeparator} contains Base32 characters. Or the lineLength &gt; 0 and lineSeparator is null.
  368.      * @since 1.15
  369.      */
  370.     public Base32(final int lineLength, final byte[] lineSeparator, final boolean useHex, final byte padding, final CodecPolicy decodingPolicy) {
  371.         this(lineLength, lineSeparator, encodeTable(useHex), padding, decodingPolicy);
  372.     }

  374.     /**
  375.      * Constructs a Base32 / Base32 Hex codec used for decoding and encoding.
  376.      * <p>
  377.      * When encoding the line length and line separator are given in the constructor.
  378.      * </p>
  379.      * <p>
  380.      * Line lengths that aren't multiples of 8 will still essentially end up being multiples of 8 in the encoded data.
  381.      * </p>
  382.      *
  383.      * @param lineLength     Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 8). If lineLength &lt;= 0,
  384.      *                       then the output will not be divided into lines (chunks). Ignored when decoding.
  385.      * @param lineSeparator  Each line of encoded data will end with this sequence of bytes.
  386.      * @param encodeTable    A Base32 alphabet.
  387.      * @param padding        padding byte.
  388.      * @param decodingPolicy The decoding policy.
  389.      * @throws IllegalArgumentException Thrown when the {@code lineSeparator} contains Base32 characters. Or the lineLength &gt; 0 and lineSeparator is null.
  390.      */
  391.     private Base32(final int lineLength, final byte[] lineSeparator, final byte[] encodeTable, final byte padding, final CodecPolicy decodingPolicy) {
  392.         super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, lineLength, toLength(lineSeparator), padding, decodingPolicy);
  393.         Objects.requireNonNull(encodeTable, "encodeTable");
  394.         this.encodeTable = encodeTable;
  395.         this.decodeTable = encodeTable == HEX_ENCODE_TABLE ? HEX_DECODE_TABLE : DECODE_TABLE;
  396.         if (lineLength > 0) {
  397.             if (lineSeparator == null) {
  398.                 throw new IllegalArgumentException("lineLength " + lineLength + " > 0, but lineSeparator is null");
  399.             }
  400.             final byte[] lineSeparatorCopy = lineSeparator.clone();
  401.             // Must be done after initializing the tables
  402.             if (containsAlphabetOrPad(lineSeparatorCopy)) {
  403.                 final String sep = StringUtils.newStringUtf8(lineSeparatorCopy);
  404.                 throw new IllegalArgumentException("lineSeparator must not contain Base32 characters: [" + sep + "]");
  405.             }
  406.             this.encodeSize = BYTES_PER_ENCODED_BLOCK + lineSeparatorCopy.length;
  407.             this.lineSeparator = lineSeparatorCopy;
  408.         } else {
  409.             this.encodeSize = BYTES_PER_ENCODED_BLOCK;
  410.             this.lineSeparator = null;
  411.         }
  412.         if (isInAlphabet(padding) || Character.isWhitespace(padding)) {
  413.             throw new IllegalArgumentException("pad must not be in alphabet or whitespace");
  414.         }
  415.     }

  417.     /**
  418.      * <p>
  419.      * 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
  420.      * 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.
  421.      * </p>
  422.      * <p>
  423.      * Ignores all non-Base32 characters. This is how chunked (for example 76 character) data is handled, since CR and LF are silently ignored, but has implications
  424.      * for other bytes, too. This method subscribes to the garbage-in, garbage-out philosophy: it will not check the provided data for validity.
  425.      * </p>
  426.      * <p>
  427.      * Output is written to {@link org.apache.commons.codec.binary.BaseNCodec.Context#buffer Context#buffer} as 8-bit octets, using
  428.      * {@link org.apache.commons.codec.binary.BaseNCodec.Context#pos Context#pos} as the buffer position
  429.      * </p>
  430.      *
  431.      * @param input   byte[] array of ASCII data to Base32 decode.
  432.      * @param inPos   Position to start reading data from.
  433.      * @param inAvail Amount of bytes available from input for decoding.
  434.      * @param context the context to be used
  435.      */
  436.     @Override
  437.     void decode(final byte[] input, int inPos, final int inAvail, final Context context) {
  438.         // package protected for access from I/O streams
  439.         if (context.eof) {
  440.             return;
  441.         }
  442.         if (inAvail < 0) {
  443.             context.eof = true;
  444.         }
  445.         final int decodeSize = this.encodeSize - 1;
  446.         for (int i = 0; i < inAvail; i++) {
  447.             final byte b = input[inPos++];
  448.             if (b == pad) {
  449.                 // We're done.
  450.                 context.eof = true;
  451.                 break;
  452.             }
  453.             final byte[] buffer = ensureBufferSize(decodeSize, context);
  454.             if (b >= 0 && b < this.decodeTable.length) {
  455.                 final int result = this.decodeTable[b];
  456.                 if (result >= 0) {
  457.                     context.modulus = (context.modulus + 1) % BYTES_PER_ENCODED_BLOCK;
  458.                     // collect decoded bytes
  459.                     context.lbitWorkArea = (context.lbitWorkArea << BITS_PER_ENCODED_BYTE) + result;
  460.                     if (context.modulus == 0) { // we can output the 5 bytes
  461.                         buffer[context.pos++] = (byte) (context.lbitWorkArea >> 32 & MASK_8BITS);
  462.                         buffer[context.pos++] = (byte) (context.lbitWorkArea >> 24 & MASK_8BITS);
  463.                         buffer[context.pos++] = (byte) (context.lbitWorkArea >> 16 & MASK_8BITS);
  464.                         buffer[context.pos++] = (byte) (context.lbitWorkArea >> 8 & MASK_8BITS);
  465.                         buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
  466.                     }
  467.                 }
  468.             }
  469.         }
  470.         // Two forms of EOF as far as Base32 decoder is concerned: actual
  471.         // EOF (-1) and first time '=' character is encountered in stream.
  472.         // This approach makes the '=' padding characters completely optional.
  473.         if (context.eof && context.modulus > 0) { // if modulus == 0, nothing to do
  474.             final byte[] buffer = ensureBufferSize(decodeSize, context);
  475.             // We ignore partial bytes, i.e. only multiples of 8 count.
  476.             // Any combination not part of a valid encoding is either partially decoded
  477.             // or will raise an exception. Possible trailing characters are 2, 4, 5, 7.
  478.             // It is not possible to encode with 1, 3, 6 trailing characters.
  479.             // For backwards compatibility 3 & 6 chars are decoded anyway rather than discarded.
  480.             // See the encode(byte[]) method EOF section.
  481.             switch (context.modulus) {
  482. //              case 0 : // impossible, as excluded above
  483.             case 1: // 5 bits - either ignore entirely, or raise an exception
  484.                 validateTrailingCharacters();
  485.             case 2: // 10 bits, drop 2 and output one byte
  486.                 validateCharacter(MASK_2BITS, context);
  487.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 2 & MASK_8BITS);
  488.                 break;
  489.             case 3: // 15 bits, drop 7 and output 1 byte, or raise an exception
  490.                 validateTrailingCharacters();
  491.                 // Not possible from a valid encoding but decode anyway
  492.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 7 & MASK_8BITS);
  493.                 break;
  494.             case 4: // 20 bits = 2*8 + 4
  495.                 validateCharacter(MASK_4BITS, context);
  496.                 context.lbitWorkArea = context.lbitWorkArea >> 4; // drop 4 bits
  497.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 8 & MASK_8BITS);
  498.                 buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
  499.                 break;
  500.             case 5: // 25 bits = 3*8 + 1
  501.                 validateCharacter(MASK_1BITS, context);
  502.                 context.lbitWorkArea = context.lbitWorkArea >> 1;
  503.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 16 & MASK_8BITS);
  504.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 8 & MASK_8BITS);
  505.                 buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
  506.                 break;
  507.             case 6: // 30 bits = 3*8 + 6, or raise an exception
  508.                 validateTrailingCharacters();
  509.                 // Not possible from a valid encoding but decode anyway
  510.                 context.lbitWorkArea = context.lbitWorkArea >> 6;
  511.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 16 & MASK_8BITS);
  512.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 8 & MASK_8BITS);
  513.                 buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
  514.                 break;
  515.             case 7: // 35 bits = 4*8 +3
  516.                 validateCharacter(MASK_3BITS, context);
  517.                 context.lbitWorkArea = context.lbitWorkArea >> 3;
  518.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 24 & MASK_8BITS);
  519.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 16 & MASK_8BITS);
  520.                 buffer[context.pos++] = (byte) (context.lbitWorkArea >> 8 & MASK_8BITS);
  521.                 buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
  522.                 break;
  523.             default:
  524.                 // modulus can be 0-7, and we excluded 0,1 already
  525.                 throw new IllegalStateException("Impossible modulus " + context.modulus);
  526.             }
  527.         }
  528.     }

  530.     /**
  531.      * <p>
  532.      * 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
  533.      * inAvail set to "-1" to alert encoder that EOF has been reached, so flush last remaining bytes (if not multiple of 5).
  534.      * </p>
  535.      *
  536.      * @param input   byte[] array of binary data to Base32 encode.
  537.      * @param inPos   Position to start reading data from.
  538.      * @param inAvail Amount of bytes available from input for encoding.
  539.      * @param context the context to be used
  540.      */
  541.     @Override
  542.     void encode(final byte[] input, int inPos, final int inAvail, final Context context) {
  543.         // package protected for access from I/O streams
  544.         if (context.eof) {
  545.             return;
  546.         }
  547.         // inAvail < 0 is how we're informed of EOF in the underlying data we're
  548.         // encoding.
  549.         if (inAvail < 0) {
  550.             context.eof = true;
  551.             if (0 == context.modulus && lineLength == 0) {
  552.                 return; // no leftovers to process and not using chunking
  553.             }
  554.             final byte[] buffer = ensureBufferSize(encodeSize, context);
  555.             final int savedPos = context.pos;
  556.             switch (context.modulus) { // % 5
  557.             case 0:
  558.                 break;
  559.             case 1: // Only 1 octet; take top 5 bits then remainder
  560.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 3) & MASK_5BITS]; // 8-1*5 = 3
  561.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea << 2) & MASK_5BITS]; // 5-3=2
  562.                 buffer[context.pos++] = pad;
  563.                 buffer[context.pos++] = pad;
  564.                 buffer[context.pos++] = pad;
  565.                 buffer[context.pos++] = pad;
  566.                 buffer[context.pos++] = pad;
  567.                 buffer[context.pos++] = pad;
  568.                 break;
  569.             case 2: // 2 octets = 16 bits to use
  570.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 11) & MASK_5BITS]; // 16-1*5 = 11
  571.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 6) & MASK_5BITS]; // 16-2*5 = 6
  572.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 1) & MASK_5BITS]; // 16-3*5 = 1
  573.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea << 4) & MASK_5BITS]; // 5-1 = 4
  574.                 buffer[context.pos++] = pad;
  575.                 buffer[context.pos++] = pad;
  576.                 buffer[context.pos++] = pad;
  577.                 buffer[context.pos++] = pad;
  578.                 break;
  579.             case 3: // 3 octets = 24 bits to use
  580.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 19) & MASK_5BITS]; // 24-1*5 = 19
  581.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 14) & MASK_5BITS]; // 24-2*5 = 14
  582.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 9) & MASK_5BITS]; // 24-3*5 = 9
  583.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 4) & MASK_5BITS]; // 24-4*5 = 4
  584.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea << 1) & MASK_5BITS]; // 5-4 = 1
  585.                 buffer[context.pos++] = pad;
  586.                 buffer[context.pos++] = pad;
  587.                 buffer[context.pos++] = pad;
  588.                 break;
  589.             case 4: // 4 octets = 32 bits to use
  590.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 27) & MASK_5BITS]; // 32-1*5 = 27
  591.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 22) & MASK_5BITS]; // 32-2*5 = 22
  592.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 17) & MASK_5BITS]; // 32-3*5 = 17
  593.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 12) & MASK_5BITS]; // 32-4*5 = 12
  594.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 7) & MASK_5BITS]; // 32-5*5 = 7
  595.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 2) & MASK_5BITS]; // 32-6*5 = 2
  596.                 buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea << 3) & MASK_5BITS]; // 5-2 = 3
  597.                 buffer[context.pos++] = pad;
  598.                 break;
  599.             default:
  600.                 throw new IllegalStateException("Impossible modulus " + context.modulus);
  601.             }
  602.             context.currentLinePos += context.pos - savedPos; // keep track of current line position
  603.             // if currentPos == 0 we are at the start of a line, so don't add CRLF
  604.             if (lineLength > 0 && context.currentLinePos > 0) { // add chunk separator if required
  605.                 System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
  606.                 context.pos += lineSeparator.length;
  607.             }
  608.         } else {
  609.             for (int i = 0; i < inAvail; i++) {
  610.                 final byte[] buffer = ensureBufferSize(encodeSize, context);
  611.                 context.modulus = (context.modulus + 1) % BYTES_PER_UNENCODED_BLOCK;
  612.                 int b = input[inPos++];
  613.                 if (b < 0) {
  614.                     b += 256;
  615.                 }
  616.                 context.lbitWorkArea = (context.lbitWorkArea << 8) + b; // BITS_PER_BYTE
  617.                 if (0 == context.modulus) { // we have enough bytes to create our output
  618.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 35) & MASK_5BITS];
  619.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 30) & MASK_5BITS];
  620.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 25) & MASK_5BITS];
  621.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 20) & MASK_5BITS];
  622.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 15) & MASK_5BITS];
  623.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 10) & MASK_5BITS];
  624.                     buffer[context.pos++] = encodeTable[(int) (context.lbitWorkArea >> 5) & MASK_5BITS];
  625.                     buffer[context.pos++] = encodeTable[(int) context.lbitWorkArea & MASK_5BITS];
  626.                     context.currentLinePos += BYTES_PER_ENCODED_BLOCK;
  627.                     if (lineLength > 0 && lineLength <= context.currentLinePos) {
  628.                         System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
  629.                         context.pos += lineSeparator.length;
  630.                         context.currentLinePos = 0;
  631.                     }
  632.                 }
  633.             }
  634.         }
  635.     }

  637.     /**
  638.      * Gets the line separator (for testing only).
  639.      *
  640.      * @return the line separator.
  641.      */
  642.     byte[] getLineSeparator() {
  643.         return lineSeparator;
  644.     }

  646.     /**
  647.      * Returns whether or not the {@code octet} is in the Base32 alphabet.
  648.      *
  649.      * @param octet The value to test
  650.      * @return {@code true} if the value is defined in the Base32 alphabet {@code false} otherwise.
  651.      */
  652.     @Override
  653.     public boolean isInAlphabet(final byte octet) {
  654.         return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
  655.     }

  657.     /**
  658.      * Validates whether decoding the final trailing character is possible in the context of the set of possible base 32 values.
  659.      * <p>
  660.      * 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
  661.      * that will be discarded.
  662.      * </p>
  663.      *
  664.      * @param emptyBitsMask The mask of the lower bits that should be empty
  665.      * @param context       the context to be used
  666.      * @throws IllegalArgumentException if the bits being checked contain any non-zero value
  667.      */
  668.     private void validateCharacter(final long emptyBitsMask, final Context context) {
  669.         // Use the long bit work area
  670.         if (isStrictDecoding() && (context.lbitWorkArea & emptyBitsMask) != 0) {
  671.             throw new IllegalArgumentException("Strict decoding: Last encoded character (before the paddings if any) is a valid " +
  672.                     "base 32 alphabet but not a possible encoding. Expected the discarded bits from the character to be zero.");
  673.         }
  674.     }

  676.     /**
  677.      * Validates whether decoding allows final trailing characters that cannot be created during encoding.
  678.      *
  679.      * @throws IllegalArgumentException if strict decoding is enabled
  680.      */
  681.     private void validateTrailingCharacters() {
  682.         if (isStrictDecoding()) {
  683.             throw new IllegalArgumentException("Strict decoding: Last encoded character(s) (before the paddings if any) are valid " +
  684.                     "base 32 alphabet but not a possible encoding. Decoding requires either 2, 4, 5, or 7 trailing 5-bit characters to create bytes.");
  685.         }
  686.     }
  687. }
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