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/*
* 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 RFC 4648
*
* @since 1.5
*/
public class Base32 extends BaseNCodec {
/**
* BASE32 characters are 5 bits in length.
* They are formed by taking a block of five octets to form a 40-bit string,
* which is converted into eight BASE32 characters.
*/
private static final int BITS_PER_ENCODED_BYTE = 5;
private static final int BYTES_PER_ENCODED_BLOCK = 8;
private static final int BYTES_PER_UNENCODED_BLOCK = 5;
/**
* Chunk separator per RFC 2045 section 2.1.
*
* @see RFC 2045 section 2.1
*/
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 7 bits, used when decoding final trailing character. */
private static final long MASK_7BITS = 0x7fL;
/** Mask used to extract 6 bits, used when decoding final trailing character. */
private static final long MASK_6BITS = 0x3fL;
/** Mask used to extract 5 bits, used when encoding Base32 bytes */
private static final int MASK_5BITS = 0x1f;
/** Mask used to extract 4 bits, used when decoding final trailing character. */
private static final long MASK_4BITS = 0x0fL;
/** Mask used to extract 3 bits, used when decoding final trailing character. */
private static final long MASK_3BITS = 0x07L;
/** Mask used to extract 2 bits, used when decoding final trailing character. */
private static final long MASK_2BITS = 0x03L;
/** Mask used to extract 1 bits, used when decoding final trailing character. */
private static final long MASK_1BITS = 0x01L;
// The static final fields above are used for the original static byte[] methods on Base32.
// The private member fields below are used with the new streaming approach, which requires
// some state be preserved between calls of encode() and decode().
/**
* Place holder for the bytes we're dealing with for our based logic.
* Bitwise operations store and extract the encoding or decoding from this variable.
*/
/**
* Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
* {@code decodeSize = {@link #BYTES_PER_ENCODED_BLOCK} - 1 + lineSeparator.length;}
*/
private final int decodeSize;
/**
* Decode table to use.
*/
private final byte[] decodeTable;
/**
* Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
* {@code encodeSize = {@link #BYTES_PER_ENCODED_BLOCK} + lineSeparator.length;}
*/
private final int encodeSize;
/**
* Encode table to use.
*/
private final byte[] encodeTable;
/**
* Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
*/
private final byte[] lineSeparator;
/**
* Creates a Base32 codec used for decoding and encoding.
*
* When encoding the line length is 0 (no chunking).
*
*
*/
public Base32() {
this(false);
}
/**
* Creates a Base32 codec used for decoding and encoding.
*
* 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.
*
* 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.
*
* 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.
*
* 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 <= 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.
*
*
* @param 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.
* @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.
*
*
* @param 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.
* @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 > 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.
*
*
* @param 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.
* @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 > 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.
*
*
* Output is written to {@link org.apache.commons.codec.binary.BaseNCodec.Context#buffer Context#buffer} as 8-bit
* octets, using {@link org.apache.commons.codec.binary.BaseNCodec.Context#pos Context#pos} as the buffer position
*
*
* @param input byte[] array of ascii data to Base32 decode.
* @param inPos Position to start reading data from.
* @param inAvail Amount of bytes available from input for decoding.
* @param context the context to be used
*
*/
@Override
void decode(final byte[] input, int inPos, final int inAvail, final Context context) {
// package protected for access from I/O streams
if (context.eof) {
return;
}
if (inAvail < 0) {
context.eof = true;
}
for (int i = 0; i < inAvail; i++) {
final byte b = input[inPos++];
if (b == pad) {
// We're done.
context.eof = true;
break;
}
final byte[] buffer = ensureBufferSize(decodeSize, context);
if (b >= 0 && b < this.decodeTable.length) {
final int result = this.decodeTable[b];
if (result >= 0) {
context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
// collect decoded bytes
context.lbitWorkArea = (context.lbitWorkArea << BITS_PER_ENCODED_BYTE) + result;
if (context.modulus == 0) { // we can output the 5 bytes
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 32) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 24) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) (context.lbitWorkArea & MASK_8BITS);
}
}
}
}
// Two forms of EOF as far as Base32 decoder is concerned: actual
// EOF (-1) and first time '=' character is encountered in stream.
// This approach makes the '=' padding characters completely optional.
if (context.eof && context.modulus >= 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
validateCharacter(MASK_2BITS, context);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 2) & MASK_8BITS);
break;
case 3 : // 15 bits, drop 7 and output 1 byte
validateCharacter(MASK_7BITS, context);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 7) & MASK_8BITS);
break;
case 4 : // 20 bits = 2*8 + 4
validateCharacter(MASK_4BITS, context);
context.lbitWorkArea = context.lbitWorkArea >> 4; // drop 4 bits
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
case 5 : // 25bits = 3*8 + 1
validateCharacter(MASK_1BITS, context);
context.lbitWorkArea = context.lbitWorkArea >> 1;
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
case 6 : // 30bits = 3*8 + 6
validateCharacter(MASK_6BITS, context);
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
validateCharacter(MASK_3BITS, context);
context.lbitWorkArea = context.lbitWorkArea >> 3;
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 24) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 16) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea >> 8) & MASK_8BITS);
buffer[context.pos++] = (byte) ((context.lbitWorkArea) & MASK_8BITS);
break;
default:
// modulus can be 0-7, and we excluded 0,1 already
throw new IllegalStateException("Impossible modulus "+context.modulus);
}
}
}
/**
*
* 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 input
* byte[] array of binary data to Base32 encode.
* @param inPos
* Position to start reading data from.
* @param inAvail
* Amount of bytes available from input for encoding.
* @param context the context to be used
*/
@Override
void encode(final byte[] input, int inPos, final int inAvail, final Context context) {
// package protected for access from I/O streams
if (context.eof) {
return;
}
// inAvail < 0 is how we're informed of EOF in the underlying data we're
// encoding.
if (inAvail < 0) {
context.eof = true;
if (0 == context.modulus && lineLength == 0) {
return; // no leftovers to process and not using chunking
}
final byte[] buffer = ensureBufferSize(encodeSize, context);
final int savedPos = context.pos;
switch (context.modulus) { // % 5
case 0 :
break;
case 1 : // Only 1 octet; take top 5 bits then remainder
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 3) & MASK_5BITS]; // 8-1*5 = 3
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea << 2) & MASK_5BITS]; // 5-3=2
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
break;
case 2 : // 2 octets = 16 bits to use
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 11) & MASK_5BITS]; // 16-1*5 = 11
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 6) & MASK_5BITS]; // 16-2*5 = 6
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 1) & MASK_5BITS]; // 16-3*5 = 1
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea << 4) & MASK_5BITS]; // 5-1 = 4
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
break;
case 3 : // 3 octets = 24 bits to use
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 19) & MASK_5BITS]; // 24-1*5 = 19
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 14) & MASK_5BITS]; // 24-2*5 = 14
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 9) & MASK_5BITS]; // 24-3*5 = 9
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 4) & MASK_5BITS]; // 24-4*5 = 4
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea << 1) & MASK_5BITS]; // 5-4 = 1
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
buffer[context.pos++] = pad;
break;
case 4 : // 4 octets = 32 bits to use
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 27) & MASK_5BITS]; // 32-1*5 = 27
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 22) & MASK_5BITS]; // 32-2*5 = 22
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 17) & MASK_5BITS]; // 32-3*5 = 17
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 12) & MASK_5BITS]; // 32-4*5 = 12
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 7) & MASK_5BITS]; // 32-5*5 = 7
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 2) & MASK_5BITS]; // 32-6*5 = 2
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea << 3) & MASK_5BITS]; // 5-2 = 3
buffer[context.pos++] = pad;
break;
default:
throw new IllegalStateException("Impossible modulus "+context.modulus);
}
context.currentLinePos += context.pos - savedPos; // keep track of current line position
// if currentPos == 0 we are at the start of a line, so don't add CRLF
if (lineLength > 0 && context.currentLinePos > 0){ // add chunk separator if required
System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
context.pos += lineSeparator.length;
}
} else {
for (int i = 0; i < inAvail; i++) {
final byte[] buffer = ensureBufferSize(encodeSize, context);
context.modulus = (context.modulus+1) % BYTES_PER_UNENCODED_BLOCK;
int b = input[inPos++];
if (b < 0) {
b += 256;
}
context.lbitWorkArea = (context.lbitWorkArea << 8) + b; // BITS_PER_BYTE
if (0 == context.modulus) { // we have enough bytes to create our output
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 35) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 30) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 25) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 20) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 15) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 10) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)(context.lbitWorkArea >> 5) & MASK_5BITS];
buffer[context.pos++] = encodeTable[(int)context.lbitWorkArea & MASK_5BITS];
context.currentLinePos += BYTES_PER_ENCODED_BLOCK;
if (lineLength > 0 && lineLength <= context.currentLinePos) {
System.arraycopy(lineSeparator, 0, buffer, context.pos, lineSeparator.length);
context.pos += lineSeparator.length;
context.currentLinePos = 0;
}
}
}
}
}
/**
* Returns whether or not the {@code octet} is in the Base32 alphabet.
*
* @param octet
* The value to test
* @return {@code true} if the value is defined in the the Base32 alphabet {@code false} otherwise.
*/
@Override
public boolean isInAlphabet(final byte octet) {
return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1;
}
/**
* Validates whether decoding the final trailing character is possible in the context
* of the set of possible base 32 values.
*
* The character is valid if the lower bits within the provided mask are zero. This
* is used to test the final trailing base-32 digit is zero in the bits that will be discarded.
*
* @param emptyBitsMask The mask of the lower bits that should be empty
* @param context the context to be used
*
* @throws IllegalArgumentException if the bits being checked contain any non-zero value
*/
private static void validateCharacter(final long emptyBitsMask, final Context context) {
// Use the long bit work area
if ((context.lbitWorkArea & emptyBitsMask) != 0) {
throw new IllegalArgumentException(
"Last encoded character (before the paddings if any) is a valid base 32 alphabet but not a possible value. " +
"Expected the discarded bits to be zero.");
}
}
}