Class Base32

  • All Implemented Interfaces:
    BinaryDecoder, BinaryEncoder, Decoder, Encoder

    public class Base32
    extends BaseNCodec
    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.

    Since:
    1.5
    Version:
    $Id: Base32.java 1619949 2014-08-22 22:56:08Z ggregory $
    See Also:
    RFC 4648
    • Field Summary

      Fields 
      Modifier and Type Field Description
      private static int BITS_PER_ENCODED_BYTE
      BASE32 characters are 5 bits in length.
      private static int BYTES_PER_ENCODED_BLOCK  
      private static int BYTES_PER_UNENCODED_BLOCK  
      private static byte[] CHUNK_SEPARATOR
      Chunk separator per RFC 2045 section 2.1.
      private static byte[] DECODE_TABLE
      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.
      private int decodeSize
      Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
      private byte[] decodeTable
      Decode table to use.
      private static byte[] ENCODE_TABLE
      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 int encodeSize
      Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
      private byte[] encodeTable
      Encode table to use.
      private static byte[] HEX_DECODE_TABLE
      This array is a lookup table that translates Unicode characters drawn from the "Base32 |Hex Alphabet" (as specified in Table 3 of RFC 4648) into their 5-bit positive integer equivalents.
      private static byte[] HEX_ENCODE_TABLE
      This array is a lookup table that translates 5-bit positive integer index values into their "Base32 Hex Alphabet" equivalents as specified in Table 3 of RFC 4648.
      private byte[] lineSeparator
      Line separator for encoding.
      private static int MASK_5BITS
      Mask used to extract 5 bits, used when encoding Base32 bytes
    • Constructor Summary

      Constructors 
      Constructor Description
      Base32()
      Creates a Base32 codec used for decoding and encoding.
      Base32​(boolean useHex)
      Creates a Base32 codec used for decoding and encoding.
      Base32​(boolean useHex, byte pad)
      Creates a Base32 codec used for decoding and encoding.
      Base32​(byte pad)
      Creates a Base32 codec used for decoding and encoding.
      Base32​(int lineLength)
      Creates a Base32 codec used for decoding and encoding.
      Base32​(int lineLength, byte[] lineSeparator)
      Creates a Base32 codec used for decoding and encoding.
      Base32​(int lineLength, byte[] lineSeparator, boolean useHex)
      Creates a Base32 / Base32 Hex codec used for decoding and encoding.
      Base32​(int lineLength, byte[] lineSeparator, boolean useHex, byte pad)
      Creates a Base32 / Base32 Hex codec used for decoding and encoding.
    • Field Detail

      • BITS_PER_ENCODED_BYTE

        private static final int BITS_PER_ENCODED_BYTE
        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.
        See Also:
        Constant Field Values
      • BYTES_PER_ENCODED_BLOCK

        private static final int BYTES_PER_ENCODED_BLOCK
        See Also:
        Constant Field Values
      • BYTES_PER_UNENCODED_BLOCK

        private static final int BYTES_PER_UNENCODED_BLOCK
        See Also:
        Constant Field Values
      • CHUNK_SEPARATOR

        private static final byte[] CHUNK_SEPARATOR
        Chunk separator per RFC 2045 section 2.1.
        See Also:
        RFC 2045 section 2.1
      • DECODE_TABLE

        private static final byte[] DECODE_TABLE
        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.
      • ENCODE_TABLE

        private static final byte[] ENCODE_TABLE
        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.
      • HEX_DECODE_TABLE

        private static final byte[] HEX_DECODE_TABLE
        This array is a lookup table that translates Unicode characters drawn from the "Base32 |Hex Alphabet" (as specified in Table 3 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.
      • HEX_ENCODE_TABLE

        private static final byte[] HEX_ENCODE_TABLE
        This array is a lookup table that translates 5-bit positive integer index values into their "Base32 Hex Alphabet" equivalents as specified in Table 3 of RFC 4648.
      • MASK_5BITS

        private static final int MASK_5BITS
        Mask used to extract 5 bits, used when encoding Base32 bytes
        See Also:
        Constant Field Values
      • decodeSize

        private final int decodeSize
        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;
      • decodeTable

        private final byte[] decodeTable
        Decode table to use.
      • encodeSize

        private final int encodeSize
        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;
      • encodeTable

        private final byte[] encodeTable
        Encode table to use.
      • lineSeparator

        private final byte[] lineSeparator
        Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
    • Constructor Detail

      • Base32

        public Base32()
        Creates a Base32 codec used for decoding and encoding.

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

      • Base32

        public Base32​(byte pad)
        Creates a Base32 codec used for decoding and encoding.

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

        Parameters:
        pad - byte used as padding byte.
      • Base32

        public Base32​(boolean useHex)
        Creates a Base32 codec used for decoding and encoding.

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

        Parameters:
        useHex - if true then use Base32 Hex alphabet
      • Base32

        public Base32​(boolean useHex,
                      byte pad)
        Creates a Base32 codec used for decoding and encoding.

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

        Parameters:
        useHex - if true then use Base32 Hex alphabet
        pad - byte used as padding byte.
      • Base32

        public Base32​(int lineLength)
        Creates a Base32 codec used for decoding and encoding.

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

        Parameters:
        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.
      • Base32

        public Base32​(int lineLength,
                      byte[] lineSeparator)
        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.

        Parameters:
        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:
        java.lang.IllegalArgumentException - The provided lineSeparator included some Base32 characters. That's not going to work!
      • Base32

        public Base32​(int lineLength,
                      byte[] lineSeparator,
                      boolean useHex)
        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.

        Parameters:
        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:
        java.lang.IllegalArgumentException - The provided lineSeparator included some Base32 characters. That's not going to work! Or the lineLength > 0 and lineSeparator is null.
      • Base32

        public Base32​(int lineLength,
                      byte[] lineSeparator,
                      boolean useHex,
                      byte pad)
        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.

        Parameters:
        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:
        java.lang.IllegalArgumentException - The provided lineSeparator included some Base32 characters. That's not going to work! Or the lineLength > 0 and lineSeparator is null.
    • Method Detail

      • decode

        void decode​(byte[] in,
                    int inPos,
                    int inAvail,
                    BaseNCodec.Context context)

        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.

        Specified by:
        decode in class BaseNCodec
        Parameters:
        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 BaseNCodec.Context.buffer as 8-bit octets, using BaseNCodec.Context.pos as the buffer position
      • encode

        void encode​(byte[] in,
                    int inPos,
                    int inAvail,
                    BaseNCodec.Context context)

        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).

        Specified by:
        encode in class BaseNCodec
        Parameters:
        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
      • isInAlphabet

        public boolean isInAlphabet​(byte octet)
        Returns whether or not the octet is in the Base32 alphabet.
        Specified by:
        isInAlphabet in class BaseNCodec
        Parameters:
        octet - The value to test
        Returns:
        true if the value is defined in the the Base32 alphabet false otherwise.