org.cryptacular.codec

Class AbstractBaseNDecoder

java.lang.Object

org.cryptacular.codec.AbstractBaseNDecoder

All Implemented Interfaces:

Decoder

Direct Known Subclasses:

Base32Decoder, Base64Decoder

public abstract class AbstractBaseNDecoder
extends Object
implements Decoder

Base decoder class for encoding schemes described in RFC 3548.

Author:

Middleware Services

Constructor Summary

Constructors

Constructor and Description
AbstractBaseNDecoder(byte[] decodingTable) Creates a new instance with given parameters.

Method Summary

Modifier and Type	Method and Description
void	decode(CharBuffer input, ByteBuffer output) Decodes characters in input buffer into bytes placed in the output buffer.
protected static byte[]	decodingTable(String alphabet, int n) Converts the given alphabet into a base-N decoding table.
void	finalize(ByteBuffer output) Performs final output decoding (e.g. padding) after all input characters have been provided.
protected abstract int	getBitsPerChar()
protected abstract int	getBlockLength()
boolean	isPaddedInput()
int	outputSize(int inputSize) Expected number of bytes in the output buffer for an input buffer of the given size.
void	setPaddedInput(boolean enabled) Determines whether padded input is accepted.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AbstractBaseNDecoder

public AbstractBaseNDecoder(byte[] decodingTable)

Creates a new instance with given parameters.

Parameters:

decodingTable - Byte array indexed by characters in the character set encoding.

Method Detail

isPaddedInput

public boolean isPaddedInput()

Returns:

True if padded input is accepted (default), false otherwise.

setPaddedInput

public void setPaddedInput(boolean enabled)

Determines whether padded input is accepted.

Parameters:

enabled - True to enable support for padded input, false otherwise.

decode

public void decode(CharBuffer input,
                   ByteBuffer output)
            throws EncodingException

Description copied from interface: Decoder

Decodes characters in input buffer into bytes placed in the output buffer. This method may be called multiple times, followed by Decoder.finalize(ByteBuffer). after all input bytes have been provided.

Specified by:

decode in interface Decoder

Parameters:

input - Input character buffer.

output - Output byte buffer.

Throws:

EncodingException - on decoding errors.

finalize

public void finalize(ByteBuffer output)
              throws EncodingException

Description copied from interface: Decoder

Performs final output decoding (e.g. padding) after all input characters have been provided.

Specified by:

finalize in interface Decoder

Parameters:

output - Output byte buffer.

Throws:

EncodingException - on decoding errors.

outputSize

public int outputSize(int inputSize)

Description copied from interface: Decoder

Expected number of bytes in the output buffer for an input buffer of the given size.

Specified by:

outputSize in interface Decoder

Parameters:

inputSize - Size of input buffer in characters.

Returns:

Minimum byte buffer size required to store all decoded characters in input buffer.

getBlockLength

protected abstract int getBlockLength()

Returns:

Number of bits in a block of encoded characters.

getBitsPerChar

protected abstract int getBitsPerChar()

Returns:

Number of bits encoding a single character.

decodingTable

protected static byte[] decodingTable(String alphabet,
                                      int n)

Converts the given alphabet into a base-N decoding table.

Parameters:

alphabet - Decoding alphabet to use.

n - Encoding base.

Returns:

Decoding table of 128 elements.