Package com.dannemann.stringcompressor

Class FourBitAsciiCompressor

java.lang.Object

com.dannemann.stringcompressor.AsciiCompressor

com.dannemann.stringcompressor.FourBitAsciiCompressor

public class FourBitAsciiCompressor
extends AsciiCompressor

Performs 4-bit-per-ASCII-character encoding and decoding.

Compression rate: 50%

Field Summary

Fields

Modifier and Type	Field	Description
static final byte[]	DEFAULT_4BIT_CHARSET	4-bit character set supported by default (ordered by ASCII): '#', '+', ',', '-', '.', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ';'

Fields inherited from class com.dannemann.stringcompressor.AsciiCompressor

PRESERVE_ORIGINAL_DEFAULT, preserveOriginal, supportedCharset, THROW_EXCEPTION_DEFAULT, throwException

Constructor Summary

Constructors

Constructor	Description
FourBitAsciiCompressor()	Creates a new compressor instance using the default 4-bit character set (DEFAULT_4BIT_CHARSET).
FourBitAsciiCompressor(boolean throwException)	Creates a new compressor instance using the default 4-bit character set (DEFAULT_4BIT_CHARSET) and with a configurable exception-throwing behavior.
FourBitAsciiCompressor(boolean throwException, boolean preserveOriginal)	Creates a new compressor instance using the default 4-bit character set (DEFAULT_4BIT_CHARSET), with configurable exception-throwing behavior and byte array data preservation.
FourBitAsciiCompressor(byte[] supportedCharset)	Creates a new compressor instance with a user defined 4-bit character set.
FourBitAsciiCompressor(byte[] supportedCharset, boolean throwException)	Creates a new compressor instance with a user defined 4-bit character set and configurable exception-throwing behavior.
FourBitAsciiCompressor(byte[] supportedCharset, boolean throwException, boolean preserveOriginal)	Creates a new compressor instance with a user defined 4-bit character set, configurable exception-throwing behavior, and byte array data preservation.

Method Summary

Modifier and Type	Method	Description
final byte[]	compress(byte[] string)	Compresses 2 characters into 1 byte (4 bits each).
byte[]	compress(String string)	Overloaded version of compress(byte[]).
final byte[]	decompress(byte[] compressed)	Restores the original string from data compressed by compress(byte[]).
protected void	validateSupportedCharset(byte[] supportedCharset)

Methods inherited from class com.dannemann.stringcompressor.AsciiCompressor

encode, getBytes, getString, getSupportedCharset, isPreserveOriginal, isThrowException, standardCharsetValidation

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_4BIT_CHARSET

public static final byte[] DEFAULT_4BIT_CHARSET

4-bit character set supported by default (ordered by ASCII): '#', '+', ',', '-', '.', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ';'

Constructor Details

FourBitAsciiCompressor

public FourBitAsciiCompressor()

Creates a new compressor instance using the default 4-bit character set (DEFAULT_4BIT_CHARSET). Uses default settings for exception throwing (AsciiCompressor.throwException is false) and byte array data preservation (AsciiCompressor.preserveOriginal is false).

FourBitAsciiCompressor

public FourBitAsciiCompressor(byte[] supportedCharset)

Creates a new compressor instance with a user defined 4-bit character set. Uses default settings for exception throwing (AsciiCompressor.throwException is false) and byte array data preservation (AsciiCompressor.preserveOriginal is false).

Parameters:

supportedCharset - The custom set of supported characters. See DEFAULT_4BIT_CHARSET for an example of how to define it.

See Also:

• AsciiCompressor.getSupportedCharset()

FourBitAsciiCompressor

public FourBitAsciiCompressor(boolean throwException)

Creates a new compressor instance using the default 4-bit character set (DEFAULT_4BIT_CHARSET) and with a configurable exception-throwing behavior. Uses default setting for byte array data preservation (AsciiCompressor.preserveOriginal is false).

Parameters:

throwException - If true, throws an exception on unsupported characters; otherwise, silently ignores them.

See Also:

• AsciiCompressor.isThrowException()

FourBitAsciiCompressor

public FourBitAsciiCompressor(byte[] supportedCharset,
 boolean throwException)

Creates a new compressor instance with a user defined 4-bit character set and configurable exception-throwing behavior. Uses default setting for byte array data preservation (AsciiCompressor.preserveOriginal is false).

Parameters:

supportedCharset - The custom set of supported characters. See DEFAULT_4BIT_CHARSET for an example of how to define it.

throwException - If true, throws an exception on unsupported characters; otherwise, silently ignores them.

See Also:

• AsciiCompressor.getSupportedCharset()
• AsciiCompressor.isThrowException()

FourBitAsciiCompressor

public FourBitAsciiCompressor(boolean throwException,
 boolean preserveOriginal)

Creates a new compressor instance using the default 4-bit character set (DEFAULT_4BIT_CHARSET), with configurable exception-throwing behavior and byte array data preservation.

Parameters:

throwException - If true, throws an exception on unsupported characters; otherwise, silently ignores them.

preserveOriginal - If true, preserves the original input byte array by working on a copy; otherwise, modifies it directly.

See Also:

• AsciiCompressor.isThrowException()
• AsciiCompressor.isPreserveOriginal()

FourBitAsciiCompressor

public FourBitAsciiCompressor(byte[] supportedCharset,
 boolean throwException,
 boolean preserveOriginal)

Creates a new compressor instance with a user defined 4-bit character set, configurable exception-throwing behavior, and byte array data preservation.

Parameters:

supportedCharset - The custom set of supported characters. See DEFAULT_4BIT_CHARSET for an example of how to define it.

throwException - If true, throws an exception on unsupported characters; otherwise, silently ignores them.

preserveOriginal - If true, preserves the original input byte array by working on a copy; otherwise, modifies it directly.

See Also:

• AsciiCompressor.getSupportedCharset()
• AsciiCompressor.isThrowException()
• AsciiCompressor.isPreserveOriginal()

Method Details

compress

public final byte[] compress(byte[] string)

Compresses 2 characters into 1 byte (4 bits each). Supports a set of 16 different characters (0000 to 1111).

Compression rate: 50%

See DEFAULT_4BIT_CHARSET for the default set of supported characters. To use a custom character set, refer to any constructor that accepts the byte[] supportedCharset parameter.

Specified by:

compress in class AsciiCompressor

Parameters:

string - String byte array to be compressed.

Returns:

A compressed byte array.

Throws:

NullPointerException - If string is null.

compress

public byte[] compress(String string)

Overloaded version of compress(byte[]).

Whenever possible, use compress(byte[]) and avoid string instantiation.

Specified by:

compress in class AsciiCompressor

decompress

public final byte[] decompress(byte[] compressed)

Restores the original string from data compressed by compress(byte[]).

Specified by:

decompress in class AsciiCompressor

Parameters:

compressed - The compressed string byte array.

Returns:

A decompressed string byte array.

validateSupportedCharset

protected void validateSupportedCharset(byte[] supportedCharset)

Specified by:

validateSupportedCharset in class AsciiCompressor