compressors
Class LZ77v01

java.lang.Object
  compressors.LZ77v01

public class LZ77v01
extends java.lang.Object

Constructor Summary

LZ77v01()

LZ77v01(java.lang.String s)

Method Summary

java.lang.String	decode() Decodes encodedData into a String, stores the string in decodedData and returns the string.
java.util.ArrayList<Tuple>	encode() Encodes string rawData, stores the encoded data in encodedData and returns encodedData
double	getCompressionFactor() Performs an analysis of the compression between rawData and encodedData, prints the results and returns the compression factor.
java.util.ArrayList<Tuple>	getEncodedData()
int	getLookAheadWindowLen()
java.lang.String	getRawData()
int	getSearchWindowLen()
static void	main(java.lang.String[] args)
void	setEncodedData(java.util.ArrayList<Tuple> encodedData)
void	setLookAheadWindowLen(int lookAheadWindowLen)
void	setRawData(java.lang.String rawData)
void	setSearchWindowLen(int searchWindowLen)

Methods inherited from class java.lang.Object

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

Constructor Detail

LZ77v01

public LZ77v01()

LZ77v01

public LZ77v01(java.lang.String s)

Method Detail

encode

public java.util.ArrayList<Tuple> encode()

Encodes string rawData, stores the encoded data in encodedData and returns encodedData

decode

public java.lang.String decode()

Decodes encodedData into a String, stores the string in decodedData and returns the string. The original message has been encoded into a collection of Tuple objects where each object contains the following information: 1. offset points backwards to the beginning of a match relative to the current location. Has a value of 0 if there is no match for the next character. 2. stringLen specifies the length of the match or 0 if there is no match for the next character. 3. nextChar is the first non-matching character following a match, or the next character if there is no match. It would not be particularly difficult at this point to iterate on the collection and to produce a binary stream containing these three values. For example, depending on the values specified for searchWindowLen and lookAheadWindowLen, the first two values listed above could be encoded into the number of bits required to contain the largest possible offset value and the largest possible stringLen value. The character from the Tuple object could be encoded into eight bits. Then, the set of bits required to describe the Tuple could be inserted into a stream of bits. This demonstration program does not produce such a compressed binary file.

getCompressionFactor

public double getCompressionFactor()

Performs an analysis of the compression between rawData and encodedData, prints the results and returns the compression factor.

getRawData

public java.lang.String getRawData()

Returns:

the rawData

setRawData

public void setRawData(java.lang.String rawData)

Parameters:

rawData - the rawData to set

getEncodedData

public java.util.ArrayList<Tuple> getEncodedData()

Returns:

the encodedData

setEncodedData

public void setEncodedData(java.util.ArrayList<Tuple> encodedData)

Parameters:

encodedData - the encodedData to set

getSearchWindowLen

public int getSearchWindowLen()

Returns:

the searchWindowLen

setSearchWindowLen

public void setSearchWindowLen(int searchWindowLen)

Parameters:

searchWindowLen - the searchWindowLen to set

getLookAheadWindowLen

public int getLookAheadWindowLen()

Returns:

the lookAheadWindowLen

setLookAheadWindowLen

public void setLookAheadWindowLen(int lookAheadWindowLen)

Parameters:

lookAheadWindowLen - the lookAheadWindowLen to set

main

public static void main(java.lang.String[] args)