org.apache.commons.compress.compressors.lzw

Class LZWInputStream

java.lang.Object

java.io.InputStream

org.apache.commons.compress.compressors.CompressorInputStream

org.apache.commons.compress.compressors.lzw.LZWInputStream

All Implemented Interfaces:

Closeable, AutoCloseable, InputStreamStatistics

Direct Known Subclasses:

ZCompressorInputStream

public abstract class LZWInputStream
extends CompressorInputStream
implements InputStreamStatistics

Generic LZW implementation. It is used internally for the Z decompressor and the Unshrinking Zip file compression method, but may be useful for third-party projects in implementing their own LZW variations.

Since:

1.10

This class is not thread-safe

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	DEFAULT_CODE_SIZE
protected BitInputStream	in
protected static int	UNUSED_PREFIX

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LZWInputStream(InputStream inputStream, ByteOrder byteOrder)

Method Summary

Modifier and Type	Method and Description
protected abstract int	addEntry(int previousCode, byte character) Add a new entry to the dictionary.
protected int	addEntry(int previousCode, byte character, int maxTableSize) Adds a new entry if the maximum table size hasn't been exceeded and returns the new index.
protected int	addRepeatOfPreviousCode() Add entry for repeat of previousCode we haven't added, yet.
void	close()
protected abstract int	decompressNextSymbol() Read the next code and expand it.
protected int	expandCodeToOutputStack(int code, boolean addedUnfinishedEntry) Expands the entry with index code to the output stack and may create a new entry
protected int	getClearCode()
protected int	getCodeSize()
long	getCompressedCount()
protected int	getPrefix(int offset)
protected int	getPrefixesLength()
protected int	getTableSize()
protected void	incrementCodeSize()
protected void	initializeTables(int maxCodeSize) Initializes the arrays based on the maximum code size.
protected void	initializeTables(int maxCodeSize, int memoryLimitInKb) Initializes the arrays based on the maximum code size.
int	read()
int	read(byte[] b, int off, int len)
protected int	readNextCode() Reads the next code from the stream.
protected void	resetCodeSize()
protected void	resetPreviousCode()
protected void	setClearCode(int codeSize) Sets the clear code based on the code size.
protected void	setCodeSize(int cs)
protected void	setPrefix(int offset, int value)
protected void	setTableSize(int newSize)

Methods inherited from class org.apache.commons.compress.compressors.CompressorInputStream

count, count, getBytesRead, getCount, getUncompressedCount, pushedBackBytes

Methods inherited from class java.io.InputStream

available, mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.commons.compress.utils.InputStreamStatistics

getUncompressedCount

Field Detail

DEFAULT_CODE_SIZE

protected static final int DEFAULT_CODE_SIZE

See Also:

Constant Field Values

UNUSED_PREFIX

protected static final int UNUSED_PREFIX

See Also:

Constant Field Values

in

protected final BitInputStream in

Constructor Detail

LZWInputStream

protected LZWInputStream(InputStream inputStream,
                         ByteOrder byteOrder)

Method Detail

addEntry

protected abstract int addEntry(int previousCode,
                                byte character)
                         throws IOException

Add a new entry to the dictionary.

Parameters:

previousCode - the previous code

character - the next character to append

Returns:

the new code

Throws:

IOException - on error

addEntry

protected int addEntry(int previousCode,
                       byte character,
                       int maxTableSize)

Adds a new entry if the maximum table size hasn't been exceeded and returns the new index.

Parameters:

previousCode - the previous code

character - the character to append

maxTableSize - the maximum table size

Returns:

the new code or -1 if maxTableSize has been reached already

addRepeatOfPreviousCode

protected int addRepeatOfPreviousCode()
                               throws IOException

Add entry for repeat of previousCode we haven't added, yet.

Returns:

new code for a repeat of the previous code or -1 if maxTableSize has been reached already

Throws:

IOException - on error

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class InputStream

Throws:

IOException

decompressNextSymbol

protected abstract int decompressNextSymbol()
                                     throws IOException

Read the next code and expand it.

Returns:

the expanded next code, negative on EOF

Throws:

IOException - on error

expandCodeToOutputStack

protected int expandCodeToOutputStack(int code,
                                      boolean addedUnfinishedEntry)
                               throws IOException

Expands the entry with index code to the output stack and may create a new entry

Parameters:

code - the code

addedUnfinishedEntry - whether unfinished entries have been added

Returns:

the new location of the output stack

Throws:

IOException - on error

getClearCode

protected int getClearCode()

getCodeSize

protected int getCodeSize()

getCompressedCount

public long getCompressedCount()

Specified by:

getCompressedCount in interface InputStreamStatistics

Returns:

the amount of raw or compressed bytes read by the stream

Since:

1.17

getPrefix

protected int getPrefix(int offset)

getPrefixesLength

protected int getPrefixesLength()

getTableSize

protected int getTableSize()

incrementCodeSize

protected void incrementCodeSize()

initializeTables

protected void initializeTables(int maxCodeSize)

Initializes the arrays based on the maximum code size.

Parameters:

maxCodeSize - maximum code size

Throws:

IllegalArgumentException - if maxCodeSize is not bigger than 0

initializeTables

protected void initializeTables(int maxCodeSize,
                                int memoryLimitInKb)
                         throws MemoryLimitException

Initializes the arrays based on the maximum code size. First checks that the estimated memory usage is below memoryLimitInKb

Parameters:

maxCodeSize - maximum code size

memoryLimitInKb - maximum allowed estimated memory usage in Kb

Throws:

MemoryLimitException - if estimated memory usage is greater than memoryLimitInKb

IllegalArgumentException - if maxCodeSize is not bigger than 0

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

readNextCode

protected int readNextCode()
                    throws IOException

Reads the next code from the stream.

Returns:

the next code

Throws:

IOException - on error

resetCodeSize

protected void resetCodeSize()

resetPreviousCode

protected void resetPreviousCode()

setClearCode

protected void setClearCode(int codeSize)

Sets the clear code based on the code size.

Parameters:

codeSize - code size

setCodeSize

protected void setCodeSize(int cs)

setPrefix

protected void setPrefix(int offset,
                         int value)

setTableSize

protected void setTableSize(int newSize)