java.util.zip
Class Deflater

java.lang.Object
  java.util.zip.Deflater

public class Deflater
extends Object

The Deflater class is used to compress bytes using the DEFLATE compression algorithm. Deflation is performed by the ZLIB compression library.

See Also:

DeflaterOutputStream, Inflater

Field Summary

static int	BEST_COMPRESSION
static int	BEST_SPEED
static int	DEFAULT_COMPRESSION
static int	DEFAULT_STRATEGY
static int	DEFLATED
static int	FILTERED
static int	HUFFMAN_ONLY
static int	NO_COMPRESSION

Constructor Summary

Deflater()
Constructs a new Deflater instance with default compression level and strategy.

Deflater(int level)
Constructs a new Deflater instance with compression level level and default compression strategy.

Deflater(int level, boolean noHeader)
Constructs a new Deflater instance with compression level level and default compression strategy.

Method Summary

int	deflate(byte[] buf) Deflates data into the supplied buffer
int	deflate(byte[] buf, int off, int nbytes) Deflates data into the supplied buffer using the region from off to nbytes - 1.
void	end() Frees all resources held onto by this Deflater.
protected void	finalize() Called by the virtual machine when there are no longer any (non-weak) references to the receiver.
void	finish() Indicates to the Deflater that all uncompressed input has been provided to it.
boolean	finished() Returns whether or not all provided data has been successfully compressed.
int	getAdler() Returns the Adler32 checksum of uncompressed data currently read.
long	getBytesRead() Returns a long int of total number of bytes read by the Deflater.
long	getBytesWritten() Returns a long int of total number of bytes of read by the Deflater.
int	getTotalIn() Returns the total number of bytes of input consumed by the deflater.
int	getTotalOut() Returns the total number of compressed bytes output by this Deflater.
boolean	needsInput() Indicates whether or not all bytes of uncompressed input have been consumed by the Deflater.
void	reset() Resets the Deflater to accept new input without affecting any previously made settings for the compression strategy or level.
void	setDictionary(byte[] buf)
void	setDictionary(byte[] buf, int off, int nbytes) Sets the dictionary to be used for compression by this Deflater.
void	setInput(byte[] buf) Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression.
void	setInput(byte[] buf, int off, int nbytes) Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression.
void	setLevel(int level) Sets the compression level to be used when compressing data.
void	setStrategy(int strategy) Sets the compression strategy to be used.

Methods inherited from class java.lang.Object

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

Field Detail

BEST_COMPRESSION

public static final int BEST_COMPRESSION

See Also:

Constant Field Values

BEST_SPEED

public static final int BEST_SPEED

See Also:

Constant Field Values

DEFAULT_COMPRESSION

public static final int DEFAULT_COMPRESSION

See Also:

Constant Field Values

DEFAULT_STRATEGY

public static final int DEFAULT_STRATEGY

See Also:

Constant Field Values

DEFLATED

public static final int DEFLATED

See Also:

Constant Field Values

FILTERED

public static final int FILTERED

See Also:

Constant Field Values

HUFFMAN_ONLY

public static final int HUFFMAN_ONLY

See Also:

Constant Field Values

NO_COMPRESSION

public static final int NO_COMPRESSION

See Also:

Constant Field Values

Constructor Detail

Deflater

public Deflater()

Constructs a new Deflater instance with default compression level and strategy.

Deflater

public Deflater(int level)

Constructs a new Deflater instance with compression level level and default compression strategy. THe compression level provided must be between 0 and 9.

Parameters:

level - the compression level to use

Deflater

public Deflater(int level,
                boolean noHeader)

Constructs a new Deflater instance with compression level level and default compression strategy. If the noHeader parameter is specified then no ZLIB header will be written as part of the compressed output. The compression level specified must be between 0 and 9.

Parameters:

level - the compression level to use

noHeader - if true do not write the ZLIB header

Method Detail

deflate

public int deflate(byte[] buf)

Deflates data into the supplied buffer

Parameters:

buf - buffer to store compressed data

Returns:

number of bytes of compressed data stored

deflate

public int deflate(byte[] buf,
                   int off,
                   int nbytes)

Deflates data into the supplied buffer using the region from off to nbytes - 1.

Parameters:

buf - buffer to store compressed data

off - offset inf buf to start storing data

nbytes - number of bytes of compressed data to store in buf

Returns:

number of bytes of compressed data stored

end

public void end()

Frees all resources held onto by this Deflater. Any unused input or output is discarded. This is also called from the finalize method.

See Also:

finalize()

finalize

protected void finalize()

Description copied from class: Object

Called by the virtual machine when there are no longer any (non-weak) references to the receiver. Subclasses can use this facility to guarantee that any associated resources are cleaned up before the receiver is garbage collected. Uncaught exceptions which are thrown during the running of the method cause it to terminate immediately, but are otherwise ignored.

Note: The virtual machine assumes that the implementation in class Object is empty.

Overrides:

finalize in class Object

finish

public void finish()

Indicates to the Deflater that all uncompressed input has been provided to it.

See Also:

finished

finished

public boolean finished()

Returns whether or not all provided data has been successfully compressed.

Returns:

true if all data has been compressed, false otherwise

getAdler

public int getAdler()

Returns the Adler32 checksum of uncompressed data currently read. If a preset dictionary is used getAdler() will return the Adler32 checksum of the dictionary used.

Returns:

The Adler32 checksum of uncompressed data or preset dictionary if used

See Also:

setDictionary(byte[]), setDictionary(byte[], int, int)

getTotalIn

public int getTotalIn()

Returns the total number of bytes of input consumed by the deflater.

Returns:

number of bytes of input read.

getTotalOut

public int getTotalOut()

Returns the total number of compressed bytes output by this Deflater.

Returns:

number of compressed bytes output.

needsInput

public boolean needsInput()

Indicates whether or not all bytes of uncompressed input have been consumed by the Deflater. If needsInput() returns true setInput() must be called before deflation can continue. If all bytes of uncompressed data have been provided to the Deflater finish() must be called to ensure the compressed data is output.

Returns:

True if input is required for deflation to continue, false otherwise

See Also:

finished(), setInput(byte[]), setInput(byte[], int, int)

reset

public void reset()

Resets the Deflater to accept new input without affecting any previously made settings for the compression strategy or level. This operation must be called after finished() returns true if the Deflater is to be reused.

See Also:

finished

setDictionary

public void setDictionary(byte[] buf)

setDictionary

public void setDictionary(byte[] buf,
                          int off,
                          int nbytes)

Sets the dictionary to be used for compression by this Deflater. setDictionary() can only be called if this Deflater supports the writing of ZLIB headers. This is the default behaviour but can be overridden using Deflater(int, boolean).

See Also:

Deflater(int, boolean)

setInput

public void setInput(byte[] buf)

Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression.

setInput

public void setInput(byte[] buf,
                     int off,
                     int nbytes)

Sets the input buffer the Deflater will use to extract uncompressed bytes for later compression. Input will be taken from the buffer region starting at off and ending at nbytes - 1.

setLevel

public void setLevel(int level)

Sets the compression level to be used when compressing data. The compression level must be a value between 0 and 9. This value must be set prior to calling setInput().

Parameters:

level - compression level to use

Throws:

IllegalArgumentException - If the compression level is invalid.

setStrategy

public void setStrategy(int strategy)

Sets the compression strategy to be used. The strategy must be one of FILTERED, HUFFMAN_ONLY or DEFAULT_STRATEGY.This value must be set prior to calling setInput().

Parameters:

strategy - compression strategy to use

Throws:

IllegalArgumentException - If the strategy specified is not one of FILTERED, HUFFMAN_ONLY or DEFAULT_STRATEGY.

getBytesRead

public long getBytesRead()

Returns a long int of total number of bytes read by the Deflater. This method performs the same as getTotalIn except it returns a long value instead of an integer

Returns:

bytes exactly read by deflater

getBytesWritten

public long getBytesWritten()

Returns a long int of total number of bytes of read by the Deflater. This method performs the same as getTotalOut except it returns a long value instead of an integer

Returns:

bytes exactly write by deflater