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Class java.util.zip.Deflater

java.lang.Object
    |
    +----java.util.zip.Deflater

public class Deflater
extends Object
This class provides support for general purpose decompression using the popular ZLIB compression library. The ZLIB compression library was initially developed as part of the PNG graphics standard and is not protected by patents. It is fully described in RFCs 1950, 1951, and 1952, which can be found at ftp://ds.internic.net/rfc in the files rfc1950.txt (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).

See Also:
Inflater

Field Summary
static int  BEST_COMPRESSION
Compression level for best compression.
static int  BEST_SPEED
Compression level for fastest compression.
static int  DEFAULT_COMPRESSION
Default compression level.
static int  DEFAULT_STRATEGY
Default compression strategy.
static int  DEFLATED
Compression method for the deflate algorithm (the only one currently supported).
static int  FILTERED
Compression strategy best used for data consisting mostly of small values with a somewhat random distribution.
static int  HUFFMAN_ONLY
Compression strategy for Huffman coding only.
static int  NO_COMPRESSION
Compression level for no compression.
 

Constructor Summary
 Deflater(int level, boolean nowrap)
Creates a new compressor using the specified compression level.
 Deflater(int level)
Creates a new compressor using the specified compression level.
 Deflater()
Creates a new compressor with the default compression level.
 

Method Summary
int  deflate(byte[] b, int off, int len)
Fills specified buffer with compressed data.
int  deflate(byte[] b)
Fills specified buffer with compressed data.
void  end()
Discards unprocessed input and frees internal data.
void  finalize()
Frees the compressor when garbage is collected.
void  finish()
When called, indicates that compression should end with the current contents of the input buffer.
boolean  finished()
Returns true if the end of the compressed data output stream has been reached.
int  getAdler()
Returns the ADLER-32 value of the uncompressed data.
int  getTotalIn()
Returns the total number of bytes input so far.
int  getTotalOut()
Returns the total number of bytes output so far.
boolean  needsInput()
Returns true if the input data buffer is empty and setInput() should be called in order to provide more input.
void  reset()
Resets deflater so that a new set of input data can be processed.
void  setDictionary(byte[] b, int off, int len)
Sets preset dictionary for compression.
void  setDictionary(byte[] b)
Sets preset dictionary for compression.
void  setInput(byte[] b, int off, int len)
Sets input data for compression.
void  setInput(byte[] b)
Sets input data for compression.
void  setLevel(int level)
Sets the current compression level to the specified value.
void  setStrategy(int strategy)
Sets the compression strategy to the specified value.
 
Methods inherited from class java.lang.Object
 clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFLATED

public static final int DEFLATED
Compression method for the deflate algorithm (the only one currently supported).

NO_COMPRESSION

public static final int NO_COMPRESSION
Compression level for no compression.

BEST_SPEED

public static final int BEST_SPEED
Compression level for fastest compression.

BEST_COMPRESSION

public static final int BEST_COMPRESSION
Compression level for best compression.

DEFAULT_COMPRESSION

public static final int DEFAULT_COMPRESSION
Default compression level.

FILTERED

public static final int FILTERED
Compression strategy best used for data consisting mostly of small values with a somewhat random distribution. Forces more Huffman coding and less string matching.

HUFFMAN_ONLY

public static final int HUFFMAN_ONLY
Compression strategy for Huffman coding only.

DEFAULT_STRATEGY

public static final int DEFAULT_STRATEGY
Default compression strategy.
Constructor Detail

Deflater

public Deflater(int level,
                boolean nowrap)
Creates a new compressor using the specified compression level. If 'nowrap' is true then the ZLIB header and checksum fields will not be used in order to support the compression format used in both GZIP and PKZIP.
Parameters:
level - the compression level (0-9)
nowrap - if true then use GZIP compatible compression

Deflater

public Deflater(int level)
Creates a new compressor using the specified compression level. Compressed data will be generated in ZLIB format.
Parameters:
level - the compression level (0-9)

Deflater

public Deflater()
Creates a new compressor with the default compression level. Compressed data will be generated in ZLIB format.
Method Detail

setInput

public void setInput(byte[] b,
                     int off,
                     int len)
Sets input data for compression. This should be called whenever needsInput() returns true indicating that more input data is required.
Parameters:
b - the input data bytes
off - the start offset of the data
len - the length of the data
See Also:
needsInput

setInput

public void setInput(byte[] b)
Sets input data for compression. This should be called whenever needsInput() returns true indicating that more input data is required.
Parameters:
b - the input data bytes
See Also:
needsInput

setDictionary

public void setDictionary(byte[] b,
                          int off,
                          int len)
Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.
Parameters:
b - the dictionary data bytes
off - the start offset of the data
len - the length of the data
See Also:
inflate, getAdler

setDictionary

public void setDictionary(byte[] b)
Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.
Parameters:
b - the dictionary data bytes
See Also:
inflate, getAdler

setStrategy

public void setStrategy(int strategy)
Sets the compression strategy to the specified value.
Parameters:
strategy - the new compression strategy
Throws:
IllegalArgumentException - if the compression strategy is invalid

setLevel

public void setLevel(int level)
Sets the current compression level to the specified value.
Parameters:
level - the new compression level (0-9)
Throws:
IllegalArgumentException - if the compression level is invalid

needsInput

public boolean needsInput()
Returns true if the input data buffer is empty and setInput() should be called in order to provide more input.

finish

public void finish()
When called, indicates that compression should end with the current contents of the input buffer.

finished

public boolean finished()
Returns true if the end of the compressed data output stream has been reached.

deflate

public int deflate(byte[] b,
                   int off,
                   int len)
Fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.
Parameters:
b - the buffer for the compressed data
off - the start offset of the data
len - the maximum number of bytes of compressed data
Returns:
the actual number of bytes of compressed data

deflate

public int deflate(byte[] b)
Fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.
Parameters:
b - the buffer for the compressed data
Returns:
the actual number of bytes of compressed data

getAdler

public int getAdler()
Returns the ADLER-32 value of the uncompressed data.

getTotalIn

public int getTotalIn()
Returns the total number of bytes input so far.

getTotalOut

public int getTotalOut()
Returns the total number of bytes output so far.

reset

public void reset()
Resets deflater so that a new set of input data can be processed. Keeps current compression level and strategy settings.

end

public void end()
Discards unprocessed input and frees internal data.

finalize

protected void finalize()
Frees the compressor when garbage is collected.
Overrides:
finalize in class Object

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