Class java.util.zip.Deflater - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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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 http://info.internet.isi.edu:80/in-notes/rfc/files/ in the files rfc1950.txt (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).

See Also:: Inflater

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

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

deflate(byte[]): Fills specified buffer with compressed data.
deflate(byte[], int, int): Fills specified buffer with compressed data.
end(): Discards unprocessed input and frees internal data.
finalize(): Frees the compressor when garbage is collected.
finish(): When called, indicates that compression should end with the current contents of the input buffer.
finished(): Returns true if the end of the compressed data output stream has been reached.
getAdler(): Returns the ADLER-32 value of the uncompressed data.
getTotalIn(): Returns the total number of bytes input so far.
getTotalOut(): Returns the total number of bytes output so far.
needsInput(): Returns true if the input data buffer is empty and setInput() should be called in order to provide more input.
reset(): Resets deflater so that a new set of input data can be processed.
setDictionary(byte[]): Sets preset dictionary for compression.
setDictionary(byte[], int, int): Sets preset dictionary for compression.
setInput(byte[]): Sets input data for compression.
setInput(byte[], int, int): Sets input data for compression.
setLevel(int): Sets the current compression level to the specified value.
setStrategy(int): Sets the compression strategy to the specified value.

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.

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.

setInput

 public synchronized 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 native synchronized 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[])

Parameters:: b - the dictionary data bytes
See Also:: inflate, getAdler

setStrategy

 public synchronized 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 synchronized 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 synchronized void finish()

When called, indicates that compression should end with the current contents of the input buffer.

finished

 public synchronized boolean finished()

Returns true if the end of the compressed data output stream has been reached.

deflate

 public native synchronized 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[])

Parameters:: b - the buffer for the compressed data
Returns:: the actual number of bytes of compressed data

getAdler

 public native synchronized int getAdler()

Returns the ADLER-32 value of the uncompressed data.

getTotalIn

 public native synchronized int getTotalIn()

Returns the total number of bytes input so far.

getTotalOut

 public native synchronized int getTotalOut()

Returns the total number of bytes output so far.

reset

 public native synchronized void reset()

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

end

 public native synchronized 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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