| java.lang.Object
 java.util.zip.Deflater
| Deflater | | public class Deflater (Code) | | This class provides support for general purpose compression 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 the specifications at
the java.util.zip
package description.
The following code fragment demonstrates a trivial compression
and decompression of a string using Deflater and
Inflater.
// Encode a String into bytes
String inputString = "blahblahblah\u20AC\u20AC";
byte[] input = inputString.getBytes("UTF-8");
// Compress the bytes
byte[] output = new byte[100];
Deflater compresser = new Deflater();
compresser.setInput(input);
compresser.finish();
int compressedDataLength = compresser.deflate(output);
// Decompress the bytes
Inflater decompresser = new Inflater();
decompresser.setInput(output, 0, compressedDataLength);
byte[] result = new byte[100];
int resultLength = decompresser.inflate(result);
decompresser.end();
// Decode the bytes into a String
String outputString = new String(result, 0, resultLength, "UTF-8");
See Also: Inflater
version:
1.35, 05/03/00
author:
David Connelly |
| Field Summary | |
| final public static int | BEST_COMPRESSION
Compression level for best compression. | | final public static int | BEST_SPEED
Compression level for fastest compression. | | final public static int | DEFAULT_COMPRESSION
Default compression level. | | final public static int | DEFAULT_STRATEGY
Default compression strategy. | | final public static int | DEFLATED
Compression method for the deflate algorithm (the only one currently
supported). | | final public static int | FILTERED
Compression strategy best used for data consisting mostly of small
values with a somewhat random distribution. | | final public static int | HUFFMAN_ONLY
Compression strategy for Huffman coding only. | | final public static int | NO_COMPRESSION
Compression level for no compression. |
| Constructor Summary | |
| public | Deflater(int level, boolean nowrap)
Creates a new compressor using the specified compression level. | | public | Deflater(int level)
Creates a new compressor using the specified compression level. | | public | Deflater()
Creates a new compressor with the default compression level. |
| Method Summary | |
| public synchronized int | deflate(byte[] b, int off, int len)
Fills specified buffer with compressed data. | | public int | deflate(byte[] b)
Fills specified buffer with compressed data. | | public synchronized void | end()
Closes the compressor and discards any unprocessed input.
This method should be called when the compressor is no longer
being used, but will also be called automatically by the
finalize() method. | | protected void | finalize()
Closes the compressor when garbage is collected. | | public synchronized void | finish()
When called, indicates that compression should end with the current
contents of the input buffer. | | public synchronized boolean | finished()
Returns true if the end of the compressed data output stream has
been reached. | | public synchronized int | getAdler()
Returns the ADLER-32 value of the uncompressed data. | | public synchronized int | getTotalIn()
Returns the total number of bytes input so far. | | public synchronized int | getTotalOut()
Returns the total number of bytes output so far. | | public boolean | needsInput()
Returns true if the input data buffer is empty and setInput()
should be called in order to provide more input. | | public synchronized void | reset()
Resets deflater so that a new set of input data can be processed. | | public synchronized void | setDictionary(byte[] b, int off, int len)
Sets preset dictionary for compression. | | public void | setDictionary(byte[] b)
Sets preset dictionary for compression. | | public synchronized void | setInput(byte[] b, int off, int len)
Sets input data for compression. | | public void | setInput(byte[] b)
Sets input data for compression. | | public synchronized void | setLevel(int level)
Sets the current compression level to the specified value. | | public synchronized void | setStrategy(int strategy)
Sets the compression strategy to the specified value. |
| BEST_COMPRESSION | | final public static int BEST_COMPRESSION(Code) | | Compression level for best compression.
|
| BEST_SPEED | | final public static int BEST_SPEED(Code) | | Compression level for fastest compression.
|
| DEFAULT_COMPRESSION | | final public static int DEFAULT_COMPRESSION(Code) | | Default compression level.
|
| DEFAULT_STRATEGY | | final public static int DEFAULT_STRATEGY(Code) | | Default compression strategy.
|
| DEFLATED | | final public static int DEFLATED(Code) | | Compression method for the deflate algorithm (the only one currently
supported).
|
| FILTERED | | final public static int FILTERED(Code) | | 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 | | final public static int HUFFMAN_ONLY(Code) | | Compression strategy for Huffman coding only.
|
| NO_COMPRESSION | | final public static int NO_COMPRESSION(Code) | | Compression level for no compression.
|
| Deflater | | public Deflater(int level, boolean nowrap)(Code) | | 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)
Parameters:
nowrap - if true then use GZIP compatible compression |
| Deflater | | public Deflater(int level)(Code) | | 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()(Code) | | Creates a new compressor with the default compression level.
Compressed data will be generated in ZLIB format.
|
| deflate | | public synchronized int deflate(byte[] b, int off, int len)(Code) | | 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
Parameters:
off - the start offset of the data
Parameters:
len - the maximum number of bytes of compressed data the actual number of bytes of compressed data |
| deflate | | public int deflate(byte[] b)(Code) | | 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 the actual number of bytes of compressed data |
| end | | public synchronized void end()(Code) | | Closes the compressor and discards any unprocessed input.
This method should be called when the compressor is no longer
being used, but will also be called automatically by the
finalize() method. Once this method is called, the behavior
of the Deflater object is undefined.
|
| finalize | | protected void finalize()(Code) | | Closes the compressor when garbage is collected.
|
| finish | | public synchronized void finish()(Code) | | When called, indicates that compression should end with the current
contents of the input buffer.
|
| finished | | public synchronized boolean finished()(Code) | | Returns true if the end of the compressed data output stream has
been reached.
true if the end of the compressed data output stream hasbeen reached |
| getAdler | | public synchronized int getAdler()(Code) | | Returns the ADLER-32 value of the uncompressed data.
the ADLER-32 value of the uncompressed data |
| getTotalIn | | public synchronized int getTotalIn()(Code) | | Returns the total number of bytes input so far.
the total number of bytes input so far |
| getTotalOut | | public synchronized int getTotalOut()(Code) | | Returns the total number of bytes output so far.
the total number of bytes output so far |
| needsInput | | public boolean needsInput()(Code) | | Returns true if the input data buffer is empty and setInput()
should be called in order to provide more input.
true if the input data buffer is empty and setInput()should be called in order to provide more input |
| reset | | public synchronized void reset()(Code) | | Resets deflater so that a new set of input data can be processed.
Keeps current compression level and strategy settings.
|
| setDictionary | | public synchronized void setDictionary(byte[] b, int off, int len)(Code) | | 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
Parameters:
off - the start offset of the data
Parameters:
len - the length of the data
See Also: Inflater.inflate
See Also: Inflater.getAdler |
| setDictionary | | public void setDictionary(byte[] b)(Code) | | 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: Inflater.inflate
See Also: Inflater.getAdler |
| setInput | | public synchronized void setInput(byte[] b, int off, int len)(Code) | | 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
Parameters:
off - the start offset of the data
Parameters:
len - the length of the data
See Also: Deflater.needsInput |
| setInput | | public void setInput(byte[] b)(Code) | | 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: Deflater.needsInput |
| setLevel | | public synchronized void setLevel(int level)(Code) | | Sets the current compression level to the specified value.
Parameters:
level - the new compression level (0-9)
exception:
IllegalArgumentException - if the compression level is invalid |
| setStrategy | | public synchronized void setStrategy(int strategy)(Code) | | Sets the compression strategy to the specified value.
Parameters:
strategy - the new compression strategy
exception:
IllegalArgumentException - if the compression strategy isinvalid |
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