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java.util.zip
Class Inflater


java.lang.Object
  extended by java.util.zip.Inflater
public class Inflater
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 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??";
 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:
Deflater

Constructor Summary
Inflater ()
          Creates a new decompressor.
Inflater (boolean nowrap)
          Creates a new decompressor.
 
Method Summary
 void end ()
          Closes the decompressor and discards any unprocessed input.
protected  void finalize ()
          Closes the decompressor when garbage is collected.
 boolean finished ()
          Returns true if the end of the compressed data stream has been reached.
 int getAdler ()
          Returns the ADLER-32 value of the uncompressed data.
 long getBytesRead ()
          Returns the total number of compressed bytes input so far.
 long getBytesWritten ()
          Returns the total number of uncompressed bytes output so far.
 int getRemaining ()
          Returns the total number of bytes remaining in the input buffer.
 int getTotalIn ()
          Returns the total number of compressed bytes input so far.
 int getTotalOut ()
          Returns the total number of uncompressed bytes output so far.
 int inflate (byte[] b)
          Uncompresses bytes into specified buffer.
 int inflate (byte[] b, int off, int len)
          Uncompresses bytes into specified buffer.
 boolean needsDictionary ()
          Returns true if a preset dictionary is needed for decompression.
 boolean needsInput ()
          Returns true if no data remains in the input buffer.
 void reset ()
          Resets inflater so that a new set of input data can be processed.
 void setDictionary (byte[] b)
          Sets the preset dictionary to the given array of bytes.
 void setDictionary (byte[] b, int off, int len)
          Sets the preset dictionary to the given array of bytes.
 void setInput (byte[] b)
          Sets input data for decompression.
 void setInput (byte[] b, int off, int len)
          Sets input data for decompression.
 
Methods inherited from class java.lang. Object
clone , equals , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait
 

Constructor Detail

Inflater 


public Inflater (boolean nowrap)
Creates a new decompressor. If the parameter 'nowrap' is true then the ZLIB header and checksum fields will not be used. This provides compatibility with the compression format used by both GZIP and PKZIP.

Note: When using the 'nowrap' option it is also necessary to provide an extra "dummy" byte as input. This is required by the ZLIB native library in order to support certain optimizations.

Parameters:
nowrap - if true then support GZIP compatible compression

Inflater 


public Inflater ()
Creates a new decompressor.

Method Detail

setInput 


public void setInput (byte[] b,
 int off,
 int len)
Sets input data for decompression. 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 input data
len - the length of the input data
See Also:
needsInput()

setInput 


public void setInput (byte[] b)
Sets input data for decompression. 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 the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.

Parameters:
b - the dictionary data bytes
off - the start offset of the data
len - the length of the data
See Also:
needsDictionary() , getAdler()

setDictionary 


public void setDictionary (byte[] b)
Sets the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.

Parameters:
b - the dictionary data bytes
See Also:
needsDictionary() , getAdler()

getRemaining 


public int getRemaining ()
Returns the total number of bytes remaining in the input buffer. This can be used to find out what bytes still remain in the input buffer after decompression has finished.

Returns:
the total number of bytes remaining in the input buffer

needsInput 


public boolean needsInput ()
Returns true if no data remains in the input buffer. This can be used to determine if #setInput should be called in order to provide more input.

Returns:
true if no data remains in the input buffer

needsDictionary 


public boolean needsDictionary ()
Returns true if a preset dictionary is needed for decompression.

Returns:
true if a preset dictionary is needed for decompression
See Also:
setDictionary(byte[], int, int)

finished 


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

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

inflate 


public int inflate (byte[] b,
 int off,
 int len)
 throws DataFormatException
Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the later case, getAdler() can be used to get the Adler-32 value of the dictionary required.

Parameters:
b - the buffer for the uncompressed data
off - the start offset of the data
len - the maximum number of uncompressed bytes
Returns:
the actual number of uncompressed bytes
Throws:
DataFormatException - if the compressed data format is invalid
See Also:
needsInput() , needsDictionary()

inflate 


public int inflate (byte[] b)
 throws DataFormatException
Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the later case, getAdler() can be used to get the Adler-32 value of the dictionary required.

Parameters:
b - the buffer for the uncompressed data
Returns:
the actual number of uncompressed bytes
Throws:
DataFormatException - if the compressed data format is invalid
See Also:
needsInput() , needsDictionary()

getAdler 


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

Returns:
the ADLER-32 value of the uncompressed data

getTotalIn 


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

Since the number of bytes may be greater than Integer.MAX_VALUE, the getBytesRead() method is now the preferred means of obtaining this information.

Returns:
the total number of compressed bytes input so far

getBytesRead 


public long getBytesRead ()
Returns the total number of compressed bytes input so far.

Returns:
the total (non-negative) number of compressed bytes input so far

getTotalOut 


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

Since the number of bytes may be greater than Integer.MAX_VALUE, the getBytesWritten() method is now the preferred means of obtaining this information.

Returns:
the total number of uncompressed bytes output so far

getBytesWritten 


public long getBytesWritten ()
Returns the total number of uncompressed bytes output so far.

Returns:
the total (non-negative) number of uncompressed bytes output so far

reset

The following code fragment demonstrates a trivial compression and decompression of a string using Deflater and Inflater . 

public void reset () 
 // Encode a String into bytes
 String inputString = "blahblahblah??";
 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");
Resets inflater so that a new set of input data can be processed.

end 


public void end ()
Closes the decompressor and discards any unprocessed input. This method should be called when the decompressor is no longer being used, but will also be called automatically by the finalize() method. Once this method is called, the behavior of the Inflater object is undefined.

finalize 


protected void finalize ()
Closes the decompressor when garbage is collected.

Overrides: See Also:
finalize Deflater in class Object

Constructor Summary
Inflater ()
          Creates a new decompressor.
Inflater (boolean nowrap)
          Creates a new decompressor.
 
Method Summary
 void end ()
          Closes the decompressor and discards any unprocessed input.
protected  void finalize ()
          Closes the decompressor when garbage is collected.
 boolean finished ()
          Return true if the end of the compressed data stream has been reached.
 int getAdler ()
          Returns the ADLER-32 value of the uncompressed data.
 int getRemaining ()
          Returns the total number of bytes remaining in the input buffer.
 int getTotalIn ()
          Returns the total number of bytes input so far.
 int getTotalOut ()
          Returns the total number of bytes output so far.
 int inflate (byte[] b)
          Uncompresses bytes into specified buffer.
 int inflate (byte[] b, int off, int len)
          Uncompresses bytes into specified buffer.
 boolean needsDictionary ()
          Returns true if a preset dictionary is needed for decompression.
 boolean needsInput ()
          Returns true if no data remains in the input buffer.
 void reset ()
          Resets inflater so that a new set of input data can be processed.
 void setDictionary (byte[] b)
          Sets the preset dictionary to the given array of bytes.
 void setDictionary (byte[] b, int off, int len)
          Sets the preset dictionary to the given array of bytes.
 void setInput (byte[] b)
          Sets input data for decompression.
 void setInput (byte[] b, int off, int len)
          Sets input data for decompression.
 
Methods inherited from class java.lang. Object
clone , equals , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait
 

Constructor Detail

Inflater 


 
public Inflater (boolean nowrap)
Creates a new decompressor. If the parameter 'nowrap' is true then the ZLIB header and checksum fields will not be used. This provides compatibility with the compression format used by both GZIP and PKZIP.

Note: When using the 'nowrap' option it is also necessary to provide an extra "dummy" byte as input. This is required by the ZLIB native library in order to support certain optimizations.

Parameters:
nowrap - if true then support GZIP compatible compression

Inflater 


 
public Inflater ()
Creates a new decompressor.

Method Detail

setInput 


 
public void setInput (byte[] b,
 int off,
 int len)
Sets input data for decompression. 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 input data
len - the length of the input data
See Also:
needsInput()

setInput 


 
public void setInput (byte[] b)
Sets input data for decompression. 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 the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.

Parameters:
b - the dictionary data bytes
off - the start offset of the data
len - the length of the data
See Also:
needsDictionary() , getAdler()

setDictionary 


 
public void setDictionary (byte[] b)
Sets the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.

Parameters:
b - the dictionary data bytes
See Also:
needsDictionary() , getAdler()

getRemaining 


 
public int getRemaining ()
Returns the total number of bytes remaining in the input buffer. This can be used to find out what bytes still remain in the input buffer after decompression has finished.

Returns:
the total number of bytes remaining in the input buffer

needsInput 


 
public boolean needsInput ()
Returns true if no data remains in the input buffer. This can be used to determine if #setInput should be called in order to provide more input.

Returns:
true if no data remains in the input buffer

needsDictionary 


 
public boolean needsDictionary ()
Returns true if a preset dictionary is needed for decompression.

Returns:
true if a preset dictionary is needed for decompression
See Also:
setDictionary(byte[], int, int)

finished 


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

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

inflate 


 
public int inflate (byte[] b,
 int off,
 int len)
 throws DataFormatException
Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the later case, getAdler() can be used to get the Adler-32 value of the dictionary required.

Parameters:
b - the buffer for the uncompressed data
off - the start offset of the data
len - the maximum number of uncompressed bytes
Returns:
the actual number of uncompressed bytes
Throws:
DataFormatException - if the compressed data format is invalid
See Also:
needsInput() , needsDictionary()

inflate 


 
public int inflate (byte[] b)
 throws DataFormatException
Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the later case, getAdler() can be used to get the Adler-32 value of the dictionary required.

Parameters:
b - the buffer for the uncompressed data
Returns:
the actual number of uncompressed bytes
Throws:
DataFormatException - if the compressed data format is invalid
See Also:
needsInput() , needsDictionary()

getAdler 


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

Returns:
the ADLER-32 value of the uncompressed data

getTotalIn 


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

Returns:
the total number of bytes input so far

getTotalOut 


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

Returns:
the total number of bytes output so far

reset 


 
public void reset ()
Resets inflater so that a new set of input data can be processed.

end 


 
public void end ()
Closes the decompressor and discards any unprocessed input. This method should be called when the decompressor is no longer being used, but will also be called automatically by the finalize() method. Once this method is called, the behavior of the Inflater object is undefined.

finalize 


 
protected void finalize ()
Closes the decompressor when garbage is collected.

Overrides:
finalize in class Object