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.

 try {
     // 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");
 } catch(java.io.UnsupportedEncodingException ex) {
     // handle
 } catch (java.util.zip.DataFormatException ex) {
     // handle
 }
 

See Also

• Deflater

Public Constructor Summary

	Inflater(boolean nowrap) Creates a new decompressor.
	Inflater() Creates a new decompressor.

Public Method Summary

void	end() Closes the decompressor and discards any unprocessed input.
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, int off, int len) Sets the preset dictionary to the given array of bytes.
void	setDictionary(byte[] b) Sets the preset dictionary to the given array of bytes.
void	setInput(byte[] b, int off, int len) Sets input data for decompression.
void	setInput(byte[] b) Sets input data for decompression.

Protected Method Summary

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

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Public Constructors

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

public Inflater ()

Creates a new decompressor.

Public Methods

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.

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

public int getAdler ()

Returns the ADLER-32 value of the uncompressed data.

Returns

• the ADLER-32 value of the uncompressed data

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

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

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

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

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

public int inflate (byte[] b)

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 latter 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()

public int inflate (byte[] b, int off, int len)

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 latter 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()

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[])

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

public void reset ()

Resets inflater so that a new set of input data can be processed.

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()

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()

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()

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()

Protected Methods

protected void finalize ()

Closes the decompressor when garbage is collected.