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Inflater.javaAPI DocJava SE 5 API10843Fri Aug 26 14:57:28 BST 2005java.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\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
Deflater
version
1.43, 08/09/05
author
David Connelly

Fields Summary
private long
strm
private byte[]
buf
private int
off
private int
len
private boolean
finished
private boolean
needDict
Constructors Summary
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.

param
nowrap if true then support GZIP compatible compression


     
	/* Zip library is loaded from System.initializeSystemClass */
	initIDs();
    
	strm = init(nowrap);
    
public Inflater()
Creates a new decompressor.

	this(false);
    
Methods Summary
public synchronized voidend()
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.

	if (strm != 0) {
	    end(strm);
	    strm = 0;
	}
    
private static native voidend(long strm)

private voidensureOpen()

	if (strm == 0)
	    throw new NullPointerException();
    
protected voidfinalize()
Closes the decompressor when garbage is collected.

	end();
    
public synchronized booleanfinished()
Returns true if the end of the compressed data stream has been reached.

return
true if the end of the compressed data stream has been reached

	return finished;
    
public synchronized intgetAdler()
Returns the ADLER-32 value of the uncompressed data.

return
the ADLER-32 value of the uncompressed data

	ensureOpen();
	return getAdler(strm);
    
private static native intgetAdler(long strm)

public synchronized longgetBytesRead()
Returns the total number of compressed bytes input so far.

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

	ensureOpen();
	return getBytesRead(strm);
    
private static native longgetBytesRead(long strm)

public synchronized longgetBytesWritten()
Returns the total number of uncompressed bytes output so far.

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

	ensureOpen();
	return getBytesWritten(strm);
    
private static native longgetBytesWritten(long strm)

public synchronized intgetRemaining()
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.

return
the total number of bytes remaining in the input buffer

	return len;
    
public intgetTotalIn()
Returns the total number of compressed bytes input so far.

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

return
the total number of compressed bytes input so far

	return (int) getBytesRead();
    
public intgetTotalOut()
Returns the total number of uncompressed bytes output so far.

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

return
the total number of uncompressed bytes output so far

	return (int) getBytesWritten();
    
public synchronized intinflate(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 later case, getAdler() can be used to get the Adler-32 value of the dictionary required.

param
b the buffer for the uncompressed data
param
off the start offset of the data
param
len the maximum number of uncompressed bytes
return
the actual number of uncompressed bytes
exception
DataFormatException if the compressed data format is invalid
see
Inflater#needsInput
see
Inflater#needsDictionary

	if (b == null) {
	    throw new NullPointerException();
	}
	if (off < 0 || len < 0 || off > b.length - len) {
	    throw new ArrayIndexOutOfBoundsException();
	}
	return inflateBytes(b, off, len);
    
public intinflate(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 later case, getAdler() can be used to get the Adler-32 value of the dictionary required.

param
b the buffer for the uncompressed data
return
the actual number of uncompressed bytes
exception
DataFormatException if the compressed data format is invalid
see
Inflater#needsInput
see
Inflater#needsDictionary

	return inflate(b, 0, b.length);
    
private native intinflateBytes(byte[] b, int off, int len)

private static native longinit(boolean nowrap)

private static native voidinitIDs()

public synchronized booleanneedsDictionary()
Returns true if a preset dictionary is needed for decompression.

return
true if a preset dictionary is needed for decompression
see
Inflater#setDictionary

	return needDict;
    
public synchronized booleanneedsInput()
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.

return
true if no data remains in the input buffer

	return len <= 0;
    
public synchronized voidreset()
Resets inflater so that a new set of input data can be processed.

	ensureOpen();
	reset(strm);
	finished = false;
	needDict = false;
	off = len = 0;
    
private static native voidreset(long strm)

private static native voidsetDictionary(long strm, byte[] b, int off, int len)

public synchronized voidsetDictionary(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.

param
b the dictionary data bytes
param
off the start offset of the data
param
len the length of the data
see
Inflater#needsDictionary
see
Inflater#getAdler

	if (strm == 0 || b == null) {
	    throw new NullPointerException();
	}
	if (off < 0 || len < 0 || off > b.length - len) {
	    throw new ArrayIndexOutOfBoundsException();
	}
	setDictionary(strm, b, off, len);
	needDict = false;
    
public voidsetDictionary(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.

param
b the dictionary data bytes
see
Inflater#needsDictionary
see
Inflater#getAdler

	setDictionary(b, 0, b.length);
    
public synchronized voidsetInput(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.

param
b the input data bytes
param
off the start offset of the input data
param
len the length of the input data
see
Inflater#needsInput

	if (b == null) {
	    throw new NullPointerException();
	}
	if (off < 0 || len < 0 || off > b.length - len) {
	    throw new ArrayIndexOutOfBoundsException();
	}
	this.buf = b;
	this.off = off;
	this.len = len;
    
public voidsetInput(byte[] b)
Sets input data for decompression. Should be called whenever needsInput() returns true indicating that more input data is required.

param
b the input data bytes
see
Inflater#needsInput

	setInput(b, 0, b.length);