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java.util.zip
Class Inflater
java.lang.Object
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
.
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
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. |
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.
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
latter
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
latter
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.
-
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Returns:
-
the total (non-negative) number of compressed bytes input so far
-
Since:
-
1.5
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
-
Since:
-
1.5
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
-