Inflater
public
class
Inflater
extends Object
| java.lang.Object | |
| ↳ | java.util.zip.Inflater |
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.
This class inflates sequences of ZLIB compressed bytes. The input byte
sequence is provided in either byte array or byte buffer, via one of the
setInput() methods. The output byte sequence is written to the
output byte array or byte buffer passed to the deflate() methods.
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\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");
} catch (java.io.UnsupportedEncodingException ex) {
// handle
} catch (java.util.zip.DataFormatException ex) {
// handle
}
See also:
Summary
Public constructors | |
|---|---|
Inflater(boolean nowrap)
Creates a new decompressor. |
|
Inflater()
Creates a new decompressor. |
|
Public methods | |
|---|---|
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[] output)
Uncompresses bytes into specified buffer. |
int
|
inflate(ByteBuffer output)
Uncompresses bytes into specified buffer. |
int
|
inflate(byte[] output, 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(ByteBuffer dictionary)
Sets the preset dictionary to the bytes in the given buffer. |
void
|
setDictionary(byte[] dictionary, int off, int len)
Sets the preset dictionary to the given array of bytes. |
void
|
setDictionary(byte[] dictionary)
Sets the preset dictionary to the given array of bytes. |
void
|
setInput(ByteBuffer input)
Sets input data for decompression. |
void
|
setInput(byte[] input, int off, int len)
Sets input data for decompression. |
void
|
setInput(byte[] input)
Sets input data for decompression. |
Inherited methods | |
|---|---|
Public constructors
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 |
boolean: if true then support GZIP compatible compression |
Public methods
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. Once this method is called, the behavior of the Inflater object is undefined.
finished
public boolean finished ()
Returns true if the end of the compressed data stream has been reached.
| Returns | |
|---|---|
boolean |
true if the end of the compressed data stream has been reached |
getAdler
public int getAdler ()
Returns the ADLER-32 value of the uncompressed data.
| Returns | |
|---|---|
int |
the ADLER-32 value of the uncompressed data |
getBytesRead
public long getBytesRead ()
Returns the total number of compressed bytes input so far.
| Returns | |
|---|---|
long |
the total (non-negative) number of compressed bytes input so far |
getBytesWritten
public long getBytesWritten ()
Returns the total number of uncompressed bytes output so far.
| Returns | |
|---|---|
long |
the total (non-negative) number of uncompressed bytes output so far |
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 | |
|---|---|
int |
the total number of bytes remaining in the input buffer |
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 | |
|---|---|
int |
the total 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 | |
|---|---|
int |
the total number of uncompressed bytes output so far |
inflate
public int inflate (byte[] output)
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.
The remaining byte count will be reduced by
the number of consumed input bytes. If the setInput(java.nio.ByteBuffer)
method was called to provide a buffer for input, the input buffer's position
will be advanced the number of consumed bytes.
These byte totals, as well as
the total bytes read
and the total bytes written
values, will be updated even in the event that a DataFormatException
is thrown to reflect the amount of data consumed and produced before the
exception occurred.
| Parameters | |
|---|---|
output |
byte: the buffer for the uncompressed data |
| Returns | |
|---|---|
int |
the actual number of uncompressed bytes |
| Throws | |
|---|---|
DataFormatException |
if the compressed data format is invalid |
See also:
inflate
public int inflate (ByteBuffer output)
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.
On success, the position of the given output byte buffer will be
advanced by as many bytes as were produced by the operation, which is equal
to the number returned by this method. Note that the position of the
output buffer will be advanced even in the event that a
DataFormatException is thrown.
The remaining byte count will be reduced by
the number of consumed input bytes. If the setInput(java.nio.ByteBuffer)
method was called to provide a buffer for input, the input buffer's position
will be advanced the number of consumed bytes.
These byte totals, as well as
the total bytes read
and the total bytes written
values, will be updated even in the event that a DataFormatException
is thrown to reflect the amount of data consumed and produced before the
exception occurred.
| Parameters | |
|---|---|
output |
ByteBuffer: the buffer for the uncompressed data |
| Returns | |
|---|---|
int |
the actual number of uncompressed bytes |
| Throws | |
|---|---|
DataFormatException |
if the compressed data format is invalid |
ReadOnlyBufferException |
if the given output buffer is read-only |
See also:
inflate
public int inflate (byte[] output,
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.
If the setInput(java.nio.ByteBuffer) method was called to provide a buffer
for input, the input buffer's position will be advanced by the number of bytes
consumed by this operation, even in the event that a DataFormatException
is thrown.
The remaining byte count will be reduced by
the number of consumed input bytes. If the setInput(java.nio.ByteBuffer)
method was called to provide a buffer for input, the input buffer's position
will be advanced the number of consumed bytes.
These byte totals, as well as
the total bytes read
and the total bytes written
values, will be updated even in the event that a DataFormatException
is thrown to reflect the amount of data consumed and produced before the
exception occurred.
| Parameters | |
|---|---|
output |
byte: the buffer for the uncompressed data |
off |
int: the start offset of the data |
len |
int: the maximum number of uncompressed bytes |
| Returns | |
|---|---|
int |
the actual number of uncompressed bytes |
| Throws | |
|---|---|
DataFormatException |
if the compressed data format is invalid |
See also:
needsDictionary
public boolean needsDictionary ()
Returns true if a preset dictionary is needed for decompression.
| Returns | |
|---|---|
boolean |
true if a preset dictionary is needed for decompression |
See also:
needsInput
public boolean needsInput ()
Returns true if no data remains in the input buffer. This can
be used to determine if one of the setInput() methods should be
called in order to provide more input.
| Returns | |
|---|---|
boolean |
true if no data remains in the input buffer |
reset
public void reset ()
Resets inflater so that a new set of input data can be processed.
setDictionary
public void setDictionary (ByteBuffer dictionary)
Sets the preset dictionary to the bytes in the given buffer. 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.
The bytes in given byte buffer will be fully consumed by this method. On return, its position will equal its limit.
| Parameters | |
|---|---|
dictionary |
ByteBuffer: the dictionary data bytes |
See also:
setDictionary
public void setDictionary (byte[] dictionary,
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 | |
|---|---|
dictionary |
byte: the dictionary data bytes |
off |
int: the start offset of the data |
len |
int: the length of the data |
See also:
setDictionary
public void setDictionary (byte[] dictionary)
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 | |
|---|---|
dictionary |
byte: the dictionary data bytes |
See also:
setInput
public void setInput (ByteBuffer input)
Sets input data for decompression.
One of the setInput() methods should be called whenever
needsInput() returns true indicating that more input data
is required.
The given buffer's position will be advanced as inflate operations are performed, up to the buffer's limit. The input buffer may be modified (refilled) between inflate operations; doing so is equivalent to creating a new buffer and setting it with this method.
Modifying the input buffer's contents, position, or limit concurrently with an inflate operation will result in undefined behavior, which may include incorrect operation results or operation failure.
| Parameters | |
|---|---|
input |
ByteBuffer: the input data bytes |
See also:
setInput
public void setInput (byte[] input,
int off,
int len)
Sets input data for decompression.
One of the setInput() methods should be called whenever
needsInput() returns true indicating that more input data
is required.
| Parameters | |
|---|---|
input |
byte: the input data bytes |
off |
int: the start offset of the input data |
len |
int: the length of the input data |
See also:
setInput
public void setInput (byte[] input)
Sets input data for decompression.
One of the setInput() methods should be called whenever
needsInput() returns true indicating that more input data
is required.
| Parameters | |
|---|---|
input |
byte: the input data bytes |
See also: