org.apache.hadoop.io.compress.zlib
Class BuiltInGzipDecompressor

java.lang.Object
  org.apache.hadoop.io.compress.zlib.BuiltInGzipDecompressor

All Implemented Interfaces:

Decompressor

@DoNotPool
public class BuiltInGzipDecompressor
extends Object
implements Decompressor

A Decompressor based on the popular gzip compressed file format. http://www.gzip.org/

Constructor Summary

BuiltInGzipDecompressor()
Creates a new (pure Java) gzip decompressor.

Method Summary

int	decompress(byte[] b, int off, int len) Decompress the data (gzip header, deflate stream, gzip trailer) in the provided buffer.
void	end() Closes the decompressor and discards any unprocessed input.
boolean	finished() Returns true if the end of the gzip substream (single "member") has been reached.
long	getBytesRead() Returns the total number of compressed bytes input so far, including gzip header/trailer bytes.
int	getRemaining() Returns the number of bytes remaining in the input buffer; normally called when finished() is true to determine amount of post-gzip-stream data.
boolean	needsDictionary() Returns true if a preset dictionary is needed for decompression.
boolean	needsInput() Returns true if the input data buffer is empty and Decompressor.setInput(byte[], int, int) should be called to provide more input.
void	reset() Resets everything, including the input buffer, regardless of whether the current gzip substream is finished.
void	setDictionary(byte[] b, int off, int len) Sets preset dictionary for compression.
void	setInput(byte[] b, int off, int len) Sets input data for decompression.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BuiltInGzipDecompressor

public BuiltInGzipDecompressor()

Creates a new (pure Java) gzip decompressor.

Method Detail

needsInput

public boolean needsInput()

Returns true if the input data buffer is empty and Decompressor.setInput(byte[], int, int) should be called to provide more input.

Specified by:

needsInput in interface Decompressor

Returns:

true if the input data buffer is empty and Decompressor.setInput(byte[], int, int) should be called in order to provide more input.

setInput

public void setInput(byte[] b,
                     int off,
                     int len)

Sets input data for decompression. This should be called if and only if Decompressor.needsInput() returns true indicating that more input data is required. (Both native and non-native versions of various Decompressors require that the data passed in via b[] remain unmodified until the caller is explicitly notified--via Decompressor.needsInput()--that the buffer may be safely modified. With this requirement, an extra buffer-copy can be avoided.)

Specified by:

setInput in interface Decompressor

Parameters:

b - Input data

off - Start offset

len - Length

decompress

public int decompress(byte[] b,
                      int off,
                      int len)
               throws IOException

Decompress the data (gzip header, deflate stream, gzip trailer) in the provided buffer.

Specified by:

decompress in interface Decompressor

Parameters:

b - Buffer for the compressed data

off - Start offset of the data

len - Size of the buffer

Returns:

the number of decompressed bytes placed into b

Throws:

IOException

getBytesRead

public long getBytesRead()

Returns the total number of compressed bytes input so far, including gzip header/trailer bytes.

Returns:

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

getRemaining

public int getRemaining()

Returns the number of bytes remaining in the input buffer; normally called when finished() is true to determine amount of post-gzip-stream data. Note that, other than the finished state with concatenated data after the end of the current gzip stream, this will never return a non-zero value unless called after setInput(byte[] b, int off, int len) and before decompress(byte[] b, int off, int len). (That is, after decompress(byte[] b, int off, int len) it always returns zero, except in finished state with concatenated data.)

Specified by:

getRemaining in interface Decompressor

Returns:

the total (non-negative) number of unprocessed bytes in input

needsDictionary

public boolean needsDictionary()

Returns true if a preset dictionary is needed for decompression.

Specified by:

needsDictionary in interface Decompressor

Returns:

true if a preset dictionary is needed for decompression

setDictionary

public void setDictionary(byte[] b,
                          int off,
                          int len)

Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined.

Specified by:

setDictionary in interface Decompressor

Parameters:

b - Dictionary data bytes

off - Start offset

len - Length

finished

public boolean finished()

Returns true if the end of the gzip substream (single "member") has been reached.

Specified by:

finished in interface Decompressor

Returns:

true if the end of the decompressed data output stream has been reached.

reset

public void reset()

Resets everything, including the input buffer, regardless of whether the current gzip substream is finished.

Specified by:

reset in interface Decompressor

end

public void end()

Closes the decompressor and discards any unprocessed input.

Specified by:

end in interface Decompressor