org.apache.hadoop.io.compress
Interface Decompressor


@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface Decompressor

Specification of a stream-based 'de-compressor' which can be plugged into a CompressionInputStream to compress data. This is modelled after Inflater


Method Summary
 int decompress(byte[] b, int off, int len)
          Fills specified buffer with uncompressed data.
 void end()
          Closes the decompressor and discards any unprocessed input.
 boolean finished()
          Returns true if the end of the decompressed data output stream has been reached.
 int getRemaining()
          Returns the number of bytes remaining in the compressed data buffer.
 boolean needsDictionary()
          Returns true if a preset dictionary is needed for decompression.
 boolean needsInput()
          Returns true if the input data buffer is empty and setInput(byte[], int, int) should be called to provide more input.
 void reset()
          Resets decompressor and input and output buffers so that a new set of input data can be processed.
 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.
 

Method Detail

setInput

void setInput(byte[] b,
              int off,
              int len)
Sets input data for decompression. This should be called if and only if 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 needsInput()--that the buffer may be safely modified. With this requirement, an extra buffer-copy can be avoided.)

Parameters:
b - Input data
off - Start offset
len - Length

needsInput

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

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

setDictionary

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.

Parameters:
b - Dictionary data bytes
off - Start offset
len - Length

needsDictionary

boolean needsDictionary()
Returns true if a preset dictionary is needed for decompression.

Returns:
true if a preset dictionary is needed for decompression

finished

boolean finished()
Returns true if the end of the decompressed data output stream has been reached. Indicates a concatenated data stream when finished() returns true and getRemaining() returns a positive value. finished() will be reset with the reset() method.

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

decompress

int decompress(byte[] b,
               int off,
               int len)
               throws IOException
Fills specified buffer with uncompressed data. Returns actual number of bytes of uncompressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.

Parameters:
b - Buffer for the compressed data
off - Start offset of the data
len - Size of the buffer
Returns:
The actual number of bytes of compressed data.
Throws:
IOException

getRemaining

int getRemaining()
Returns the number of bytes remaining in the compressed data buffer. Indicates a concatenated data stream if finished() returns true and getRemaining() returns a positive value. If finished() returns true and getRemaining() returns a zero value, indicates that the end of data stream has been reached and is not a concatenated data stream.

Returns:
The number of bytes remaining in the compressed data buffer.

reset

void reset()
Resets decompressor and input and output buffers so that a new set of input data can be processed. If finished()} returns true and getRemaining() returns a positive value, reset() is called before processing of the next data stream in the concatenated data stream. finished() will be reset and will return false when reset() is called.


end

void end()
Closes the decompressor and discards any unprocessed input.



Copyright © 2012 Apache Software Foundation. All Rights Reserved.