Package org.apache.hadoop.io.compress

Interface Decompressor

@Public @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

    Modifier and Type
    Method
    Description
    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 Details

    • 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 uncompressed data
      off - Start offset of the data
      len - Size of the buffer
      Returns:
      The actual number of bytes of uncompressed data.
      Throws:
      IOException - raised on errors performing I/O.

    • 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.