org.apache.hadoop.io.compress

接口 Compressor

所有已知实现类:

BuiltInZlibDeflater, BZip2DummyCompressor, SnappyCompressor, ZlibCompressor

public interface Compressor

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

方法概要

方法

限定符和类型	方法和说明
int	compress(byte[] b, int off, int len) Fills specified buffer with compressed data.
void	end() Closes the compressor and discards any unprocessed input.
void	finish() When called, indicates that compression should end with the current contents of the input buffer.
boolean	finished() Returns true if the end of the compressed data output stream has been reached.
long	getBytesRead() Return number of uncompressed bytes input so far.
long	getBytesWritten() Return number of compressed bytes output so far.
boolean	needsInput() Returns true if the input data buffer is empty and #setInput() should be called to provide more input.
void	reinit(Configuration conf) Prepare the compressor to be used in a new stream with settings defined in the given Configuration
void	reset() Resets compressor 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 compression.

方法详细资料

setInput

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

Sets input data for compression. This should be called whenever #needsInput() returns true indicating that more input data is required.

参数:

b - Input data

off - Start offset

len - Length

needsInput

boolean needsInput()

Returns true if the input data buffer is empty and #setInput() should be called to provide more input.

返回:

true if the input data buffer is empty and #setInput() 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.

参数:

b - Dictionary data bytes

off - Start offset

len - Length

getBytesRead

long getBytesRead()

Return number of uncompressed bytes input so far.

getBytesWritten

long getBytesWritten()

Return number of compressed bytes output so far.

finish

void finish()

When called, indicates that compression should end with the current contents of the input buffer.

finished

boolean finished()

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

返回:

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

compress

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

Fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.

参数:

b - Buffer for the compressed data

off - Start offset of the data

len - Size of the buffer

返回:

The actual number of bytes of compressed data.

抛出:

IOException

reset

void reset()

Resets compressor so that a new set of input data can be processed.

end

void end()

Closes the compressor and discards any unprocessed input.

reinit

void reinit(Configuration conf)

Prepare the compressor to be used in a new stream with settings defined in the given Configuration

参数:

conf - Configuration from which new setting are fetched