Package org.iq80.snappy

Class AbstractSnappyOutputStream

java.lang.Object

java.io.OutputStream

org.iq80.snappy.AbstractSnappyOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

Direct Known Subclasses:

SnappyFramedOutputStream, SnappyOutputStream

abstract class AbstractSnappyOutputStream
extends OutputStream

This is a base class supporting both the SnappyOutputStream and SnappyFramedOutputStream.

Delegates writing the header bytes and individual frames to the specific implementations. Implementations may also override the crc32 checksum calculation.

Since:

0.4

Field Summary

Fields

Modifier and Type	Field	Description
private final int	blockSize
private final byte[]	buffer
private boolean	closed
private final double	minCompressionRatio
private final OutputStream	out
private final byte[]	outputBuffer
private int	position
private final BufferRecycler	recycler

Constructor Summary

Constructors

Constructor	Description
AbstractSnappyOutputStream(OutputStream out, int blockSize, double minCompressionRatio)

Method Summary

Modifier and Type	Method	Description
protected int	calculateCRC32C(byte[] data, int offset, int length)	Calculates a CRC32C checksum over the data.
final void	close()
private void	copyToBuffer(byte[] input, int offset, int length)
final void	flush()
private void	flushBuffer()	Compresses and writes out any buffered data.
void	write(byte[] input, int offset, int length)
void	write(int b)
protected abstract void	writeBlock(OutputStream out, byte[] data, int offset, int length, boolean compressed, int crc32c)	Write a frame (block) to out.
private void	writeCompressed(byte[] input, int offset, int length)	Calculates the crc, compresses the data, determines if the compression ratio is acceptable and calls writeBlock(OutputStream, byte[], int, int, boolean, int) to actually write the frame.
protected abstract void	writeHeader(OutputStream out)	Writes the implementation specific header or "marker bytes" to out.

Methods inherited from class java.io.OutputStream

nullOutputStream, write

Methods inherited from class java.lang.Object

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

Field Details

recycler

private final BufferRecycler recycler

blockSize

private final int blockSize

buffer

private final byte[] buffer

outputBuffer

private final byte[] outputBuffer

minCompressionRatio

private final double minCompressionRatio

out

private final OutputStream out

position

private int position

closed

private boolean closed

Constructor Details

AbstractSnappyOutputStream

public AbstractSnappyOutputStream(OutputStream out,
 int blockSize,
 double minCompressionRatio)
                           throws IOException

Parameters:

out - The underlying OutputStream to write to. Must not be null.

blockSize - The block size (of raw data) to compress before writing frames to out.

minCompressionRatio - Defines the minimum compression ratio (compressedLength / rawLength) that must be achieved to write the compressed data. This must be in (0, 1.0].

Throws:

IOException

Method Details

writeHeader

protected abstract void writeHeader(OutputStream out)
                             throws IOException

Writes the implementation specific header or "marker bytes" to out.

Parameters:

out - The underlying OutputStream.

Throws:

IOException

write

public void write(int b)
           throws IOException

Specified by:

write in class OutputStream

Throws:

IOException

write

public void write(byte[] input,
 int offset,
 int length)
           throws IOException

Overrides:

write in class OutputStream

Throws:

IOException

flush

public final void flush()
                 throws IOException

Specified by:

flush in interface Flushable

Overrides:

flush in class OutputStream

Throws:

IOException

close

public final void close()
                 throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class OutputStream

Throws:

IOException

copyToBuffer

private void copyToBuffer(byte[] input,
 int offset,
 int length)

flushBuffer

private void flushBuffer()
                  throws IOException

Compresses and writes out any buffered data. This does nothing if there is no currently buffered data.

Throws:

IOException

writeCompressed

private void writeCompressed(byte[] input,
 int offset,
 int length)
                      throws IOException

Calculates the crc, compresses the data, determines if the compression ratio is acceptable and calls writeBlock(OutputStream, byte[], int, int, boolean, int) to actually write the frame.

Parameters:

input - The byte[] containing the raw data to be compressed.

offset - The offset into input where the data starts.

length - The amount of data in input.

Throws:

IOException

calculateCRC32C

protected int calculateCRC32C(byte[] data,
 int offset,
 int length)

Calculates a CRC32C checksum over the data.

This can be overridden to provider alternative implementations (such as returning 0 if checksums are not desired).

Returns:

The CRC32 checksum.

writeBlock

protected abstract void writeBlock(OutputStream out,
 byte[] data,
 int offset,
 int length,
 boolean compressed,
 int crc32c)
                            throws IOException

Write a frame (block) to out.

Parameters:

out - The OutputStream to write to.

data - The data to write.

offset - The offset in data to start at.

length - The length of data to use.

compressed - Indicates if data is the compressed or raw content. This is based on whether the compression ratio desired is reached.

crc32c - The calculated checksum.

Throws:

IOException