Class UnsafeChunkDecoder

java.lang.Object

com.ning.compress.lzf.ChunkDecoder

com.ning.compress.lzf.impl.UnsafeChunkDecoder

public class UnsafeChunkDecoder
extends ChunkDecoder

Highly optimized ChunkDecoder implementation that uses Sun JDK's Unsafe class (which may be included by other JDK's as well; IBM's apparently does).

Credits for the idea go to Dain Sundstrom, who kindly suggested this use, and is all-around great source for optimization tips and tricks. Big thanks also to LZ4-java developers, whose stellar performance made me go back and see what more I can do to optimize this code!

Field Summary

Fields

Modifier and Type	Field	Description
private static final long	BYTE_ARRAY_OFFSET
private static final sun.misc.Unsafe	unsafe

Fields inherited from class ChunkDecoder

BYTE_NULL, HEADER_BYTES

Constructor Summary

Constructors

Constructor	Description
UnsafeChunkDecoder()

Method Summary

Modifier and Type	Method	Description
private static final void	copyLong(byte[] buffer, int inputIndex, int outputIndex, int length, int outputEnd8)
private static final void	copyLongTail(byte[] buffer, int inputIndex, int outputIndex, int length)
private static final int	copyOverlappingLong(byte[] out, int outPos, int offset, int len)
private final int	copyOverlappingShort(byte[] out, int outPos, int offset, int len)
private static final void	copyUpTo32(byte[] in, int inputIndex, byte[] out, int outputIndex, int lengthMinusOne)
private static final void	copyUpTo32(byte[] buffer, int inputIndex, int outputIndex, int lengthMinusOne)
final void	decodeChunk(byte[] in, int inPos, byte[] out, int outPos, int outEnd)	Main decode method for individual chunks.
final int	decodeChunk(InputStream is, byte[] inputBuffer, byte[] outputBuffer)	Main decode from a stream.
int	skipOrDecodeChunk(InputStream is, byte[] inputBuffer, byte[] outputBuffer, long maxToSkip)

Methods inherited from class ChunkDecoder

_reportArrayOverflow, _reportCorruptHeader, calculateUncompressedSize, decode, decode, decode, decode, readFully, readHeader, skipFully, uint16

Methods inherited from class Object

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

Field Details

unsafe

private static final sun.misc.Unsafe unsafe

BYTE_ARRAY_OFFSET

private static final long BYTE_ARRAY_OFFSET

Constructor Details

UnsafeChunkDecoder

public UnsafeChunkDecoder()

Method Details

decodeChunk

public final int decodeChunk(InputStream is,
 byte[] inputBuffer,
 byte[] outputBuffer)
                      throws IOException

Description copied from class: ChunkDecoder

Main decode from a stream. Decompressed bytes are placed in the outputBuffer, inputBuffer is a "scratch-area".

Specified by:

decodeChunk in class ChunkDecoder

Parameters:

is - An input stream of LZF compressed bytes

inputBuffer - A byte array used as a scratch area.

outputBuffer - A byte array in which the result is returned

Returns:

The number of bytes placed in the outputBuffer.

Throws:

IOException

decodeChunk

public final void decodeChunk(byte[] in,
 int inPos,
 byte[] out,
 int outPos,
 int outEnd)
                       throws LZFException

Description copied from class: ChunkDecoder

Main decode method for individual chunks.

Specified by:

decodeChunk in class ChunkDecoder

Throws:

LZFException

skipOrDecodeChunk

public int skipOrDecodeChunk(InputStream is,
 byte[] inputBuffer,
 byte[] outputBuffer,
 long maxToSkip)
                      throws IOException

Specified by:

skipOrDecodeChunk in class ChunkDecoder

Returns:

If positive number, number of bytes skipped; if -1, end-of-stream was reached; otherwise, amount of content decoded (using formula of returnValue = -(decodedAmount + 2))

Throws:

IOException

copyOverlappingShort

private final int copyOverlappingShort(byte[] out,
 int outPos,
 int offset,
 int len)

copyOverlappingLong

private static final int copyOverlappingLong(byte[] out,
 int outPos,
 int offset,
 int len)

copyUpTo32

private static final void copyUpTo32(byte[] buffer,
 int inputIndex,
 int outputIndex,
 int lengthMinusOne)

copyUpTo32

private static final void copyUpTo32(byte[] in,
 int inputIndex,
 byte[] out,
 int outputIndex,
 int lengthMinusOne)

copyLong

private static final void copyLong(byte[] buffer,
 int inputIndex,
 int outputIndex,
 int length,
 int outputEnd8)

copyLongTail

private static final void copyLongTail(byte[] buffer,
 int inputIndex,
 int outputIndex,
 int length)