Package org.apache.lucene.util.compress

Class LZ4

java.lang.Object

org.apache.lucene.util.compress.LZ4

public final class LZ4
extends java.lang.Object

LZ4 compression and decompression routines. https://github.com/lz4/lz4/tree/dev/lib http://fastcompression.blogspot.fr/p/lz4.html The high-compression option is a simpler version of the one of the original algorithm, and only retains a better hash table that remembers about more occurrences of a previous 4-bytes sequence, and removes all the logic about handling of the case when overlapping matches are found.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LZ4.FastCompressionHashTable	Simple lossy LZ4.HashTable that only stores the last ocurrence for each hash on 2^14 bytes of memory.
(package private) static class	LZ4.HashTable	A record of previous occurrences of sequences of 4 bytes.
static class	LZ4.HighCompressionHashTable	A higher-precision LZ4.HashTable.

Field Summary

Fields

Modifier and Type	Field	Description
(package private) static int	HASH_LOG_HC
(package private) static int	HASH_TABLE_SIZE_HC
(package private) static int	LAST_LITERALS
(package private) static int	MAX_DISTANCE
(package private) static int	MEMORY_USAGE
(package private) static int	MIN_MATCH
(package private) static int	OPTIMAL_ML

Constructor Summary

Constructors

Modifier	Constructor	Description
private	LZ4()

Method Summary

Modifier and Type	Method	Description
private static int	commonBytes(byte[] b, int o1, int o2, int limit)
static void	compress(byte[] bytes, int off, int len, DataOutput out, LZ4.HashTable ht)	Compress bytes[off:off+len] into out using at most 16KB of memory.
static int	decompress(DataInput compressed, int decompressedLen, byte[] dest)	Decompress at least decompressedLen bytes into dest[dOff:].
private static void	encodeLastLiterals(byte[] bytes, int anchor, int literalLen, DataOutput out)
private static void	encodeLen(int l, DataOutput out)
private static void	encodeLiterals(byte[] bytes, int token, int anchor, int literalLen, DataOutput out)
private static void	encodeSequence(byte[] bytes, int anchor, int matchRef, int matchOff, int matchLen, DataOutput out)
private static int	hash(int i, int hashBits)
private static int	hashHC(int i)
private static int	readInt(byte[] buf, int i)

Methods inherited from class java.lang.Object

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

Field Detail

MEMORY_USAGE

static final int MEMORY_USAGE

See Also:

Constant Field Values

MIN_MATCH

static final int MIN_MATCH

See Also:

Constant Field Values

MAX_DISTANCE

static final int MAX_DISTANCE

See Also:

Constant Field Values

LAST_LITERALS

static final int LAST_LITERALS

See Also:

Constant Field Values

HASH_LOG_HC

static final int HASH_LOG_HC

See Also:

Constant Field Values

HASH_TABLE_SIZE_HC

static final int HASH_TABLE_SIZE_HC

See Also:

Constant Field Values

OPTIMAL_ML

static final int OPTIMAL_ML

See Also:

Constant Field Values

Constructor Detail

LZ4

private LZ4()

Method Detail

hash

private static int hash(int i,
                        int hashBits)

hashHC

private static int hashHC(int i)

readInt

private static int readInt(byte[] buf,
                           int i)

commonBytes

private static int commonBytes(byte[] b,
                               int o1,
                               int o2,
                               int limit)

decompress

public static int decompress(DataInput compressed,
                             int decompressedLen,
                             byte[] dest)
                      throws java.io.IOException

Decompress at least decompressedLen bytes into dest[dOff:]. Please note that dest must be large enough to be able to hold all decompressed data (meaning that you need to know the total decompressed length).

Throws:

java.io.IOException

encodeLen

private static void encodeLen(int l,
                              DataOutput out)
                       throws java.io.IOException

Throws:

java.io.IOException

encodeLiterals

private static void encodeLiterals(byte[] bytes,
                                   int token,
                                   int anchor,
                                   int literalLen,
                                   DataOutput out)
                            throws java.io.IOException

Throws:

java.io.IOException

encodeLastLiterals

private static void encodeLastLiterals(byte[] bytes,
                                       int anchor,
                                       int literalLen,
                                       DataOutput out)
                                throws java.io.IOException

Throws:

java.io.IOException

encodeSequence

private static void encodeSequence(byte[] bytes,
                                   int anchor,
                                   int matchRef,
                                   int matchOff,
                                   int matchLen,
                                   DataOutput out)
                            throws java.io.IOException

Throws:

java.io.IOException

compress

public static void compress(byte[] bytes,
                            int off,
                            int len,
                            DataOutput out,
                            LZ4.HashTable ht)
                     throws java.io.IOException

Compress bytes[off:off+len] into out using at most 16KB of memory. ht shouldn't be shared across threads but can safely be reused.

Throws:

java.io.IOException