com.google.appengine.tools.mapreduce.impl.util

Class LevelDbConstants

java.lang.Object

com.google.appengine.tools.mapreduce.impl.util.LevelDbConstants

public final class LevelDbConstants
extends Object

A set of constants needed by LevelDbInputReader and LevelDbOutputWriter.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LevelDbConstants.RecordType An enumerated type that describes the type of the record being stored.

Field Summary

Fields

Modifier and Type	Field and Description
static int	BLOCK_SIZE The size of the blocks records are written in.
static int	CRC_MASK_DELTA CRC Mask.
static int	HEADER_LENGTH Header length in data.

Constructor Summary

Constructors

Constructor and Description
LevelDbConstants()

Method Summary

Methods

Modifier and Type	Method and Description
static long	maskCrc(long crc) Masks the CRC.
static long	unmaskCrc(long maskedCrc) Unmasks the CRC.

Methods inherited from class java.lang.Object

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

Field Detail

BLOCK_SIZE

public static final int BLOCK_SIZE

The size of the blocks records are written in.

See Also:

Constant Field Values

HEADER_LENGTH

public static final int HEADER_LENGTH

Header length in data.

See Also:

Constant Field Values

CRC_MASK_DELTA

public static final int CRC_MASK_DELTA

CRC Mask. Comes from http://leveldb.googlecode.com/svn/trunk/util/crc32c.h

See Also:

Constant Field Values

Constructor Detail

LevelDbConstants

public LevelDbConstants()

Method Detail

maskCrc

public static long maskCrc(long crc)

Masks the CRC. Motivation taken from leveldb: it is problematic to compute the CRC of a string that contains embedded CRCs. Therefore we recommend that CRCs stored somewhere (e.g., in files) should be masked before being stored.

Parameters:

crc - the CRC to mask.

Returns:

the masked CRC.

unmaskCrc

public static long unmaskCrc(long maskedCrc)

Unmasks the CRC.

Parameters:

maskedCrc - a masked CRC.

Returns:

an unmasked CRC.