Package org.apache.hadoop.util

Class PureJavaCrc32

java.lang.Object

org.apache.hadoop.util.PureJavaCrc32

All Implemented Interfaces:

Checksum

@Public
@Stable
public class PureJavaCrc32
extends Object
implements Checksum

A pure-java implementation of the CRC32 checksum that uses the same polynomial as the built-in native CRC32. This is to avoid the JNI overhead for certain uses of Checksumming where many small pieces of data are checksummed in succession. The current version is ~10x to 1.8x as fast as Sun's native java.util.zip.CRC32 in Java 1.6

See Also:

• CRC32

Constructor Summary

Constructors

Constructor	Description
PureJavaCrc32()	Create a new PureJavaCrc32 object.

Method Summary

Modifier and Type	Method	Description
long	getValue()
static int	mod(long x)	Compute x mod p, where p is the CRC32 polynomial.
void	reset()
void	update(byte[] b, int offset, int len)
final void	update(int b)

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.zip.Checksum

update, update

Constructor Details

PureJavaCrc32

public PureJavaCrc32()

Create a new PureJavaCrc32 object.

Method Details

getValue

public long getValue()

Specified by:

getValue in interface Checksum

reset

public void reset()

Specified by:

reset in interface Checksum

update

public void update(byte[] b,
 int offset,
 int len)

Specified by:

update in interface Checksum

mod

public static int mod(long x)

Compute x mod p, where p is the CRC32 polynomial.

Parameters:

x - the input value

Returns:

x mod p

update

public final void update(int b)

Specified by:

update in interface Checksum