Package org.apache.hadoop.util

Class CrcUtil

java.lang.Object

org.apache.hadoop.util.CrcUtil

@LimitedPrivate({"Common","HDFS","MapReduce","Yarn"})
@Unstable
public final class CrcUtil
extends java.lang.Object

This class provides utilities for working with CRCs.

Field Summary

Fields

Modifier and Type	Field	Description
static int	CASTAGNOLI_POLYNOMIAL
static int	GZIP_POLYNOMIAL
static int	MULTIPLICATIVE_IDENTITY

Method Summary

Modifier and Type	Method	Description
static int	compose(int crcA, int crcB, long lengthB, int mod)	compose.
static int	composeWithMonomial(int crcA, int crcB, int monomial, int mod)	composeWithMonomial.
static int	getMonomial(long lengthBytes, int mod)	Compute x^(lengthBytes * 8) mod mod, where mod is in "reversed" (little-endian) format such that mod & 1 represents x^31 and has an implicit term x^32.
static byte[]	intToBytes(int value)
static int	readInt(byte[] buf, int offset)	Reads 4-byte big-endian int value from buf starting at offset.
static java.lang.String	toMultiCrcString(byte[] bytes)	For use with debug statements; verifies bytes.length on creation, expecting it to be divisible by CRC byte size, and returns a list of hex formatted values.
static java.lang.String	toSingleCrcString(byte[] bytes)	For use with debug statements; verifies bytes.length on creation, expecting it to represent exactly one CRC, and returns a hex formatted value.
static void	writeInt(byte[] buf, int offset, int value)	Writes big-endian representation of value into buf starting at offset.

Methods inherited from class java.lang.Object

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

Field Detail

MULTIPLICATIVE_IDENTITY

public static final int MULTIPLICATIVE_IDENTITY

See Also:

Constant Field Values

GZIP_POLYNOMIAL

public static final int GZIP_POLYNOMIAL

See Also:

Constant Field Values

CASTAGNOLI_POLYNOMIAL

public static final int CASTAGNOLI_POLYNOMIAL

See Also:

Constant Field Values

Method Detail

getMonomial

public static int getMonomial(long lengthBytes,
                              int mod)

Compute x^(lengthBytes * 8) mod mod, where mod is in "reversed" (little-endian) format such that mod & 1 represents x^31 and has an implicit term x^32.

Parameters:

lengthBytes - lengthBytes.

mod - mod.

Returns:

monomial.

composeWithMonomial

public static int composeWithMonomial(int crcA,
                                      int crcB,
                                      int monomial,
                                      int mod)

composeWithMonomial.

Parameters:

crcA - crcA.

crcB - crcB.

monomial - Precomputed x^(lengthBInBytes * 8) mod mod

mod - mod.

Returns:

compose with monomial.

compose

public static int compose(int crcA,
                          int crcB,
                          long lengthB,
                          int mod)

compose.

Parameters:

crcA - crcA.

crcB - crcB.

lengthB - length of content corresponding to crcB, in bytes.

mod - mod.

Returns:

compose result.

intToBytes

public static byte[] intToBytes(int value)

Parameters:

value - value.

Returns:

4-byte array holding the big-endian representation of value.

writeInt

public static void writeInt(byte[] buf,
                            int offset,
                            int value)
                     throws java.io.IOException

Writes big-endian representation of value into buf starting at offset. buf.length must be greater than or equal to offset + 4.

Parameters:

buf - buf size.

offset - offset.

value - value.

Throws:

java.io.IOException - raised on errors performing I/O.

readInt

public static int readInt(byte[] buf,
                          int offset)
                   throws java.io.IOException

Reads 4-byte big-endian int value from buf starting at offset. buf.length must be greater than or equal to offset + 4.

Parameters:

offset - offset.

buf - buf.

Returns:

int.

Throws:

java.io.IOException - raised on errors performing I/O.

toSingleCrcString

public static java.lang.String toSingleCrcString(byte[] bytes)
                                          throws java.io.IOException

For use with debug statements; verifies bytes.length on creation, expecting it to represent exactly one CRC, and returns a hex formatted value.

Parameters:

bytes - bytes.

Returns:

a list of hex formatted values.

Throws:

java.io.IOException - raised on errors performing I/O.

toMultiCrcString

public static java.lang.String toMultiCrcString(byte[] bytes)
                                         throws java.io.IOException

For use with debug statements; verifies bytes.length on creation, expecting it to be divisible by CRC byte size, and returns a list of hex formatted values.

Parameters:

bytes - bytes.

Returns:

a list of hex formatted values.

Throws:

java.io.IOException - raised on errors performing I/O.