org.apache.hadoop.util
Class DataChecksum

java.lang.Object
  org.apache.hadoop.util.DataChecksum

All Implemented Interfaces:

Checksum

public class DataChecksum
extends Object
implements Checksum

This class provides inteface and utilities for processing checksums for DFS data transfers.

Field Summary

static int	CHECKSUM_CRC32
static int	CHECKSUM_NULL
static int	HEADER_LEN
static int	SIZE_OF_INTEGER

Method Summary

boolean	compare(byte[] buf, int offset) Compares the checksum located at buf[offset] with the current checksum.
int	getBytesPerChecksum()
static int	getChecksumHeaderSize()
int	getChecksumSize()
int	getChecksumType()
byte[]	getHeader()
int	getNumBytesInSum()
long	getValue()
static DataChecksum	newDataChecksum(byte[] bytes, int offset) Creates a DataChecksum from HEADER_LEN bytes from arr[offset].
static DataChecksum	newDataChecksum(DataInputStream in) This constructucts a DataChecksum by reading HEADER_LEN bytes from input stream in
static DataChecksum	newDataChecksum(int type, int bytesPerChecksum)
void	reset()
void	update(byte[] b, int off, int len)
void	update(int b)
void	writeHeader(DataOutputStream out) Writes the checksum header to the output stream out.
int	writeValue(byte[] buf, int offset, boolean reset) Writes the current checksum to a buffer.
int	writeValue(DataOutputStream out, boolean reset) Writes the current checksum to the stream.

Methods inherited from class java.lang.Object

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

Field Detail

HEADER_LEN

public static final int HEADER_LEN

See Also:

Constant Field Values

CHECKSUM_NULL

public static final int CHECKSUM_NULL

See Also:

Constant Field Values

CHECKSUM_CRC32

public static final int CHECKSUM_CRC32

See Also:

Constant Field Values

SIZE_OF_INTEGER

public static final int SIZE_OF_INTEGER

See Also:

Constant Field Values

Method Detail

newDataChecksum

public static DataChecksum newDataChecksum(int type,
                                           int bytesPerChecksum)

newDataChecksum

public static DataChecksum newDataChecksum(byte[] bytes,
                                           int offset)

Creates a DataChecksum from HEADER_LEN bytes from arr[offset].

Returns:

DataChecksum of the type in the array or null in case of an error.

newDataChecksum

public static DataChecksum newDataChecksum(DataInputStream in)
                                    throws IOException

This constructucts a DataChecksum by reading HEADER_LEN bytes from input stream in

Throws:

IOException

writeHeader

public void writeHeader(DataOutputStream out)
                 throws IOException

Writes the checksum header to the output stream out.

Throws:

IOException

getHeader

public byte[] getHeader()

writeValue

public int writeValue(DataOutputStream out,
                      boolean reset)
               throws IOException

Writes the current checksum to the stream. If reset is true, then resets the checksum.

Returns:

number of bytes written. Will be equal to getChecksumSize();

Throws:

IOException

writeValue

public int writeValue(byte[] buf,
                      int offset,
                      boolean reset)
               throws IOException

Writes the current checksum to a buffer. If reset is true, then resets the checksum.

Returns:

number of bytes written. Will be equal to getChecksumSize();

Throws:

IOException

compare

public boolean compare(byte[] buf,
                       int offset)

Compares the checksum located at buf[offset] with the current checksum.

Returns:

true if the checksum matches and false otherwise.

getChecksumType

public int getChecksumType()

getChecksumSize

public int getChecksumSize()

getBytesPerChecksum

public int getBytesPerChecksum()

getNumBytesInSum

public int getNumBytesInSum()

getChecksumHeaderSize

public static int getChecksumHeaderSize()

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 off,
                   int len)

Specified by:

update in interface Checksum

update

public void update(int b)

Specified by:

update in interface Checksum