kafka.utils.checksum

Interface ChecksumWithInPlaceUpdate

All Superinterfaces:

Checksum

All Known Implementing Classes:

Adler32WithInPlaceUpdate

public interface ChecksumWithInPlaceUpdate
extends Checksum

ChecksumWithInPlaceUpdate is an extension of the Checksum interface with provision of additional method `append` and `inPlaceUpdate`. Typically, checksum packages do not provide optimal support for in place update kind of operations, even though certain algorithms (e.g., Adler32) support these operations. Using this interface we are including inPlaceUpdate and append operations as first class methods. `restore` method is to initialize the checksum and length values from previously calculated values to avoid re-computation. If a certain algorithm doesn't support these operations, they can continue implementing a sub-optimal or no-op (can raise exception) for these methods. NOTE: This additional inPlaceUpdate method are not part of the existing checksum interface which is implemented by various checksum classes including Adler32.

Method Summary

Modifier and Type	Method and Description
void	append(ByteBuffer update) Appends a buffer at the end and updates the checksum
long	length() Return the length of file till which the checksum has been calculated.
void	restore(long checksum, long length) Restores the state to a previously calculated checksum value and length for a given file.
void	update(ByteBuffer updated, ByteBuffer previous, long offset) In-place update a buffer at offset and update the checksum.

Methods inherited from interface java.util.zip.Checksum

getValue, reset, update, update

Method Detail

append

void append(ByteBuffer update)

Appends a buffer at the end and updates the checksum

Parameters:

update - the append buffer

update

void update(ByteBuffer updated,
            ByteBuffer previous,
            long offset)

In-place update a buffer at offset and update the checksum. This requires the buffer previous and the new updated buffer to be of the same length.

Parameters:

updated - the buffer containing the updated data from offset

previous - the buffer containing the previous data from offset

offset - the position from which the data is to be updated

restore

void restore(long checksum,
             long length)

Restores the state to a previously calculated checksum value and length for a given file. This is useful when this information is present, for example when a file is being reopened we can reuse the checksum information from the time it was previously opened.

Parameters:

checksum - the checksum value to be restored

length - the total length of the file till which checksum was calculated to be restored

length

long length()

Return the length of file till which the checksum has been calculated.

Returns:

the length of the file till which checksum has been calculated