net.openhft.chronicle.wire

Interface Sequence

public interface Sequence

Defines a contract for mapping a write position (typically in a persistent store such as Chronicle Queue) to a logical sequence number, and vice versa. This is crucial for systems that need to assign ordered sequence numbers to messages or events written at potentially non-contiguous positions.

Field Summary

Fields

Modifier and Type	Field and Description
static long	NOT_FOUND Returned by getSequence(long) when a sequence number cannot be found for the given position and retrying is unlikely to succeed.
static long	NOT_FOUND_RETRY Returned by getSequence(long) when a sequence number cannot be found for the given position but the operation may succeed if retried.

Method Summary

Modifier and Type	Method and Description
long	getSequence(long forWritePosition) gets the sequence for a writePosition
void	setSequence(long sequence, long position) Sets the sequence number for the given write position.
long	toIndex(long headerNumber, long sequence) Combines a headerNumber (such as a cycle count) and a sequence within that header into a single index value.
long	toSequenceNumber(long index) Extracts the lower-order sequence number from an index previously created by toIndex(long, long).

Field Detail

NOT_FOUND_RETRY

static final long NOT_FOUND_RETRY

Returned by getSequence(long) when a sequence number cannot be found for the given position but the operation may succeed if retried.

See Also:

Constant Field Values

NOT_FOUND

static final long NOT_FOUND

Returned by getSequence(long) when a sequence number cannot be found for the given position and retrying is unlikely to succeed.

See Also:

Constant Field Values

Method Detail

getSequence

long getSequence(long forWritePosition)

gets the sequence for a writePosition

This method will only return a valid sequence number of the write position if the write position is the last write position in the queue. YOU CAN NOT USE THIS METHOD TO LOOK UP RANDOM SEQUENCES FOR ANY WRITE POSITION. NOT_FOUND_RETRY will be return if a sequence number can not be found ( so retry ) or NOT_FOUND if you should not retry

Parameters:

forWritePosition - the last write position, expected to be the end of queue

Returns:

NOT_FOUND_RETRY if the sequence for this write position can not be found (you can retry), or NOT_FOUND if it can't be found and there is no point in retrying

setSequence

void setSequence(long sequence,
                 long position)

Sets the sequence number for the given write position.

Parameters:

sequence - The sequence number to associate with the position.

position - The write position for which the sequence number should be recorded.

toIndex

long toIndex(long headerNumber,
             long sequence)

Combines a headerNumber (such as a cycle count) and a sequence within that header into a single index value.

Parameters:

headerNumber - The higher-order part of the index, for example a cycle number.

sequence - The lower-order sequence number within the header.

Returns:

A combined index representing the header and sequence.

toSequenceNumber

long toSequenceNumber(long index)

Extracts the lower-order sequence number from an index previously created by toIndex(long, long).

Parameters:

index - The combined index.

Returns:

The sequence number extracted from the index.