org.agrona.concurrent

Class RecordBuffer

java.lang.Object

org.agrona.concurrent.RecordBuffer

public class RecordBuffer
extends java.lang.Object

A record buffer is an off-heap buffer with a series of records and a header that can be written to or read from multiple threads.

The buffer has a position field at the start, then a variable sized header, then a series of records. Each record has a status tag and a key.

NB: its possible for an element to be overwritten as you're reading Out of the buffer, take care.

  +----------------------------+
  |           Header           |
  |                           ...
  +----------------------------+
  |        Position Field      |
  +----------------------------+
  |        Status Field 0      |
  +----------------------------+
  |         Key Field 0        |
  +----------------------------+
  |           Record 0         |
  |                           ...
  +----------------------------+
  |        Status Field 1      |
  +----------------------------+
  |         Key Field 1        |
  +----------------------------+
  |           Record 1         |
  |                           ...
  +----------------------------+
  |                           ...
 

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	RecordBuffer.RecordHandler Callback interface for reading elements out of the buffer.
static interface	RecordBuffer.RecordWriter Interface for safely writing to the buffer.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DID_NOT_CLAIM_RECORD

Constructor Summary

Constructors

Constructor and Description
RecordBuffer(AtomicBuffer buffer, int headerSize, int recordSize)

Method Summary

Modifier and Type	Method and Description
int	claimRecord(int key) Claim a record in the buffer.
void	commit(int claimedOffset) Commit a claimed record into the buffer.
void	forEach(RecordBuffer.RecordHandler handler) Read each record out of the buffer in turn.
int	get(int key) Search for the first record with the specified key.
void	initialise() Initialise the buffer if you're the first thread to begin writing
boolean	isInitialised() Check if the buffer has been initialised.
boolean	withRecord(int key, RecordBuffer.RecordWriter writer) High level and safe way of writing a record to the buffer.

Methods inherited from class java.lang.Object

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

Field Detail

DID_NOT_CLAIM_RECORD

public static final int DID_NOT_CLAIM_RECORD

See Also:

Constant Field Values

Constructor Detail

RecordBuffer

public RecordBuffer(AtomicBuffer buffer,
                    int headerSize,
                    int recordSize)

Method Detail

initialise

public void initialise()

Initialise the buffer if you're the first thread to begin writing

isInitialised

public boolean isInitialised()

Check if the buffer has been initialised.

Returns:

true if the buffer has been initialised.

forEach

public void forEach(RecordBuffer.RecordHandler handler)

Read each record out of the buffer in turn.

Parameters:

handler - the handler is called once for each record in the buffer.

get

public int get(int key)

Search for the first record with the specified key.

Parameters:

key - the key to search for.

Returns:

the offset of the start of the record within the buffer or DID_NOT_CLAIM_RECORD if no record with the specified key.

withRecord

public boolean withRecord(int key,
                          RecordBuffer.RecordWriter writer)

High level and safe way of writing a record to the buffer.

Parameters:

key - the key to associate the record with

writer - the callback which is passed the record to write.

Returns:

whether the write succeeded or not.

claimRecord

public int claimRecord(int key)

Claim a record in the buffer. Each record has a unique key.

Parameters:

key - the key to claim the record with.

Returns:

the offset at which record was claimed or DID_NOT_CLAIM_RECORD if the claim failed.

See Also:

commit(int)

commit

public void commit(int claimedOffset)

Commit a claimed record into the buffer.

Parameters:

claimedOffset - the offset of the record to commit.

See Also:

claimRecord(int)