Class PhantomReferenceLimitedPageSource

java.lang.Object

org.terracotta.offheapstore.paging.PhantomReferenceLimitedPageSource

All Implemented Interfaces:

PageSource

public class PhantomReferenceLimitedPageSource
extends Object
implements PageSource

A PhantomReference based limited byte buffer source.

This buffer source tracks 'freeing' of allocated byte buffers using phantom references to the allocated buffers and an associated reference queue. An AtomicLong is then used to track number of available bytes for allocation.

Field Summary

Fields

Modifier and Type	Field	Description
private final ReferenceQueue<ByteBuffer>	allocatedBuffers
private final Map<PhantomReference<ByteBuffer>, Integer>	bufferSizes
private final AtomicLong	max

Constructor Summary

Constructors

Constructor	Description
PhantomReferenceLimitedPageSource(long max)	Create a source that will allocate at most max bytes.

Method Summary

Modifier and Type	Method	Description
Page	allocate(int size, boolean thief, boolean victim, OffHeapStorageArea owner)	Allocates a byte buffer of the given size.
void	free(Page buffer)	Frees the supplied buffer.
private void	processQueue()
String	toString()

Methods inherited from class Object

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

Field Details

allocatedBuffers

private final ReferenceQueue<ByteBuffer> allocatedBuffers

bufferSizes

private final Map<PhantomReference<ByteBuffer>, Integer> bufferSizes

max

private final AtomicLong max

Constructor Details

PhantomReferenceLimitedPageSource

public PhantomReferenceLimitedPageSource(long max)

Create a source that will allocate at most max bytes.

Parameters:

max - the maximum total size of all available buffers

Method Details

allocate

public Page allocate(int size,
 boolean thief,
 boolean victim,
 OffHeapStorageArea owner)

Allocates a byte buffer of the given size.

This BufferSource places no restrictions on the requested size of the buffer.

Specified by:

allocate in interface PageSource

Parameters:

size - size of page to allocate

thief - true if the allocation can steal space from victims

victim - true if the allocated page should be eligible for stealing

owner - owner from which subsequent steal should occur

Returns:

an allocated page, or null in the case of failure

free

public void free(Page buffer)

Frees the supplied buffer.

This implementation is a no-op, no validation of the supplied buffer is attempted, as freeing of allocated buffers is monitored via phantom references.

Specified by:

free in interface PageSource

processQueue

private void processQueue()

toString

public String toString()

Overrides:

toString in class Object