Class CachingBufferPool

java.lang.Object

org.xerial.snappy.pool.CachingBufferPool

All Implemented Interfaces:

BufferPool

public final class CachingBufferPool
extends Object
implements BufferPool

A BufferPool implementation which caches values at fixed sizes.

Pooled instances are held as SoftReference to allow GC if necessary.

The current fixed sizes are calculated as follows:

• Values invalid input: '<' 4KB return 4KB
• 4KB - 32KB to 2KB
• 32KB - 512KB to 16KB
• 512KB - 2MB to 128KB
• 2MB - 16MB to 512KB
• 16MB - 128MB to 4MB
• 128MB - 512MB to 16MB
• 512MB - 1.5 GB to 128MB
• Values > 1.5GB return Integer.MAX_VALUE

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static interface	CachingBufferPool.IntFunction<E>

Field Summary

Fields

Modifier and Type	Field	Description
private static final CachingBufferPool.IntFunction<byte[]>	ARRAY_FUNCTION
private final ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<ByteBuffer>>>	buffers
private final ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<byte[]>>>	bytes
private static final CachingBufferPool.IntFunction<ByteBuffer>	DBB_FUNCTION
private static final CachingBufferPool	INSTANCE

Constructor Summary

Constructors

Modifier	Constructor	Description
private	CachingBufferPool()

Method Summary

Modifier and Type	Method	Description
(package private) static int	adjustSize(int size)
byte[]	allocateArray(int size)	Returns a byte[] of size or greater length.
ByteBuffer	allocateDirect(int size)	Returns a direct ByteBuffer of size or greater capacity.
static BufferPool	getInstance()	Returns instance of CachingBufferPool for using cached buffers.
private static <E> E	getOrCreate(int size, ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<E>>> map, CachingBufferPool.IntFunction<E> creator)
private static <E> ConcurrentLinkedDeque<SoftReference<E>>	optimisticGetEntry(Integer key, ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<E>>> map)
void	releaseArray(byte[] buffer)	Returns instance to pool for potential future reuse.
void	releaseDirect(ByteBuffer buffer)	Returns instance to pool for potential future reuse.
private static <E> void	returnValue(E value, Integer size, ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<E>>> map)
private static int	roundToPowers(int number, int bits)
String	toString()

Methods inherited from class Object

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

Field Details

ARRAY_FUNCTION

private static final CachingBufferPool.IntFunction<byte[]> ARRAY_FUNCTION

DBB_FUNCTION

private static final CachingBufferPool.IntFunction<ByteBuffer> DBB_FUNCTION

INSTANCE

private static final CachingBufferPool INSTANCE

bytes

private final ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<byte[]>>> bytes

buffers

private final ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<ByteBuffer>>> buffers

Constructor Details

CachingBufferPool

private CachingBufferPool()

Method Details

getInstance

public static BufferPool getInstance()

Returns instance of CachingBufferPool for using cached buffers.

Returns:

instance of CachingBufferPool for using cached buffers.

allocateArray

public byte[] allocateArray(int size)

Returns a byte[] of size or greater length.

Specified by:

allocateArray in interface BufferPool

Parameters:

size - The minimum size array required. Must be >= 0.

Returns:

A byte[] with length of at least size.

See Also:

• BufferPool.releaseArray(byte[])

releaseArray

public void releaseArray(byte[] buffer)

Returns instance to pool for potential future reuse.

Must not be returned more than 1 time. Must not be used by caller after return.

Specified by:

releaseArray in interface BufferPool

Parameters:

buffer - Instance to return to pool. Must not be null. Must not be returned more than 1 time. Must not be used by caller after return.

allocateDirect

public ByteBuffer allocateDirect(int size)

Returns a direct ByteBuffer of size or greater capacity.

Specified by:

allocateDirect in interface BufferPool

Parameters:

size - The minimum size buffer required. Must be >= 0.

Returns:

A ByteBuffer of size or greater capacity.

See Also:

• BufferPool.releaseDirect(ByteBuffer)
• ByteBuffer.allocateDirect(int)

releaseDirect

public void releaseDirect(ByteBuffer buffer)

Returns instance to pool for potential future reuse.

Must not be returned more than 1 time. Must not be used by caller after return.

Specified by:

releaseDirect in interface BufferPool

Parameters:

buffer - Instance to return to pool. Must not be null. Must not be returned more than 1 time. Must not be used by caller after return.

getOrCreate

private static <E> E getOrCreate(int size,
 ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<E>>> map,
 CachingBufferPool.IntFunction<E> creator)

adjustSize

static int adjustSize(int size)

roundToPowers

private static int roundToPowers(int number,
 int bits)

optimisticGetEntry

private static <E>
ConcurrentLinkedDeque<SoftReference<E>> optimisticGetEntry(Integer key,
 ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<E>>> map)

returnValue

private static <E> void returnValue(E value,
 Integer size,
 ConcurrentMap<Integer, ConcurrentLinkedDeque<SoftReference<E>>> map)

toString

public String toString()

Overrides:

toString in class Object