de.ruedigermoeller.heapoff

Class FSTByteBufferOffheap

java.lang.Object

de.ruedigermoeller.heapoff.FSTByteBufferOffheap

public class FSTByteBufferOffheap
extends Object

Core offheap implementation. The offheap is initialized with a fixed size. Multi threaded access is granted using createAccess(). Concurrent read operations perform ok'ish (low blocked time), concurrent write is possible but threads probably will be blocked often. Objects added to the heap have to implement Serializable. Use this as a base for higher level collection implementation. In order to get dynamically growing offheaps, consider writing a collection wrapper managing ~1GB slices of FSTByteBufferOffheap objects. Each object can be stored with a 'tag'. When iterating the off heap, it is possible to only read the Tag Object to improve performance. E.g. if you write a lot of bloaty 'Person' objects, you'd like to add {name, firstname} as a tag so you can search the offheap without the need to completely deserialize every object. In general iterating this for search should be replaced by some kind indexing at a higher level if the amount of data is huge. Searching using iteration (Tag's only) processes ~500.000 objects per second (core I7 3 Ghz). You can provide your own Buffer object in order to use this on a memory mapped file. Note there is no 'overwrite' operation. You only can add objects, so there is the need to 'reorganize' a heap buffer from time to time.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FSTByteBufferOffheap.ByteBufferEntry
static class	FSTByteBufferOffheap.GetObjectBufferResult
class	FSTByteBufferOffheap.OffHeapAccess
class	FSTByteBufferOffheap.OffHeapIterator

Field Summary

Fields

Modifier and Type	Field and Description
static int	HEADER_SIZE

Constructor Summary

Constructors

Constructor and Description
FSTByteBufferOffheap(ByteBuffer buffer)
FSTByteBufferOffheap(ByteBuffer buffer, FSTConfiguration conf) Warning: the configuration object passed cannot be shared with another offheap instance or stream !!
FSTByteBufferOffheap(int sizeMB)
FSTByteBufferOffheap(int sizeMB, FSTConfiguration conf) Warning: the configuration object passed cannot be shared with another offheap instance !!

Method Summary

Methods

Modifier and Type	Method and Description
FSTByteBufferOffheap.OffHeapAccess	createAccess()
FSTConfiguration	getConf()
int	getLastPosition()
int	getSize()
FSTByteBufferOffheap.OffHeapIterator	iterator()

Methods inherited from class java.lang.Object

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

Field Detail

HEADER_SIZE

public static final int HEADER_SIZE

See Also:

Constant Field Values

Constructor Detail

FSTByteBufferOffheap

public FSTByteBufferOffheap(int sizeMB)
                     throws IOException

Throws:

IOException

FSTByteBufferOffheap

public FSTByteBufferOffheap(int sizeMB,
                    FSTConfiguration conf)
                     throws IOException

Warning: the configuration object passed cannot be shared with another offheap instance !!

Parameters:

sizeMB -

conf -

Throws:

IOException

FSTByteBufferOffheap

public FSTByteBufferOffheap(ByteBuffer buffer)
                     throws IOException

Throws:

IOException

FSTByteBufferOffheap

public FSTByteBufferOffheap(ByteBuffer buffer,
                    FSTConfiguration conf)
                     throws IOException

Warning: the configuration object passed cannot be shared with another offheap instance or stream !!

Parameters:

buffer -

conf -

Throws:

IOException

Method Detail

getConf

public FSTConfiguration getConf()

createAccess

public FSTByteBufferOffheap.OffHeapAccess createAccess()

Returns:

a heap access object. An OffHeapReadAccess can be used to access the OffHeap from a single thread. In order to access concurrent, each Thread must have its own instance of OffHeapAccess. Try to cache the access Object, as the creation is expensive.

getLastPosition

public int getLastPosition()

getSize

public int getSize()

Returns:

iterator

public FSTByteBufferOffheap.OffHeapIterator iterator()