org.jctools.util

Class UnsafeRefArrayAccess

java.lang.Object

org.jctools.util.UnsafeRefArrayAccess

public final class UnsafeRefArrayAccess
extends Object

A concurrent access enabling class used by circular array based queues this class exposes an offset computation method along with differently memory fenced load/store methods into the underlying array. The class is pre-padded and the array is padded on either side to help with False sharing prvention. It is expected theat subclasses handle post padding.

Offset calculation is separate from access to enable the reuse of a give compute offset.

Load/Store methods using a buffer parameter are provided to allow the prevention of final field reload after a LoadLoad barrier.

Author:

nitsanw

Field Summary

Fields

Modifier and Type	Field and Description
static long	REF_ARRAY_BASE
static int	REF_ELEMENT_SHIFT

Constructor Summary

Constructors

Constructor and Description
UnsafeRefArrayAccess()

Method Summary

Modifier and Type	Method and Description
static long	calcElementOffset(long index)
static <E> E	lpElement(E[] buffer, long offset) A plain load (no ordering/fences) of an element from a given offset.
static <E> E	lvElement(E[] buffer, long offset) A volatile load (load + LoadLoad barrier) of an element from a given offset.
static <E> void	soElement(E[] buffer, long offset, E e) An ordered store(store + StoreStore barrier) of an element to a given offset
static <E> void	spElement(E[] buffer, long offset, E e) A plain store (no ordering/fences) of an element to a given offset

Methods inherited from class java.lang.Object

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

Field Detail

REF_ARRAY_BASE

public static final long REF_ARRAY_BASE

REF_ELEMENT_SHIFT

public static final int REF_ELEMENT_SHIFT

Constructor Detail

UnsafeRefArrayAccess

public UnsafeRefArrayAccess()

Method Detail

spElement

public static <E> void spElement(E[] buffer,
                                 long offset,
                                 E e)

A plain store (no ordering/fences) of an element to a given offset

Parameters:

buffer - this.buffer

offset - computed via calcElementOffset(long)

e - an orderly kitty

soElement

public static <E> void soElement(E[] buffer,
                                 long offset,
                                 E e)

An ordered store(store + StoreStore barrier) of an element to a given offset

Parameters:

buffer - this.buffer

offset - computed via calcElementOffset(long)

e - an orderly kitty

lpElement

public static <E> E lpElement(E[] buffer,
                              long offset)

A plain load (no ordering/fences) of an element from a given offset.

Parameters:

buffer - this.buffer

offset - computed via calcElementOffset(long)

Returns:

the element at the offset

lvElement

public static <E> E lvElement(E[] buffer,
                              long offset)

A volatile load (load + LoadLoad barrier) of an element from a given offset.

Parameters:

buffer - this.buffer

offset - computed via calcElementOffset(long)

Returns:

the element at the offset

calcElementOffset

public static long calcElementOffset(long index)

Parameters:

index - desirable element index

Returns:

the offset in bytes within the array for a given index.