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The official Couchbase JVM Core IO Library
/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.couchbase.client.core.deps.org.jctools.util;
import static com.couchbase.client.core.deps.org.jctools.util.UnsafeAccess.UNSAFE;
@InternalAPI
public final class UnsafeRefArrayAccess
{
public static final long REF_ARRAY_BASE;
public static final int REF_ELEMENT_SHIFT;
static
{
final int scale = UnsafeAccess.UNSAFE.arrayIndexScale(Object[].class);
if (4 == scale)
{
REF_ELEMENT_SHIFT = 2;
}
else if (8 == scale)
{
REF_ELEMENT_SHIFT = 3;
}
else
{
throw new IllegalStateException("Unknown pointer size: " + scale);
}
REF_ARRAY_BASE = UnsafeAccess.UNSAFE.arrayBaseOffset(Object[].class);
}
/**
* A plain store (no ordering/fences) of an element to a given offset
*
* @param buffer this.buffer
* @param offset computed via {@link UnsafeRefArrayAccess#calcRefElementOffset(long)}
* @param e an orderly kitty
*/
public static void spRefElement(E[] buffer, long offset, E e)
{
UNSAFE.putObject(buffer, offset, e);
}
/**
* An ordered store of an element to a given offset
*
* @param buffer this.buffer
* @param offset computed via {@link UnsafeRefArrayAccess#calcCircularRefElementOffset}
* @param e an orderly kitty
*/
public static void soRefElement(E[] buffer, long offset, E e)
{
UNSAFE.putOrderedObject(buffer, offset, e);
}
/**
* A plain load (no ordering/fences) of an element from a given offset.
*
* @param buffer this.buffer
* @param offset computed via {@link UnsafeRefArrayAccess#calcRefElementOffset(long)}
* @return the element at the offset
*/
@SuppressWarnings("unchecked")
public static E lpRefElement(E[] buffer, long offset)
{
return (E) UNSAFE.getObject(buffer, offset);
}
/**
* A volatile load of an element from a given offset.
*
* @param buffer this.buffer
* @param offset computed via {@link UnsafeRefArrayAccess#calcRefElementOffset(long)}
* @return the element at the offset
*/
@SuppressWarnings("unchecked")
public static E lvRefElement(E[] buffer, long offset)
{
return (E) UNSAFE.getObjectVolatile(buffer, offset);
}
/**
* @param index desirable element index
* @return the offset in bytes within the array for a given index
*/
public static long calcRefElementOffset(long index)
{
return REF_ARRAY_BASE + (index << REF_ELEMENT_SHIFT);
}
/**
* Note: circular arrays are assumed a power of 2 in length and the `mask` is (length - 1).
*
* @param index desirable element index
* @param mask (length - 1)
* @return the offset in bytes within the circular array for a given index
*/
public static long calcCircularRefElementOffset(long index, long mask)
{
return REF_ARRAY_BASE + ((index & mask) << REF_ELEMENT_SHIFT);
}
/**
* This makes for an easier time generating the atomic queues, and removes some warnings.
*/
@SuppressWarnings("unchecked")
public static E[] allocateRefArray(int capacity)
{
return (E[]) new Object[capacity];
}
}