net.openhft.chronicle.hash.hashing.Accesses Maven / Gradle / Ivy

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/*
 *     Copyright (C) 2015  higherfrequencytrading.com
 *
 *     This program is free software: you can redistribute it and/or modify
 *     it under the terms of the GNU Lesser General Public License as published by
 *     the Free Software Foundation, either version 3 of the License.
 *
 *     This program is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU Lesser General Public License for more details.
 *
 *     You should have received a copy of the GNU Lesser General Public License
 *     along with this program.  If not, see .
 */

package net.openhft.chronicle.hash.hashing;

import net.openhft.lang.io.Bytes;

import java.nio.ByteBuffer;

/**
 * Static methods returning useful {@link Access} implementations.
 */
public final class Accesses {

    private Accesses() {
    }

    /**
     * Returns the {@code Access} delegating {@code getXXX(input, offset)} methods to {@code
     * sun.misc.Unsafe.getXXX(input, offset)}.
     * 
     * 
Usage example: 
{@code
     * class Pair {
     *     long first, second;
     * 
     *     static final long pairDataOffset =
     *         theUnsafe.objectFieldOffset(Pair.class.getDeclaredField("first"));
     * 

     *     static long hashPair(Pair pair, LongHashFunction hashFunction) {
     *         return hashFunction.hash(pair, Accesses.unsafe(), pairDataOffset, 16L);
     *     }
     * }}
     * 
     * {@code null} is a valid input, on accepting {@code null} {@code Unsafe} just interprets
     * the given offset as a wild memory address.
     *
     * @param  the type of objects to access
     * @return the unsafe memory {@code Access}
     */
    public static  Access unsafe() {
        return (Access) UnsafeAccess.INSTANCE;
    }

    /**
     * Returns the {@code Access} to any {@link ByteBuffer}.
     *
     * @return the {@code Access} to {@link ByteBuffer}s
     */
    public static Access toByteBuffer() {
        return ByteBufferAccess.INSTANCE;
    }

    public static Access toBytes() {
        return BytesAccess.INSTANCE;
    }
}