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/*
 * Copyright 2015 Higher Frequency Trading
 *
 *  http://www.higherfrequencytrading.com
 *  
 *  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 net.openhft.chronicle.hash;

import net.openhft.chronicle.bytes.*;
import net.openhft.chronicle.algo.hashing.LongHashFunction;
import org.jetbrains.annotations.Nullable;

/**
 * Dual bytes/object access to keys/values/elements.
 * 
 * 

Bytes access: {@link #access()} + {@link #handle()} + {@link #offset()} + {@link #size()}. * *

Object access: {@link #get()}. * *

In most cases, each particular value wraps either some object or some bytes. Object * is marshalled to bytes lazily on demand, and bytes are lazily deserialized to object, * accordingly. * * @param type of the accessed objects * @param type of the handle for bytes access */ public interface Value { /** * Returns access to the value's bytes. */ ReadAccess access(); /** * Returns a handle to access the value's bytes. */ T handle(); /** * Returns the offset to the value's bytes. */ long offset(); /** * Returns the size of the value's bytes. */ long size(); default long hash(LongHashFunction f) { return f.hash(handle(), access(), offset(), size()); } default boolean equivalent(ReadAccess access, T2 handle, long offset) { return Access.equivalent(access(), handle(), offset(), access, handle, offset, size()); } default > boolean equivalent( Accessor accessor, S source, long index) { return equivalent(accessor.access(source), accessor.handle(source), accessor.offset(source, index)); } default void writeTo(WriteAccess access, T2 handle, long offset) { Access.copy(access(), handle(), offset(), access, handle, offset, size()); } default void writeTo(StreamingDataOutput output) { long offset = output.accessPositionOffset(); output.skip(size()); writeTo(output.access(), output.accessHandle(), offset); } default > void writeTo( Accessor accessor, S source, long index) { writeTo(accessor.access(source), accessor.handle(source), accessor.offset(source, index)); } /** * Returns "cached" object, generally not eligible for using outside some context, or a block, * synchronized with locks, or lambda, etc. * * If the {@code Value} is object wrapper -- this method just returns this object. */ V get(); /** * Reads the object from the value's bytes, trying to reuse the given object * (might be {@code null}). */ V getUsing(@Nullable V usingInstance); static boolean bytesEquivalent(Value v1, Value v2) { if (v1.size() != v2.size()) return false; return Access.equivalent(v1.access(), v1.handle(), v1.offset(), v2.access(), v2.handle(), v2.offset(), v1.size()); } }





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