net.openhft.chronicle.hash.serialization.DataAccess Maven / Gradle / Ivy
/*
* Copyright 2012-2018 Chronicle Map Contributors
*
* 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.serialization;
import net.openhft.chronicle.hash.ChronicleHash;
import net.openhft.chronicle.hash.ChronicleHashBuilder;
import net.openhft.chronicle.hash.Data;
import net.openhft.chronicle.map.ChronicleMapBuilder;
import net.openhft.chronicle.wire.Marshallable;
import org.jetbrains.annotations.NotNull;
import java.nio.ByteBuffer;
/**
* Strategy of accessing flat byte contents of objects, using a reusable {@link Data} object, cached
* inside the {@code DataAccess} instance. This strategy interface is suitable for types of objects,
* that are already in fact sequences of bytes ({@code byte[]}, {@link ByteBuffer}, etc.) and
* shouldn't be serialized, and allows to avoid extra data copying. Accessed bytes should be later
* readable by some {@link BytesReader}.
*
*
Read {@link
* DataAccess} and {@code SizedReader} and
* custom
* serialization checklist sections in the Chronicle Map tutorial for more information on this
* interface, how to implement and use it properly.
*
* @param the type of objects accessed
* @see ChronicleHashBuilder#keyReaderAndDataAccess(SizedReader, DataAccess)
* @see ChronicleMapBuilder#valueReaderAndDataAccess(SizedReader, DataAccess)
*/
public interface DataAccess extends StatefulCopyable>, Marshallable {
/**
* Obtain {@code Data} accessor to the bytes of the given object. Typically a {@code Data}
* instance should be cached in a field of this {@code DataAccess}, so always the same object
* is returned.
*
* @param instance the object to access bytes (serialized form) of
* @return an accessor to the bytes of the given object
*/
Data getData(@NotNull T instance);
/**
* Clear references to the accessed object (provided in {@link #getData(Object)} method) in
* caching fields of this {@code DataAccess} or the cached {@link Data} object, returned from
* {@link #getData(Object)}.
*
* {@code DataAccess} is cached itself in thread-local variables for {@link ChronicleHash}
* instances, this method prevents leaking of accessed objects (they are not eligible for
* garbage collection while there are some references).
*/
void uninit();
}