net.openhft.chronicle.map.PrepareValueBytes Maven / Gradle / Ivy
/*
* Copyright 2014 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.map;
import net.openhft.lang.io.Bytes;
import net.openhft.lang.model.Byteable;
import java.io.Serializable;
/**
* Strategy of preparing bytes of off-heap memory before assigning them into {@link Byteable}
* value during {@link ChronicleMap#acquireUsing(Object, Object)
* chronicleMap.acquireUsing()} call, when the given key is absent in the map. Example: if you
* want {@code 1L} to be the off-heap updatable ChronicleMap's {@linkplain
* ChronicleMapBuilder#defaultValue(Object) default value}.
* PrepareValueBytes) configure} custom {@code PrepareValueBytes} strategy in {@link
* ChronicleMapBuilder}: {@code
* ChronicleMapBuilder.of(Key.class, LongValue.class)
* .prepareDefaultValueBytes((bytes, k) -> bytes.writeLong(1L))
* ...
* .create();}
*
* Although the value type is not used in the API, {@link PrepareValueBytes} is not intended
* to be generic by value type, because strategy should know the value layout and
* {@linkplain Byteable#maxSize() how much bytes} does it take in memory.
*
* @param the key type of {@link ChronicleMap}, on which {@code acquireUsing()} is queried
* @param the value type of {@link ChronicleMap}, on which {@code acquireUsing()} is queried
*/
public interface PrepareValueBytes extends Serializable {
/**
* Prepares bytes before assigning them into {@link Byteable}. The given bytes' position
* corresponds to the start of value bytes to be assigned into. This method should increment
* the given bytes' position by {@linkplain Byteable#maxSize() the value size}. Bytes' contents
* outside of this range shouldn't be altered.
*
* @param bytes the bytes, positioned at the first value byte. Bytes' {@linkplain Bytes#limit(
* long) limit} and {@linkplain Bytes#remaining()} are not specified, but it is guaranteed that
* the latter is not less than {@linkplain Byteable#maxSize() the value size}.
* @param key the key which is absent in the {@link ChronicleMap} during {@link
* ChronicleMap#acquireUsing(Object, Object) acquireUsing()} call and value bytes are prepared
* for
*/
void prepare(Bytes bytes, K key);
}