MapContext.java

/*
 *      Copyright (C) 2012, 2016  higherfrequencytrading.com
 *      Copyright (C) 2016 Roman Leventov
 *
 *      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 <http://www.gnu.org/licenses/>.
 */

package net.openhft.chronicle.map;

import net.openhft.chronicle.bytes.BytesStore;
import net.openhft.chronicle.hash.ChronicleHash;
import net.openhft.chronicle.hash.HashContext;
import net.openhft.chronicle.hash.Data;

/**
 * Context, in which {@link MapEntry MapEntries} are accessed. {@code MapContext} allows to access
 * {@link MapEntryOperations}, configured for the accessed {@link ChronicleMap} via {@link
 * ChronicleMapBuilder#entryOperations(MapEntryOperations)}. {@code MapContext} implements {@code
 * MapEntryOperations} by delegation to the configured {@code entryOperations}. The same for
 * {@link DefaultValueProvider}: {@code MapContext} delegates to the {@code DefaultValueProvider}
 * configured for the accessed {@code ChronicleMap} via {@link
 * ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider)}, or the default {@code
 * DefaultValueProvider} implementation.
 * 
 * @param <K> the map key type
 * @param <V> the map value type
 * @param <R> the return type of {@link MapEntryOperations} specified for the queried map
 */
public interface MapContext<K, V, R>
        extends HashContext<K>, MapEntryOperations<K, V, R>, DefaultValueProvider<K, V> {
    /**
     * Returns the accessed {@code ChronicleMap}. Synonym to {@link #map()}.
     */
    @Override
    ChronicleHash<K, ?, ?, ?> hash();

    /**
     * Returns the accessed {@code ChronicleMap}. Synonym to {@link #hash()}.
     */
    ChronicleMap<K, V> map();

    /**
     * Wraps the given value as a {@code Data}. Useful when you need to pass a value
     * to some method accepting {@code Data}, for example, {@link MapEntryOperations#replaceValue(
     * MapEntry, Data)}, without allocating new objects (i. e. garbage) and {@code ThreadLocals}.
     *
     * <p>The returned {@code Data} object shouldn't outlive this {@code MapContext}.
     *
     * @param value the value object to wrap
     * @return the value as {@code Data}
     */
    Data<V> wrapValueAsData(V value);

    /**
     * Wraps the given value bytes as a {@code Data}. Useful when you need to pass a value
     * to some method accepting {@code Data}, for example, {@link MapEntryOperations#replaceValue(
     * MapEntry, Data)}, without allocating manual deserialization and {@code ThreadLocals}.
     *
     * <p>The returned {@code Data} object shouldn't outlive this {@code MapContext}.
     *
     * @param valueBytes the value bytes to wrap
     * @param offset offset within the given valueBytes, the actual value bytes start from
     * @param size length of the value bytes sequence
     * @return the value bytes as {@code Data}
     */
    Data<V> wrapValueBytesAsData(BytesStore valueBytes, long offset, long size);
}