/*
* 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.Byteable;
import net.openhft.chronicle.core.util.SerializableFunction;
import net.openhft.chronicle.hash.ChronicleHash;
import net.openhft.chronicle.hash.serialization.SizedReader;
import net.openhft.chronicle.hash.serialization.SizedWriter;
import org.jetbrains.annotations.NotNull;
import java.io.*;
import java.util.Map;
import java.util.concurrent.ConcurrentMap;
/**
* {@code ChronicleMap} provides concurrent access to a <i>Chronicle Map key-value store</i> from a
* JVM process.
*
* <p>For information on <ul> <li>how to construct a {@code ChronicleMap}</li> <li>{@code
* ChronicleMap} flavors and properties</li> <li>available configurations</li> </ul> see {@link
* ChronicleMapBuilder} documentation.
*
* <p>Functionally this interface defines some methods supporting garbage-free off-heap programming:
* {@link #getUsing(Object, Object)}, {@link #acquireUsing(Object, Object)}.
*
* <p>Roughly speaking, {@code ChronicleMap} compares keys and values by their binary serialized
* form, that shouldn't necessary be the same equality relation as defined by built-in {@link
* Object#equals(Object)} method, which is prescribed by general {@link Map} contract.
*
* <p>Note that {@code ChronicleMap} extends {@link Closeable}, don't forget to {@linkplain #close()
* close} map when it is no longer needed.
*
* @param <K> the map key type
* @param <V> the map value type
* @see ChronicleMapBuilder#create()
* @see ChronicleMapBuilder#createPersistedTo(File)
* @see ChronicleMapBuilder#createOrRecoverPersistedTo(File, boolean)
*/
public interface ChronicleMap<K, V> extends ConcurrentMap<K, V>,
ChronicleHash<K, MapEntry<K, V>, MapSegmentContext<K, V, ?>,
ExternalMapQueryContext<K, V, ?>> {
/**
* Delegates to {@link ChronicleMapBuilder#of(Class, Class)} for convenience.
*
* @param keyClass class of the key type of the Chronicle Map to create
* @param valueClass class of the value type of the Chronicle Map to create
* @param <K> the key type of the Chronicle Map to create
* @param <V> the value type of the Chronicle Map to create
* @return a new {@code ChronicleMapBuilder} for the given key and value classes
*/
static <K, V> ChronicleMapBuilder<K, V> of(Class<K> keyClass, Class<V> valueClass) {
return ChronicleMapBuilder.of(keyClass, valueClass);
}
/**
* Returns the value to which the specified key is mapped, or {@code null} if this map contains
* no mapping for the key.
*
* <p>If the value class allows reusing, consider {@link #getUsing(Object, Object)} method
* instead of this to reduce garbage creation. Read <a
* href="https://github.com/OpenHFT/Chronicle-Map#single-key-queries">the section about usage
* patterns in the Chronicle Map 3 Tutorial</a> for more.
*
* @param key the key whose associated value is to be returned
* @return the value to which the specified key is mapped after this method call, or {@code
* null} if no value is mapped
* @see #getUsing(Object, Object)
*/
@Override
V get(Object key);
/**
* Returns the value to which the specified key is mapped, read to the provided {@code value}
* object, if possible, or returns {@code null}, if this map contains no mapping for the key.
*
* <p>If the specified key is present in the map, the value data is read to the provided {@code
* value} object via value reader's {@link SizedReader#read(net.openhft.chronicle.bytes.Bytes, long, Object)
* read(StreamingDataInput, size, value)} method. If the value deserializer is able to reuse the
* given {@code value} object, calling this method instead of {@link #get(Object)} could help to
* reduce garbage creation.
*
* <p>The provided {@code value} object is allowed to be {@code null}, in this case {@code
* map.getUsing(key, null)} call is semantically equivalent to simple {@code map.get(key)}
* call.
*
* @param key the key whose associated value is to be returned
* @param usingValue the object to read value data in, if possible
* @return the value to which the specified key is mapped, or {@code null} if this map contains
* no mapping for the key
* @see #get(Object)
* @see #acquireUsing(Object, Object)
* @see ChronicleMapBuilder#valueMarshallers(SizedReader, SizedWriter)
*/
V getUsing(K key, V usingValue);
/**
* Acquire a value for a key, creating if absent.
*
* <p>If the specified key is absent in the map, {@linkplain
* ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider) default value provider} is
* called. Then this object is put to this map for the specified key.
*
* <p>Then, either if the key was initially absent in the map or already present, the value is
* deserialized just as during {@link #getUsing(Object, Object) getUsing(key, usingValue)} call,
* passed the same {@code key} and {@code usingValue} as into this method call. This means, as
* in {@link #getUsing}, {@code usingValue} could safely be {@code null}, in this case a new
* value instance is created to deserialize the data.
*
* <p>In code, {@code acquireUsing} is specified as :
* <pre>{@code
* V acquireUsing(K key, V usingValue) {
* if (!containsKey(key))
* put(key, defaultValue(key));
* return getUsing(key, usingValue);
* }}</pre>
*
*
* <p>Where {@code defaultValue(key)} returns {@link
* ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider) defaultValueProvider}.
*
* <p>If the {@code ChronicleMap} is off-heap updatable, i. e. created via {@link
* ChronicleMapBuilder} builder (values are {@link Byteable}), there is one more option of what
* to do if the key is absent in the map. By default, value bytes are just zeroed out, no
* default value, either provided for key or constant, is put for the absent key.
*
* @param key the key whose associated value is to be returned
* @param usingValue the object to read value data in, if present. Can not be null
* @return value to which the given key is mapping after this call, either found or created
* @see #getUsing(Object, Object)
*/
V acquireUsing(@NotNull K key, V usingValue);
@NotNull
net.openhft.chronicle.core.io.Closeable acquireContext(@NotNull K key, @NotNull V usingValue);
/**
* Returns the result of application of the given function to the value to which the given key
* is mapped. If there is no mapping for the key, {@code null} is returned from {@code
* getMapped()} call without application of the given function. This method is primarily useful
* when accessing {@code ChronicleMap} implementation which delegates it's requests to some
* remote node (server) and pulls the result through serialization/deserialization path, and
* probably network. In this case, when you actually need only a part of the map value's state
* (e. g. a single field) it's cheaper to extract it on the server side and transmit lesser
* bytes.
*
* @param key the key whose associated value is to be queried
* @param function a function to transform the value to the actually needed result,
* which should be smaller than the map value
* @param <R> the result type
* @return the result of applying the function to the mapped value, or {@code null} if there
* is no mapping for the key
*/
<R> R getMapped(K key, @NotNull SerializableFunction<? super V, R> function);
/**
* Exports all the entries to a {@link File} storing them in JSON format, an attempt is
* made where possible to use standard java serialisation and keep the data human readable, data
* serialized using the custom serialises are converted to a binary format which is not human
* readable but this is only done if the Keys or Values are not {@link Serializable}.
* This method can be used in conjunction with {@link ChronicleMap#putAll(File)} and is
* especially useful if you wish to import/export entries from one chronicle map into another.
* This import and export of the entries can be performed even when the versions of ChronicleMap
* differ. This method is not performant and as such we recommend it is not used in performance
* sensitive code.
*
* @param toFile the file to store all the entries to, the entries will be stored in JSON
* format
* @throws IOException its not possible store the data to {@code toFile}
* @see ChronicleMap#putAll(File)
*/
void getAll(File toFile) throws IOException;
/**
* Imports all the entries from a {@link File}, the {@code fromFile} must be created
* using or the same format as {@link ChronicleMap#get(Object)}, this method behaves
* similar to {@link Map#put(Object, Object)} where existing
* entries are overwritten. A write lock is only held while each individual entry is inserted
* into the map, not over all the entries in the {@link File}
*
* @param fromFile the file containing entries ( in JSON format ) which will be deserialized and
* {@link Map#put(Object, Object)} into the map
* @throws IOException its not possible read the {@code fromFile}
* @see ChronicleMap#getAll(File)
*/
void putAll(File fromFile) throws IOException;
/**
* @return the class of {@code <V>}
*/
Class<V> valueClass();
}