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Off-Heap concurrent hash map intended to store GBs of serialized data
/*
* Copyright (C) 2014 Robert Stupp, Koeln, Germany, robert-stupp.de
*
* 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 org.caffinitas.ohc;
import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.caffinitas.ohc.histo.EstimatedHistogram;
public interface OHCache extends Closeable
{
long USE_DEFAULT_EXPIRE_AT = -1L;
long NEVER_EXPIRE = Long.MAX_VALUE;
/**
* Same as {@link #put(Object, Object, long)} but uses the configured default TTL, if any.
*
* @param key key of the entry to be added. Must not be {@code null}.
* @param value value of the entry to be added. Must not be {@code null}.
*/
void put(K key, V value);
/**
* Adds the key/value.
* If the entry size of key/value exceeds the configured maximum entry length, any previously existing entry
* for the key is removed.
*
* @param key key of the entry to be added. Must not be {@code null}.
* @param value value of the entry to be added. Must not be {@code null}.
* @param expireAt timestamp in milliseconds since "epoch" (like {@link System#currentTimeMillis() System.currentTimeMillis()})
* when the entry shall expire. Pass {@link #USE_DEFAULT_EXPIRE_AT} for the configured default
* time-to-live or {@link #NEVER_EXPIRE} to let it never expire.
*/
void put(K key, V value, long expireAt);
/**
* Same as {@link #addOrReplace(Object, Object, Object, long)} but uses the configured default TTL, if any.
*
* @param key key of the entry to be added or replaced. Must not be {@code null}.
* @param old if the entry exists, it's serialized value is compared to the serialized value of {@code old}
* and only replaced, if it matches.
* @param value value of the entry to be added. Must not be {@code null}.
* @return {@code true} on success or {@code false} if the existing value does not matcuh {@code old}
*/
boolean addOrReplace(K key, V old, V value);
/**
* Adds key/value if either the key is not present or the existing value matches parameter {@code old}.
* If the entry size of key/value exceeds the configured maximum entry length, the old value is removed.
*
* @param key key of the entry to be added or replaced. Must not be {@code null}.
* @param old if the entry exists, it's serialized value is compared to the serialized value of {@code old}
* and only replaced, if it matches.
* @param value value of the entry to be added. Must not be {@code null}.
* @param expireAt timestamp in milliseconds since "epoch" (like {@link System#currentTimeMillis() System.currentTimeMillis()})
* when the entry shall expire. Pass {@link #USE_DEFAULT_EXPIRE_AT} for the configured default
* time-to-live or {@link #NEVER_EXPIRE} to let it never expire.
* @return {@code true} on success or {@code false} if the existing value does not matcuh {@code old}
*/
boolean addOrReplace(K key, V old, V value, long expireAt);
/**
* Same as {@link #putIfAbsent(Object, Object, long)} but uses the configured default TTL, if any.
*
* @param key key of the entry to be added. Must not be {@code null}.
* @param value value of the entry to be added. Must not be {@code null}.
* @return {@code true} on success or {@code false} if the key is already present.
*/
boolean putIfAbsent(K key, V value);
/**
* Adds the key/value if the key is not present.
* If the entry size of key/value exceeds the configured maximum entry length, any previously existing entry
* for the key is removed.
*
* @param key key of the entry to be added. Must not be {@code null}.
* @param value value of the entry to be added. Must not be {@code null}.
* @param expireAt timestamp in milliseconds since "epoch" (like {@link System#currentTimeMillis() System.currentTimeMillis()})
* when the entry shall expire. Pass {@link #USE_DEFAULT_EXPIRE_AT} for the configured default
* time-to-live or {@link #NEVER_EXPIRE} to let it never expire.
* @return {@code true} on success or {@code false} if the key is already present.
*/
boolean putIfAbsent(K key, V value, long expireAt);
/**
* This is effectively a shortcut to add all entries in the given map {@code m}.
*
* @param m entries to be added
*/
void putAll(Map m);
/**
* Remove a single entry for the given key.
*
* @param key key of the entry to be removed. Must not be {@code null}.
*/
void remove(K key);
/**
* This is effectively a shortcut to remove the entries for all keys given in the iterable {@code keys}.
*
* @param keys keys to be removed
*/
void removeAll(Iterable keys);
/**
* Removes all entries from the cache.
*/
void clear();
/**
* Get the value for a given key.
*
* @param key key of the entry to be retrieved. Must not be {@code null}.
* @return either the non-{@code null} value or {@code null} if no entry for the requested key exists
*/
V get(K key);
/**
* Checks whether an entry for a given key exists.
* Usually, this is more efficient than testing for {@code null} via {@link #get(Object)}.
*
* @param key key of the entry to be retrieved. Must not be {@code null}.
* @return either {@code true} if an entry for the given key exists or {@code false} if no entry for the requested key exists
*/
boolean containsKey(K key);
/**
* Returns a closeable byte buffer.
* You must close the returned {@link DirectValueAccess} instance after use.
* After closing, you must not call any of the methods of the {@link java.nio.ByteBuffer}
* returned by {@link DirectValueAccess#buffer()}.
*
* @return reference-counted byte buffer or {@code null} if key does not exist.
*/
DirectValueAccess getDirect(K key);
/**
* Like {@link OHCache#getDirect(Object)}, but allows skipping the update of LRU stats when {@code updateLRU}
* is {@code false}.
*
* @return reference-counted byte buffer or {@code null} if key does not exist.
*/
DirectValueAccess getDirect(K key, boolean updateLRU);
// cache loader support
/**
* Shortcut to call {@link #getWithLoader(Object, CacheLoader, long, TimeUnit)} using the default entry
* time-to-live. Note that the cache has to be configured with an {@link java.util.concurrent.Executor} to
* schedule the load process.
*
* Note that the future may indicate a failure via it's {@link Future#get() get} methods if the
* {@link CacheLoader#load(Object)} implementation threw an error or a runtime exception occured due to
* not enough memory for example.
*
*
* @param key key of the value to load
* @param loader loader implementation to use
* @return a future to process the load request asynchronously.
*/
Future getWithLoaderAsync(K key, CacheLoader loader);
/**
* Shortcut to call {@link #getWithLoader(Object, CacheLoader, long, TimeUnit)} using the default entry
* time-to-live. Note that the cache has to be configured with an {@link java.util.concurrent.Executor} to
* schedule the load process.
*
* Note that the future may indicate a failure via it's {@link Future#get() get} methods if the
* {@link CacheLoader#load(Object)} implementation threw an error or a runtime exception occured due to
* not enough memory for example.
*
*
* @param key key of the value to load
* @param loader loader implementation to use
* @return a future to process the load request asynchronously.
*/
Future getWithLoaderAsync(K key, CacheLoader loader, long expireAt);
/**
* Effectively calls {@link #getWithLoaderAsync(Object, CacheLoader) getWithLoaderAsync(key, loader)}{@code .}{@link Future#get() get()}.
*
* @param key key of the value to load
* @param loader loader implementation to use
* @return the loaded value or {@code null}
* @throws InterruptedException as from the contract of {@link Future#get()}
* @throws ExecutionException thrown if the {@link CacheLoader#load(Object)} implementation threw an error or a
* runtime exception occured due to not enough memory for example.
*/
V getWithLoader(K key, CacheLoader loader) throws InterruptedException, ExecutionException;
/**
* Effectively calls {@link #getWithLoaderAsync(Object, CacheLoader) getWithLoaderAsync(key, loader)}{@code .}{@link Future#get(long, TimeUnit) get(timeout, unit)}.
*
* @param key key of the value to load
* @param loader loader implementation to use
* @param timeout timeout value to be passed to {@link Future#get(long, TimeUnit)}
* @param unit timeout unit to be passed to {@link Future#get(long, TimeUnit)}
* @return the loaded value or {@code null}
* @throws InterruptedException as from the contract of {@link Future#get()}
* @throws ExecutionException thrown if the {@link CacheLoader#load(Object)} implementation threw an error or a
* runtime exception occured due to not enough memory for example.
* @throws TimeoutException as from the contract of {@link Future#get(long, TimeUnit)}
*/
V getWithLoader(K key, CacheLoader loader, long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException;
// iterators
/**
* Builds an iterator over the N most recently used keys returning deserialized objects.
* You must call {@code close()} on the returned iterator.
*
* Note: During a rehash, the implementation might return keys twice or not at all.
*
*/
CloseableIterator hotKeyIterator(int n);
/**
* Builds an iterator over all keys returning deserialized objects.
* You must call {@code close()} on the returned iterator.
*
* Note: During a rehash, the implementation might return keys twice or not at all.
*
*/
CloseableIterator keyIterator();
/**
* Builds an iterator over all keys returning direct byte buffers.
* Do not use a returned {@code ByteBuffer} after calling any method on the iterator.
* You must call {@code close()} on the returned iterator.
*
* Note: During a rehash, the implementation might return keys twice or not at all.
*
*/
CloseableIterator hotKeyBufferIterator(int n);
/**
* Builds an iterator over all keys returning direct byte buffers.
* Do not use a returned {@code ByteBuffer} after calling any method on the iterator.
* You must call {@code close()} on the returned iterator.
*
* Note: During a rehash, the implementation might return keys twice or not at all.
*
*/
CloseableIterator keyBufferIterator();
// serialization
boolean deserializeEntry(ReadableByteChannel channel) throws IOException;
boolean serializeEntry(K key, WritableByteChannel channel) throws IOException;
int deserializeEntries(ReadableByteChannel channel) throws IOException;
int serializeHotNEntries(int n, WritableByteChannel channel) throws IOException;
int serializeHotNKeys(int n, WritableByteChannel channel) throws IOException;
CloseableIterator deserializeKeys(ReadableByteChannel channel) throws IOException;
// statistics / information
void resetStatistics();
long size();
int[] hashTableSizes();
long[] perSegmentSizes();
EstimatedHistogram getBucketHistogram();
int segments();
long capacity();
long memUsed();
long freeCapacity();
float loadFactor();
OHCacheStats stats();
/**
* Modify the cache's capacity.
* Lowering the capacity will not immediately remove any entry nor will it immediately free allocated (off heap) memory.
*
* Future operations will even allocate in flight, temporary memory - i.e. setting capacity to 0 does not
* disable the cache, it will continue to work but cannot add more data.
*
*/
void setCapacity(long capacity);
}
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