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GraphHopper is a fast and memory efficient Java road routing engine working seamlessly with OpenStreetMap data.

There is a newer version: 0.7.0

/*
 *  Licensed to GraphHopper and Peter Karich under one or more contributor
 *  license agreements. See the NOTICE file distributed with this work for 
 *  additional information regarding copyright ownership.
 * 
 *  GraphHopper licenses this file to you 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 com.graphhopper.storage;

import java.io.Closeable;

/**
 * Interface for a storage abstraction. Currently is serves just the purpose to ensure the same
 * methods and names through all kind of 'storable' things in graphhopper.
 * 
 * Then the lifecycle is identical for all such objects:
 * 

 * object creation via new
 * optional configuration via additional setters and getters which are not in this
 * interface
 * if(!storable.loadExisting()) storable.create()
 * usage storable and optional flush() calls in-between. Keep in mind that some data structure
 * could require a call to increase memory while usage. E.g. DataAccess.ensureCapacity()
 * Finally do close() which does no flush()
 * 
 * 
 * @author Peter Karich
 */
public interface Storable extends Closeable
{
    /**
     * @return true if successfully loaded from persistent storage.
     */
    boolean loadExisting();

    /**
     * Creates the underlying storage. First operation if it cannot be loaded.
     */
    T create( long byteCount );

    /**
     * This method makes sure that the underlying data is written to the storage. Keep in mind that
     * a disc normally has an IO cache so that flush() is (less) probably not save against power
     * loses.
     */
    void flush();

    /**
     * This method makes sure that the underlying used resources are released. WARNING: it does NOT
     * flush on close!
     */
    @Override
    void close();

    boolean isClosed();

    /**
     * @return the allocated storage size in bytes
     */
    long getCapacity();
}