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IdProvider.java
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IdProvider.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.index.gbptree;
import java.io.IOException;
import org.neo4j.io.pagecache.PageCursor;
/**
* Provide tree node (page) ids which can be used for storing tree node data.
* Bytes on returned page ids must be empty (all zeros).
*/
interface IdProvider
{
/**
* Acquires a page id, guaranteed to currently not be used. The bytes on the page at this id
* are all guaranteed to be zero at the point of returning from this method.
*
* @param stableGeneration current stable generation.
* @param unstableGeneration current unstable generation.
* @return page id guaranteed to current not be used and whose bytes are all zeros.
* @throws IOException on {@link PageCursor} error.
*/
long acquireNewId( long stableGeneration, long unstableGeneration ) throws IOException;
/**
* Releases a page id which has previously been used, but isn't anymore, effectively allowing
* it to be reused and returned from {@link #acquireNewId(long, long)}.
*
* @param stableGeneration current stable generation.
* @param unstableGeneration current unstable generation.
* @param id page id to release.
* @throws IOException on {@link PageCursor} error.
*/
void releaseId( long stableGeneration, long unstableGeneration, long id ) throws IOException;
}