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Input/output abstraction layer for Neo4j.

There is a newer version: 2025.02.0

/*
 * 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 .
 */
package org.neo4j.io.pagecache.impl;

import java.io.File;
import java.io.IOException;
import java.nio.file.NoSuchFileException;

import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.pagecache.PageEvictionCallback;
import org.neo4j.io.pagecache.PageSwapper;
import org.neo4j.io.pagecache.PageSwapperFactory;

/**
 * A factory for SingleFilePageSwapper instances.
 *
 * @see org.neo4j.io.pagecache.impl.SingleFilePageSwapper
 */
public class SingleFilePageSwapperFactory implements PageSwapperFactory
{
    private FileSystemAbstraction fs;

    @Override
    public void setFileSystemAbstraction( FileSystemAbstraction fs )
    {
        this.fs = fs;
    }

    @Override
    public PageSwapper createPageSwapper(
            File file,
            int filePageSize,
            PageEvictionCallback onEviction,
            boolean createIfNotExist ) throws IOException
    {
        if ( !fs.fileExists( file ) )
        {
            if ( createIfNotExist )
            {
                fs.create( file ).close();
            }
            else
            {
                throw new NoSuchFileException( file.getPath(), null, "Cannot map non-existing file" );
            }
        }
        return new SingleFilePageSwapper( file, fs, filePageSize, onEviction );
    }

    @Override
    public void syncDevice()
    {
        // Nothing do to, since we `fsync` files individually in `force()`.
    }

    @Override
    public String implementationName()
    {
        return "single";
    }

    @Override
    public int getCachePageSizeHint()
    {
        return 8192;
    }

    @Override
    public boolean isCachePageSizeHintStrict()
    {
        return false;
    }

    @Override
    public long getRequiredBufferAlignment()
    {
        return 1;
    }
}