/* -*- tab-width: 4 -*-
*
* Electric(tm) VLSI Design System
*
* File: BTree.java
*
* Copyright (c) 2009 Sun Microsystems and Static Free Software
*
* Electric(tm) 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.
*
* Electric(tm) 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 Electric(tm); see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, Mass 02111-1307, USA.
*/
package com.sun.electric.database.geometry.btree;
import java.io.*;
import java.util.*;
/**
* API for a PageStorage with some sort of cache; the {@see
* CachedPage} class provides an interface for interacting with the
* cache.
*/
public abstract class CachingPageStorage extends PageStorage {
public CachingPageStorage(int pageSize) {
super(pageSize);
}
/**
* Creates space in the cache for pageid, but only actually reads
* the bytes if readBytes is true; if the page was not already
* in the cache and readBytes is false, subsequent calls to
* setDirty()/flush() will overwrite data previously on the page.
*/
public abstract CachedPage getPage(int pageid, boolean readBytes);
/** Write a page <i>through</i> the cache to nonvolatile storage */
public abstract void writePage(int pageid, byte[] buf, int ofs);
/** A page which is currently in the cache; pages can be dirty or clean. */
public abstract class CachedPage {
/** gets the byte[] for this page; it is okay to manipulate it directly, but you must call setDirty() and flush() afterwards */
public abstract byte[] getBuf();
/** the pageid of this cached page */
public abstract int getPageId();
/** indicates that the page has been accessed (either a read or a write) for purposes of least-recently-used calculations */
public abstract void touch();
/** marks the page as "dirty"; that is, in need of being written back to nonvolatile storage */
public abstract void setDirty();
/** if the page is dirty, write it back to nonvolatile storage and mark it not dirty */
public abstract void flush();
/** returns true if the page is marked dirty */
public abstract boolean isDirty();
}
}