/*
* Copyright 2004-2011 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.index;
import org.h2.constant.ErrorCode;
import org.h2.constant.SysProperties;
import org.h2.engine.Constants;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.store.Data;
import org.h2.store.Page;
import org.h2.store.PageStore;
/**
* Overflow data for a leaf page. Format:
* <ul>
* <li>page type: byte (0)</li>
* <li>checksum: short (1-2)</li>
* <li>parent page id (0 for root): int (3-6)</li>
* <li>more data: next overflow page id: int (7-10)</li>
* <li>last remaining size: short (7-8)</li>
* <li>data (11-/9-)</li>
* </ul>
*/
public class PageDataOverflow extends Page {
/**
* The start of the data in the last overflow page.
*/
static final int START_LAST = 9;
/**
* The start of the data in a overflow page that is not the last one.
*/
static final int START_MORE = 11;
private static final int START_NEXT_OVERFLOW = 7;
/**
* The page store.
*/
private final PageStore store;
/**
* The page type.
*/
private int type;
/**
* The parent page (overflow or leaf).
*/
private int parentPageId;
/**
* The next overflow page, or 0.
*/
private int nextPage;
private Data data;
private int start;
private int size;
/**
* Create an object from the given data page.
*
* @param store the page store
* @param pageId the page id
* @param data the data page
*/
private PageDataOverflow(PageStore store, int pageId, Data data) {
this.store = store;
setPos(pageId);
this.data = data;
}
/**
* Read an overflow page.
*
* @param store the page store
* @param data the data
* @param pageId the page id
* @return the page
*/
public static Page read(PageStore store, Data data, int pageId) {
PageDataOverflow p = new PageDataOverflow(store, pageId, data);
p.read();
return p;
}
/**
* Create a new overflow page.
*
* @param store the page store
* @param page the page id
* @param type the page type
* @param parentPageId the parent page id
* @param next the next page or 0
* @param all the data
* @param offset the offset within the data
* @param size the number of bytes
* @return the page
*/
static PageDataOverflow create(PageStore store, int page,
int type, int parentPageId, int next,
Data all, int offset, int size) {
Data data = store.createData();
PageDataOverflow p = new PageDataOverflow(store, page, data);
store.logUndo(p, null);
data.writeByte((byte) type);
data.writeShortInt(0);
data.writeInt(parentPageId);
if (type == Page.TYPE_DATA_OVERFLOW) {
data.writeInt(next);
} else {
data.writeShortInt(size);
}
p.start = data.length();
data.write(all.getBytes(), offset, size);
p.type = type;
p.parentPageId = parentPageId;
p.nextPage = next;
p.size = size;
return p;
}
/**
* Read the page.
*/
private void read() {
data.reset();
type = data.readByte();
data.readShortInt();
parentPageId = data.readInt();
if (type == (Page.TYPE_DATA_OVERFLOW | Page.FLAG_LAST)) {
size = data.readShortInt();
nextPage = 0;
} else if (type == Page.TYPE_DATA_OVERFLOW) {
nextPage = data.readInt();
size = store.getPageSize() - data.length();
} else {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "page:" + getPos() + " type:" + type);
}
start = data.length();
}
/**
* Read the data into a target buffer.
*
* @param target the target data page
* @return the next page, or 0 if no next page
*/
int readInto(Data target) {
target.checkCapacity(size);
if (type == (Page.TYPE_DATA_OVERFLOW | Page.FLAG_LAST)) {
target.write(data.getBytes(), START_LAST, size);
return 0;
}
target.write(data.getBytes(), START_MORE, size);
return nextPage;
}
int getNextOverflow() {
return nextPage;
}
private void writeHead() {
data.writeByte((byte) type);
data.writeShortInt(0);
data.writeInt(parentPageId);
}
public void write() {
writeData();
store.writePage(getPos(), data);
}
private void writeData() {
data.reset();
writeHead();
if (type == Page.TYPE_DATA_OVERFLOW) {
data.writeInt(nextPage);
} else {
data.writeShortInt(size);
}
}
public String toString() {
return "page[" + getPos() + "] data leaf overflow parent:" + parentPageId + " next:" + nextPage;
}
/**
* Get the estimated memory size.
*
* @return number of double words (4 bytes)
*/
public int getMemory() {
return (Constants.MEMORY_PAGE_DATA_OVERFLOW + store.getPageSize()) >> 2;
}
void setParentPageId(int parent) {
store.logUndo(this, data);
this.parentPageId = parent;
}
public void moveTo(Session session, int newPos) {
// load the pages into the cache, to ensure old pages
// are written
Page parent = store.getPage(parentPageId);
if (parent == null) {
throw DbException.throwInternalError();
}
PageDataOverflow next = null;
if (nextPage != 0) {
next = (PageDataOverflow) store.getPage(nextPage);
}
store.logUndo(this, data);
PageDataOverflow p2 = PageDataOverflow.create(store, newPos, type, parentPageId, nextPage, data, start, size);
store.update(p2);
if (next != null) {
next.setParentPageId(newPos);
store.update(next);
}
if (parent instanceof PageDataOverflow) {
PageDataOverflow p1 = (PageDataOverflow) parent;
p1.setNext(getPos(), newPos);
} else {
PageDataLeaf p1 = (PageDataLeaf) parent;
p1.setOverflow(getPos(), newPos);
}
store.update(parent);
store.free(getPos());
}
private void setNext(int old, int nextPage) {
if (SysProperties.CHECK && old != this.nextPage) {
DbException.throwInternalError("move " + this + " " + nextPage);
}
store.logUndo(this, data);
this.nextPage = nextPage;
data.setInt(START_NEXT_OVERFLOW, nextPage);
}
/**
* Free this page.
*/
void free() {
store.logUndo(this, data);
store.free(getPos());
}
public boolean canRemove() {
return true;
}
public boolean isStream() {
return true;
}
}