/*******************************************************************************
* Copyright 2010 Cees De Groot, Alex Boisvert, Jan Kotek
*
* Licensed 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 de.mxro.thrd.jdbm2V22.recman;
/**
* Class describing a page that holds data.
*/
final class DataPage extends PageHeader {
// offsets
private static final short O_FIRST = PageHeader.SIZE; // short firstrowid
static final short O_DATA = (short) (O_FIRST + Magic.SZ_SHORT);
final short DATA_PER_PAGE ;
/**
* Constructs a data page view from the indicated block.
*/
DataPage(BlockIo block, int blockSize) {
super(block);
DATA_PER_PAGE = (short) (blockSize - O_DATA);
}
/**
* Factory method to create or return a data page for the indicated block.
*/
static DataPage getDataPageView(BlockIo block, int blockSize) {
BlockView view = block.getView();
if (view != null && view instanceof DataPage)
return (DataPage) view;
else
return new DataPage(block, blockSize);
}
/** Returns the first rowid's offset */
short getFirst() {
return block.readShort(O_FIRST);
}
/** Sets the first rowid's offset */
void setFirst(short value) {
paranoiaMagicOk();
if (value > 0 && value < O_DATA)
throw new Error("DataPage.setFirst: offset " + value + " too small");
block.writeShort(O_FIRST, value);
}
}