/*
* Copyright 2008 Niclas Hedhman.
*
* 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 org.qi4j.entitystore.swift;
import java.io.IOException;
import java.io.RandomAccessFile;
/**
* Record has been deleted and we want to restore it.
*
* Block Structure
* [blockSize] 4 bytes
* [usage] 1 byte (0=Unused, 1=prime, 2=mirror, 3=primeChanged, 4=mirrorChanged)
* [instanceVersion] 8 bytes
* [schemaVersion] 4 bytes
* [identitySize] 1 byte
* [identity] IDENTITY_MAX_LENGTH bytes
* [mirrorPointer] 8 bytes
* [primeDataLength] 4 bytes
* [primeData] n bytes
* [mirrorDataLength] 4 bytes
* [mirrorData] n bytes
*/
public class UndoDeleteCommand
implements UndoCommand
{
private long position;
private byte usage;
public UndoDeleteCommand( long position, byte usage )
{
this.position = position;
this.usage = usage;
}
public void undo( RandomAccessFile dataFile, IdentityFile idFile )
throws IOException
{
dataFile.seek( position );
dataFile.skipBytes( 4 );
dataFile.writeByte( usage );
}
public void save( RandomAccessFile undoJournal ) throws IOException
{
undoJournal.writeLong( position );
undoJournal.writeByte( usage );
}
static UndoDeleteCommand load( RandomAccessFile undoJournal )
throws IOException
{
long position = undoJournal.readLong();
byte usage = undoJournal.readByte();
return new UndoDeleteCommand( position, usage );
}
}