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MemoryAccess.java
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MemoryAccess.java
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/*
* Copyright (c) 2002-2017 "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 Affero 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.impl.store.cursors;
import static java.lang.String.format;
abstract class MemoryAccess
{
long virtualAddress;
PageManager pageMan;
long pageId;
long base;
int offset;
long lockToken;
protected abstract int dataBound();
final void closeAccess()
{
if ( pageMan != null )
{
try
{
pageMan.releasePage( pageId, base, offset, lockToken );
}
finally
{
pageMan = null;
}
}
}
public final boolean hasPageReference()
{
return pageMan != null;
}
final void initializeMemoryAccess( long virtualAddress, PageManager pageMan, long pageId, long base, int offset )
{
if ( this.pageMan != null )
{
if ( this.pageMan != pageMan || this.pageId != pageId )
{
closeAccess();
}
else
{
lockRelease();
}
}
this.virtualAddress = virtualAddress;
this.pageMan = pageMan;
this.pageId = pageId;
this.base = base;
this.offset = offset;
}
final void moveToOtherPage( long virtualAddress, long pageId, long base, int offset )
{
assert this.pageMan != null : "Memory access must be initialized before moving";
this.virtualAddress = virtualAddress;
this.pageId = pageId;
this.base = base;
this.offset = offset;
}
final void moveWithinPage( long virtualAddress, int offset )
{
assert this.pageMan != null : "Memory access must be initialized before moving";
this.virtualAddress = virtualAddress;
this.offset = offset;
}
final void lockShared()
{
lockToken = pageMan.sharedLock( pageId, base, offset );
}
final void lockExclusive()
{
lockToken = pageMan.exclusiveLock( pageId, base, offset );
}
final void lockRelease()
{
pageMan.releaseLock( pageId, base, offset, lockToken );
lockToken = 0;
}
final long address( int offset, int size )
{
if ( pageMan == null )
{
throw new IllegalStateException( "Cursor has not been initialized." );
}
assert withinBounds( offset, size );
return this.base + this.offset + offset;
}
private boolean withinBounds( int offset, int size )
{
int bound = dataBound();
if ( offset + size > bound )
{
throw new IndexOutOfBoundsException( format(
"This cursor is bounded to %d bytes, tried to access %d bytes at offset %d.",
bound, size, offset ) );
}
return true;
}
}