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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
using System;
using Lucene.Net.Support;
using CRC32 = Lucene.Net.Support.CRC32;
namespace Lucene.Net.Store
{
/// <summary>Writes bytes through to a primary IndexOutput, computing
/// checksum. Note that you cannot use seek().
/// </summary>
public class ChecksumIndexOutput:IndexOutput
{
internal IndexOutput main;
internal IChecksum digest;
private bool isDisposed;
public ChecksumIndexOutput(IndexOutput main)
{
this.main = main;
digest = new CRC32();
}
public override void WriteByte(byte b)
{
digest.Update(b);
main.WriteByte(b);
}
public override void WriteBytes(byte[] b, int offset, int length)
{
digest.Update(b, offset, length);
main.WriteBytes(b, offset, length);
}
public virtual long Checksum
{
get { return digest.Value; }
}
public override void Flush()
{
main.Flush();
}
protected override void Dispose(bool disposing)
{
if (isDisposed) return;
if (disposing)
{
main.Close();
}
isDisposed = true;
}
public override long FilePointer
{
get { return main.FilePointer; }
}
public override void Seek(long pos)
{
throw new System.SystemException("not allowed");
}
/// <summary> Starts but does not complete the commit of this file (=
/// writing of the final checksum at the end). After this
/// is called must call <see cref="FinishCommit" /> and the
/// <see cref="Dispose" /> to complete the commit.
/// </summary>
public virtual void PrepareCommit()
{
long checksum = Checksum;
// Intentionally write a mismatched checksum. This is
// because we want to 1) test, as best we can, that we
// are able to write a long to the file, but 2) not
// actually "commit" the file yet. This (prepare
// commit) is phase 1 of a two-phase commit.
long pos = main.FilePointer;
main.WriteLong(checksum - 1);
main.Flush();
main.Seek(pos);
}
/// <summary>See <see cref="PrepareCommit" /> </summary>
public virtual void FinishCommit()
{
main.WriteLong(Checksum);
}
public override long Length
{
get { return main.Length; }
}
}
}
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