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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;
namespace Lucene.Net.Support
{
public class CRC32 : IChecksum
{
private static readonly UInt32[] crcTable = InitializeCRCTable();
private static UInt32[] InitializeCRCTable()
{
UInt32[] crcTable = new UInt32[256];
for (UInt32 n = 0; n < 256; n++)
{
UInt32 c = n;
for (int k = 8; --k >= 0; )
{
if ((c & 1) != 0)
c = 0xedb88320 ^ (c >> 1);
else
c = c >> 1;
}
crcTable[n] = c;
}
return crcTable;
}
private UInt32 crc = 0;
public long Value
{
get
{
return crc & 0xffffffffL;
}
}
public void Reset()
{
crc = 0;
}
public void Update(int bval)
{
UInt32 c = ~crc;
c = crcTable[(c ^ bval) & 0xff] ^ (c >> 8);
crc = ~c;
}
public void Update(byte[] buf, int off, int len)
{
UInt32 c = ~crc;
while (--len >= 0)
c = crcTable[(c ^ buf[off++]) & 0xff] ^ (c >> 8);
crc = ~c;
}
public void Update(byte[] buf)
{
Update(buf, 0, buf.Length);
}
}
}
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