Lucene.Net  3.0.3
Lucene.Net is a port of the Lucene search engine library, written in C# and targeted at .NET runtime users.
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CRC32.cs
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3  * Licensed to the Apache Software Foundation (ASF) under one
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21 
22 using System;
23 
24 namespace Lucene.Net.Support
25 {
26  public class CRC32 : IChecksum
27  {
28  private static readonly UInt32[] crcTable = InitializeCRCTable();
29 
30  private static UInt32[] InitializeCRCTable()
31  {
32  UInt32[] crcTable = new UInt32[256];
33  for (UInt32 n = 0; n < 256; n++)
34  {
35  UInt32 c = n;
36  for (int k = 8; --k >= 0; )
37  {
38  if ((c & 1) != 0)
39  c = 0xedb88320 ^ (c >> 1);
40  else
41  c = c >> 1;
42  }
43  crcTable[n] = c;
44  }
45  return crcTable;
46  }
47 
48  private UInt32 crc = 0;
49 
50  public long Value
51  {
52  get
53  {
54  return crc & 0xffffffffL;
55  }
56  }
57 
58  public void Reset()
59  {
60  crc = 0;
61  }
62 
63  public void Update(int bval)
64  {
65  UInt32 c = ~crc;
66  c = crcTable[(c ^ bval) & 0xff] ^ (c >> 8);
67  crc = ~c;
68  }
69 
70  public void Update(byte[] buf, int off, int len)
71  {
72  UInt32 c = ~crc;
73  while (--len >= 0)
74  c = crcTable[(c ^ buf[off++]) & 0xff] ^ (c >> 8);
75  crc = ~c;
76  }
77 
78  public void Update(byte[] buf)
79  {
80  Update(buf, 0, buf.Length);
81  }
82  }
83 }