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Initial commit - WPinternals 2.6
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//
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// Copyright (c) 2008-2011, Kenneth Bell
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//
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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//
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namespace DiscUtils
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{
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/// <summary>
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/// Calculates CRC32 of buffers.
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/// </summary>
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internal sealed class Crc32BigEndian : Crc32
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{
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private static readonly uint[][] Tables;
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static Crc32BigEndian()
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{
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Tables = new uint[4][];
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Tables[(int)Crc32Algorithm.Common] = CalcTable(0x04C11DB7);
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Tables[(int)Crc32Algorithm.Castagnoli] = CalcTable(0x1EDC6F41);
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Tables[(int)Crc32Algorithm.Koopman] = CalcTable(0x741B8CD7);
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Tables[(int)Crc32Algorithm.Aeronautical] = CalcTable(0x814141AB);
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}
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public Crc32BigEndian(Crc32Algorithm algorithm)
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: base(Tables[(int)algorithm])
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{
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}
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public static uint Compute(Crc32Algorithm algorithm, byte[] buffer, int offset, int count)
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{
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return Process(Tables[(int)algorithm], 0xFFFFFFFF, buffer, offset, count) ^ 0xFFFFFFFF;
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}
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public override void Process(byte[] buffer, int offset, int count)
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{
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_value = Process(Table, _value, buffer, offset, count);
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}
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private static uint[] CalcTable(uint polynomial)
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{
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uint[] table = new uint[256];
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for (uint i = 0; i < 256; ++i)
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{
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uint crc = i << 24;
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for (int j = 8; j > 0; --j)
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{
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if ((crc & 0x80000000) != 0)
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{
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crc = (crc << 1) ^ polynomial;
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}
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else
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{
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crc <<= 1;
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}
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}
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table[i] = crc;
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}
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return table;
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}
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private static uint Process(uint[] table, uint accumulator, byte[] buffer, int offset, int count)
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{
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uint value = accumulator;
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for (int i = 0; i < count; ++i)
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{
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byte b = buffer[offset + i];
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value = table[(value >> 24) ^ b] ^ (value << 8);
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}
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return value;
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}
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}
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}
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