mirror of
https://github.com/nzbget/nzbget.git
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85 lines
2.0 KiB
C++
85 lines
2.0 KiB
C++
// This file is part of par2cmdline (a PAR 2.0 compatible file verification and
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// repair tool). See http://parchive.sourceforge.net for details of PAR 2.0.
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//
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// Copyright (c) 2003 Peter Brian Clements
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//
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// par2cmdline is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// par2cmdline is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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#include "nzbget.h"
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#include "par2cmdline.h"
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#ifdef _MSC_VER
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#ifdef _DEBUG
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#undef THIS_FILE
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static char THIS_FILE[]=__FILE__;
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#define new DEBUG_NEW
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#endif
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#endif
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namespace Par2
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{
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// The one and only CCITT CRC32 lookup table
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crc32table ccitttable(0xEDB88320L);
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// Construct the CRC32 lookup table from the specified polynomial
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void GenerateCRC32Table(u32 polynomial, u32 (&table)[256])
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{
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for (u32 i = 0; i <= 255 ; i++)
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{
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u32 crc = i;
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for (u32 j = 0; j < 8; j++)
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{
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crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
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}
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table[i] = crc;
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}
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}
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// Construct a CRC32 lookup table for windowing
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void GenerateWindowTable(u64 window, u32 (&target)[256])
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{
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for (u32 i=0; i<=255; i++)
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{
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u32 crc = ccitttable.table[i];
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for (u64 j=0; j<window; j++)
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{
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crc = ((crc >> 8) & 0x00ffffffL) ^ ccitttable.table[(u8)crc];
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}
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target[i] = crc;
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}
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}
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// Construct the mask value to apply to the CRC when windowing
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u32 ComputeWindowMask(u64 window)
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{
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u32 result = ~0;
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while (window > 0)
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{
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result = CRCUpdateChar(result, (char)0);
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window--;
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}
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result ^= ~0;
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return result;
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}
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} // end namespace Par2
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