/usr/include/libpar2/crc.h is in libpar2-dev 0.4-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 | // This file is part of par2cmdline (a PAR 2.0 compatible file verification and
// repair tool). See http://parchive.sourceforge.net for details of PAR 2.0.
//
// Copyright (c) 2003 Peter Brian Clements
//
// par2cmdline is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// par2cmdline is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
#ifndef __CRC_H__
#define __CRC_H__
// These global functions are used to compute the CCITT CRC32 checksum of
// blocks of data.
// The CRC for a block of data may be computed piecemeal be repeatedly
// calling CRCUpdateChar, and CRCUpdateBlock.
// Given the CRC for a block of data in a buffer, CRCSlideChar may be used
// to quickly compute the CRC for the block of data in the buffer that is the
// same size but offset one character later in the buffer.
// Construct the CRC32 lookup table from the specified polynomial
void GenerateCRC32Table(u32 polynomial, u32 (&table)[256]);
// A CRC32 lookup table
struct crc32table
{
crc32table(u32 polynomial)
{
GenerateCRC32Table(polynomial, table);
}
u32 table[256];
};
// The one and only CCITT CRC32 lookup table
extern crc32table ccitttable;
// Update the CRC using one character
inline u32 CRCUpdateChar(u32 crc, u8 ch)
{
return ((crc >> 8) & 0x00ffffffL) ^ ccitttable.table[(u8)crc ^ ch];
}
// Update the CRC using a block of characters in a buffer
inline u32 CRCUpdateBlock(u32 crc, size_t length, const void *buffer)
{
const unsigned char *current = (const unsigned char *)buffer;
while (length-- > 0)
{
crc = ((crc >> 8) & 0x00ffffffL) ^ ccitttable.table[(u8)crc ^ (*current++)];
}
return crc;
}
// Update the CRC using a block of 0s.
inline u32 CRCUpdateBlock(u32 crc, size_t length)
{
while (length-- > 0)
{
crc = ((crc >> 8) & 0x00ffffffL) ^ ccitttable.table[(u8)crc];
}
return crc;
}
// Construct a CRC32 lookup table for windowing
void GenerateWindowTable(u64 window, u32 (&windowtable)[256]);
// Construct the mask value to apply to the CRC when windowing
u32 ComputeWindowMask(u64 window);
// Slide the CRC along a buffer by one character (removing the old and adding the new).
// The new character is added using the main CCITT CRC32 table, and the old character
// is removed using the windowtable.
inline u32 CRCSlideChar(u32 crc, u8 chNew, u8 chOld, const u32 (&windowtable)[256])
{
return ((crc >> 8) & 0x00ffffffL) ^ ccitttable.table[(u8)crc ^ chNew] ^ windowtable[chOld];
}
/*
char *buffer;
u64 window;
//...
u32 windowtable[256];
GenerateWindowTable(window, windowtable);
u32 windowmask = ComputeWindowMask(window);
u32 crc = ~0 ^ CRCUpdateBlock(~0, window, buffer);
crc = windowmask ^ CRCSlideChar(windowmask ^ crc, buffer[window], buffer[0], windowtable);
assert(crc == ~0 ^ CRCUpdateBlock(~0, window, buffer+1));
*/
#endif // __CRC_H__
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