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sortix--sortix/sortix/crc32.cpp

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/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2012.
Copyright(C) Krzysztof Dabrowski 1999, 2000.
Copyright(C) ElysiuM deeZine 1999, 2000.
Based on implementation by Finn Yannick Jacobs.
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This file is part of Sortix.
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Sortix 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 3 of the License, or (at your option) any later
version.
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Sortix 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.
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You should have received a copy of the GNU General Public License along with
Sortix. If not, see <http://www.gnu.org/licenses/>.
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crc32.cpp
Calculates a CRC32 Checksum of binary data.
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*******************************************************************************/
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#include <sortix/kernel/platform.h>
#include <sortix/kernel/crc32.h>
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namespace Sortix {
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namespace CRC32 {
void GenerateTable(uint32_t tabel[256])
{
uint32_t poly = 0xEDB88320U;
for ( uint32_t i = 0; i < 256; i++ )
{
uint32_t crc = i;
for ( uint32_t j = 8; 0 < j; j-- )
{
if ( crc & 1 ) { crc = (crc >> 1) ^ poly; }
else { crc >>= 1; }
}
tabel[i] = crc;
}
}
uint32_t Continue(uint32_t tabel[256], uint32_t crc, uint8_t* block,
size_t size)
{
for ( size_t i = 0; i < size; i++ )
{
crc = ((crc >> 8) & 0x00FFFFFF) ^ tabel[(crc ^ *block++) & 0xFF];
}
return crc;
}
uint32_t Finish(uint32_t crc)
{
return crc ^ 0xFFFFFFFF;
}
uint32_t Hash(uint8_t* block, size_t size)
{
uint32_t tabel[256];
GenerateTable(tabel);
return Finish(Continue(tabel, START_SEED, block, size));
}
} // namespace CRC32
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} // namespace Sortix