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94 lines
2.6 KiB
C++
94 lines
2.6 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2012.
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Copyright(C) Krzysztof Dabrowski 1999, 2000.
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Copyright(C) ElysiuM deeZine 1999, 2000.
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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
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along
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with Sortix. If not, see <http://www.gnu.org/licenses/>.
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crc32.cpp
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Calculates a CRC32 Checksum on binary data.
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*******************************************************************************/
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#include <stdlib.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <errno.h>
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#include <error.h>
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#include "crc32.h"
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void GenerateCRC32Table(uint32_t tabel[256])
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{
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uint32_t poly = 0xEDB88320U;
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for ( uint32_t i = 0; i < 256; i++ )
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{
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uint32_t crc = i;
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for ( uint32_t j = 8; 0 < j; j-- )
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{
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if ( crc & 1 ) { crc = (crc >> 1) ^ poly; }
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else { crc >>= 1; }
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}
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tabel[i] = crc;
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}
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}
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uint32_t ContinueCRC32(uint32_t tabel[256], uint32_t crc, uint8_t* block,
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size_t size)
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{
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for ( size_t i = 0; i < size; i++ )
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{
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crc = ((crc >> 8) & 0x00FFFFFF) ^ tabel[(crc ^ *block++) & 0xFF];
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}
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return crc;
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}
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uint32_t FinishCRC32(uint32_t crc)
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{
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return crc ^ 0xFFFFFFFF;
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}
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uint32_t CRC32(uint8_t* block, size_t size)
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{
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uint32_t tabel[256];
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GenerateCRC32Table(tabel);
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return FinishCRC32(ContinueCRC32(tabel, CRC32_START_SEED, block, size));
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}
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bool CRC32File(uint32_t* result, const char* name, int fd, off_t offset,
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off_t length)
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{
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uint32_t tabel[256];
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GenerateCRC32Table(tabel);
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uint32_t crc = CRC32_START_SEED;
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const size_t BUFFER_SIZE = 16UL * 1024UL;
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uint8_t buffer[BUFFER_SIZE];
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off_t sofar = 0;
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ssize_t amount = 0;
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while ( sofar < length &&
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0 < (amount = pread(fd, buffer, BUFFER_SIZE, offset + sofar)) )
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{
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if ( length - sofar < amount ) { amount = length - sofar; }
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crc = ContinueCRC32(tabel, crc, buffer, amount);
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sofar += amount;
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}
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if ( amount < 0 ) { error(0, errno, "read: %s", name); return false; }
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if ( sofar < length ) { error(0, EIO, "read: %s", name); return false; }
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crc = FinishCRC32(crc);
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*result = crc;
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return true;
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}
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