source: bootcd/isolinux/syslinux-6.03/gpxe/src/crypto/crc32.c @ dd1be7c

/*
 * Little-endian CRC32 implementation.
 *
 * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
 *
 * This program 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 any later version.
 *
 * This program 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <gpxe/crc32.h>

#define CRCPOLY         0xedb88320

/**
 * Calculate 32-bit little-endian CRC checksum
 *
 * @v seed      Initial value
 * @v data      Data to checksum
 * @v len       Length of data
 *
 * Usually @a seed is initially zero or all one bits, depending on the
 * protocol. To continue a CRC checksum over multiple calls, pass the
 * return value from one call as the @a seed parameter to the next.
 */
u32 crc32_le ( u32 seed, const void *data, size_t len )
{
        u32 crc = seed;
        const u8 *src = data;
        u32 mult;
        int i;

        while ( len-- ) {
                crc ^= *src++;
                for ( i = 0; i < 8; i++ ) {
                        mult = ( crc & 1 ) ? CRCPOLY : 0;
                        crc = ( crc >> 1 ) ^ mult;
                }
        }

        return crc;
}