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Annotation of qemu/roms/ipxe/src/crypto/crc32.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Little-endian CRC32 implementation.
        !             3:  *
        !             4:  * Copyright (c) 2009 Joshua Oreman <[email protected]>.
        !             5:  *
        !             6:  * This program is free software; you can redistribute it and/or
        !             7:  * modify it under the terms of the GNU General Public License as
        !             8:  * published by the Free Software Foundation; either version 2 of the
        !             9:  * License, or any later version.
        !            10:  *
        !            11:  * This program is distributed in the hope that it will be useful, but
        !            12:  * WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            14:  * General Public License for more details.
        !            15:  *
        !            16:  * You should have received a copy of the GNU General Public License
        !            17:  * along with this program; if not, write to the Free Software
        !            18:  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            19:  */
        !            20: 
        !            21: FILE_LICENCE ( GPL2_OR_LATER );
        !            22: 
        !            23: #include <ipxe/crc32.h>
        !            24: 
        !            25: #define CRCPOLY                0xedb88320
        !            26: 
        !            27: /**
        !            28:  * Calculate 32-bit little-endian CRC checksum
        !            29:  *
        !            30:  * @v seed     Initial value
        !            31:  * @v data     Data to checksum
        !            32:  * @v len      Length of data
        !            33:  *
        !            34:  * Usually @a seed is initially zero or all one bits, depending on the
        !            35:  * protocol. To continue a CRC checksum over multiple calls, pass the
        !            36:  * return value from one call as the @a seed parameter to the next.
        !            37:  */
        !            38: u32 crc32_le ( u32 seed, const void *data, size_t len )
        !            39: {
        !            40:        u32 crc = seed;
        !            41:        const u8 *src = data;
        !            42:        u32 mult;
        !            43:        int i;
        !            44: 
        !            45:        while ( len-- ) {
        !            46:                crc ^= *src++;
        !            47:                for ( i = 0; i < 8; i++ ) {
        !            48:                        mult = ( crc & 1 ) ? CRCPOLY : 0;
        !            49:                        crc = ( crc >> 1 ) ^ mult;
        !            50:                }
        !            51:        }
        !            52: 
        !            53:        return crc;
        !            54: }

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