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Annotation of hatari/src/utils.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Hatari - utils.c
        !             3:  *
        !             4:  * This file is distributed under the GNU Public License, version 2 or at
        !             5:  * your option any later version. Read the file gpl.txt for details.
        !             6:  *
        !             7:  * Utils functions :
        !             8:  *     - CRC32
        !             9:  *
        !            10:  * This file contains various utility functions used by different parts of Hatari.
        !            11:  */
        !            12: const char Utils_rcsid[] = "Hatari $Id: utils.c,v 1.2 2008/10/05 20:41:50 npomarede Exp $";
        !            13: 
        !            14: 
        !            15: /* 2008/07/08  [NP]    File creation, CRC32 functions.                         */
        !            16: 
        !            17: 
        !            18: #include "utils.h"
        !            19: 
        !            20: 
        !            21: 
        !            22: 
        !            23: /************************************************************************/
        !            24: /* Functions used to compute the CRC32 of a stream of bytes.           */
        !            25: /* These functions require a pointer to an unsigned int (Uint32) to    */
        !            26: /* store the resulting CRC.                                            */
        !            27: /*     crc32_reset : call this once to reset the CRC, before adding    */
        !            28: /*             some bytes.                                             */
        !            29: /*     crc32_add_byte : update the current CRC with a new byte.        */
        !            30: /************************************************************************/
        !            31: 
        !            32: /*--------------------------------------------------------------*/
        !            33: /* Reset the crc32 value. This should be done before calling   */
        !            34: /* crc32_add_byte().                                           */
        !            35: /*--------------------------------------------------------------*/
        !            36: 
        !            37: void   crc32_reset ( Uint32 *crc )
        !            38: {
        !            39:        *crc = 0xffffffff;
        !            40: }
        !            41: 
        !            42: 
        !            43: /*--------------------------------------------------------------*/
        !            44: /* Update the current value of crc with a new byte.            */
        !            45: /* Call crc32_reset() first to init the crc value.             */
        !            46: /*--------------------------------------------------------------*/
        !            47: 
        !            48: void   crc32_add_byte ( Uint32 *crc , Uint8 c )
        !            49: {
        !            50:        int     bit;
        !            51:     
        !            52:        for ( bit=0 ; bit<8; bit++ )
        !            53:        {
        !            54:                if ( ( c & 0x80 ) ^ ( *crc & 0x80000000 ) )
        !            55:                        *crc = ( *crc << 1 ) ^ CRC32_POLY;
        !            56: 
        !            57:                else
        !            58:                        *crc = *crc << 1;
        !            59: 
        !            60:             c <<= 1;
        !            61:         }
        !            62: }
        !            63: 
        !            64: 
        !            65: /************************************************************************/
        !            66: 
        !            67: 

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