#include "lib_crc.h"
#define                 P_32        0xEDB88320L

static int              crc_tab32_init          = FALSE;

static unsigned long    crc_tab32[256];


static void             init_crc32_tab( void );


    /*******************************************************************\
    *                                                                   *
    *   unsigned long update_crc_32( unsigned long crc, char c );       *
    *                                                                   *
    *   The function update_crc_32 calculates a  new  CRC-32  value     *
    *   based  on  the  previous value of the CRC and the next byte     *
    *   of the data to be checked.                                      *
    *                                                                   *
    \*******************************************************************/

unsigned long update_crc_32( unsigned long crc, char c ) {

    unsigned long tmp, long_c;

    long_c = 0x000000ffL & (unsigned long) c;

    if ( ! crc_tab32_init ) init_crc32_tab();

    tmp = crc ^ long_c;
    crc = (crc >> 8) ^ crc_tab32[ tmp & 0xff ];

    return crc;

}  /* update_crc_32 */


    /*******************************************************************\
    *                                                                   *
    *   static void init_crc32_tab( void );                             *
    *                                                                   *
    *   The function init_crc32_tab() is used  to  fill  the  array     *
    *   for calculation of the CRC-32 with values.                      *
    *                                                                   *
    \*******************************************************************/

static void init_crc32_tab( void ) {

    int i, j;
    unsigned long crc;

    for (i=0; i<256; i++) {

        crc = (unsigned long) i;

        for (j=0; j<8; j++) {

            if ( crc & 0x00000001L ) crc = ( crc >> 1 ) ^ P_32;
            else                     crc =   crc >> 1;
        }

        crc_tab32[i] = crc;
    }

    crc_tab32_init = TRUE;

}  /* init_crc32_tab */