lib_crc.c

crc-16 crc-8 crc-32各种CRC校验C源代码

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

unsigned short update_crc_dnp( unsigned short crc, char c ) {

    unsigned short tmp, short_c;

    short_c = 0x00ff & (unsigned short) c;

    if ( ! crc_tabdnp_init ) init_crcdnp_tab();

    tmp =  crc       ^ short_c;
    crc = (crc >> 8) ^ crc_tabdnp[ tmp & 0xff ];

    return crc;

}  /* update_crc_dnp */



    /*******************************************************************\
    *                                                                   *
    *   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_crc16_tab( void );                             *
    *                                                                   *
    *   The function init_crc16_tab() is used  to  fill  the  array     *
    *   for calculation of the CRC-16 with values.                      *
    *                                                                   *
    \*******************************************************************/

static void init_crc16_tab( void ) {

    int i, j;
    unsigned short crc, c;

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

        crc = 0;
        c   = (unsigned short) i;

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

            if ( (crc ^ c) & 0x0001 ) crc = ( crc >> 1 ) ^ P_16;
            else                      crc =   crc >> 1;

            c = c >> 1;
        }

        crc_tab16[i] = crc;
    }

    crc_tab16_init = TRUE;

}  /* init_crc16_tab */



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

static void init_crcdnp_tab( void ) {

    int i, j;
    unsigned short crc, c;

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

        crc = 0;
        c   = (unsigned short) i;

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

            if ( (crc ^ c) & 0x0001 ) crc = ( crc >> 1 ) ^ P_DNP;
            else                      crc =   crc >> 1;

            c = c >> 1;
        }

        crc_tabdnp[i] = crc;
    }

    crc_tabdnp_init = TRUE;

}  /* init_crcdnp_tab */



    /*******************************************************************\
    *                                                                   *
    *   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 */



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

static void init_crcccitt_tab( void ) {

    int i, j;
    unsigned short crc, c;

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

        crc = 0;
        c   = ((unsigned short) i) << 8;

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

            if ( (crc ^ c) & 0x8000 ) crc = ( crc << 1 ) ^ P_CCITT;
            else                      crc =   crc << 1;

            c = c << 1;
        }

        crc_tabccitt[i] = crc;
    }

    crc_tabccitt_init = TRUE;

}  /* init_crcccitt_tab */