/*
Copyright (C) Magna Carta Software, Inc. 1990.  All Rights Reserved
C TELECOMM TOOLKIT v1.0
CRCCCITT.C -- ROUTINES TO HANDLE CRC-CCITT CALCULATION.
*/


#if !defined(TYPES_DEFINED)
    typedef unsigned char   BYTE;
    typedef unsigned short  WORD;
    #define TYPES_DEFINED
#endif


#define CRC_CCITT               0X1021


WORD crc_ccitt(WORD crc, WORD ch)
{
    WORD i;
    ch <<= 8;
    for (i=8; i > 0; i--) {
        if ((ch ^ crc) & 0X8000) crc = (crc << 1) ^ CRC_CCITT;
        else crc <<= 1;
        ch <<=1;
    }

    return (crc);
}