#include "paulcommoncrc.h"

PaulCommonCRC::PaulCommonCRC(QObject *parent) :
    QObject(parent)
{
    initLookUpTableForCRC();
}

void PaulCommonCRC::initLookUpTableForCRC( void )
{
    unsigned int i;
    unsigned int tmp;

    for (i=0; i<256; i++)
    {
        tmp = 0;
        if((i & 1) != 0) {
            tmp = tmp ^ 0x1021;
        }
        if((i & 2) != 0) {
            tmp = tmp ^ 0x2042;
        }
        if((i & 4) != 0) {
            tmp = tmp ^ 0x4084;
        }
        if((i & 8) != 0) {
            tmp = tmp ^ 0x8108;
        }
        if((i & 16) != 0) {
            tmp = tmp ^ 0x1231;
        }
        if((i & 32) != 0) {
            tmp = tmp ^ 0x2462;
        }
        if((i & 64) != 0) {
            tmp = tmp ^ 0x48c4;
        }
        if((i & 128) != 0) {
            tmp = tmp ^ 0x9188;
        }
        lookUpTableForCRC[i] = tmp;
    }
}

void PaulCommonCRC::GetCRCAsTwoBytes(unsigned char* data, unsigned char* crcAsTwoBytes, unsigned int sizeOfData)
{
    unsigned int Chk;
    unsigned int j;
    Chk = 0xffff; // reset the syndrom to all ones
    for (j=0; j<sizeOfData; j++) {
        Chk = Crc_opt(data[j], Chk);
    }
    crcAsTwoBytes[0] = (unsigned char) (Chk >> 8);
    crcAsTwoBytes[1] = (unsigned char) (Chk & 0x00ff);
}

unsigned int PaulCommonCRC::Crc_opt( unsigned char D, unsigned int Chk)
{
    return(((Chk << 8) & 0xff00)^lookUpTableForCRC [(((Chk >> 8)^D) & 0x00ff)]);
}