32baseten.h

inline unsigned int isodd(unsigned int x) { return x & 1; }

template <class T>
inline T tempow( T m, T num) //template pow
{
    T o=m;

    while(num>1){
        num--;
        o*=m;
    }
    return o;
}

//table of 10s up to 64bit uint
static const unsigned int tabp10[]={ //1, 10, 100 ... 10^39
    1,
    tempow((unsigned int)10,(unsigned int)1),
    tempow((unsigned int)10,(unsigned int)2),
    tempow((unsigned int)10,(unsigned int)3),
    tempow((unsigned int)10,(unsigned int)4),
    tempow((unsigned int)10,(unsigned int)5),
    tempow((unsigned int)10,(unsigned int)6),
    tempow((unsigned int)10,(unsigned int)7),
    tempow((unsigned int)10,(unsigned int)8),
    tempow((unsigned int)10,(unsigned int)9),
    tempow((unsigned int)10,(unsigned int)10),
    tempow((unsigned int)10,(unsigned int)11)
};

template <class T>
inline T powt10(T num)
{
    return tabp10[num];
}

unsigned int baseTwoDigits(unsigned int x) {
    return x ? 32 - __builtin_clz(x) : 0;
}

static unsigned int logt10(unsigned int x) {
    static const unsigned char guess[33] = {
        0, 0, 0, 0, 1, 1, 1, 2, 2, 2,
        3, 3, 3, 3, 4, 4, 4, 5, 5, 5,
        6, 6, 6, 6, 7, 7, 7, 8, 8, 8,
        9, 9, 9
    };
    unsigned int digits = guess[baseTwoDigits(x)];
    return digits + (x >= tabp10[digits]);
}

//double any substring of a number
inline unsigned int brusselDouble(unsigned int n, unsigned int offsetLeft/*offset left*/, unsigned int length/*length*/){
    unsigned int tnum  = n %powt10(offsetLeft+length) /powt10(offsetLeft);          //parse target number

    unsigned int mag = powt10(logt10(tnum));    //compensate magnitude difference
    bool magDif = ((tnum<<1)>=mag);

    unsigned int tnum2 = tnum<<1;               //double
    tnum2 *=powt10(offsetLeft);                 //trailing zeros

    unsigned int prefix=  n/powt10(offsetLeft+length) * powt10(offsetLeft+length+magDif);   //substring prefix
    unsigned int suffix = n%powt10(offsetLeft);                                             //substring suffix

    unsigned int out = prefix+tnum2+suffix;     //concatenate

    return out;
}

//divide any substring of a number
inline unsigned int brusselDivide(unsigned int n, unsigned int offsetLeft, unsigned int length){
    unsigned int tnum  = n%powt10(offsetLeft+length) /powt10(offsetLeft);           //parse target number
    if(isodd(tnum)){return 0;}

    unsigned int mag = powt10((int8_t)logt10(tnum)-1);  //compensate magnitude difference
    bool magDif = (tnum<(mag<<1));

    unsigned int prefix = n/powt10(offsetLeft+length) * powt10(offsetLeft+length-magDif);   //substring prefix
    unsigned int suffix = n%powt10(offsetLeft);                                             //substring suffix
    unsigned int tnum2 = tnum>>1;               //halve

    tnum2 *=powt10(offsetLeft);                 //trailing zeros

    unsigned int out = prefix+tnum2+suffix;     //concatenate

    return out;
}