ftoa.h

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#ifndef STM32TPL_FTOA_H_INCLUDED
#define STM32TPL_FTOA_H_INCLUDED
 
#include <type_traits>
#include <math.h>
 
template<typename T> typename std::enable_if<std::is_floating_point<T>::value, char*>::type  ftoa(T f, char * buf, int precision){
    char * ptr = buf;
    char * p = ptr;
    char * p1;
    char c;
    long intPart;
 
    #define MAX_PRECISION   (10)
    static const double rounders[MAX_PRECISION + 1] =
    {
        0.5,                // 0
        0.05,               // 1
        0.005,              // 2
        0.0005,             // 3
        0.00005,            // 4
        0.000005,           // 5
        0.0000005,          // 6
        0.00000005,         // 7
        0.000000005,        // 8
        0.0000000005,       // 9
        0.00000000005       // 10
    };
 
    if(isinf(f)){
        buf[0] = 'i';
        buf[1] = 'n';
        buf[2] = 'f';
        buf[3] = '\0';
 
    }
    else if(isnan(f)){
        buf[0] = 'n';
        buf[1] = 'a';
        buf[2] = 'n';
        buf[3] = '\0';
 
    }
    else if(!isnormal(f)){
            buf[0] = 's';
            buf[1] = 'u';
            buf[2] = 'b';
            buf[3] = 'n';
            buf[4] = 'o';
            buf[5] = 'r';
            buf[6] = 'm';
            buf[7] = 'a';
            buf[8] = 'l';
            buf[9] = '\0';
 
        }
 
    // check precision bounds
    if (precision > MAX_PRECISION)
        precision = MAX_PRECISION;
 
    // sign stuff
    if (f < 0)
    {
        f = -f;
        *ptr++ = '-';
    }
 
    if (precision < 0)  // negative precision == automatic precision guess
    {
        if (f < 1.0) precision = 6;
        else if (f < 10.0) precision = 5;
        else if (f < 100.0) precision = 4;
        else if (f < 1000.0) precision = 3;
        else if (f < 10000.0) precision = 2;
        else if (f < 100000.0) precision = 1;
        else precision = 0;
    }
 
    // round value according the precision
    if (precision){
        f += rounders[precision];
    }
 
    // integer part...
    intPart = f;
    f -= intPart;
 
    if (!intPart)
        *ptr++ = '0';
    else
    {
        // save start pointer
        p = ptr;
 
        // convert (reverse order)
        while (intPart)
        {
            *p++ = '0' + intPart % 10;
            intPart /= 10;
        }
 
        // save end pos
        p1 = p;
 
        // reverse result
        while (p > ptr)
        {
            c = *--p;
            *p = *ptr;
            *ptr++ = c;
        }
 
        // restore end pos
        ptr = p1;
    }
 
    // decimal part
    if (precision)
    {
        // place decimal point
        *ptr++ = '.';
 
        // convert
        while (precision--)
        {
            f *= 10.0;
            c = f;
            //TODO Niekedy vypisuje //////////// (pretečenie)
            *ptr++ = '0' + c;
            f -= c;
        }
    }
 
    // terminating zero
    *ptr = 0;
 
    return buf;
}
 
 
#endif // STM32TPL_FTOA_H_INCLUDED