Ok, so I have a working ftoa and the needed ulltoa (unsigned long long). I use unsigned long longs to get 12 digit precision decimals. It uses a lot of looping to brute-force calculate the result. No floating point math is used, I simply read the data from the float then expand it into whole numbers. Here it is:
Code:
I can comment all of the steps in here if anybody wants to figure out what I am doing. But the function right now works. Doing cout << ftoa(-M_PI) << endl << -M_PI << endl; Gives
Code:
I can add in a rounding feature, but for the case that you really do want a tiny number, this function will print it.
Code:
void ulltoa(unsigned long long number, char *buffer, int base)
{
char *b = (char*)malloc(15);
*b = 0;
while(number)
{
int x = number % 10;
b++;
*b = '0' + x;
number /= 10;
}
while(*b)
*(buffer++) = *(b--);
*buffer = 0;
free(b);
}
char* floatToString(float num)
{
unsigned long long fraction = 1000000000000LL;
unsigned long long f = 0;
unsigned long long d = 0;
unsigned int data = *((int*)(&num));
signed char e = data >> 23;
e &= 0xff;
e -= 127;
bool sign = data & 0b10000000000000000000000000000000;
unsigned int sig = data & 0b00000000011111111111111111111111;
sig |= 0b00000000100000000000000000000000;
sig <<= 8;
for(int i = 23; i; i--)
{
bool a = sig & 0b10000000000000000000000000000000;
if(a)
{
unsigned long long ft = fraction, dt = 0;
for(int ei = e; ei != 0; ei -= (ei >= 0 ? 1 : -1))
{
if(ei > 0)
{
ft <<= 1;
dt <<= 1;
}
else
{
ft >>= 1;
dt >>= 1;
}
while(ft >= 1000000000000LL)
{
ft -= 1000000000000LL;
dt ++;
}
}
d += dt;
f += ft;
while(f >= 1000000000000LL)
{
f -= 1000000000000LL;
d ++;
}
}
fraction >>= 1;
sig <<= 1;
}
char *buffer = (char*)malloc(30);
char dbuffer[15],fbuffer[15];
ulltoa(d,dbuffer,10);
ulltoa(f,fbuffer,10);
if(sign)
{
*buffer = '-';
*(buffer+1) = 0;
}
else
*buffer = 0;
strcat(buffer, dbuffer);
strcat(buffer, ".");
int zeros = 12 - strlen(fbuffer);
while(zeros--)
*(buffer++) = '0';
strcat(buffer, fbuffer);
return buffer;
}I can comment all of the steps in here if anybody wants to figure out what I am doing. But the function right now works. Doing cout << ftoa(-M_PI) << endl << -M_PI << endl; Gives
Code:
-3.141592502588
-3.141592