/*
  Low level precision floating point lib
  Author: Henrik Schiøler
*/

//low precision floating pt type
typedef struct myfloat
{
        signed char mantissa;
        signed char exponent;
} myfloat_type;


//convert from double to low precision type
void doub2mydouble(double arg, myfloat_type *res)
{
   int exponent;
   double temp;
   exponent = ceil(log(abs(arg))/log(2)); //base 2 logarithm
   temp=arg*pow(2,7-exponent);
   res->mantissa = (signed char)temp;
   res->exponent = exponent-7;
}

//convert from low precision type to double
double myfloat2double(myfloat_type *arg1)
{
  double res = (double)(arg1->mantissa) * pow(2,arg1->exponent);
   return res;
}

//multiply to low precision types
void mult_float(myfloat_type *arg1,myfloat_type *arg2,myfloat_type *result)
{
  int temp;
  unsigned char sign;
  
  sign=0x80 & ((unsigned char)arg1-> mantissa ^ (unsigned char)arg2-> mantissa); //find sign of result 
  
  char i=0;
   temp = (int)(arg1-> mantissa) * (int)(arg2-> mantissa);
   
   temp = temp & 0x7f00; //take away sign from product
  
   while(abs(temp)>128)
   {
      i++;
      temp=temp>>1;
   }
   
   result->mantissa = (unsigned char) temp;
   
   result->mantissa = result->mantissa | sign; //add recorded sign
   
   result->exponent = arg1->exponent + arg2->exponent + i;
   
}