#4 bug in dtoa

[Edwin Chen]

The correct way should be:

char dtoa( char aBuf, double aD )
{
double tmpTrunc = trunc( aD );
int tmpTruncInt = (int)tmpTrunc;
char tmpRes = itoa( aBuf, tmpTruncInt );
tmpRes++ = '.';

 static const int    biggestPowerOfTen   = 1000000; // = pow( 10, LONG_DIGITS );

 double              tmpMantissa         = ( tmpTruncInt >= 0 ) ? aD - tmpTrunc : tmpTrunc - aD;

 return uitoa( tmpRes, (int)( biggestPowerOfTen * tmpMantissa) );

}

There is still a small issue with rounding but on the original code the decimal portion was not being decoded.

[Nimrods]

Hi. This actually does not solve the entire issue with the dtoa here. Assuming your number is 3.04, the tmpMantissa will be 0.04. So biggestPowerOfTen * tmpMantissa will be 40000, and the result will be "3.40000"

[Remi Chateauneu]

Hi Nimrods
Thanks for your contribution.
Do you want to contribute this fix yourself to this project ?
Remi

[Edwin Chen]

That is an issue! The code needs to left zero pad. Sorry i haven't tested this code but it is starting point:

char dtoa( char aBuf, double aD )
{
double tmpTrunc = trunc( aD );
int tmpTruncInt = (int)tmpTrunc;
char tmpRes = itoa( aBuf, tmpTruncInt );

tmpRes++ = '.';
 static const int    biggestPowerOfTen   = 10000; // = pow( 10, LONG_DIGITS );

 double              tmpMantissa         = ( tmpTruncInt >= 0 ) ? aD - tmpTrunc : tmpTrunc - aD;
 unsigned int        decimal             = (unsigned int)( biggestPowerOfTen * tmpMantissa)';

 // Left-zero padding
 size_t              pad                 = 4u - ilog_10( decimal );
 memcpy( tmpRes, "0000", pad );
 tempRes += pad;

 return uitoa( tmpRes, decimal );
}

[Nimrods]

Thanks. I'll give it a try.