실수에서 정수형변환시 값손실

size_t utils_floatToText(double data,
                         uint8_t * string,
                         size_t length)
{
    size_t intLength;
    size_t decLength;
    int64_t intPart;
    double decPart;
 
    if (data <= (double)INT64_MIN || data >= (double)INT64_MAX) return 0;
 
    intPart = (int64_t)data;
    decPart = data - intPart;
    if (decPart < 0)
    {
        decPart = 1 - decPart;
    }
    else
    {
        decPart = 1 + decPart;
    }
 
    if (decPart <= 1 + FLT_EPSILON)
    {
        decPart = 0;
    }
 
    if (intPart == 0 && data < 0)
    {
        // deal with numbers between -1 and 0
        if (length < 4) return 0;   // "-0.n"
        string[0] = '-';
        string[1] = '0';
        intLength = 2;
    }
    else
    {
        intLength = utils_intToText(intPart, string, length);
        if (intLength == 0) return 0;
    }
    decLength = 0;
    if (decPart >= FLT_EPSILON)
    {
        int i;
        double noiseFloor;
 
        if (intLength >= length - 1) return 0;
 
        i = 0;
        noiseFloor = FLT_EPSILON;
        do
        {
            decPart *= 10;
            noiseFloor *= 10;
            fprintf(stderr,"decPart = %f , (int64)dec Part = %d,noiseFloor = %f \n",decPart,(int64_t)decPart,noiseFloor);
            i++;
        } while (decPart - (int64_t)decPart > noiseFloor);
 
        decLength = utils_intToText(decPart, string + intLength, length - intLength);
        if (decLength <= 1) return 0;
 
        // replace the leading 1 with a dot
        string[intLength] = '.';
    }
    fprintf(stderr,"decPart = %f , convert = %s \n",decPart,string + intLength);
    return intLength + decLength;
}