/// <summary>
/// Convert a 64-bit floating point number to a fixed notation string.
/// </summary>
internal static void ToFixedString(StringBuilder result, ulong ieeeMantissa,
uint ieeeExponent, int precision, RyuFormatOptions options,
NumberFormatInfo info)
{
bool zero = true, soft = (options & RyuFormatOptions.SoftPrecision) != 0;
int exponent = Decode(ieeeMantissa, ieeeExponent, out ulong mantissa), start =
result.Length;
ulong mShift = mantissa << MANTISSA_SHIFT;
uint digits;
if (exponent >= -RyuFloat64.DOUBLE_MANTISSA_BITS)
{
int idx = (exponent < 0) ? 0 : RyuUtils.IndexForExponent(exponent), p10bits =
Pow10BitsForIndex(idx), i = RyuUtils.LengthForIndex(idx) - 1, p =
RyuTables.POW10_OFFSET_D[idx] + i, j = p10bits - exponent + MANTISSA_SHIFT;
for (; i >= 0; i--)
{
digits = RyuUtils.MulShiftMod1E9(mShift, RyuTables.POW10_SPLIT_D[p, 0],
RyuTables.POW10_SPLIT_D[p, 1], RyuTables.POW10_SPLIT_D[p, 2], j);
if (!zero)
{
RyuUtils.Append9Digits(result, digits);
}
else if (digits != 0U)
{
RyuUtils.AppendNDigits(result, RyuUtils.DecimalLength9(digits),
digits);
zero = false;
}
p--;
}
}
if (zero)
{
result.Append(RyuUtils.ZERO);
}
if ((options & RyuFormatOptions.ThousandsSeparators) != 0)
{
RyuUtils.AddThousands(result, start, info);
}
if (precision > 0 && (!soft || exponent < 0))
{
result.Append(info.NumberDecimalSeparator);
}
if (exponent < 0)
{
// 0 = don't round up; 1 = round up unconditionally; 2 = round up if odd
int idx = (-exponent) >> 4, roundFlag = 0, i = 0, blocks = precision / 9 + 1,
minBlock = RyuTables.MIN_BLOCK_2_D[idx];
if (blocks <= minBlock)
{
RyuUtils.Append0(result, precision);
i = blocks;
}
else if (i < minBlock)
{
RyuUtils.Append0(result, 9 * minBlock);
i = minBlock;
}
int p = RyuTables.POW10_OFFSET_2_D[idx] + i - minBlock, pMax = RyuTables.
POW10_OFFSET_2_D[idx + 1], j = MANTISSA_SHIFT + POW10_ADDITIONAL_BITS -
exponent - (idx << 4);
for (; i < blocks; ++i)
{
if (p >= pMax)
{
// If the remaining digits are all 0, then no rounding required
if (!soft)
{
RyuUtils.Append0(result, precision - 9 * i);
}
break;
}
digits = RyuUtils.MulShiftMod1E9(mShift, RyuTables.POW10_SPLIT_2_D[p, 0],
RyuTables.POW10_SPLIT_2_D[p, 1], RyuTables.POW10_SPLIT_2_D[p, 2], j);
if (i < blocks - 1)
{
RyuUtils.Append9Digits(result, digits);
}
else
{
int maximum = precision - 9 * i;
uint lastDigit = RyuUtils.LastDigit(ref digits, 9 - maximum);
// Is m * 10^(additionalDigits + 1) / 2^(-e2) integer?
if (lastDigit > 5U)
{
roundFlag = 1;
}
else if (lastDigit < 5U)
{
roundFlag = 0;
}
else if (HasTrailingZeroes(exponent, precision + 1, mantissa))
{
roundFlag = 2;
}
else
{
roundFlag = 1;
}
if (maximum > 0)
{
RyuUtils.AppendCDigits(result, digits, maximum);
}
break;
}
p++;
}
if (roundFlag != 0 && RyuUtils.RoundResult(result, start, roundFlag,
out int decimalIndex, info))
{
if (decimalIndex > 0)
{
result[decimalIndex++] = RyuUtils.ZERO;
result[decimalIndex] = info.NumberDecimalSeparator[0];
}
result.Append(RyuUtils.ZERO);
}
if (soft && precision > 0)
{
RyuUtils.SoftenResult(result, info);
}
}
else if (!soft)
{
RyuUtils.Append0(result, precision);
}
}