private static bool TryParseNumber(ReadOnlySpan <byte> source, ref Number.NumberBuffer number, out int bytesConsumed, ParseNumberOptions options, out bool textUsedExponentNotation)
{
Debug.Assert(number.DigitsCount == 0);
Debug.Assert(number.Scale == 0);
Debug.Assert(number.IsNegative == false);
Debug.Assert(number.HasNonZeroTail == false);
number.CheckConsistency();
textUsedExponentNotation = false;
if (source.Length == 0)
{
bytesConsumed = 0;
return(false);
}
Span <byte> digits = number.Digits;
int srcIndex = 0;
int dstIndex = 0;
// Consume the leading sign if any.
byte c = source[srcIndex];
switch (c)
{
case Utf8Constants.Minus:
number.IsNegative = true;
goto case Utf8Constants.Plus;
case Utf8Constants.Plus:
srcIndex++;
if (srcIndex == source.Length)
{
bytesConsumed = 0;
return(false);
}
c = source[srcIndex];
break;
default:
break;
}
int startIndexDigitsBeforeDecimal = srcIndex;
int digitCount = 0;
int maxDigitCount = digits.Length - 1;
// Throw away any leading zeroes
while (srcIndex != source.Length)
{
c = source[srcIndex];
if (c != '0')
{
break;
}
srcIndex++;
}
if (srcIndex == source.Length)
{
bytesConsumed = srcIndex;
number.CheckConsistency();
return(true);
}
int startIndexNonLeadingDigitsBeforeDecimal = srcIndex;
int hasNonZeroTail = 0;
while (srcIndex != source.Length)
{
c = source[srcIndex];
int value = (byte)(c - (byte)('0'));
if (value > 9)
{
break;
}
srcIndex++;
digitCount++;
if (digitCount >= maxDigitCount)
{
// For decimal and binary floating-point numbers, we only
// need to store digits up to maxDigCount. However, we still
// need to keep track of whether any additional digits past
// maxDigCount were non-zero, as that can impact rounding
// for an input that falls evenly between two representable
// results.
hasNonZeroTail |= value;
}
}
number.HasNonZeroTail = (hasNonZeroTail != 0);
int numDigitsBeforeDecimal = srcIndex - startIndexDigitsBeforeDecimal;
int numNonLeadingDigitsBeforeDecimal = srcIndex - startIndexNonLeadingDigitsBeforeDecimal;
Debug.Assert(dstIndex == 0);
int numNonLeadingDigitsBeforeDecimalToCopy = Math.Min(numNonLeadingDigitsBeforeDecimal, maxDigitCount);
source.Slice(startIndexNonLeadingDigitsBeforeDecimal, numNonLeadingDigitsBeforeDecimalToCopy).CopyTo(digits);
dstIndex = numNonLeadingDigitsBeforeDecimalToCopy;
number.Scale = numNonLeadingDigitsBeforeDecimal;
if (srcIndex == source.Length)
{
digits[dstIndex] = 0;
number.DigitsCount = dstIndex;
bytesConsumed = srcIndex;
number.CheckConsistency();
return(true);
}
int numDigitsAfterDecimal = 0;
if (c == Utf8Constants.Period)
{
//
// Parse the digits after the decimal point.
//
srcIndex++;
int startIndexDigitsAfterDecimal = srcIndex;
while (srcIndex != source.Length)
{
c = source[srcIndex];
int value = (byte)(c - (byte)('0'));
if (value > 9)
{
break;
}
srcIndex++;
digitCount++;
if (digitCount >= maxDigitCount)
{
// For decimal and binary floating-point numbers, we only
// need to store digits up to maxDigCount. However, we still
// need to keep track of whether any additional digits past
// maxDigCount were non-zero, as that can impact rounding
// for an input that falls evenly between two representable
// results.
hasNonZeroTail |= value;
}
}
number.HasNonZeroTail = (hasNonZeroTail != 0);
numDigitsAfterDecimal = srcIndex - startIndexDigitsAfterDecimal;
int startIndexOfDigitsAfterDecimalToCopy = startIndexDigitsAfterDecimal;
if (dstIndex == 0)
{
// Not copied any digits to the Number struct yet. This means we must continue discarding leading zeroes even though they appeared after the decimal point.
while (startIndexOfDigitsAfterDecimalToCopy < srcIndex && source[startIndexOfDigitsAfterDecimalToCopy] == '0')
{
number.Scale--;
startIndexOfDigitsAfterDecimalToCopy++;
}
}
int numDigitsAfterDecimalToCopy = Math.Min(srcIndex - startIndexOfDigitsAfterDecimalToCopy, maxDigitCount - dstIndex);
source.Slice(startIndexOfDigitsAfterDecimalToCopy, numDigitsAfterDecimalToCopy).CopyTo(digits.Slice(dstIndex));
dstIndex += numDigitsAfterDecimalToCopy;
// We "should" really NUL terminate, but there are multiple places we'd have to do this and it is a precondition that the caller pass in a fully zero=initialized Number.
if (srcIndex == source.Length)
{
if (numDigitsBeforeDecimal == 0 && numDigitsAfterDecimal == 0)
{
// For compatibility. You can say "5." and ".5" but you can't say "."
bytesConsumed = 0;
return(false);
}
digits[dstIndex] = 0;
number.DigitsCount = dstIndex;
bytesConsumed = srcIndex;
number.CheckConsistency();
return(true);
}
}
if (numDigitsBeforeDecimal == 0 && numDigitsAfterDecimal == 0)
{
bytesConsumed = 0;
return(false);
}
if ((c & ~0x20u) != 'E')
{
digits[dstIndex] = 0;
number.DigitsCount = dstIndex;
bytesConsumed = srcIndex;
number.CheckConsistency();
return(true);
}
//
// Parse the exponent after the "E"
//
textUsedExponentNotation = true;
srcIndex++;
if ((options & ParseNumberOptions.AllowExponent) == 0)
{
bytesConsumed = 0;
return(false);
}
if (srcIndex == source.Length)
{
bytesConsumed = 0;
return(false);
}
bool exponentIsNegative = false;
c = source[srcIndex];
switch (c)
{
case Utf8Constants.Minus:
exponentIsNegative = true;
goto case Utf8Constants.Plus;
case Utf8Constants.Plus:
srcIndex++;
if (srcIndex == source.Length)
{
bytesConsumed = 0;
return(false);
}
c = source[srcIndex];
break;
default:
break;
}
// If the next character isn't a digit, an exponent wasn't specified
if ((byte)(c - (byte)('0')) > 9)
{
bytesConsumed = 0;
return(false);
}
if (!TryParseUInt32D(source.Slice(srcIndex), out uint absoluteExponent, out int bytesConsumedByExponent))
{
// Since we found at least one digit, we know that any failure to parse means we had an
// exponent that was larger than uint.MaxValue, and we can just eat characters until the end
absoluteExponent = uint.MaxValue;
// This also means that we know there was at least 10 characters and we can "eat" those, and
// continue eating digits from there
srcIndex += 10;
while (srcIndex != source.Length)
{
c = source[srcIndex];
int value = (byte)(c - (byte)('0'));
if (value > 9)
{
break;
}
srcIndex++;
}
}
srcIndex += bytesConsumedByExponent;
if (exponentIsNegative)
{
if (number.Scale < int.MinValue + (long)absoluteExponent)
{
// A scale underflow means all non-zero digits are all so far to the right of the decimal point, no
// number format we have will be able to see them. Just pin the scale at the absolute minimum
// and let the converter produce a 0 with the max precision available for that type.
number.Scale = int.MinValue;
}
else
{
number.Scale -= (int)absoluteExponent;
}
}
else
{
if (number.Scale > int.MaxValue - (long)absoluteExponent)
{
// A scale overflow means all non-zero digits are all so far to the right of the decimal point, no
// number format we have will be able to see them. Just pin the scale at the absolute maximum
// and let the converter produce a 0 with the max precision available for that type.
number.Scale = int.MaxValue;
}
else
{
number.Scale += (int)absoluteExponent;
}
}
digits[dstIndex] = 0;
number.DigitsCount = dstIndex;
bytesConsumed = srcIndex;
number.CheckConsistency();
return(true);
}
/// <summary>
/// Formats a Decimal as a UTF8 string.
/// </summary>
/// <param name="value">Value to format</param>
/// <param name="destination">Buffer to write the UTF8-formatted value to</param>
/// <param name="bytesWritten">Receives the length of the formatted text in bytes</param>
/// <param name="format">The standard format to use</param>
/// <returns>
/// true for success. "bytesWritten" contains the length of the formatted text in bytes.
/// false if buffer was too short. Iteratively increase the size of the buffer and retry until it succeeds.
/// </returns>
/// <remarks>
/// Formats supported:
/// G/g (default)
/// F/f 12.45 Fixed point
/// E/e 1.245000e1 Exponential
/// </remarks>
/// <exceptions>
/// <cref>System.FormatException</cref> if the format is not valid for this data type.
/// </exceptions>
public static unsafe bool TryFormat(decimal value, Span <byte> destination, out int bytesWritten, StandardFormat format = default)
{
if (format.IsDefault)
{
format = 'G';
}
switch (format.Symbol)
{
case 'g':
case 'G':
{
if (format.Precision != StandardFormat.NoPrecision)
{
throw new NotSupportedException(SR.Argument_GWithPrecisionNotSupported);
}
byte *pDigits = stackalloc byte[Number.DecimalNumberBufferLength];
Number.NumberBuffer number = new Number.NumberBuffer(Number.NumberBufferKind.Decimal, pDigits, Number.DecimalNumberBufferLength);
Number.DecimalToNumber(ref value, ref number);
if (number.Digits[0] == 0)
{
number.IsNegative = false; // For Decimals, -0 must print as normal 0.
}
bool success = TryFormatDecimalG(ref number, destination, out bytesWritten);
#if DEBUG
// This DEBUG segment exists to close a code coverage hole inside TryFormatDecimalG(). Because we don't call RoundNumber() on this path, we have no way to feed
// TryFormatDecimalG() a number where trailing zeros before the decimal point have been cropped. So if the chance comes up, we'll crop the zeroes
// ourselves and make a second call to ensure we get the same outcome.
if (success)
{
Span <byte> digits = number.Digits;
int numDigits = number.DigitsCount;
if (numDigits != 0 && number.Scale == numDigits && digits[numDigits - 1] == '0')
{
while (numDigits != 0 && digits[numDigits - 1] == '0')
{
digits[numDigits - 1] = 0;
numDigits--;
}
number.DigitsCount = numDigits;
number.CheckConsistency();
byte[] buffer2 = new byte[destination.Length];
bool success2 = TryFormatDecimalG(ref number, buffer2, out int bytesWritten2);
Debug.Assert(success2);
Debug.Assert(bytesWritten2 == bytesWritten);
for (int i = 0; i < bytesWritten; i++)
{
Debug.Assert(destination[i] == buffer2[i]);
}
}
}
#endif // DEBUG
return(success);
}
case 'f':
case 'F':
{
byte *pDigits = stackalloc byte[Number.DecimalNumberBufferLength];
Number.NumberBuffer number = new Number.NumberBuffer(Number.NumberBufferKind.Decimal, pDigits, Number.DecimalNumberBufferLength);
Number.DecimalToNumber(ref value, ref number);
byte precision = (format.Precision == StandardFormat.NoPrecision) ? (byte)2 : format.Precision;
Number.RoundNumber(ref number, number.Scale + precision, isCorrectlyRounded: false);
Debug.Assert((number.Digits[0] != 0) || !number.IsNegative); // For Decimals, -0 must print as normal 0. As it happens, Number.RoundNumber already ensures this invariant.
return(TryFormatDecimalF(ref number, destination, out bytesWritten, precision));
}
case 'e':
case 'E':
{
byte *pDigits = stackalloc byte[Number.DecimalNumberBufferLength];
Number.NumberBuffer number = new Number.NumberBuffer(Number.NumberBufferKind.Decimal, pDigits, Number.DecimalNumberBufferLength);
Number.DecimalToNumber(ref value, ref number);
byte precision = (format.Precision == StandardFormat.NoPrecision) ? (byte)6 : format.Precision;
Number.RoundNumber(ref number, precision + 1, isCorrectlyRounded: false);
Debug.Assert((number.Digits[0] != 0) || !number.IsNegative); // For Decimals, -0 must print as normal 0. As it happens, Number.RoundNumber already ensures this invariant.
return(TryFormatDecimalE(ref number, destination, out bytesWritten, precision, exponentSymbol: (byte)format.Symbol));
}
default:
return(FormattingHelpers.TryFormatThrowFormatException(out bytesWritten));
}
}
