public static bool TryParseDecimal(ReadOnlySpan <char> value, bool allowThousands, out decimal result)
{
result = 0;
if (value.Length == 0)
{
return(false);
}
ulong preResult = 0;
bool isLargeNumber = false;
int i = 0;
int end = value.Length;
var state = ParseState.LeadingWhite;
bool negative = false;
bool noIntegerPart = false;
sbyte scale = 0;
while (i < end)
{
var c = value[i++];
switch (state)
{
case ParseState.LeadingWhite:
if (JsonUtils.IsWhiteSpace(c))
{
break;
}
if (c == '-')
{
negative = true;
state = ParseState.Sign;
}
else if (c == '.')
{
noIntegerPart = true;
state = ParseState.FractionNumber;
if (i == end)
{
return(false);
}
}
else if (c == '0')
{
state = ParseState.DecimalPoint;
}
else if (c > '0' && c <= '9')
{
preResult = (ulong)(c - '0');
state = ParseState.Number;
}
else
{
return(false);
}
break;
case ParseState.Sign:
if (c == '.')
{
noIntegerPart = true;
state = ParseState.FractionNumber;
if (i == end)
{
return(false);
}
}
else if (c == '0')
{
state = ParseState.DecimalPoint;
}
else if (c > '0' && c <= '9')
{
preResult = (ulong)(c - '0');
state = ParseState.Number;
}
else
{
return(false);
}
break;
case ParseState.Number:
if (c == '.')
{
state = ParseState.FractionNumber;
}
else if (c >= '0' && c <= '9')
{
if (isLargeNumber)
{
checked
{
result = 10 * result + (c - '0');
}
}
else
{
preResult = 10 * preResult + (ulong)(c - '0');
if (preResult > ulong.MaxValue / 10 - 10)
{
isLargeNumber = true;
result = preResult;
}
}
}
else if (JsonUtils.IsWhiteSpace(c))
{
state = ParseState.TrailingWhite;
}
else if (allowThousands && c == ',')
{
}
else
{
return(false);
}
break;
case ParseState.DecimalPoint:
if (c == '.')
{
state = ParseState.FractionNumber;
}
else
{
return(false);
}
break;
case ParseState.FractionNumber:
if (JsonUtils.IsWhiteSpace(c))
{
if (noIntegerPart)
{
return(false);
}
state = ParseState.TrailingWhite;
}
else if (c == 'e' || c == 'E')
{
if (noIntegerPart && scale == 0)
{
return(false);
}
state = ParseState.Exponent;
}
else if (c >= '0' && c <= '9')
{
if (isLargeNumber)
{
checked
{
result = 10 * result + (c - '0');
}
}
else
{
preResult = 10 * preResult + (ulong)(c - '0');
if (preResult > ulong.MaxValue / 10 - 10)
{
isLargeNumber = true;
result = preResult;
}
}
scale++;
}
else
{
return(false);
}
break;
case ParseState.Exponent:
bool expNegative = false;
if (c == '-')
{
if (i == end)
{
return(false);
}
expNegative = true;
c = value[i++];
}
else if (c == '+')
{
if (i == end)
{
return(false);
}
c = value[i++];
}
//skip leading zeroes
while (c == '0' && i < end)
{
c = value[i++];
}
if (c > '0' && c <= '9')
{
var exp = SignedInteger <long> .ParseInt64(value.Slice(i - 1, end - i + 1));
if (exp < sbyte.MinValue || exp > sbyte.MaxValue)
{
return(false);
}
if (!expNegative)
{
exp = (sbyte)-exp;
}
if (exp >= 0 || scale > -exp)
{
scale += (sbyte)exp;
}
else
{
for (int j = 0; j < -exp - scale; j++)
{
if (isLargeNumber)
{
checked
{
result = 10 * result;
}
}
else
{
preResult = 10 * preResult;
if (preResult > ulong.MaxValue / 10)
{
isLargeNumber = true;
result = preResult;
}
}
}
scale = 0;
}
//set i to end of string, because ParseInt16 eats number and all trailing whites
i = end;
}
else
{
return(false);
}
break;
case ParseState.TrailingWhite:
if (!JsonUtils.IsWhiteSpace(c))
{
return(false);
}
break;
}
}
if (!isLargeNumber)
{
var mid = (int)(preResult >> 32);
var lo = (int)(preResult & 0xffffffff);
result = new decimal(lo, mid, 0, negative, (byte)scale);
}
else
{
var bits = decimal.GetBits(result);
result = new decimal(bits[0], bits[1], bits[2], negative, (byte)scale);
}
return(true);
}
public override long ParseInt64(ReadOnlySpan <char> value) => SignedInteger <int> .ParseInt64(value);