/// <summary> Parses a number whose format follows the JSON specification
/// (RFC 4627). Roughly speaking, a valid number consists of an optional
/// minus sign, one or more digits (starting with 1 to 9 unless the only
/// digit is 0), an optional decimal point with one or more digits, and
/// an optional letter E or e with one or more digits (the exponent). </summary>
/// <param name='str'>A string to parse.</param>
/// <param name='integersOnly'>If true, no decimal points or exponents
/// are allowed in the string.</param>
/// <param name='positiveOnly'>If true, only positive numbers are
/// allowed (the leading minus is disallowed).</param>
/// <param name='failOnExponentOverflow'>If true, this function
/// will return null if the exponent is less than -(2^64) or greater than
/// 2^64-1 (unless the value is 0). If false, this function will return
/// a CBOR object representing positive or negative infinity if the exponent
/// is greater than 2^64-1 (unless the value is 0), and will return zero
/// if the exponent is less than -(2^64).</param>
/// <returns>A CBOR object that represents the parsed number.</returns>
public static CBORObject ParseJSONNumber(string str,
bool integersOnly,
bool positiveOnly,
bool failOnExponentOverflow
)
{
if (String.IsNullOrEmpty(str))
return null;
char c = str[0];
bool negative = false;
int index = 0;
if (index >= str.Length)
return null;
c = str[index];
if (c == '-' && !positiveOnly) {
negative = true;
index++;
}
if (index >= str.Length)
return null;
c = str[index];
index++;
bool negExp = false;
FastInteger fastNumber = new FastInteger(0);
FastInteger exponentAdjust = new FastInteger(0);
FastInteger fastExponent = new FastInteger(0);
if (c >= '1' && c <= '9') {
fastNumber.AddInt((int)(c - '0'));
while (index < str.Length) {
c = str[index];
if (c >= '0' && c <= '9') {
index++;
fastNumber.Multiply(10);
fastNumber.AddInt((int)(c - '0'));
} else {
break;
}
}
} else if (c != '0') {
return null;
}
if (!integersOnly) {
if (index < str.Length && str[index] == '.') {
// Fraction
index++;
if (index >= str.Length)
return null;
c = str[index];
index++;
if (c >= '0' && c <= '9') {
// Adjust the exponent for this
// fractional digit
exponentAdjust.AddInt(-1);
fastNumber.Multiply(10);
fastNumber.AddInt((int)(c - '0'));
while (index < str.Length) {
c = str[index];
if (c >= '0' && c <= '9') {
index++;
// Adjust the exponent for this
// fractional digit
exponentAdjust.AddInt(-1);
fastNumber.Multiply(10);
fastNumber.AddInt((int)(c - '0'));
} else {
break;
}
}
} else {
// Not a fraction
return null;
}
}
if (index < str.Length && (str[index] == 'e' || str[index] == 'E')) {
// Exponent
index++;
if (index >= str.Length)
return null;
c = str[index];
if (c == '-') {
negExp = true;
index++;
}
if (c == '+') index++;
if (index >= str.Length)
return null;
c = str[index];
index++;
if (c >= '0' && c <= '9') {
fastExponent.AddInt((int)(c - '0'));
while (index < str.Length) {
c = str[index];
if (c >= '0' && c <= '9') {
index++;
fastExponent.Multiply(10);
fastExponent.AddInt((int)(c - '0'));
} else {
break;
}
}
} else {
// Not an exponent
return null;
}
}
}
if (negExp)
fastExponent.Negate();
if (negative)
fastNumber.Negate();
fastExponent.Add(exponentAdjust);
if (index != str.Length) {
// End of the string wasn't reached, so isn't a number
return null;
}
// No fractional part
if(fastExponent.Sign==0){
if(fastNumber.CanFitInInt32())
return CBORObject.FromObject(fastNumber.AsInt32());
else
return CBORObject.FromObject(fastNumber.AsBigInteger());
} else {
if(fastNumber.Sign==0){
return CBORObject.FromObject(0);
}
if(fastNumber.CanFitInInt32() && fastExponent.CanFitInInt32()){
return CBORObject.FromObject(new ExtendedDecimal(
fastNumber.AsBigInteger(),fastExponent.AsBigInteger()));
} else {
BigInteger bigintExponent=fastExponent.AsBigInteger();
if(!fastExponent.CanFitInInt32()){
if (bigintExponent.CompareTo(UInt64MaxValue) > 0) {
// Exponent is higher than the highest representable
// integer of major type 0
if (failOnExponentOverflow)
return null;
else
return (fastExponent.Sign < 0) ?
CBORObject.FromObject(Double.NegativeInfinity) :
CBORObject.FromObject(Double.PositiveInfinity);
}
if (bigintExponent.CompareTo(LowestMajorType1) < 0) {
// Exponent is lower than the lowest representable
// integer of major type 1
if (failOnExponentOverflow)
return null;
else
return CBORObject.FromObject(0);
}
}
return CBORObject.FromObject(new ExtendedDecimal(
fastNumber.AsBigInteger(),bigintExponent));
}
}
}
