private static CBORNumber RationalToNumber(
CBORObject o,
int tagName)
{
if (o.Type != CBORType.Array)
{
return(null); // "Big fraction must be an array";
}
if (tagName == 270)
{
if (o.Count != 3)
{
return(null); // "Extended big fraction requires exactly 3 items";
}
if (!IsUntaggedInteger(o[2]))
{
return(null); // "Third item must be an integer";
}
}
else
{
if (o.Count != 2)
{
return(null); // "Big fraction requires exactly 2 items";
}
}
if (!IsUntaggedIntegerOrBignum(o[0]))
{
return(null); // "Numerator is not an integer or bignum";
}
if (!IsUntaggedIntegerOrBignum(o[1]))
{
return(null); // "Denominator is not an integer or bignum");
}
EInteger numerator = IntegerOrBignum(o[0]);
EInteger denominator = IntegerOrBignum(o[1]);
if (denominator.Sign <= 0)
{
return(null); // "Denominator may not be negative or zero");
}
ERational erat = ERational.Create(numerator, denominator);
if (tagName == 270)
{
if (numerator.Sign < 0)
{
return(null); // "Numerator may not be negative");
}
if (!o[2].CanValueFitInInt32())
{
return(null); // "Invalid options";
}
int options = o[2].AsInt32Value();
switch (options)
{
case 0:
break;
case 1:
erat = erat.Negate();
break;
case 2:
if (!numerator.IsZero || denominator.CompareTo(1) != 0)
{
return(null); // "invalid values");
}
erat = ERational.PositiveInfinity;
break;
case 3:
if (!numerator.IsZero || denominator.CompareTo(1) != 0)
{
return(null); // "invalid values");
}
erat = ERational.NegativeInfinity;
break;
case 4:
case 5:
case 6:
case 7:
if (denominator.CompareTo(1) != 0)
{
return(null); // "invalid values");
}
erat = ERational.CreateNaN(
numerator,
options >= 6,
options == 5 || options == 7);
break;
default: return(null); // "Invalid options");
}
}
return(CBORNumber.FromObject(erat));
}