/**
* Reads a number or returns null.
*/
private Token TryReadNumber()
{
buffer.Mark();
StringBuilder sb = new StringBuilder();
StringBuilder radix = null;
char c = GetChar();
bool hasDigit = false;
// optional + or -
if (c == '+' || c == '-')
{
sb.Append(c);
c = GetChar();
}
// optional digits
while (char.IsDigit(c))
{
sb.Append(c);
c = GetChar();
hasDigit = true;
}
// optional .
if (c == '.')
{
sb.Append(c);
c = GetChar();
}
else if (c == '#')
{
// PostScript radix number takes the form base#number
radix = sb;
sb = new StringBuilder();
c = GetChar();
}
else if (sb.Length == 0 || !hasDigit)
{
// failure
buffer.Reset();
return(null);
}
else
{
// integer
buffer.Seek(buffer.Position - 1);
return(new Token(sb.ToString(), TokenKind.INTEGER));
}
// required digit
if (char.IsDigit(c))
{
sb.Append(c);
c = GetChar();
}
else
{
// failure
buffer.Reset();
return(null);
}
// optional digits
while (char.IsDigit(c))
{
sb.Append(c);
c = GetChar();
}
// optional E
if (c == 'E')
{
sb.Append(c);
c = GetChar();
// optional minus
if (c == '-')
{
sb.Append(c);
c = GetChar();
}
// required digit
if (char.IsDigit(c))
{
sb.Append(c);
c = GetChar();
}
else
{
// failure
buffer.Reset();
return(null);
}
// optional digits
while (char.IsDigit(c))
{
sb.Append(c);
c = GetChar();
}
}
buffer.Seek(buffer.Position - 1);
if (radix != null)
{
int val = Convert.ToInt32(sb.ToString(), int.Parse(radix.ToString()));
return(new Token(val.ToString(), TokenKind.INTEGER));
}
return(new Token(sb.ToString(), TokenKind.REAL));
}