/// <summary>
/// Returns the next character using the given options, or <see cref="DONE"/> if there
/// are no more characters, and advance the position to the next
/// character.
/// </summary>
/// <param name="options">One or more of the following options, bitwise-OR-ed
/// together: <see cref="RuleCharacterIteratorOptions.ParseVariables"/>,
/// <see cref="RuleCharacterIteratorOptions.ParseEscapes"/>,
/// <see cref="RuleCharacterIteratorOptions.SkipWhitespace"/>.</param>
/// <returns>The current 32-bit code point, or <see cref="DONE"/>.</returns>
public virtual int Next(RuleCharacterIteratorOptions options)
{
int c = DONE;
isEscaped = false;
for (; ;)
{
c = Current();
Advance(UTF16.GetCharCount(c));
if (c == SymbolTable.SYMBOL_REF && buf == null &&
(options & RuleCharacterIteratorOptions.ParseVariables) != 0 && sym != null)
{
string name = sym.ParseReference(text, pos, text.Length);
// If name == null there was an isolated SYMBOL_REF;
// return it. Caller must be prepared for this.
if (name == null)
{
break;
}
bufPos = 0;
buf = sym.Lookup(name);
if (buf == null)
{
throw new ArgumentException(
"Undefined variable: " + name);
}
// Handle empty variable value
if (buf.Length == 0)
{
buf = null;
}
continue;
}
if ((options & RuleCharacterIteratorOptions.SkipWhitespace) != 0 &&
PatternProps.IsWhiteSpace(c))
{
continue;
}
if (c == '\\' && (options & RuleCharacterIteratorOptions.ParseEscapes) != 0)
{
int[] offset = new int[] { 0 };
c = Utility.UnescapeAt(Lookahead(), offset);
Jumpahead(offset[0]);
isEscaped = true;
if (c < 0)
{
throw new ArgumentException("Invalid escape");
}
}
break;
}
return(c);
}