/// <summary>
/// When an error was encountered, runs the lexer's DFA to match a terminal in the input ahead
/// </summary>
/// <param name="originIndex">The current start index in the input text</param>
/// <returns>The matching DFA state and length</returns>
internal TokenMatch RunDFAOnError(int originIndex)
{
if (RecoveryDistance <= 0)
{
OnError(new UnexpectedCharError(text.GetValue(originIndex).ToString(), text.GetPositionAt(originIndex)));
return(new TokenMatch(1));
}
else
{
int index = -1;
// index of the separator terminal, if any
for (int i = 0; i != symTerminals.Count; i++)
{
if (symTerminals[i].ID == separatorID)
{
index = i;
break;
}
}
FuzzyMatcher handler = new FuzzyMatcher(automaton, index, text, OnError, RecoveryDistance, originIndex);
return(handler.Run());
}
}
/// <summary>
/// Reports on the lexical error at the specified index
/// </summary>
/// <param name="index">The index in the input where the error occurs</param>
private void OnError(int index)
{
ParseErrorType errorType = ParseErrorType.UnexpectedChar;
bool atEnd = text.IsEnd(index);
string value = "";
if (atEnd)
{
// the end of input was not expected
// there is necessarily some input before because an empty input would have matched the $
char c = text.GetValue(index - 1);
if (c >= 0xD800 && c <= 0xDBFF)
{
// a trailing UTF-16 high surrogate
index--;
errorType = ParseErrorType.IncorrectUTF16NoLowSurrogate;
}
else
{
errorType = ParseErrorType.UnexpectedEndOfInput;
}
}
else
{
char c = text.GetValue(index);
if (c >= 0xD800 && c <= 0xDBFF && !text.IsEnd(index + 1))
{
// a UTF-16 high surrogate
// if next next character is a low surrogate, also get it
char c2 = text.GetValue(index + 1);
if (c2 >= 0xDC00 && c2 <= 0xDFFF)
{
value = new string(new [] { c, c2 });
}
else
{
errorType = ParseErrorType.IncorrectUTF16NoLowSurrogate;
}
}
else if (c >= 0xDC00 && c <= 0xDFFF && index > 0)
{
// a UTF-16 low surrogate
// if the previous character is a high surrogate, also get it
char c2 = text.GetValue(index - 1);
if (c2 >= 0xD800 && c2 <= 0xDBFF)
{
index--;
value = new string(new [] { c2, c });
}
else
{
errorType = ParseErrorType.IncorrectUTF16NoHighSurrogate;
}
}
if (value.Length == 0)
{
value = c.ToString();
}
}
switch (errorType)
{
case ParseErrorType.UnexpectedEndOfInput:
errors(new UnexpectedEndOfInput(text.GetPositionAt(index)));
break;
case ParseErrorType.UnexpectedChar:
errors(new UnexpectedCharError(value, text.GetPositionAt(index)));
break;
case ParseErrorType.IncorrectUTF16NoHighSurrogate:
case ParseErrorType.IncorrectUTF16NoLowSurrogate:
errors(new IncorrectEncodingSequence(text.GetPositionAt(index), text.GetValue(index), errorType));
break;
default:
break;
}
}
