static RegexExpression _ParseModifier(RegexExpression expr, ParseContext pc)
{
var line = pc.Line;
var column = pc.Column;
var position = pc.Position;
switch (pc.Current)
{
case '*':
expr = new RegexRepeatExpression(expr);
expr.SetLocation(line, column, position);
pc.Advance();
break;
case '+':
expr = new RegexRepeatExpression(expr, 1);
expr.SetLocation(line, column, position);
pc.Advance();
break;
case '?':
expr = new RegexOptionalExpression(expr);
expr.SetLocation(line, column, position);
pc.Advance();
break;
case '{':
pc.Advance();
pc.TrySkipWhiteSpace();
pc.Expecting('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ',', '}');
var min = -1;
var max = -1;
if (',' != pc.Current && '}' != pc.Current)
{
var l = pc.CaptureBuffer.Length;
pc.TryReadDigits();
min = int.Parse(pc.GetCapture(l));
pc.TrySkipWhiteSpace();
}
if (',' == pc.Current)
{
pc.Advance();
pc.TrySkipWhiteSpace();
pc.Expecting('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '}');
if ('}' != pc.Current)
{
var l = pc.CaptureBuffer.Length;
pc.TryReadDigits();
max = int.Parse(pc.GetCapture(l));
pc.TrySkipWhiteSpace();
}
}
else
{
max = min;
}
pc.Expecting('}');
pc.Advance();
expr = new RegexRepeatExpression(expr, min, max);
expr.SetLocation(line, column, position);
break;
}
return(expr);
}
static RegexExpression _FromFA <TAccept>(CharFA <TAccept> fa, HashSet <CharFA <TAccept> > visited)
{
if (!visited.Add(fa))
{
return(null);
}
var trgs = fa.FillInputTransitionRangesGroupedByState();
bool isAccepting = fa.IsAccepting;
RegexExpression expr = null;
foreach (var trg in trgs)
{
if (1 == trg.Value.Count && 1 == trg.Value[0].Length)
{
RegexExpression le = new RegexLiteralExpression(trg.Value[0][0]);
var next = _FromFA(trg.Key, visited);
if (null != next)
{
le = new RegexConcatExpression(le, next);
}
if (null == expr)
{
expr = le;
}
else
{
expr = new RegexOrExpression(expr, le);
}
}
else
{
var csel = new List <RegexCharsetEntry>();
foreach (var rng in trg.Value)
{
if (rng.First == rng.Last)
{
csel.Add(new RegexCharsetCharEntry(rng.First));
}
else
{
csel.Add(new RegexCharsetRangeEntry(rng.First, rng.Last));
}
}
RegexExpression cse = new RegexCharsetExpression(csel);
var next = _FromFA(trg.Key, visited);
if (null != next)
{
cse = new RegexConcatExpression(cse, next);
}
if (null == expr)
{
expr = cse;
}
else
{
expr = new RegexOrExpression(expr, cse);
}
}
}
var isLoop = false;
foreach (var val in fa.Descendants)
{
if (val == fa)
{
isLoop = true;
break;
}
}
if (isAccepting && !fa.IsFinal && !isLoop)
{
expr = new RegexOptionalExpression(expr);
}
return(expr);
}