private Expression CharSetToExpression(BitArray charSet)
{
Expression expression = null;
for (int i = 0; i < charSet.Length; i++)
{
if (charSet.Get(i))
{
var io = new Expression.IO {
Byte = (byte)i, In = true, Out = true
};
if (expression == null)
{
expression = io;
}
else
{
expression = new Expression.Union
{
Left = expression,
Right = io,
};
}
}
}
if (expression == null)
{
expression = new Expression.Nothing();
}
return(expression);
}
private Expression ParseToParenOrEnd()
{
Expression unionTree = null;
Expression concatTree = null;
while (_codeIndex < _code.Length && _code[_codeIndex] != ')' && _code[_codeIndex] != '}')
{
if (_code[_codeIndex] == '|')
{
_codeIndex++;
concatTree = concatTree ?? new Expression.Empty();
if (unionTree == null)
{
unionTree = concatTree;
}
else
{
unionTree = new Expression.Union {
Left = unionTree, Right = concatTree
};
}
concatTree = null;
continue;
}
else
{
var term = ParseTerm();
if (concatTree == null)
{
concatTree = term;
}
else
{
concatTree = new Expression.Concat {
Left = concatTree, Right = term
};
}
}
}
concatTree = concatTree ?? new Expression.Empty();
if (unionTree == null)
{
return(concatTree);
}
unionTree = new Expression.Union {
Left = unionTree, Right = concatTree
};
return(unionTree);
}
private Expression ParseTerm()
{
Expression curTree = ParseUnstarredTerm();
bool shouldContinue = true;
while (_codeIndex < _code.Length)
{
switch (_code[_codeIndex])
{
case (byte)'*':
curTree = new Expression.Star {
Sub = curTree
};
break;
case (byte)'+':
curTree = new Expression.Concat
{
Left = curTree,
Right = new Expression.Star {
Sub = curTree
},
};
break;
case (byte)'?':
curTree = new Expression.Union
{
Left = new Expression.Empty(),
Right = curTree,
};
break;
default:
shouldContinue = false;
break;
}
if (!shouldContinue)
{
break;
}
_codeIndex++;
}
return(curTree);
}
