/*
* This is a related computation: it takes a RegexTree and computes the
* leading substring if it see one. It's quite trivial and gives up easily.
*/
internal static RegexPrefix Prefix(RegexTree tree)
{
RegexNode curNode;
RegexNode concatNode = null;
int nextChild = 0;
curNode = tree._root;
for (;;)
{
switch (curNode._type)
{
case RegexNode.Concatenate:
if (curNode.ChildCount() > 0)
{
concatNode = curNode;
nextChild = 0;
}
break;
case RegexNode.Greedy:
case RegexNode.Capture:
curNode = curNode.Child(0);
concatNode = null;
continue;
case RegexNode.Oneloop:
case RegexNode.Onelazy:
if (curNode._m > 0)
{
string pref = string.Empty.PadRight(curNode._m, curNode._ch);
return(new RegexPrefix(pref, 0 != (curNode._options & RegexOptions.IgnoreCase)));
}
else
{
return(RegexPrefix.Empty);
}
case RegexNode.One:
return(new RegexPrefix(curNode._ch.ToString(CultureInfo.InvariantCulture), 0 != (curNode._options & RegexOptions.IgnoreCase)));
case RegexNode.Multi:
return(new RegexPrefix(curNode._str, 0 != (curNode._options & RegexOptions.IgnoreCase)));
case RegexNode.Bol:
case RegexNode.Eol:
case RegexNode.Boundary:
case RegexNode.ECMABoundary:
case RegexNode.Beginning:
case RegexNode.Start:
case RegexNode.EndZ:
case RegexNode.End:
case RegexNode.Empty:
case RegexNode.Require:
case RegexNode.Prevent:
break;
default:
return(RegexPrefix.Empty);
}
if (concatNode == null || nextChild >= concatNode.ChildCount())
{
return(RegexPrefix.Empty);
}
curNode = concatNode.Child(nextChild++);
}
}
/*
* The main FC computation. It does a shortcutted depth-first walk
* through the tree and calls CalculateFC to emits code before
* and after each child of an interior node, and at each leaf.
*/
private RegexFC RegexFCFromRegexTree(RegexTree tree)
{
RegexNode curNode;
int curChild;
curNode = tree._root;
curChild = 0;
for (;;)
{
if (curNode._children == null)
{
// This is a leaf node
CalculateFC(curNode._type, curNode, 0);
}
else if (curChild < curNode._children.Count && !_skipAllChildren)
{
// This is an interior node, and we have more children to analyze
CalculateFC(curNode._type | BeforeChild, curNode, curChild);
if (!_skipchild)
{
curNode = (RegexNode)curNode._children[curChild];
// this stack is how we get a depth first walk of the tree.
PushInt(curChild);
curChild = 0;
}
else
{
curChild++;
_skipchild = false;
}
continue;
}
// This is an interior node where we've finished analyzing all the children, or
// the end of a leaf node.
_skipAllChildren = false;
if (IntIsEmpty())
{
break;
}
curChild = PopInt();
curNode = curNode._next;
CalculateFC(curNode._type | AfterChild, curNode, curChild);
if (_failed)
{
return(null);
}
curChild++;
}
if (FCIsEmpty())
{
return(null);
}
return(PopFC());
}