/// <summary>
/// Yet another related computation: it takes a RegexTree and computes
/// the leading anchors that it encounters.
/// </summary>
public static int Anchors(RegexTree tree)
{
RegexNode curNode;
RegexNode concatNode = null;
int nextChild = 0;
int result = 0;
curNode = tree.Root;
for (; ;)
{
switch (curNode.NType)
{
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.Bol:
case RegexNode.Eol:
case RegexNode.Boundary:
case RegexNode.ECMABoundary:
case RegexNode.Beginning:
case RegexNode.Start:
case RegexNode.EndZ:
case RegexNode.End:
return(result | AnchorFromType(curNode.NType));
case RegexNode.Empty:
case RegexNode.Require:
case RegexNode.Prevent:
break;
default:
return(result);
}
if (concatNode == null || nextChild >= concatNode.ChildCount())
{
return(result);
}
curNode = concatNode.Child(nextChild++);
}
}
/// <summary>
/// Nested repeaters just get multiplied with each other if they're not
/// too lumpy
/// </summary>
private RegexNode ReduceRep()
{
RegexNode u = this;
RegexNode child;
int type = Type();
int min = M;
int max = N;
for (; ;)
{
if (u.ChildCount() == 0)
{
break;
}
child = u.Child(0);
// multiply reps of the same type only
if (child.Type() != type)
{
int childType = child.Type();
if (!(childType >= Oneloop && childType <= Setloop && type == Loop ||
childType >= Onelazy && childType <= Setlazy && type == Lazyloop))
{
break;
}
}
// child can be too lumpy to blur, e.g., (a {100,105}) {3} or (a {2,})?
// [but things like (a {2,})+ are not too lumpy...]
if (u.M == 0 && child.M > 1 || child.N < child.M * 2)
{
break;
}
u = child;
if (u.M > 0)
{
u.M = min = ((int.MaxValue - 1) / u.M < min) ? int.MaxValue : u.M * min;
}
if (u.N > 0)
{
u.N = max = ((int.MaxValue - 1) / u.N < max) ? int.MaxValue : u.N * max;
}
}
return(min == int.MaxValue ? new RegexNode(Nothing, Options) : u);
}
/// <summary>
/// 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.
/// </summary>
public static RegexPrefix Prefix(RegexTree tree)
{
RegexNode curNode = tree.Root;
RegexNode concatNode = null;
int nextChild = 0;
for (; ;)
{
switch (curNode.NType)
{
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:
// In release, cutoff at a length to which we can still reasonably construct a string
// In debug, use a smaller cutoff to exercise the cutoff path in tests
const int Cutoff =
#if DEBUG
50;
#else
1_000_000;
#endif
if (curNode.M > 0 && curNode.M < Cutoff)
{
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(), 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++);
}
}