void InsertNode(PathTreeNode node, PathTreeNode parentNode, PathTreeNode previousNode)
{
parentNode.ChildrenCount += 1;
node.Parent = parentNode;
if (previousNode == null)
{
// We're inserting at the beginning.
var insertBefore = parentNode.FirstChild;
node.Next = insertBefore;
if (insertBefore != null)
{
insertBefore.Previous = node;
}
parentNode.FirstChild = node;
return;
}
// We are appending inbetween other nodes
var next = previousNode.Next;
previousNode.Next = node;
node.Previous = previousNode;
node.Next = next;
if (next != null)
{
next.Previous = node;
}
}
static void PrettyPrint(StringBuilder builder, PathTreeNode node, string indent)
{
builder.Append(indent);
if (node.Next == null)
{
builder.Append("\\-");
indent += " ";
}
else
{
builder.Append("|-");
indent += "| ";
}
builder.Append(node.Segment);
if (node.IdCount != 0)
{
builder.AppendFormat(" ({0})", node.IdCount);
}
node = node.FirstChild;
while (node != null)
{
builder.AppendLine();
PrettyPrint(builder, node, indent);
node = node.Next;
}
}
bool IsDeadSubtree(PathTreeNode node)
{
// We do a DFS here, looking for any live node in a tree.
// We know that leaves are live, so DFS works better here.
var stack = new Stack <PathTreeNode> ();
stack.Push(node);
while (stack.Count != 0)
{
node = stack.Pop();
if (node.IsLive)
{
return(false);
}
var child = node.FirstChild;
while (child != null)
{
stack.Push(child);
child = child.Next;
}
}
return(true);
}
internal static (PathTreeNode root, PathTreeNode leaf) CreateSubTree(string path, int start)
{
PathTreeNode lastNode = null, rootNode = null;
while (start < path.Length)
{
var nextSep = path.IndexOf(Path.DirectorySeparatorChar, start);
int length = nextSep == -1 ? path.Length - start : nextSep - start;
if (length != 0)
{
var node = new PathTreeNode(path, start, length);
if (lastNode != null)
{
lastNode.FirstChild = node;
node.Parent = lastNode;
lastNode.ChildrenCount = 1;
}
else
{
rootNode = node;
}
lastNode = node;
}
start = start + length + 1;
}
return(rootNode, lastNode);
}
bool TryFind(string path, out PathTreeNode result, out PathTreeNode parent, out PathTreeNode previousNode, out int lastIndex)
{
lastIndex = 0;
parent = rootNode;
var currentNode = parent.FirstChild;
previousNode = null;
var remainingSegments = path.AsSpan().TrimEnd(Path.DirectorySeparatorChar);
while (currentNode != null)
{
var currentSegment = currentNode.GetSegment();
// Chunk by directory separator
int currentIndex = remainingSegments.IndexOf(Path.DirectorySeparatorChar);
int segmentLength = currentIndex == -1 ? remainingSegments.Length : currentIndex;
var toAddSegment = remainingSegments.Slice(0, segmentLength);
int comparisonResult = currentSegment.CompareTo(toAddSegment, FilePath.PathComparison);
// We need to insert in this node's position.
if (comparisonResult > 0)
{
break;
}
// Keep searching if we still have items.
if (comparisonResult < 0)
{
previousNode = currentNode;
currentNode = currentNode.Next;
continue;
}
// We found this segment in the tree.
remainingSegments = remainingSegments.Slice(Math.Min(currentIndex + 1, remainingSegments.Length));
lastIndex += currentIndex + 1;
// We found the node already, register the ID.
if (currentIndex == -1 || remainingSegments.Length == 0)
{
result = currentNode;
return(true);
}
// We go to the first child of this segment and repeat the algorithm.
parent = currentNode;
previousNode = null;
currentNode = parent.FirstChild;
}
result = null;
return(false);
}
public PathTree()
{
rootNode = new PathTreeNode("", 0, 1);
if (!Platform.IsWindows)
{
rootNode.FirstChild = new PathTreeNode("/", 0, 0)
{
Parent = rootNode,
};
rootNode.ChildrenCount = 1;
}
}
bool TryFind(string path, out PathTreeNode result, out PathTreeNode parent, out PathTreeNode previousNode, out int lastIndex)
{
lastIndex = 0;
parent = rootNode;
var currentNode = parent.FirstChild;
previousNode = null;
while (currentNode != null)
{
int currentIndex = path.IndexOf(Path.DirectorySeparatorChar, lastIndex);
int comparisonResult = string.Compare(currentNode.FullPath, currentNode.Start, path, lastIndex, currentNode.Length);
// We need to insert in this node's position.
if (comparisonResult > 0)
{
break;
}
// Keep searching.
if (comparisonResult < 0)
{
previousNode = currentNode;
currentNode = currentNode.Next;
continue;
}
// We found this segment in the tree.
lastIndex = currentIndex + 1;
// We found the node already, register the ID.
if (currentIndex == -1 || lastIndex == path.Length)
{
result = currentNode;
return(true);
}
// We go to the first child of this segment and repeat the algorithm.
parent = currentNode;
previousNode = null;
currentNode = parent.FirstChild;
}
result = null;
return(false);
}
public void CreateSubTree(string sep)
{
var path = MakePath("a", "b", "c") + sep;
var(first, leaf) = PathTreeNode.CreateSubTree(path, 0);
PathTreeNode a;
if (Platform.IsWindows)
{
AssertPathTreeSubtree(first, "C:");
Assert.AreEqual(1, first.ChildrenCount);
a = first.FirstChild;
Assert.AreSame(first, a.Parent);
}
else
{
a = first;
}
AssertPathTreeSubtree(a, "a");
Assert.AreEqual(1, a.ChildrenCount);
var b = a.FirstChild;
Assert.AreSame(a, b.Parent);
AssertPathTreeSubtree(b, "b");
Assert.AreEqual(1, b.ChildrenCount);
var c = b.FirstChild;
Assert.AreSame(b, c.Parent);
AssertPathTreeSubtree(c, "c");
Assert.AreEqual(0, c.ChildrenCount);
Assert.AreSame(c, leaf);
Assert.IsNull(c.FirstChild);
void AssertPathTreeSubtree(PathTreeNode node, string segment)
{
Assert.AreEqual(segment, node.Segment);
Assert.IsNull(node.Next);
Assert.AreSame(node.FirstChild, node.LastChild);
}
}
public PathTreeNode AddNode(string path, object id, out bool isModified)
{
if (TryFind(path, out var result, out var parent, out var previousNode, out var lastIndex))
{
isModified = !result.IsLive;
result.RegisterId(id);
return(result);
}
// At this point, we need to create a new node.
isModified = true;
var(first, leaf) = PathTreeNode.CreateSubTree(path, lastIndex);
leaf.RegisterId(id);
InsertNode(first, parent, previousNode);
return(leaf);
}
public PathTreeNode AddNode(string path, object id)
{
if (TryFind(path, out var result, out var parent, out var previousNode, out var lastIndex))
{
result.RegisterId(id);
return(result);
}
// At this point, we need to create a new node.
var(first, leaf) = PathTreeNode.CreateSubTree(path, lastIndex);
if (id != null)
{
leaf.RegisterId(id);
}
InsertNode(first, parent, previousNode);
return(leaf);
}
internal PathTreeNode RemoveNode(PathTreeNode result, object id, out bool isModified)
{
var parent = result.Parent;
isModified = result.UnregisterId(id) && !result.IsLive;
if (isModified)
{
var nodeToRemove = result;
var lastToRemove = pathRoot;
while (nodeToRemove != lastToRemove && IsDeadSubtree(nodeToRemove))
{
parent.ChildrenCount -= 1;
if (parent.FirstChild == nodeToRemove)
{
parent.FirstChild = nodeToRemove.Next;
}
if (nodeToRemove.Previous != null)
{
nodeToRemove.Previous.Next = nodeToRemove.Next;
}
if (nodeToRemove.Next != null)
{
nodeToRemove.Next.Previous = nodeToRemove.Previous;
}
nodeToRemove.Next = null;
nodeToRemove.Previous = null;
nodeToRemove.Parent = null;
nodeToRemove = parent;
parent = nodeToRemove.Parent;
}
}
return(result);
}
[TestCase(1)] // Should not crash
public void EmptySubTrie(int startIndex)
{
var(node, leaf) = PathTreeNode.CreateSubTree(string.Empty, startIndex);
Assert.IsNull(node);
Assert.IsNull(leaf);
}
public void JustSlash()
{
var(node, leaf) = PathTreeNode.CreateSubTree(Path.DirectorySeparatorChar.ToString(), 0);
Assert.IsNull(node);
Assert.IsNull(leaf);
}