private static RemovalResult RemoveEdgeRecursive(INodeProvider <Guid, object, EdgeData> nodes, Guid nodeId, EdgeData data, int treeOrder)
{
var node = nodes.GetNode(nodeId, NodeAccess.ReadWrite);
try
{
if (node.Data.Equals(LeafNodeData))
{
var removeResult = node.Edges.Remove(data);
return(new RemovalResult(node.Edges.Count, removeResult, false));
}
else
{
var edgeIndex = FindLeadingEdgeIndex(data, node);
var edge = node.Edges[node.Edges.Keys[edgeIndex]];
var res = RemoveEdgeRecursive(nodes, edge.ToNodeId, data, treeOrder);
if (!res.WasRemoved)
{
return(res);
}
if (res.RemainingCount < treeOrder / 2)
{
#region Reorganize sub nodes
// Take data from a sibling
if (edgeIndex < node.Edges.Count - 1)
{
return(MergeNodes(nodes, node, edgeIndex, edgeIndex + 1, treeOrder));
}
else
{
return(MergeNodes(nodes, node, edgeIndex - 1, edgeIndex, treeOrder));
}
#endregion
}
else
{
return(res);
}
}
}
finally
{
nodes.SetNode(nodeId, node);
}
}
private static RemovalResult MergeNodes(INodeProvider <Guid, object, EdgeData> nodes, Node <Guid, object, EdgeData> node, int leftIndex, int rightIndex, int treeOrder)
{
var leftKey = node.Edges.Keys[leftIndex];
var leftNodeId = node.Edges[leftKey].ToNodeId;
var leftNode = nodes.GetNode(leftNodeId, NodeAccess.ReadWrite);
var rightKey = node.Edges.Keys[rightIndex];
var rightNodeId = node.Edges[rightKey].ToNodeId;
var rightNode = nodes.GetNode(rightNodeId, NodeAccess.ReadWrite);
if (!leftNode.Data.Equals(rightNode.Data))
{
throw new InvalidOperationException("Both nodes must be of same type");
}
if (leftNode.Data.Equals(InternalNodeData))
{
var maxEdgeKey = leftNode.Edges.Keys[leftNode.Edges.Count - 1];
var maxEdge = leftNode.Edges[maxEdgeKey];
leftNode.Edges.Remove(maxEdgeKey);
leftNode.AddEdge(new Edge <Guid, EdgeData>(maxEdge.ToNodeId, LeftEdge(nodes, rightNode).Data));
}
if ((leftNode.Edges.Count + rightNode.Edges.Count) <= treeOrder)
{
// Take all from left node
for (int i = 0; i < leftNode.Edges.Count; i++)
{
EdgeData removalKey = leftNode.Edges.Keys[i];
rightNode.AddEdge(leftNode.Edges[removalKey]);
}
nodes.SetNode(rightNodeId, rightNode);
nodes.Remove(leftNodeId);
node.Edges.Remove(leftKey);
if (node.Edges.Count == 1)
{
// When no more nodes remaining copy from child
node.SetData(rightNode.Data);
node.Edges.Clear();
foreach (var childEdge in rightNode.Edges.Values)
{
node.AddEdge(childEdge);
}
nodes.Remove(rightNodeId);
}
return(new RemovalResult(node.Edges.Count, true, true));
}
else
{
// Decide how many edges to take from right node
int numberToTake = (leftNode.Edges.Count + rightNode.Edges.Count) / 2 - leftNode.Edges.Count;
// Copy or merge?
if (numberToTake > 0)
{
// Copy edges from right -> left
for (int i = 0; i < numberToTake; i++)
{
EdgeData removalKey = rightNode.Edges.Keys[0];
leftNode.AddEdge(rightNode.Edges[removalKey]);
rightNode.Edges.Remove(removalKey);
}
node.Edges.Remove(leftKey);
node.AddEdge(new Edge <Guid, EdgeData>(leftNodeId, LeftEdge(nodes, rightNode).Data));
nodes.SetNode(leftNodeId, leftNode);
nodes.SetNode(rightNodeId, rightNode);
// No edges were removed
return(new RemovalResult(node.Edges.Count, true, true));
}
else
if (numberToTake < 0)
{
// Copy edges from left -> right
for (int i = 0; i < Math.Abs(numberToTake); i++)
{
EdgeData removalKey = leftNode.Edges.Keys[leftNode.Edges.Count - 1];
rightNode.AddEdge(leftNode.Edges[removalKey]);
leftNode.Edges.Remove(removalKey);
}
node.Edges.Remove(leftKey);
node.AddEdge(new Edge <Guid, EdgeData>(leftNodeId, LeftEdge(nodes, rightNode).Data));
nodes.SetNode(leftNodeId, leftNode);
nodes.SetNode(rightNodeId, rightNode);
// No edges were removed
return(new RemovalResult(node.Edges.Count, true, true));
}
throw new ArgumentException("Nothing to copy");
}
}
/// <summary>
/// Makes room in the tree for new data
/// </summary>
/// <param name="nodes">Node provider which contains tree nodes</param>
/// <param name="nodeId">Current node ID</param>
/// <param name="isRoot">Determines if current node is root node</param>
/// <param name="data">Data to make room for</param>
/// <returns>Result of the operation</returns>
private static SplitResult SplitTree(INodeProvider <Guid, object, EdgeData> nodes, Guid nodeId, bool isRoot, EdgeData data, int treeOrder)
{
var currentNode = nodes.GetNode(nodeId, NodeAccess.ReadWrite);
if (isRoot)
{
if (currentNode.Data.Equals(InternalNodeData))
{
#region Is root internal ?
var leadingEdge = FindLeadingEdge(data, currentNode);
var result = SplitTree(nodes, leadingEdge.ToNodeId, false, data, treeOrder);
if (result != null)
{
currentNode.AddEdge(new Edge <Guid, EdgeData>(result.CreatedNodeId, result.RightKey));
if (currentNode.Edges.Count == (treeOrder + 1))
{
// Split root to 2 internal nodes
Guid leftNodeId = Guid.NewGuid();
Guid rightNodeId = Guid.NewGuid();
Node <Guid, object, EdgeData> leftNode = new Node <Guid, object, EdgeData>(NodeType.TreeInternal, InternalNodeData);
Node <Guid, object, EdgeData> rightNode = new Node <Guid, object, EdgeData>(NodeType.TreeInternal, InternalNodeData);
var keys = currentNode.Edges.Keys;
for (int i = 0; i < keys.Count; i++)
{
if (i < keys.Count / 2)
{
leftNode.AddEdge(currentNode.Edges[keys[i]]);
}
else
{
rightNode.AddEdge(currentNode.Edges[keys[i]]);
}
}
//Set last edges
SetLastInternalKey(leftNode);
SetLastInternalKey(rightNode);
currentNode.Edges.Clear();
currentNode.AddEdge(new Edge <Guid, EdgeData>(leftNodeId, LeftEdge(nodes, rightNode).Data));
currentNode.AddEdge(new Edge <Guid, EdgeData>(rightNodeId, EdgeData.MaxValue));
nodes.SetNode(leftNodeId, leftNode);
nodes.SetNode(rightNodeId, rightNode);
}
nodes.SetNode(nodeId, currentNode);
}
else
{
return(null);
}
#endregion
}
else
{
#region Root is a leaf
if (currentNode.Edges.Count == treeOrder)
{
// Split root to internal nodes
Guid leftNodeId = Guid.NewGuid();
Guid rightNodeId = Guid.NewGuid();
Node <Guid, object, EdgeData> leftNode = new Node <Guid, object, EdgeData>(NodeType.TreeLeaf, LeafNodeData);
Node <Guid, object, EdgeData> rightNode = new Node <Guid, object, EdgeData>(NodeType.TreeLeaf, LeafNodeData);
var keys = currentNode.Edges.Keys;
for (int i = 0; i < keys.Count; i++)
{
if (i < keys.Count / 2)
{
leftNode.AddEdge(currentNode.Edges[keys[i]]);
}
else
{
rightNode.AddEdge(currentNode.Edges[keys[i]]);
}
}
currentNode.Edges.Clear();
currentNode.AddEdge(new Edge <Guid, EdgeData>(leftNodeId, LeftEdge(nodes, rightNode).Data));
currentNode.AddEdge(new Edge <Guid, EdgeData>(rightNodeId, EdgeData.MaxValue));
currentNode.SetData(InternalNodeData);
nodes.SetNode(leftNodeId, leftNode);
nodes.SetNode(rightNodeId, rightNode);
nodes.SetNode(nodeId, currentNode);
}
#endregion
}
return(null);
}
else
{
if (currentNode.Data.Equals(InternalNodeData))
{
var leadingEdge = FindLeadingEdge(data, currentNode);
var result = SplitTree(nodes, leadingEdge.ToNodeId, false, data, treeOrder);
if (result != null)
{
currentNode.AddEdge(new Edge <Guid, EdgeData>(result.CreatedNodeId, result.RightKey));
if (currentNode.Edges.Count == treeOrder)
{
Guid newInternalId = Guid.NewGuid();
Node <Guid, object, EdgeData> newInternal = new Node <Guid, object, EdgeData>(NodeType.TreeInternal, InternalNodeData);
var keys = currentNode.Edges.Keys;
for (int i = 0; i < keys.Count / 2; i++)
{
newInternal.AddEdge(currentNode.Edges[keys[i]]);
}
int nrToRemove = keys.Count / 2;
for (int i = 0; i < nrToRemove; i++)
{
currentNode.Edges.RemoveAt(0);
}
// Set last edge of left internal node to MaxInt
SetLastInternalKey(newInternal);
nodes.SetNode(newInternalId, newInternal);
nodes.SetNode(nodeId, currentNode);
return(new SplitResult(newInternalId, newInternal, LeftEdge(nodes, currentNode).Data));
}
else
{
nodes.SetNode(nodeId, currentNode);
return(null);
}
}
else
{
return(null);
}
}
else
if (currentNode.Data.Equals(LeafNodeData))
{
Guid newLeafId = Guid.NewGuid();
Node <Guid, object, EdgeData> newLeaf = new Node <Guid, object, EdgeData>(NodeType.TreeLeaf, LeafNodeData);
var keys = currentNode.Edges.Keys;
for (int i = 0; i < keys.Count / 2; i++)
{
newLeaf.AddEdge(currentNode.Edges[keys[i]]);
}
int nrToRemove = keys.Count / 2;
for (int i = 0; i < nrToRemove; i++)
{
currentNode.Edges.RemoveAt(0);
}
nodes.SetNode(newLeafId, newLeaf);
nodes.SetNode(nodeId, currentNode);
return(new SplitResult(newLeafId, newLeaf, LeftEdge(nodes, currentNode).Data));
}
else
{
throw new ArgumentException("Unexpected node data");
}
}
}
/// <summary>
/// Gets next leaf in tree compared to given sample data
/// </summary>
/// <param name="nodes">Node provider</param>
/// <param name="rootNodeId">Root node id</param>
/// <param name="sampleData">Sample data in the current leaf</param>
/// <returns>Leaf node next in comparison to sample data, or null if no more leaves are found</returns>
private static Node <Guid, object, EdgeData> NextLeaf(INodeProvider <Guid, object, EdgeData> nodes, Guid rootNodeId, EdgeData sampleData)
{
var node = nodes.GetNode(rootNodeId, NodeAccess.Read);
Guid id = rootNodeId;
Guid nextInternalParentId = Guid.Empty;
while (node.Data.Equals(InternalNodeData))
{
var leadingEdgeIndex = FindLeadingEdgeIndex(sampleData, node);
if (leadingEdgeIndex < node.Edges.Count - 1)
{
nextInternalParentId = node.Edges[node.Edges.Keys[leadingEdgeIndex + 1]].ToNodeId;
}
// Advance to next internal node
node = nodes.GetNode(node.Edges[node.Edges.Keys[leadingEdgeIndex]].ToNodeId, NodeAccess.Read);
}
if (nextInternalParentId.Equals(Guid.Empty))
{
return(null);
}
else
{
return(LeftLeaf(nodes, nodes.GetNode(nextInternalParentId, NodeAccess.Read)));
}
}
/// <summary>
/// Finds an edge which leads to given hash
/// </summary>
/// <param name="data">Data to find</param>
/// <param name="node">Internal node</param>
/// <returns>Edge which leads to hash</returns>
private static Edge <Guid, EdgeData> FindLeadingEdge(EdgeData data, Node <Guid, object, EdgeData> node)
{
return(node.Edges[node.Edges.Keys[FindLeadingEdgeIndex(data, node)]]);
}
/// <summary>
/// Finds an edge index which leads to given hash
/// </summary>
/// <param name="data">Data to find</param>
/// <param name="node">Internal node</param>
/// <returns>Edge index which leads to hash</returns>
private static int FindLeadingEdgeIndex(EdgeData data, Node <Guid, object, EdgeData> node)
{
if (node.Data.Equals(InternalNodeData))
{
// Find tree edge which leads to the hash
var keys = node.Edges.Keys;
int i = 0;
int step = keys.Count;
while (true)
{
if (step > 1)
{
step = step / 2;
}
if (data.CompareTo(keys[i]) < 0)
{
// Data is smaller, try going left
if (i == 0)
{
// There is no place to go
return(i);
}
if (data.CompareTo(keys[i - 1]) >= 0)
{
// Going left would lead us into the region of greater
return(i);
}
else
{
i = i - step;
}
}
else
{
// Data is greater, try going right
if (i == keys.Count - 1)
{
// There is no place to go
return(i);
}
else
{
i = i + step;
}
}
//while (i < keys.Count && data.CompareTo(keys[i]) >= 0)
//{
// i++;
//}
}
//return i;
}
else
{
throw new ArgumentException("Internal node expected");
}
}
/// <summary>
/// Looks for leaf tree node which is supposed to have an edge with given hash
/// </summary>
/// <param name="nodes">Node provider</param>
/// <param name="rootNodeId">Root node ID to start the search from</param>
/// <param name="edgeHash">Hash to find</param>
/// <returns>Leaf node which is supposed to contain the edge</returns>
private static FindResult FindLeafNode(INodeProvider <Guid, object, EdgeData> nodes, Guid rootNodeId, EdgeData data)
{
var node = nodes.GetNode(rootNodeId, NodeAccess.Read);
Guid id = rootNodeId;
while (node.Data.Equals(InternalNodeData))
{
var leadingEdge = FindLeadingEdge(data, node);
// Advance to next internal node
node = nodes.GetNode(leadingEdge.ToNodeId, NodeAccess.Read);
id = leadingEdge.ToNodeId;
}
return(new FindResult(id, node));
}
/// <summary>
/// Removes the edge from the tree
/// </summary>
/// <param name="nodes">Node provider which hosts the nodes</param>
/// <param name="rootNodeId">Tree root node ID</param>
/// <param name="data">Edge to find</param>
/// <returns>True if edge was removed</returns>
public static bool RemoveEdge(INodeProvider <Guid, object, EdgeData> nodes, Guid rootNodeId, EdgeData data, int treeOrder)
{
var result = RemoveEdgeRecursive(nodes, rootNodeId, data, treeOrder);
return(result.WasRemoved);
}
/// <summary>
/// Finds the edge in tree
/// </summary>
/// <param name="nodes">Node provider which hosts the nodes</param>
/// <param name="rootNodeId">Tree root node ID</param>
/// <param name="data">Edge to find</param>
/// <param name="toNodeId">New to node ID</param>
/// <returns>True if edge was found</returns>
public static bool TrySetEdgeToNode(INodeProvider <Guid, object, EdgeData> nodes, Guid rootNodeId, EdgeData data, Guid toNodeId)
{
var result = FindLeafNode(nodes, rootNodeId, data);
if (result == null)
{
throw new KeyNotFoundException();
}
else
{
if (!result.Node.Data.Equals(LeafNodeData))
{
throw new InvalidOperationException("Leaf node expected");
}
result.Node.SetEdgeToNode(data, toNodeId);
nodes.SetNode(result.NodeId, result.Node);
return(true);
}
}
/// <summary>
/// Finds the edge in tree
/// </summary>
/// <param name="nodes">Node provider which hosts the nodes</param>
/// <param name="rootNodeId">Tree root node ID</param>
/// <param name="data">Edge to find</param>
/// <param name="value">Edge result</param>
/// <returns>True if edge was found</returns>
public static bool TryFindEdge(INodeProvider <Guid, object, EdgeData> nodes, Guid rootNodeId, EdgeData data, out Edge <Guid, EdgeData> value)
{
var result = FindLeafNode(nodes, rootNodeId, data);
if (result == null)
{
throw new KeyNotFoundException();
}
else
{
if (!result.Node.Data.Equals(LeafNodeData))
{
throw new InvalidOperationException("Leaf node expected");
}
return(result.Node.Edges.TryGetValue(data, out value));
}
}
/// <summary>
/// Creates new instance of SplitResult type
/// </summary>
/// <param name="createdNodeId">New node ID which was created</param>
/// <param name="createdNode">Node which was created</param>
/// <param name="rightKey">Minimum key value of the right sibling node of the new node</param>
public SplitResult(Guid createdNodeId, Node <Guid, object, EdgeData> createdNode, EdgeData rightKey)
{
this.CreatedNodeId = createdNodeId;
this.CreatedNode = createdNode;
this.RightKey = rightKey;
}
