/// <summary>
/// Splits this node to left and right nodes.
/// </summary>
public void Split(out TreeNode <K, V> leftNode, out TreeNode <K, V> rightNode)
{
Debug.Assert(IsOverflow, "This node is not yet overflowing.");
bool isLeaf = IsLeaf;
var halfCount = nodeManager.MinEntriesPerNode;
var middleEntry = entries[halfCount];
// Get larger entries and children for new node.
var largeEntries = new Tuple <K, V> [halfCount];
uint[] largeChildren = null;
// Copy larger entries to newer node.
entries.CopyTo(halfCount + 1, largeEntries, 0, halfCount);
// Copy child node ids if not a leaf.
if (!isLeaf)
{
largeChildren = new uint[halfCount + 1];
childrenIds.CopyTo(halfCount + 1, largeChildren, 0, halfCount);
}
// Create larger node
var largeNode = nodeManager.Create(largeEntries, largeChildren);
// All child nodes moved to newer node must refresh their parentId.
if (!isLeaf)
{
for (int i = 0; i < largeChildren.Length; i++)
{
nodeManager.Find(largeChildren[i]).ParentId = largeNode.id;
}
}
// Remove all large entries and children ids from this node.
// Entries list must also remove the middle entry because it will go to the parent node.
entries.RemoveRange(halfCount);
if (!isLeaf)
{
childrenIds.RemoveRange(halfCount + 1);
}
// Try getting parent node
var parentNode = parentId == 0 ? null : nodeManager.Find(parentId);
// If no parent, create a new parent node with the middle entry
if (parentNode == null)
{
parentNode = nodeManager.CreateNewRoot(
middleEntry.Item1,
middleEntry.Item2,
id,
largeNode.id
);
// Reassign parent id
this.ParentId = parentNode.id;
largeNode.ParentId = parentNode.id;
}
// Move the middle element to the parent node.
else
{
int insertIndex = 0;
parentNode.InsertAsParent(
middleEntry.Item1,
middleEntry.Item2,
id,
largeNode.id,
out insertIndex
);
// Reassign parent id for large node only because this node's already been set.
largeNode.ParentId = parentNode.id;
// Split parent node if overflowing.
if (parentNode.IsOverflow)
{
Split();
}
}
// Output nodes
leftNode = this;
rightNode = largeNode;
// Mark this node dirty
nodeManager.MarkAsChanged(this);
}
