private bool RedistributeBranchElements(TreeBranch branch, int childIndex, TreeBranch child)
{
// We distribute the nodes in the child branch with the branch
// immediately to the right. If that's not possible, then we distribute
// with the left.
// If branch has only a single value, return immediately
int branchSize = branch.ChildCount;
if (branchSize == 1)
{
return(false);
}
int leftI, rightI;
TreeBranch left, right;
if (childIndex < branchSize - 1)
{
// Distribute with the right
leftI = childIndex;
rightI = childIndex + 1;
left = child;
right = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex + 1)));
branch.SetChild(right.Id, childIndex + 1);
}
else
{
// Distribute with the left
leftI = childIndex - 1;
rightI = childIndex;
left = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex - 1)));
right = child;
branch.SetChild(left.Id, childIndex - 1);
}
// Get the mid value key reference
Key midKey = branch.GetKey(rightI);
// Perform the merge,
Key newMidKey = left.Merge(right, midKey);
// Reset the leaf element count
branch.SetChildLeafElementCount(left.LeafElementCount, leftI);
branch.SetChildLeafElementCount(right.LeafElementCount, rightI);
// If after the merge the right branch is empty, we need to remove it
if (right.IsEmpty)
{
// Delete the node
DeleteNode(right.Id);
// And remove it from the branch,
branch.RemoveChild(rightI);
return(true);
}
// Otherwise set the key reference
branch.SetKeyToLeft(newMidKey, rightI);
return(false);
}
public void DeleteLeaf(Key key)
{
// Set up the state
StackFrame frame = StackEnd(0);
NodeId thisRef = frame.NodeId;
TreeBranch branchNode = null;
int deleteNodeSize = -1;
Key leftKey = null;
// Walk back through the rest of the stack
int sz = FrameCount;
for (int i = 1; i < sz; ++i)
{
// Find the child_i for the child
// This is the child_i of the child in the current branch
int childIndex = frame.ChildIndex;
// Move the stack frame,
frame = StackEnd(i);
NodeId childId = thisRef;
thisRef = frame.NodeId;
TreeBranch childBranch = branchNode;
branchNode = (TreeBranch)UnfreezeNode(FetchNode(thisRef));
if (deleteNodeSize == -1)
{
deleteNodeSize =
(int)branchNode.GetChildLeafElementCount(childIndex);
}
// If the child branch is empty,
if (childBranch == null || childBranch.IsEmpty)
{
// Delete the reference to it,
if (childIndex == 0 && branchNode.ChildCount > 1)
{
leftKey = branchNode.GetKey(1);
}
branchNode.RemoveChild(childIndex);
// Delete the child branch,
DeleteNode(childId);
}
// Not empty,
else
{
// Replace with the new child node reference
branchNode.SetChild(childBranch.Id, childIndex);
// Set the element count
long newChildSize =
branchNode.GetChildLeafElementCount(childIndex) -
deleteNodeSize;
branchNode.SetChildLeafElementCount(newChildSize, childIndex);
// Can we set the left key reference?
if (childIndex > 0 && leftKey != null)
{
branchNode.SetKeyToLeft(leftKey, childIndex);
leftKey = null;
}
// Has the size of the child reached the lower threshold?
if (childBranch.ChildCount <= 2)
{
// If it has, we need to redistribute the children,
RedistributeBranchElements(branchNode, childIndex, childBranch);
}
}
}
// Finally, set the root node
// If the branch node is a single element, we set the root as the child,
if (branchNode.ChildCount == 1)
{
// This shrinks the height of the tree,
RootNodeId = branchNode.GetChild(0);
DeleteNode(branchNode.Id);
if (TreeHeight != -1)
{
TreeHeight = TreeHeight - 1;
}
}
else
{
// Otherwise, we set the branch node.
RootNodeId = branchNode.Id;
}
// Reset the object
Reset();
}
public void InsertLeaf(Key newLeafKey, TreeLeaf newLeaf, bool before)
{
int leafSize = newLeaf.Length;
if (leafSize <= 0)
{
throw new ArgumentException("size <= 0");
}
// The current absolute position and key
Key newKey = newLeafKey;
// The frame at the end of the stack,
StackFrame frame = StackEnd(0);
object[] info;
object[] rInfo = new object[5];
Key leftKey;
long curAbsolutePos;
// If we are inserting the new leaf after,
if (!before)
{
info = new object[] {
currentLeaf.Id,
(long)currentLeaf.Length,
newLeafKey,
newLeaf.Id,
(long)newLeaf.Length
};
leftKey = null;
curAbsolutePos = frame.Offset + currentLeaf.Length;
}
// Otherwise we are inserting the new leaf before,
else
{
// If before and current_leaf key is different than new_leaf key, we
// generate an error
if (!currentLeafKey.Equals(newLeafKey))
{
throw new InvalidOperationException("Can't insert different new key before.");
}
info = new Object[] {
newLeaf.Id,
(long)newLeaf.Length,
currentLeafKey,
currentLeaf.Id,
(long)currentLeaf.Length
};
leftKey = newLeafKey;
curAbsolutePos = frame.Offset - 1;
}
bool insertTwoNodes = true;
int sz = FrameCount;
// Walk the stack from the end
for (int i = 1; i < sz; ++i)
{
// child_i is the previous frame's child_i
int childIndex = frame.ChildIndex;
frame = StackEnd(i);
// The child ref of this stack element
NodeId childId = frame.NodeId;
// Fetch it
TreeBranch branch = (TreeBranch)UnfreezeNode(FetchNode(childId));
// Do we have two nodes to insert into the branch?
if (insertTwoNodes)
{
TreeBranch insertBranch;
int insertIndex = childIndex;
// If the branch is full,
if (branch.IsFull)
{
// Create a new node,
TreeBranch leftBranch = branch;
TreeBranch rightBranch = CreateBranch();
// Split the branch,
Key midpointKey = leftBranch.MidPointKey;
// And move half of this branch into the new branch
leftBranch.MoveLastHalfInto(rightBranch);
// We split so we need to return a split flag,
rInfo[0] = leftBranch.Id;
rInfo[1] = leftBranch.LeafElementCount;
rInfo[2] = midpointKey;
rInfo[3] = rightBranch.Id;
rInfo[4] = rightBranch.LeafElementCount;
// Adjust insert_n and insert_branch
if (insertIndex >= leftBranch.ChildCount)
{
insertIndex -= leftBranch.ChildCount;
insertBranch = rightBranch;
rInfo[4] = (long)rInfo[4] + newLeaf.Length;
// If insert_n == 0, we change the midpoint value to the left
// key value,
if (insertIndex == 0 && leftKey != null)
{
rInfo[2] = leftKey;
leftKey = null;
}
}
else
{
insertBranch = leftBranch;
rInfo[1] = (long)rInfo[1] + newLeaf.Length;
}
}
// If it's not full,
else
{
insertBranch = branch;
rInfo[0] = insertBranch.Id;
insertTwoNodes = false;
}
// Insert the two children nodes
insertBranch.Insert((NodeId)info[0], (long)info[1],
(Key)info[2],
(NodeId)info[3], (long)info[4],
insertIndex);
// Copy r_nfo to nfo
for (int p = 0; p < rInfo.Length; ++p)
{
info[p] = rInfo[p];
}
// Adjust the left key reference if necessary
if (leftKey != null && insertIndex > 0)
{
insertBranch.SetKeyToLeft(leftKey, insertIndex);
leftKey = null;
}
}
else
{
branch.SetChild((NodeId)info[0], childIndex);
info[0] = branch.Id;
branch.SetChildLeafElementCount(
branch.GetChildLeafElementCount(childIndex) + leafSize, childIndex);
// Adjust the left key reference if necessary
if (leftKey != null && childIndex > 0)
{
branch.SetKeyToLeft(leftKey, childIndex);
leftKey = null;
}
}
} // For all elements in the stack,
// At the end, if we still have a split then we make a new root and
// adjust the stack accordingly
if (insertTwoNodes)
{
TreeBranch newRoot = CreateBranch();
newRoot.Set((NodeId)info[0], (long)info[1],
(Key)info[2],
(NodeId)info[3], (long)info[4]);
RootNodeId = newRoot.Id;
if (TreeHeight != -1)
{
TreeHeight = TreeHeight + 1;
}
}
else
{
RootNodeId = (NodeId)info[0];
}
// Now reset the position,
Reset();
SetupForPosition(newKey, curAbsolutePos);
}
private bool RedistributeBranchElements(TreeBranch branch, int childIndex, TreeBranch child)
{
// We distribute the nodes in the child branch with the branch
// immediately to the right. If that's not possible, then we distribute
// with the left.
// If branch has only a single value, return immediately
int branchSize = branch.ChildCount;
if (branchSize == 1) {
return false;
}
int leftI, rightI;
TreeBranch left, right;
if (childIndex < branchSize - 1) {
// Distribute with the right
leftI = childIndex;
rightI = childIndex + 1;
left = child;
right = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex + 1)));
branch.SetChild(right.Id, childIndex + 1);
} else {
// Distribute with the left
leftI = childIndex - 1;
rightI = childIndex;
left = (TreeBranch)UnfreezeNode(FetchNode(branch.GetChild(childIndex - 1)));
right = child;
branch.SetChild(left.Id, childIndex - 1);
}
// Get the mid value key reference
Key midKey = branch.GetKey(rightI);
// Perform the merge,
Key newMidKey = left.Merge(right, midKey);
// Reset the leaf element count
branch.SetChildLeafElementCount(left.LeafElementCount, leftI);
branch.SetChildLeafElementCount(right.LeafElementCount, rightI);
// If after the merge the right branch is empty, we need to remove it
if (right.IsEmpty) {
// Delete the node
DeleteNode(right.Id);
// And remove it from the branch,
branch.RemoveChild(rightI);
return true;
}
// Otherwise set the key reference
branch.SetKeyToLeft(newMidKey, rightI);
return false;
}
