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-rw-r--r--adenosine-pds/src/mst.rs34
1 files changed, 27 insertions, 7 deletions
diff --git a/adenosine-pds/src/mst.rs b/adenosine-pds/src/mst.rs
index 23f1fdb..8a28117 100644
--- a/adenosine-pds/src/mst.rs
+++ b/adenosine-pds/src/mst.rs
@@ -223,28 +223,48 @@ pub fn generate_mst(
serialize_wip_tree(db, root.unwrap_or(empty_node))
}
+// this routine assumes that entries are added in sorted key order. AKA, the `entry` being added is
+// "further right" in the tree than any existing entries
fn insert_entry(mut node: WipNode, entry: WipEntry) -> WipNode {
- // if we are higher on tree than existing node, replace it with new layer first
- if entry.height > node.height {
+ // if we are higher on tree than existing node, replace it (recursively) with new layers first
+ while entry.height > node.height {
node = WipNode {
- height: entry.height,
+ height: node.height + 1,
left: Some(Box::new(node)),
entries: vec![],
}
- };
+ }
// if we are lower on tree, then need to descend first
if entry.height < node.height {
- // we should never be lower down the left than an existing node, and always to the right
+ // if no entries at this node, then we should insert down "left" (which is just "down", not
+ // "before" any entries)
+ if node.entries.is_empty() {
+ if let Some(left) = node.left {
+ node.left = Some(Box::new(insert_entry(*left, entry)));
+ return node;
+ } else {
+ panic!("hit existing totally empty MST node");
+ }
+ }
let mut last = node.entries.pop().expect("hit empty existing entry list");
assert!(entry.key > last.key);
if last.right.is_some() {
last.right = Some(Box::new(insert_entry(*last.right.unwrap(), entry)));
} else {
- last.right = Some(Box::new(WipNode {
+ let mut new_node = WipNode {
height: entry.height,
left: None,
entries: vec![entry],
- }));
+ };
+ // may need to (recursively) insert multiple filler layers
+ while new_node.height + 1 < node.height {
+ new_node = WipNode {
+ height: new_node.height + 1,
+ left: Some(Box::new(new_node)),
+ entries: vec![],
+ }
+ }
+ last.right = Some(Box::new(new_node));
}
node.entries.push(last);
return node;