logos.std.data.persistent.bt.mutate

Outcome of a recursive insert: whether an existing key was replaced, and whether the visited node split.

Outcome of a recursive remove: whether the key was found, and whether the visited node underflowed and needs the parent to rebalance.

Inserts key/val into the tree rooted at root, growing a new root when the old root splits. Returns the previous value if key already existed (mirrors Rust BTreeMap::insert).

Removes qkey from the tree rooted at root, collapsing the root while it’s a branch with a single remaining child. Returns true if the key was found and removed.

Recursively inserts key/val (positioned by qkey) into the subtree rooted at arc, CoW-cloning any node not owned by cur_snapshot_id and splitting on overflow. Returns an InsertOutcome reporting whether an existing key was replaced and whether arc split.

Returns the max key of arc’s subtree, relying on the leaf/branch max-key invariant.

Rebalances branch child i of parent_branch after underflow: merges with a sibling when the combined length fits max_keys, otherwise borrows one (key, child) pair from whichever sibling has more keys.

Rebalances leaf child i of parent_branch after underflow: merges with a sibling when the combined length fits max_keys, otherwise borrows one entry from whichever sibling has more keys.

Recursively removes qkey from the subtree rooted at arc, CoW-cloning any node not owned by cur_snapshot_id and rebalancing children that underflow. Returns a RemoveOutcome reporting whether the key was found and whether arc itself underflowed.

Splits branch in half, moving the upper half of keys/children/subtree_size into a freshly allocated right branch; branch keeps the lower half.

Splits leaf in half, moving the upper half of entries into a freshly allocated right leaf; leaf keeps the lower half. Panics if keys.len() != vals.len().

Inserts new_arc at index idx in v, shifting later elements right. Caller must ensure idx <= v.len(); the shift is whole-handle swaps (no refcount churn).