Module frontier

Available on crate feature internal only.

Frontier things can be inserted into and updated, always representing the rightmost (most recently inserted) element of a tree.

In sketch: the structure of a single Tier contains eight Nodes, the bottom-most of which contains a Leaf. Alternatively, a tier can be a summarized Hash of what its contents would be, and contain nothing at all besides this hash.

At every level of a frontier::Tier, the rightmost child of a frontier::Node is a frontier::Node; all leftward siblings are complete::Nodes. When the child of a frontier::Node becomes entirely full (all its possible leaves are inserted), it is transformed into a complete::Node and appended to the list of complete siblings of its parent, thus shifting the frontier rightwards.

At any given time, the frontier is always fully materialized; no node within it is ever summarized as a hash. It is at the point when a frontier::Node becomes full and is then finalized into a complete::Node that it is pruned, if it contains no witnessed children.

At the tip of the frontier, however deeply nested (perhaps within multiple Tiers), there is a single Item, which is either a Commitment or a hash of one. Commitments can be inserted either with the intent to remember them, or with the intent to immediately forget them; this determines whether the Item is a commitment or merely its hash.

Structs

Full

The result of Frontier::insert_owned when the Frontier is full.

Item

The hash of the most-recently-inserted item, stored at the tip of the frontier.

Leaf

The frontier (rightmost) leaf in a frontier of a tree.

Node

A frontier of a node in a tree, into which items can be inserted.

Tier

A frontier of a tier of the tiered commitment tree, being an 8-deep quad-tree of items.

Top

The frontier of the top level of some part of the commitment tree, which may be empty, but may not be finalized or hashed.

Enums

Insert

Either an item or just its hash, to be used when inserting into a tree.

InsertMut

The mutable-reference version of an Insert<T>, distinct from Insert<&mut T> because it also allows mutation of the contained hash.

TrackForgotten

Whether or not to track forgotten elements of the tree.

Traits

Focus

A type which can be the focus of an Frontier tree: it can be finalized to make a Complete tree.

Forget

Forget about the authentication path to a given index.

Frontier

A frontier of a tree supporting the insertion of new elements and the updating of the most-recently-inserted element.

GetPosition

Get the position of the next insertion into the tree.