Struct fork_tree::ForkTree

pub struct ForkTree<H, N, V> { /* private fields */ }

A tree data structure that stores several nodes across multiple branches.

Top-level branches are called roots. The tree has functionality for finalizing nodes, which means that node is traversed, and all competing branches are pruned. It also guarantees that nodes in the tree are finalized in order. Each node is uniquely identified by its hash but can be ordered by its number. In order to build the tree an external function must be provided when interacting with the tree to establish a node’s ancestry.

Implementations

impl<H, N, V> ForkTree<H, N, V>

where H: PartialEq, N: Ord,

pub fn new() -> ForkTree<H, N, V>

Create a new empty tree instance.

pub fn rebalance(&mut self)

Rebalance the tree.

For each tree level sort child nodes by max branch depth (decreasing).

Most operations in the tree are performed with depth-first search starting from the leftmost node at every level, since this tree is meant to be used in a blockchain context, a good heuristic is that the node we’ll be looking for at any point will likely be in one of the deepest chains (i.e. the longest ones).

pub fn import<F, E>( &mut self, hash: H, number: N, data: V, is_descendent_of: &F ) -> Result<bool, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>,

Import a new node into the tree.

The given function is_descendent_of should return true if the second hash (target) is a descendent of the first hash (base).

This method assumes that nodes in the same branch are imported in order.

Returns true if the imported node is a root.

pub fn roots(&self) -> impl Iterator<Item = (&H, &N, &V)>

Iterates over the existing roots in the tree.

pub fn iter(&self) -> impl Iterator<Item = (&H, &N, &V)>

Iterates the nodes in the tree in pre-order.

pub fn map<VT, F>(self, f: &mut F) -> ForkTree<H, N, VT>

where F: FnMut(&H, &N, V) -> VT,

Map fork tree into values of new types.

Tree traversal technique (e.g. BFS vs DFS) is left as not specified and may be subject to change in the future. In other words, your predicates should not rely on the observed traversal technique currently in use.

pub fn find_node_where<F, E, P>( &self, hash: &H, number: &N, is_descendent_of: &F, predicate: &P ) -> Result<Option<&Node<H, N, V>>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>, P: Fn(&V) -> bool,

Find a node in the tree that is the deepest ancestor of the given block hash and which passes the given predicate.

The given function is_descendent_of should return true if the second hash (target) is a descendent of the first hash (base).

pub fn find_node_where_mut<F, E, P>( &mut self, hash: &H, number: &N, is_descendent_of: &F, predicate: &P ) -> Result<Option<&mut Node<H, N, V>>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>, P: Fn(&V) -> bool,

Same as find_node_where, but returns mutable reference.

pub fn find_node_index_where<F, E, P>( &self, hash: &H, number: &N, is_descendent_of: &F, predicate: &P ) -> Result<Option<Vec<usize>>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>, P: Fn(&V) -> bool,

Same as find_node_where, but returns indices.

The returned indices represent the full path to reach the matching node starting from one of the roots, i.e. the earliest index in the traverse path goes first, and the final index in the traverse path goes last.

If a node is found that matches the predicate the returned path should always contain at least one index, otherwise None is returned.

pub fn prune<F, E, P>( &mut self, hash: &H, number: &N, is_descendent_of: &F, predicate: &P ) -> Result<impl Iterator<Item = (H, N, V)>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>, P: Fn(&V) -> bool,

Prune the tree, removing all non-canonical nodes.

We find the node in the tree that is the deepest ancestor of the given hash and that passes the given predicate. If such a node exists, we re-root the tree to this node. Otherwise the tree remains unchanged.

The given function is_descendent_of should return true if the second hash (target) is a descendent of the first hash (base).

Returns all pruned nodes data.

pub fn finalize_root(&mut self, hash: &H) -> Option<V>

Finalize a root in the tree and return it, return None in case no root with the given hash exists. All other roots are pruned, and the children of the finalized node become the new roots.

pub fn finalize<F, E>( &mut self, hash: &H, number: N, is_descendent_of: &F ) -> Result<FinalizationResult<V>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>,

Finalize a node in the tree. This method will make sure that the node being finalized is either an existing root (and return its data), or a node from a competing branch (not in the tree), tree pruning is done accordingly. The given function is_descendent_of should return true if the second hash (target) is a descendent of the first hash (base).

pub fn finalize_with_ancestors<F, E>( &mut self, hash: &H, number: N, is_descendent_of: &F ) -> Result<FinalizationResult<V>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>,

Finalize a node in the tree and all its ancestors. The given function is_descendent_of should return true if the second hash (target) is

pub fn finalizes_any_with_descendent_if<F, P, E>( &self, hash: &H, number: N, is_descendent_of: &F, predicate: P ) -> Result<Option<bool>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>, P: Fn(&V) -> bool,

Checks if any node in the tree is finalized by either finalizing the node itself or a node’s descendent that’s not in the tree, guaranteeing that the node being finalized isn’t a descendent of (or equal to) any of the node’s children. Returns Some(true) if the node being finalized is a root, Some(false) if the node being finalized is not a root, and None if no node in the tree is finalized. The given predicate is checked on the prospective finalized root and must pass for finalization to occur. The given function is_descendent_of should return true if the second hash (target) is a descendent of the first hash (base).

pub fn finalize_with_descendent_if<F, P, E>( &mut self, hash: &H, number: N, is_descendent_of: &F, predicate: P ) -> Result<FinalizationResult<V>, Error<E>>

where E: Error, F: Fn(&H, &H) -> Result<bool, E>, P: Fn(&V) -> bool,

Finalize a root in the tree by either finalizing the node itself or a node’s descendent that’s not in the tree, guaranteeing that the node being finalized isn’t a descendent of (or equal to) any of the root’s children. The given predicate is checked on the prospective finalized root and must pass for finalization to occur. The given function is_descendent_of should return true if the second hash (target) is a descendent of the first hash (base).

pub fn drain_filter<F>(&mut self, filter: F) -> impl Iterator<Item = (H, N, V)>

where F: Fn(&H, &N, &V) -> FilterAction,

Remove from the tree some nodes (and their subtrees) using a filter predicate.

The filter is called over tree nodes and returns a filter action:

• Remove if the node and its subtree should be removed;
• KeepNode if we should maintain the node and keep processing the tree.
• KeepTree if we should maintain the node and its entire subtree.

An iterator over all the pruned nodes is returned.

Trait Implementations

impl<H: Clone, N: Clone, V: Clone> Clone for ForkTree<H, N, V>

fn clone(&self) -> ForkTree<H, N, V>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<H: Debug, N: Debug, V: Debug> Debug for ForkTree<H, N, V>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<H, N, V> Decode for ForkTree<H, N, V>

where Vec<Node<H, N, V>>: Decode, Option<N>: Decode,

fn decode<__CodecInputEdqy: Input>( __codec_input_edqy: &mut __CodecInputEdqy ) -> Result<Self, Error>

Attempt to deserialise the value from input.

fn decode_into<I>( input: &mut I, dst: &mut MaybeUninit<Self> ) -> Result<DecodeFinished, Error>

where I: Input,

Attempt to deserialize the value from input into a pre-allocated piece of memory.

fn skip<I>(input: &mut I) -> Result<(), Error>

where I: Input,

Attempt to skip the encoded value from input.

fn encoded_fixed_size() -> Option<usize>

Returns the fixed encoded size of the type.

impl<H, N, V> Encode for ForkTree<H, N, V>

where Vec<Node<H, N, V>>: Encode, Option<N>: Encode,

fn size_hint(&self) -> usize

If possible give a hint of expected size of the encoding.

fn encode_to<__CodecOutputEdqy: Output + ?Sized>( &self, __codec_dest_edqy: &mut __CodecOutputEdqy )

Convert self to a slice and append it to the destination.

fn encode(&self) -> Vec<u8>

Convert self to an owned vector.

fn using_encoded<R, F>(&self, f: F) -> R

where F: FnOnce(&[u8]) -> R,

Convert self to a slice and then invoke the given closure with it.

fn encoded_size(&self) -> usize

Calculates the encoded size.

impl<H: PartialEq, N: PartialEq, V: PartialEq> PartialEq for ForkTree<H, N, V>

fn eq(&self, other: &ForkTree<H, N, V>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<H, N, V> EncodeLike for ForkTree<H, N, V>

where Vec<Node<H, N, V>>: Encode, Option<N>: Encode,

impl<H, N, V> StructuralPartialEq for ForkTree<H, N, V>