Struct NullifierTree 

pub struct NullifierTree<Backend = Smt> { /* private fields */ }

The sparse merkle tree of all nullifiers in the blockchain.

A nullifier can only ever be spent once and its value in the tree is the block number at which it was spent.

The tree guarantees that once a nullifier has been inserted into the tree, its block number does not change. Note that inserting the nullifier multiple times with the same block number is valid.

Implementations

impl<Backend> NullifierTree<Backend>

where Backend: SmtBackendReader<Error = MerkleError>,

pub const DEPTH: u8 = SMT_DEPTH

The depth of the nullifier tree.

pub fn new_unchecked(backend: Backend) -> Self

Creates a new NullifierTree from its inner representation.

Invariants

Assumes the provided SMT upholds the guarantees of the NullifierTree. Specifically:

• Nullifiers are only spent once and their block numbers do not change.
• Nullifier leaf values must be valid according to NullifierBlock.

pub fn root(&self) -> Word

Returns the root of the nullifier SMT.

pub fn num_nullifiers(&self) -> usize

Returns the number of spent nullifiers in this tree.

pub fn entries(&self) -> impl Iterator<Item = (Nullifier, BlockNumber)>

Returns an iterator over the nullifiers and their block numbers in the tree.

pub fn open(&self, nullifier: &Nullifier) -> NullifierWitness

Returns a NullifierWitness of the leaf associated with the nullifier.

Conceptually, such a witness is a Merkle path to the leaf, as well as the leaf itself.

This witness is a proof of the current block number of the given nullifier. If that block number is zero, it proves that the nullifier is unspent.

pub fn get_block_num(&self, nullifier: &Nullifier) -> Option<BlockNumber>

Returns the block number for the given nullifier or None if the nullifier wasn’t spent yet.

impl<Backend> NullifierTree<Backend>

where Backend: SmtBackend<Error = MerkleError>,

pub fn compute_mutations<I>( &self, nullifiers: impl IntoIterator<Item = (Nullifier, BlockNumber), IntoIter = I>, ) -> Result<NullifierMutationSet, NullifierTreeError>

where I: Iterator<Item = (Nullifier, BlockNumber)> + Clone,

Computes a mutation set resulting from inserting the provided nullifiers into this nullifier tree.

Errors

Returns an error if:

• a nullifier in the provided iterator was already spent.
• the list of provided nullifiers contains duplicates.

pub fn mark_spent( &mut self, nullifier: Nullifier, block_num: BlockNumber, ) -> Result<(), NullifierTreeError>

Marks the given nullifier as spent at the given block number.

Errors

Returns an error if:

• the nullifier was already spent.

pub fn apply_mutations( &mut self, mutations: NullifierMutationSet, ) -> Result<(), NullifierTreeError>

Applies mutations to the nullifier tree.

Errors

Returns an error if:

• mutations was computed on a tree with a different root than this one.

impl NullifierTree<Smt>

pub fn with_entries( entries: impl IntoIterator<Item = (Nullifier, BlockNumber)>, ) -> Result<Self, NullifierTreeError>

Creates a new nullifier tree from the provided entries.

This is a convenience method that creates an SMT backend with the provided entries and wraps it in a NullifierTree.

Errors

Returns an error if:

• the provided entries contain multiple block numbers for the same nullifier.

impl<Backend> NullifierTree<LargeSmt<Backend>>

where Backend: SmtStorage,

pub fn with_storage_from_entries( storage: Backend, entries: impl IntoIterator<Item = (Nullifier, BlockNumber)>, ) -> Result<Self, NullifierTreeError>

Creates a new nullifier tree from the provided entries using the given storage backend

This is a convenience method that creates an SMT on the provided storage backend using the provided entries and wraps it in a NullifierTree.

Errors

Returns an error if:

• the provided entries contain multiple block numbers for the same nullifier.

Panics

Panics if a storage error is encountered.

pub fn reader( &self, ) -> Result<NullifierTree<LargeSmt<Backend::Reader>>, LargeSmtError>

Returns a read-only nullifier tree backed by a reader view of this tree’s storage.

The returned tree shares the same root and entries as self, but its storage is a read-only snapshot produced by SmtStorage::reader. The returned tree cannot be mutated.

Trait Implementations

impl<Backend: Clone> Clone for NullifierTree<Backend>

fn clone(&self) -> NullifierTree<Backend>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<Backend: Debug> Debug for NullifierTree<Backend>

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

Formats the value using the given formatter.

impl<Backend> Default for NullifierTree<Backend>

where Backend: Default,

fn default() -> Self

Returns the “default value” for a type.

impl Deserializable for NullifierTree

fn read_from<R: ByteReader>( source: &mut R, ) -> Result<Self, DeserializationError>

Reads a sequence of bytes from the provided source, attempts to deserialize these bytes into Self, and returns the result.

fn min_serialized_size() -> usize

Returns the minimum serialized size for one instance of this type.

fn read_from_bytes(bytes: &[u8]) -> Result<Self, DeserializationError>

Attempts to deserialize the provided bytes into Self and returns the result.

fn read_from_bytes_with_budget( bytes: &[u8], budget: usize, ) -> Result<Self, DeserializationError>

Deserializes Self from bytes with a byte budget limit.

impl<Backend: Eq> Eq for NullifierTree<Backend>

impl<Backend: PartialEq> PartialEq for NullifierTree<Backend>

fn eq(&self, other: &NullifierTree<Backend>) -> bool

Equality operator ==.

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

Inequality operator !=.

impl Serializable for NullifierTree

fn write_into<W: ByteWriter>(&self, target: &mut W)

Serializes self into bytes and writes these bytes into the target.

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

Serializes self into a vector of bytes.

fn get_size_hint(&self) -> usize

Returns an estimate of how many bytes are needed to represent self.

impl<Backend: PartialEq> StructuralPartialEq for NullifierTree<Backend>