Enum exonum_merkledb::HashTag

#[repr(u8)]#[non_exhaustive]pub enum HashTag {
    Blob,
    ListBranchNode,
    ListNode,
    MapNode,
    MapBranchNode,
}

Prefixes for different types of objects stored in the database. These prefixes are necessary to provide domain separation among hashed objects of different types.

In MerkleDB, all data is presented as objects. Objects are divided into blobs and collections (lists / maps), which in their turn are divided into hashable and non-hashable. The hashable collections are ProofListIndex and ProofMapIndex. For these collections, one can define a single hash which would reflect the entire collection contents. This hash can then be used that a collection contains (or does not contain) certain elements.

Different hashes for leaf and branch nodes of the list are used to secure Merkle tree from the pre-image attack. See more information here.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Blob

Hash prefix of a blob (i.e., a type implementing BinaryValue, which is stored in the DB as byte sequence).

ListBranchNode

Hash prefix of a branch node in a Merkle tree built for a Merkelized list.

ListNode

Hash prefix of a Merkelized list.

MapNode

Hash prefix of a Merkelized map.

MapBranchNode

Hash prefix of a branch node in a Merkle Patricia tree built for a Merkelized map.

Methods

impl HashTag

pub fn hash_leaf(value: &[u8]) -> Hash

Obtains a hashed value of a leaf in a Merkle tree.

pub fn hash_node(left_hash: &Hash, right_hash: &Hash) -> Hash

Obtains a hashed value of a branch in a Merkle tree.

pub fn hash_single_node(hash: &Hash) -> Hash

Obtains a hashed value of a Merkle tree branch with one child.

pub fn hash_list_node(len: u64, root: Hash) -> Hash

Obtains hash of a Merkelized list. len is the length of the list, and root is the hash of the root node of the Merkle tree corresponding to the list.

h = sha256( HashTag::ListNode || len as u64 || merkle_root )

pub fn empty_list_hash() -> Hash

Obtains hash of an empty Merkelized list.

h = sha256( HashTag::ListNode || 0 || Hash::zero() )

pub fn hash_list<V: BinaryValue + ?Sized>(values: &[V]) -> Hash

Computes the hash for a Merkelized list containing the given values.

pub fn hash_map_node(root: Hash) -> Hash

Obtains hash of a Merkelized map. root is the recursively defined hash of the root node of the binary Patricia Merkle tree corresponding to the map.

h = sha256( HashTag::MapNode || merkle_root )

pub fn hash_map_branch(branch_node: &[u8]) -> Hash

Obtains hash of a branch node in a Merkle Patricia tree. branch_node is the binary serialization of the node.

h = sha256( HashTag::MapBranchNode || branch_node )

See ProofMapIndex for details how branch nodes are serialized.

pub fn hash_single_entry_map(path: &ProofPath, child_hash: &Hash) -> Hash

Obtains hash of a Merkelized map with a single entry.

h = sha256( HashTag::MapBranchNode || path || child_hash )

See ProofMapIndex for details how path is serialized.

pub fn empty_map_hash() -> Hash

Obtains hash of an empty Merkelized map.

The hash is computed as

sha256( HashTag::MapNode || Hash::zero() )

Trait Implementations

impl Clone for HashTag

fn clone(&self) -> HashTag

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for HashTag

impl Debug for HashTag

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

Formats the value using the given formatter.