Crate diem_jellyfish_merkle[−][src]
Expand description
This module implements JellyfishMerkleTree backed by storage module. The tree itself doesn’t
persist anything, but realizes the logic of R/W only. The write path will produce all the
intermediate results in a batch for storage layer to commit and the read path will return
results directly. The public APIs are only new, put_value_sets, put_value_set and
get_with_proof. After each put with a value_set based on a known version, the tree will
return a new root hash with a TreeUpdateBatch containing all the new nodes and indices of
stale nodes.
A Jellyfish Merkle Tree itself logically is a 256-bit sparse Merkle tree with an optimization that any subtree containing 0 or 1 leaf node will be replaced by that leaf node or a placeholder node with default hash value. With this optimization we can save CPU by avoiding hashing on many sparse levels in the tree. Physically, the tree is structurally similar to the modified Patricia Merkle tree of Ethereum but with some modifications. A standard Jellyfish Merkle tree will look like the following figure:
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■: the [`Value`] type this tree stores.A Jellyfish Merkle Tree consists of InternalNode and LeafNode. InternalNode is like
branch node in ethereum patricia merkle with 16 children to represent a 4-level binary tree and
LeafNode is similar to that in patricia merkle too. In the above figure, each bell in the
jellyfish is an InternalNode while each tentacle is a LeafNode. It is noted that
Jellyfish merkle doesn’t have a counterpart for extension node of ethereum patricia merkle.
Modules
This module implements JellyfishMerkleIterator. Initialized with a version and a key, the
iterator generates all the key-value pairs in this version of the tree, starting from the
smallest key that is greater or equal to the given key, by performing a depth first traversal
on the tree.
Node types of JellyfishMerkleTree
This module implements the functionality to restore a JellyfishMerkleTree from small chunks
of accounts.
Structs
The Jellyfish Merkle tree data structure. See crate for description.
Indicates a node becomes stale since stale_since_version.
This is a wrapper of NodeBatch,
StaleNodeIndexBatch and some stats of nodes that represents
the incremental updates of a tree and pruning indices after applying a write set,
which is a vector of hashed_account_address and new_value pairs.
Traits
TestValue defines the types of data that can be stored in a Jellyfish Merkle tree and used in
tests.
TreeReader defines the interface between
JellyfishMerkleTree
and underlying storage holding nodes.
Value defines the types of data that can be stored in a Jellyfish Merkle tree.
Type Definitions
Node batch that will be written into db atomically with other batches.
StaleNodeIndex batch that will be written into db atomically
with other batches.