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Exonum MerkleDB

Travis Build Status Docs.rs rust 1.36.0+ required License: Apache-2.0

Exonum MerkleDB is a persistent storage implementation based on RocksDB which provides APIs to work with merkelized data structures.

Available Database Objects

  • Entry is a specific index that stores only one value. Useful for global values, such as configuration. Similar to a combination of Box and Option.
  • ListIndex is a list of items stored in a sequential order. Similar to Vec.
  • SparseListIndex is a list of items stored in a sequential order. Similar to ListIndex, but may contain indices without elements.
  • MapIndex is a map of keys and values. Similar to BTreeMap.
  • ProofListIndex is a Merkelized version of ListIndex that supports cryptographic proofs of existence and is implemented as a Merkle tree.
  • ProofMapIndex is a Merkelized version of MapIndex that supports cryptographic proofs of existence and is implemented as a binary Merkle Patricia tree.
  • KeySetIndex and ValueSetIndex are sets of items, similar to BTreeSet and HashSet accordingly.

Usage

Include exonum-merkledb as a dependency in your Cargo.toml:

[dependencies]
exonum-merkledb = "0.13.0-rc.2"

If you need only to read the data you can create Snapshot. Objects created from Snapshot provide a read-only access to the storage data. To modify data you need to create an object based on Fork. Fork and Snapshot can be obtained from the Database object. Currently only one database backend is supported - RockDB.

use std::path::Path;
use exonum_merkledb::{ProofListIndex, Database, ListProof, DbOptions, RocksDB};

let db_options = DbOptions::default();
let db = RocksDB::open(&Path::new("db"), &db_options).unwrap();
let list_name = "list";

// Read-only list
let snapshot = db.snapshot();
let list: ProofListIndex<_, u8> = ProofListIndex::new(list_name, &snapshot);

// Mutable list
let fork = db.fork();
let mut list: ProofListIndex<_, u8> = ProofListIndex::new(list_name, &fork);

After adding elements to the object you can obtain cryptographic proofs for their existence or absence.

list.push(1);

assert_eq!(ListProof::Leaf(1), list.get_proof(0));

if let ListProof::Absent(_proof) = list.get_proof(1) {
    println!("Element with index 1 is absent")
}

Further Reading

License

exonum-merkledb is licensed under the Apache License (Version 2.0). See LICENSE for details.