This tree structure is a binary merkle tree with branch compression via split indexes. See here for a basic explanation of its purpose.
To quickly get started and get a feel for the Merkle-BIT, you can use the already implemented HashTree structure.
```rust use std::error::Error; use starling::hash_tree::HashTree;
fn main() -> Result<Ok(), Error> {
let tree = HashTree::new(8)?;
// Keys must be [u8; 32]
let mut key: [u8; 32] = [0xFF; 32];
// Value to be put into the tree
let value: Vec<u8> = vec![0xDDu8];
// Inserting an element changes the root node
let root = tree.insert(None, &mut [&key], &mut [&value])?;
let retrieved_value = tree.get(&root, &mut [&key])?;
// Removing a root only deletes elements that are referenced only by that root
tree.remove(&root)?;
Ok(())
}
```
This structure can be used for small amounts of data, but all the data in the tree will persist in memory unless explicitly pruned.
For larger numbers of items to store in the tree, it is recommended to connect the structure to a database by implementing the
Database trait for your database. This structure will also take advantage of batch writes if your database supports it.
Starling supports a number of serialization and hashing schemes for use in the tree, which should be selected based on your performance and application needs.
Currently integrated serialization schemes include:
* bincode
* serde-json
* serde-cbor
* serde-yaml
* serde-pickle
* ron
It should be noted that any serialization scheme will work with starling, provided you implement the Encode and Decode traits for the node types.
Currently integrated tree hashing schemes include:
* Blake2b via blake2_rfc
* Groestl via groestl
* SHA2 via openssl
* SHA3 via tiny-keccak
* Keccak via tiny-keccak
* SeaHash via seahash
* FxHash via fxhash
* and most updated hashes from RustCrypto
You may also use the default Rust hasher, or implement the Hasher trait for your own hashing scheme (unless using a hash from
RustCrypto, then you will want to enable the use_digest feature, which implements Hasher for Digest).
You can also use RocksDB to handle storing and loading from disk.
You can use the RocksTree with a serialization scheme via the --features="use_rocksdb use_bincode" command line flags
or by enabling the features in your Cargo.toml manifest.
Some enabled features must be used in combination, or you must implement the required traits yourself (E.g. using the
use_rocksdb feature alone will generate a compiler error, you must also select a serialization scheme, such as use_bincode or implement it for your data).
Finally, you can take advantage of the use_hashbrown feature to use the crate which will soon replace the existing HashMap,
providing up to 10% performance gains. This feature will be deprecated once hashbrown is incorporated into the standard library.
To use the full power of the Merkle-BIT structure, you should customize the structures stored in the tree to match your needs.
If you provide your own implementation of the traits for each component of the tree structure, the tree can utilize them over the default implementation. ```rust use starling::merkle_bit::MerkleBIT; use std::path::PathBuf; use std::error::Error;
fn main() -> Result<Ok, Error> {
// A path to a database to be opened
let path = PathBuf::new("some path");
// Your own database library
let db = YourDB::open(&path);
// These type annotations are required to specialize the Merkle BIT
// Check the documentation for the required trait bounds for each of these types.
let mbit = MerkleBIT<DatabaseType,
BranchType,
LeafType,
DataType,
NodeType,
HasherType,
ValueType>::from_db(db, depth);
// Keys must be 32 bytes long
let key: [u8; 32] = [0xFF; 32];
// An example value created from ValueType.
let value: ValueType = ValueType::new("Some value");
// You can specify a previous root to add to, in this case there is no previous root
let root: [u8; 32] = mbit.insert(None, &mut [&key], &mut [&value])?;
// Retrieving the inserted value
let inserted_values: HashMap<&[u8], Option<ValueType>> = mbit.get(&root, &mut [&key])?;
// Removing a tree root
mbit.remove(&root)?;
Ok(())
}
```
The MerkleBIT also supports generating and verifying merkle inclusion proofs, and may be used like below:
```rust
use starling::hash_tree::HashTree;
use std::error::Error;
fn main() -> Result<Ok, Error> {
let tree = HashTree::new(8)?;
let mut key: [u8; 32] = [0xFF; 32];
let value: Vec<u8> = vec![0xDDu8];
let root: [u8; 32] = tree.insert(None, &mut [&key], &mut [&value])?;
// An inclusion proof that proves membership of a key in the tree
let proof: Vec<([u8; 32], bool)> = tree.generate_inclusion_proof(&root, &key)?;
// The verifying tree may be empty
let empty_tree = HashTree::new(8)?;
// If the proof is valid, it will return Ok(())
empty_tree.verify_inclusion_proof(&root, &key, &value, &proof)?;
Ok(())
}
```
Licensed under either of
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
The project is currently undergoing rapid development and it should be noted that minor releases may include breaking changes to the API. These changes will be noted in the Changelog of each release, but if we broke something or forgot to mention such a change, please file an issue or submit a pull request and we will review it at our earliest convenience.
Special thanks to Niall Moore for assistance with the early phases of this project.