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path_hash.rs
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path_hash.rs
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// Copyright (C) 2019-2023 Aleo Systems Inc.
// This file is part of the snarkVM library.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at:
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use super::BooleanHash;
use snarkvm_console_algorithms::{Keccak, Poseidon, BHP};
use snarkvm_console_types::prelude::*;
#[cfg(not(feature = "serial"))]
use rayon::prelude::*;
/// A trait for a Merkle path hash function.
pub trait PathHash: Clone + Send + Sync {
type Hash: Copy + Clone + Debug + Default + PartialEq + Eq + FromBytes + ToBytes + Send + Sync;
/// Returns the hash of the given child nodes.
fn hash_children(&self, children: &[Self::Hash]) -> Result<Self::Hash>;
/// Returns the empty hash.
fn hash_empty<const ARITY: u8>(&self) -> Result<Self::Hash> {
let children = vec![Self::Hash::default(); ARITY as usize];
self.hash_children(&children)
}
/// Returns the hash for each child node.
/// If there are no children, the supplied empty node hash is used instead.
fn hash_all_children(
&self,
child_nodes: &[Option<Vec<Self::Hash>>],
empty_node_hash: Self::Hash,
) -> Result<Vec<Self::Hash>> {
let hash_children = |children: &Option<Vec<Self::Hash>>| {
if let Some(children) = children { self.hash_children(children) } else { Ok(empty_node_hash) }
};
match child_nodes.len() {
0 => Ok(vec![]),
1..=100 => child_nodes.iter().map(hash_children).collect(),
_ => cfg_iter!(child_nodes).map(hash_children).collect(),
}
}
}
impl<E: Environment, const NUM_WINDOWS: u8, const WINDOW_SIZE: u8> PathHash for BHP<E, NUM_WINDOWS, WINDOW_SIZE> {
type Hash = Field<E>;
/// Returns the hash of the given child nodes.
fn hash_children(&self, children: &[Self::Hash]) -> Result<Self::Hash> {
let mut input = Vec::new();
// Prepend the nodes with a `true` bit.
input.push(true);
for child in children {
child.write_bits_le(&mut input);
}
// Hash the input.
Hash::hash(self, &input)
}
}
impl<E: Environment, const RATE: usize> PathHash for Poseidon<E, RATE> {
type Hash = Field<E>;
/// Returns the hash of the given child nodes.
fn hash_children(&self, children: &[Self::Hash]) -> Result<Self::Hash> {
let mut input = Vec::with_capacity(1 + children.len());
// Prepend the nodes with a `1field` byte.
input.push(Self::Hash::one());
for child in children {
input.push(*child);
}
// Hash the input.
Hash::hash(self, &input)
}
}
impl<const TYPE: u8, const VARIANT: usize> PathHash for Keccak<TYPE, VARIANT> {
type Hash = BooleanHash<VARIANT>;
/// Returns the hash of the given child nodes.
fn hash_children(&self, children: &[Self::Hash]) -> Result<Self::Hash> {
let mut input = Vec::new();
// Prepend the nodes with a `true` bit.
input.push(true);
for child in children {
input.extend_from_slice(child.as_slice());
}
// Hash the input.
let output = Hash::hash(self, &input)?;
// Read the first VARIANT bits.
let mut result = BooleanHash::new();
result.0.copy_from_slice(&output[..VARIANT]);
Ok(result)
}
}