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Use a clearer algorithm for the merkle

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Should also be more efficient due to not shifting as often.
This commit is contained in:
Luke Parker
2023-07-03 18:18:31 -04:00
parent e066083404
commit 23b19fcd91
1 changed files with 19 additions and 9 deletions
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28
coins/monero/src/merkle.rs
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@@ -1,3 +1,5 @@
use std_shims::vec::Vec;
use crate::hash;
pub fn merkle_root(root: [u8; 32], leafs: &[[u8; 32]]) -> [u8; 32] {
@@ -16,16 +18,24 @@ pub fn merkle_root(root: [u8; 32], leafs: &[[u8; 32]]) -> [u8; 32] {
}
let low_pow_2 = high_pow_2 / 2;
// Merge hashes until we're at the low_pow_2
let mut i = high_pow_2 - hashes.len();
while hashes.len() != low_pow_2 {
let l = hashes.remove(i);
let r = hashes.remove(i);
hashes.insert(i, hash(&[l.as_ref(), &r].concat()));
i += 1;
// Merge right-most hashes until we're at the low_pow_2
{
let overage = hashes.len() - low_pow_2;
let mut rightmost = hashes.drain((low_pow_2 - overage) ..);
// This is true since we took overage from beneath and above low_pow_2, taking twice as
// many elements as overage
debug_assert_eq!(rightmost.len() % 2, 0);
let mut paired_hashes = Vec::with_capacity(overage);
while let Some(left) = rightmost.next() {
let right = rightmost.next().unwrap();
paired_hashes.push(hash(&[left.as_ref(), &right].concat()));
}
drop(rightmost);
hashes.extend(paired_hashes);
assert_eq!(hashes.len(), low_pow_2);
}
assert_eq!(hashes.len(), i);
assert_eq!(hashes.len(), low_pow_2);
// Do a traditional pairing off
let mut new_hashes = Vec::with_capacity(hashes.len() / 2);