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use buffett_crypto::hash::{hash, hashv, Hash};
pub struct Poh {
last_hash: Hash,
num_hashes: u64,
}
#[derive(Debug)]
pub struct PohEntry {
pub num_hashes: u64,
pub id: Hash,
pub mixin: Option<Hash>,
}
impl Poh {
pub fn new(last_hash: Hash) -> Self {
Poh {
last_hash,
num_hashes: 0,
}
}
pub fn hash(&mut self) {
self.last_hash = hash(&self.last_hash.as_ref());
self.num_hashes += 1;
}
pub fn record(&mut self, mixin: Hash) -> PohEntry {
let num_hashes = self.num_hashes + 1;
self.last_hash = hashv(&[&self.last_hash.as_ref(), &mixin.as_ref()]);
self.num_hashes = 0;
PohEntry {
num_hashes,
id: self.last_hash,
mixin: Some(mixin),
}
}
pub fn tick(&mut self) -> PohEntry {
self.hash();
let num_hashes = self.num_hashes;
self.num_hashes = 0;
PohEntry {
num_hashes,
id: self.last_hash,
mixin: None,
}
}
}
#[cfg(test)]
pub fn verify(initial: Hash, entries: &[PohEntry]) -> bool {
let mut last_hash = initial;
for entry in entries {
assert!(entry.num_hashes != 0);
for _ in 1..entry.num_hashes {
last_hash = hash(&last_hash.as_ref());
}
let id = match entry.mixin {
Some(mixin) => hashv(&[&last_hash.as_ref(), &mixin.as_ref()]),
None => hash(&last_hash.as_ref()),
};
if id != entry.id {
return false;
}
last_hash = id;
}
true
}