117 lines
2.5 KiB
Rust
117 lines
2.5 KiB
Rust
//! The `Poh` module provides an object for generating a Proof of History.
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//! It records Hashes items on behalf of its users.
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use hash::{hash, hashv, Hash};
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pub struct Poh {
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prev_id: Hash,
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id: Hash,
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num_hashes: u64,
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pub tick_height: u64,
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}
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#[derive(Debug)]
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pub struct PohEntry {
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pub prev_id: Hash,
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pub num_hashes: u64,
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pub id: Hash,
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pub mixin: Option<Hash>,
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}
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impl Poh {
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pub fn new(prev_id: Hash, tick_height: u64) -> Self {
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Poh {
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prev_id,
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num_hashes: 0,
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id: prev_id,
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tick_height,
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}
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}
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pub fn hash(&mut self) {
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self.id = hash(&self.id.as_ref());
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self.num_hashes += 1;
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}
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pub fn record(&mut self, mixin: Hash) -> PohEntry {
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self.id = hashv(&[&self.id.as_ref(), &mixin.as_ref()]);
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let prev_id = self.prev_id;
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self.prev_id = self.id;
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let num_hashes = self.num_hashes + 1;
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self.num_hashes = 0;
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PohEntry {
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prev_id,
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num_hashes,
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id: self.id,
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mixin: Some(mixin),
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}
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}
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// emissions of Ticks (i.e. PohEntries without a mixin) allows
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// validators to parallelize the work of catching up
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pub fn tick(&mut self) -> PohEntry {
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self.hash();
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let num_hashes = self.num_hashes;
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self.num_hashes = 0;
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let prev_id = self.prev_id;
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self.prev_id = self.id;
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self.tick_height += 1;
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PohEntry {
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prev_id,
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num_hashes,
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id: self.id,
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mixin: None,
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}
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}
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}
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#[cfg(test)]
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pub fn verify(initial: Hash, entries: &[PohEntry]) -> bool {
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let mut prev_id = initial;
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for entry in entries {
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assert!(entry.num_hashes != 0);
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assert!(prev_id == entry.prev_id);
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for _ in 1..entry.num_hashes {
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prev_id = hash(&prev_id.as_ref());
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}
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prev_id = match entry.mixin {
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Some(mixin) => hashv(&[&prev_id.as_ref(), &mixin.as_ref()]),
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None => hash(&prev_id.as_ref()),
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};
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if prev_id != entry.id {
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return false;
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}
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}
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true
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}
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#[cfg(test)]
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mod tests {
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use hash::Hash;
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use poh::{self, PohEntry};
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#[test]
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#[should_panic]
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fn test_poh_verify_assert() {
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poh::verify(
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Hash::default(),
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&[PohEntry {
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prev_id: Hash::default(),
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num_hashes: 0,
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id: Hash::default(),
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mixin: None,
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}],
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);
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}
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}
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