362 lines
9.8 KiB
Rust
362 lines
9.8 KiB
Rust
#![feature(rustc_private)]
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extern crate rustc;
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extern crate rand;
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mod sha256;
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trait Hashable: Clone + Copy {
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fn combine(&Self, &Self) -> Self;
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fn blank() -> Self;
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}
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#[derive(Clone)]
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struct IncrementalMerkleTree<T: Hashable> {
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cursor: Leaf<T>,
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depth: usize
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}
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#[derive(Clone)]
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enum Leaf<T: Hashable> {
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Left{parent: Parent<T>, content: T},
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Right{parent: Parent<T>, left: T, content: T}
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}
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#[derive(Clone)]
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enum Parent<T: Hashable> {
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Empty,
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Left{parent: Box<Parent<T>>},
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Right{left: T, parent: Box<Parent<T>>}
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}
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impl<T: Hashable> Parent<T> {
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fn ascend<'a, F: FnMut(Option<&'a T>) -> bool>(&'a self, mut cb: F) {
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match *self {
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Parent::Empty => {
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if cb(None) {
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self.ascend(cb);
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}
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},
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Parent::Left{ref parent} => {
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if cb(None) {
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parent.ascend(cb);
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}
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},
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Parent::Right{ref left, ref parent} => {
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if cb(Some(left)) {
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parent.ascend(cb);
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}
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}
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}
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}
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fn advance(self, hash: T) -> Parent<T> {
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match self {
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Parent::Empty => {
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Parent::Right {
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left: hash,
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parent: Box::new(Parent::Empty)
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}
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},
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Parent::Left{parent} => {
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Parent::Right {
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left: hash,
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parent: parent
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}
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},
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Parent::Right{left, parent} => {
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Parent::Left{
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parent: Box::new(parent.advance(T::combine(&left, &hash)))
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}
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}
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}
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}
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}
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impl<T: Hashable> IncrementalMerkleTree<T> {
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fn new(d: usize, initial: T) -> IncrementalMerkleTree<T> {
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assert!(d != 0);
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IncrementalMerkleTree {
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cursor: Leaf::Left{parent: Parent::Empty, content: initial},
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depth: d
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}
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}
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fn completed(&self) -> bool {
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match self.cursor {
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Leaf::Left{..} => false,
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Leaf::Right{ref parent, ..} => {
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let complete = &mut true;
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let depth = &mut (self.depth - 1);
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parent.ascend(|left| {
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if *depth == 0 {
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return false;
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}
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if left.is_none() {
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*complete = false;
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return false;
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}
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*depth -= 1;
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true
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});
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*complete
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}
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}
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}
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fn append(self, obj: T) -> IncrementalMerkleTree<T> {
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match self.cursor {
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Leaf::Left{parent, content} => {
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IncrementalMerkleTree {
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cursor: Leaf::Right{
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parent: parent,
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left: content,
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content: obj
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},
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depth: self.depth
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}
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},
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Leaf::Right{parent, left, content} => {
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IncrementalMerkleTree {
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cursor: Leaf::Left{
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parent: parent.advance(T::combine(&left, &content)),
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content: obj
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},
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depth: self.depth
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}
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}
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}
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}
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fn unfilled(&self, mut skip: usize) -> usize {
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let parent = match self.cursor {
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Leaf::Left{ref parent, ..} => {
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if skip == 0 {
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return 0;
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} else {
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skip -= 1;
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parent
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}
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},
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Leaf::Right{ref parent, ..} => {
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parent
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}
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};
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let mut depth = &mut 0;
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parent.ascend(|left| {
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*depth += 1;
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match left {
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Some(_) => {
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return true;
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},
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None => {
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if skip == 0 {
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return false;
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} else {
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skip -= 1;
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return true;
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}
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}
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}
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});
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return *depth;
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}
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fn root(&self) -> T {
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self.root_advanced(Some(T::blank()).iter().cycle())
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}
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fn root_advanced<'a, I: Iterator<Item=&'a T>>(&self, mut it: I) -> T where T: 'a {
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let (parent, mut child) = match self.cursor {
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Leaf::Left{ref parent, ref content} => {
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(parent, T::combine(content, it.next().unwrap()))
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},
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Leaf::Right{ref parent, ref left, ref content} => {
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(parent, T::combine(left, content))
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}
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};
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let mut depth = self.depth - 1;
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{
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let child = &mut child;
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parent.ascend(move |left| {
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if depth == 0 {
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return false;
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}
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match left {
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Some(left) => {
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*child = T::combine(left, &*child);
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},
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None => {
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*child = T::combine(&*child, it.next().unwrap());
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}
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}
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depth = depth - 1;
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true
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});
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}
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return child;
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}
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}
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#[derive(Clone)]
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struct IncrementalWitness<T: Hashable> {
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tree: IncrementalMerkleTree<T>,
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delta: IncrementalDelta<T>
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}
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#[derive(Clone)]
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struct IncrementalDelta<T: Hashable> {
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filled: Vec<T>,
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active: Option<IncrementalMerkleTree<T>>
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}
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impl<T: Hashable> IncrementalWitness<T> {
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fn new(from: &IncrementalMerkleTree<T>) -> IncrementalWitness<T> {
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IncrementalWitness {
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tree: from.clone(),
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delta: IncrementalDelta {
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filled: vec![],
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active: None
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}
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}
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}
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fn append(&mut self, object: T) {
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match self.delta.active.take() {
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Some(active) => {
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let active = active.append(object);
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if active.completed() {
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self.delta.filled.push(active.root());
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} else {
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self.delta.active = Some(active);
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}
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},
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None => {
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match self.tree.unfilled(self.delta.filled.len()) {
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0 => {
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self.delta.filled.push(object);
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},
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i => {
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self.delta.active = Some(IncrementalMerkleTree::new(i, object));
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}
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}
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}
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}
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}
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fn root(&self) -> T {
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self.tree.root_advanced(self.delta.filled.iter() // use filled values
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.chain(self.delta.active.as_ref().map(|x| x.root()).as_ref()) // then use the active root
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.chain(Some(T::blank()).iter().cycle())) // then fill in with blanks
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}
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}
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mod test {
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use super::{IncrementalMerkleTree, IncrementalWitness};
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use super::sha256::*;
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#[test]
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fn test_root() {
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let a = Sha256Digest::rand(0);
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let tree = IncrementalMerkleTree::new(3, a);
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assert_eq!(tree.root(), Sha256Digest([94, 162, 216, 229, 230, 128, 153, 35, 89, 40, 180, 159, 125, 27, 48, 80, 181, 73, 7, 195, 182, 223, 83, 165, 59, 200, 234, 181, 106, 3, 243, 228]));
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let b = Sha256Digest::rand(1);
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let tree = tree.append(b);
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assert_eq!(tree.root(), Sha256Digest([222, 23, 196, 222, 130, 80, 115, 139, 134, 72, 108, 150, 235, 75, 216, 5, 63, 101, 2, 237, 51, 47, 165, 216, 40, 15, 209, 176, 10, 192, 224, 26]));
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}
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#[test]
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fn test_unfilled() {
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let a = Sha256Digest::rand(0);
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let mut tree = IncrementalMerkleTree::new(3, a);
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for i in 0..4 {
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let b = Sha256Digest::rand(i+1);
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tree = tree.append(b);
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}
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assert_eq!(tree.unfilled(0), 0);
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assert_eq!(tree.unfilled(1), 1);
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assert_eq!(tree.unfilled(2), 3);
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}
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#[test]
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fn test_complete() {
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let a = Sha256Digest::rand(0);
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let mut tree = IncrementalMerkleTree::new(3, a);
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for i in 0..7 {
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assert_eq!(tree.completed(), false);
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let b = Sha256Digest::rand(i+1);
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tree = tree.append(b);
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}
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assert_eq!(tree.completed(), true);
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}
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#[test]
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fn test_witness() {
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let a = Sha256Digest::rand(0);
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let mut tree = IncrementalMerkleTree::new(3, a);
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let mut witness = IncrementalWitness::new(&tree);
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assert_eq!(tree.root(), witness.root());
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assert_eq!(witness.delta.filled.len(), 0);
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assert!(witness.delta.active.is_none());
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for i in 1..8 {
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let b = Sha256Digest::rand(i);
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witness.append(b);
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tree = tree.append(b);
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match i {
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1 => {
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assert_eq!(witness.delta.filled.len(), 1);
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assert!(witness.delta.active.is_none());
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},
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i if i <= 2 => {
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assert_eq!(witness.delta.filled.len(), 1);
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assert!(witness.delta.active.is_some());
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},
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i if i == 3 => {
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assert_eq!(witness.delta.filled.len(), 2);
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assert!(witness.delta.active.is_none());
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},
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i if i < 7 => {
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assert_eq!(witness.delta.filled.len(), 2);
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assert!(witness.delta.active.is_some());
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},
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a @ _ => {
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assert_eq!(a, 7);
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assert_eq!(witness.delta.filled.len(), 3);
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assert!(witness.delta.active.is_none());
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}
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}
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assert_eq!(tree.root(), witness.root());
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}
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}
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} |