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Merge pull request #52 from nuttycom/witness_at_depth 

Compute witnesses as of checkpoint depth rather than as of a root hash.
This commit is contained in:
Kris Nuttycombe 2023-03-07 12:11:07 -07:00 committed by GitHub
parent 42dfd970b5 1db85f347e
commit 9a0e39af3a
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8 changed files with 919 additions and 868 deletions
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5
bridgetree/CHANGELOG.md
View File

@ -7,6 +7,11 @@ and this project adheres to Rust's notion of
## [Unreleased]
### Changed
- `BridgeTree::witness` now takes a checkpoint depth rather than a root hash to
identify the tree state with respect to which the witness should be constructed.
### Removed
- The `testing` module has been removed in favor of depending on

8
bridgetree/proptest-regressions/bridgetree.txt
View File

@ -1,8 +0,0 @@
# Seeds for failure cases proptest has generated in the past. It is
# automatically read and these particular cases re-run before any
# novel cases are generated.
#
# It is recommended to check this file in to source control so that
# everyone who runs the test benefits from these saved cases.
cc a64e0d40c9287f2975a27447d266e4dd7228e44de99d000df39c4610598f486a # shrinks to tree = BridgeTree { depth: 8, prior_bridges: [MerkleBridge { prior_position: None, auth_fragments: {}, frontier: NonEmptyFrontier { position: Position(0), leaf: Left("a"), ommers: [] } }, MerkleBridge { prior_position: Some(Position(0)), auth_fragments: {}, frontier: NonEmptyFrontier { position: Position(1), leaf: Right("a", "a"), ommers: [] } }], current_bridge: Some(MerkleBridge { prior_position: Some(Position(1)), auth_fragments: {Position(1): AuthFragment { position: Position(1), altitudes_observed: 0, values: [] }}, frontier: NonEmptyFrontier { position: Position(1), leaf: Right("a", "a"), ommers: [] } }), saved: {Position(1): 1}, checkpoints: [Checkpoint { bridges_len: 1, is_witnessed: false, forgotten: {} }], max_checkpoints: 10 }
cc 736aee7c92f418b3b7391b0ae253ca4dc18f9b6cc625c0c34f0e568d26421e92 # shrinks to tree = BridgeTree { depth: 8, prior_bridges: [], current_bridge: None, saved: {}, checkpoints: [], max_checkpoints: 10 }

10
bridgetree/proptest-regressions/lib.txt
View File

@ -4,5 +4,11 @@
#
# It is recommended to check this file in to source control so that
# everyone who runs the test benefits from these saved cases.
cc 190d23d28fc081e651e779d6209951363ee8a21752233cb72471626d14dd8bad # shrinks to ops = [Append("a"), Append("a"), Append("a")]
cc 81533fad8faadbdfdc9547e07f0491e40172a2f5fe4e8768d289389ed2e3cbcb # shrinks to ops = [Append(SipHashable(0)), Append(SipHashable(0)), Append(SipHashable(0))]
cc a64e0d40c9287f2975a27447d266e4dd7228e44de99d000df39c4610598f486a # shrinks to tree = BridgeTree { depth: 8, prior_bridges: [MerkleBridge { prior_position: None, auth_fragments: {}, frontier: NonEmptyFrontier { position: Position(0), leaf: Left("a"), ommers: [] } }, MerkleBridge { prior_position: Some(Position(0)), auth_fragments: {}, frontier: NonEmptyFrontier { position: Position(1), leaf: Right("a", "a"), ommers: [] } }], current_bridge: Some(MerkleBridge { prior_position: Some(Position(1)), auth_fragments: {Position(1): AuthFragment { position: Position(1), altitudes_observed: 0, values: [] }}, frontier: NonEmptyFrontier { position: Position(1), leaf: Right("a", "a"), ommers: [] } }), saved: {Position(1): 1}, checkpoints: [Checkpoint { bridges_len: 1, is_witnessed: false, forgotten: {} }], max_checkpoints: 10 }
cc 736aee7c92f418b3b7391b0ae253ca4dc18f9b6cc625c0c34f0e568d26421e92 # shrinks to tree = BridgeTree { depth: 8, prior_bridges: [], current_bridge: None, saved: {}, checkpoints: [], max_checkpoints: 10 }
cc f1a0c0e8114919f9f675e0b31cdecf37af31579e365119312a7ebefcabb639f1 # shrinks to ops = [Append(SipHashable(0)), Checkpoint, Checkpoint, Mark, Checkpoint, Checkpoint, Checkpoint, Checkpoint, Checkpoint, Authpath(Position(0), 6)]
cc ac8dad1a92cb9563a291802cbd3dfca2a89da35fe4ed377701f5ad85b43700f4 # shrinks to ops = [Append("a"), Append("a"), Checkpoint, Checkpoint, Checkpoint, Mark, Checkpoint, Authpath(Position(1), 2)]
cc cebb95fe896dc1d1e3c9a65efd50e786e6a4a3503c86fb2a6817bb05d25e751e # shrinks to tree = BridgeTree { depth: 8, prior_bridges: [MerkleBridge { prior_position: None, tracking: {Address { level: Level(2), index: 0 }}, ommers: {}, frontier: NonEmptyFrontier { position: Position(3), leaf: "a", ommers: ["a", "aa"] } }], current_bridge: Some(MerkleBridge { prior_position: Some(Position(3)), tracking: {Address { level: Level(2), index: 0 }}, ommers: {}, frontier: NonEmptyFrontier { position: Position(3), leaf: "a", ommers: ["a", "aa"] } }), saved: {Position(3): 0}, checkpoints: [Checkpoint { bridges_len: 0, marked: {Position(3)}, forgotten: {Position(3): 0} }], max_checkpoints: 10 }
cc cdab33688ef9270768481b72d1615ff1d209fdb3d8d45be2ad564a8d5e0addc1 # shrinks to ops = [Append(SipHashable(0)), Mark, Mark, Checkpoint, Mark, Rewind, Append(SipHashable(0)), Mark]
cc 4058fadeb645f982bb83d666ea20c9541c9b920438877c145ee750cb09e22337 # shrinks to ops = [Append(SipHashable(0), Ephemeral), Append(SipHashable(0), Ephemeral), CurrentLeaf, CurrentLeaf, Append(SipHashable(0), Ephemeral), Append(SipHashable(0), Ephemeral), Append(SipHashable(0), Checkpoint { id: (), is_marked: true }), Unmark(Position(4))]
cc befc65ab8360534feebaa4c0e3da24518d134b03326235f1ccede15ad998d066 # shrinks to ops = [Append("a", Ephemeral), Append("a", Checkpoint { id: (), is_marked: true }), Append("a", Ephemeral), Append("a", Checkpoint { id: (), is_marked: false }), Authpath(Position(1), 0)]

488
bridgetree/src/lib.rs
View File

@ -31,13 +31,13 @@
//!
//! In this module, the term "ommer" is used as for the sibling of a parent node in a binary tree.
use serde::{Deserialize, Serialize};
use std::collections::{BTreeMap, BTreeSet};
use std::collections::{BTreeMap, BTreeSet, VecDeque};
use std::convert::TryFrom;
use std::fmt::Debug;
use std::mem::size_of;
use std::ops::Range;
pub use incrementalmerkletree::{Address, Hashable, Level, Position};
pub use incrementalmerkletree::{Address, Hashable, Level, Position, Retention};
/// Validation errors that can occur during reconstruction of a Merkle frontier from
/// its constituent parts.
@ -482,7 +482,7 @@ impl<'a, H: Hashable + Ord + Clone + 'a> MerkleBridge<H> {
/// will track the information necessary to create a witness for the leaf most
/// recently appended to this bridge's frontier.
#[must_use]
pub fn successor(&self, mark_current_leaf: bool) -> Self {
pub fn successor(&self, track_current_leaf: bool) -> Self {
let mut result = Self {
prior_position: Some(self.frontier.position()),
tracking: self.tracking.clone(),
@ -490,7 +490,7 @@ impl<'a, H: Hashable + Ord + Clone + 'a> MerkleBridge<H> {
frontier: self.frontier.clone(),
};
if mark_current_leaf {
if track_current_leaf {
result.track_current_leaf();
}
@ -614,48 +614,51 @@ impl<'a, H: Hashable + Ord + Clone + 'a> MerkleBridge<H> {
/// previous state.
#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct Checkpoint {
/// The unique identifier for this checkpoint.
id: usize,
/// The number of bridges that will be retained in a rewind.
bridges_len: usize,
/// A flag indicating whether or not the current state of the tree
/// had been marked at the time the checkpoint was created.
is_marked: bool,
/// A set of the positions that have been marked during the period that this
/// checkpoint is the current checkpoint.
marked: BTreeSet<Position>,
/// When a mark is forgotten, if the index of the forgotten mark is <= bridge_idx we
/// record it in the current checkpoint so that on rollback, we restore the forgotten
/// marks to the BridgeTree's "saved" list. If the mark was newly created since the
/// checkpoint, we don't need to remember when we forget it because both the mark
/// creation and removal will be reverted in the rollback.
forgotten: BTreeMap<Position, usize>,
/// When a mark is forgotten, we add it to the checkpoint's forgotten set but
/// don't immediately remove it from the `saved` map; that removal occurs when
/// the checkpoint is eventually dropped.
forgotten: BTreeSet<Position>,
}
impl Checkpoint {
/// Creates a new checkpoint from its constituent parts.
pub fn from_parts(
id: usize,
bridges_len: usize,
is_marked: bool,
marked: BTreeSet<Position>,
forgotten: BTreeMap<Position, usize>,
forgotten: BTreeSet<Position>,
) -> Self {
Self {
id,
bridges_len,
is_marked,
marked,
forgotten,
}
}
/// Creates a new empty checkpoint for the specified [`BridgeTree`] state.
pub fn at_length(bridges_len: usize, is_marked: bool) -> Self {
pub fn at_length(bridges_len: usize, id: usize) -> Self {
Checkpoint {
id,
bridges_len,
is_marked,
marked: BTreeSet::new(),
forgotten: BTreeMap::new(),
forgotten: BTreeSet::new(),
}
}
/// The unique identifier for the checkpoint, which is simply an automatically incrementing
/// index over all checkpoints that have ever been created in the history of the tree.
pub fn id(&self) -> usize {
self.id
}
/// Returns the length of the [`BridgeTree::prior_bridges`] vector of the [`BridgeTree`] to
/// which this checkpoint refers.
///
@ -665,15 +668,6 @@ impl Checkpoint {
self.bridges_len
}
/// Returns whether the current state of the tree had been marked at the point that
/// this checkpoint was made.
///
/// In the event of a rewind, the rewind logic will ensure that mark information is
/// properly reconstituted for the checkpointed tree state.
pub fn is_marked(&self) -> bool {
self.is_marked
}
/// Returns a set of the positions that have been marked during the period that this
/// checkpoint is the current checkpoint.
pub fn marked(&self) -> &BTreeSet<Position> {
@ -682,7 +676,7 @@ impl Checkpoint {
/// Returns the set of previously-marked positions that have had their marks removed
/// during the period that this checkpoint is the current checkpoint.
pub fn forgotten(&self) -> &BTreeMap<Position, usize> {
pub fn forgotten(&self) -> &BTreeSet<Position> {
&self.forgotten
}
@ -714,9 +708,6 @@ impl Checkpoint {
// using the specified rewrite function. Used during garbage collection.
fn rewrite_indices<F: Fn(usize) -> usize>(&mut self, f: F) {
self.bridges_len = f(self.bridges_len);
for v in self.forgotten.values_mut() {
*v = f(*v)
}
}
}
@ -732,8 +723,11 @@ pub struct BridgeTree<H, const DEPTH: u8> {
/// A map from positions for which we wish to be able to compute a
/// witness to index in the bridges vector.
saved: BTreeMap<Position, usize>,
/// A stack of bridge indices to which it's possible to rewind directly.
checkpoints: Vec<Checkpoint>,
/// A deque of bridge indices to which it's possible to rewind directly.
/// This deque must be maintained to have a minimum size of 1 and a maximum
/// size of `max_checkpoints` in order to correctly maintain mark & rewind
/// semantics.
checkpoints: VecDeque<Checkpoint>,
/// The maximum number of checkpoints to retain. If this number is
/// exceeded, the oldest checkpoint will be dropped when creating
/// a new checkpoint.
@ -764,24 +758,34 @@ pub enum BridgeTreeError {
impl<H, const DEPTH: u8> BridgeTree<H, DEPTH> {
/// Construct an empty BridgeTree value with the specified maximum number of checkpoints.
pub fn new(max_checkpoints: usize) -> Self {
///
/// Panics if `max_checkpoints < 1` because mark/rewind logic depends upon the presence
/// of checkpoints to function.
pub fn new(max_checkpoints: usize, initial_checkpoint_id: usize) -> Self {
assert!(max_checkpoints >= 1);
Self {
prior_bridges: vec![],
current_bridge: None,
saved: BTreeMap::new(),
checkpoints: vec![],
checkpoints: VecDeque::from(vec![Checkpoint::at_length(0, initial_checkpoint_id)]),
max_checkpoints,
}
}
/// Removes the oldest checkpoint. Returns true if successful and false if
/// there are no checkpoints.
/// Removes the oldest checkpoint if there are more than `max_checkpoints`. Returns true if
/// successful and false if there are not enough checkpoints.
fn drop_oldest_checkpoint(&mut self) -> bool {
if self.checkpoints.is_empty() {
false
} else {
self.checkpoints.remove(0);
if self.checkpoints.len() > self.max_checkpoints {
let c = self
.checkpoints
.pop_front()
.expect("Checkpoints deque is known to be non-empty.");
for pos in c.forgotten.iter() {
self.saved.remove(pos);
}
true
} else {
false
}
}
@ -802,7 +806,7 @@ impl<H, const DEPTH: u8> BridgeTree<H, DEPTH> {
}
/// Returns the checkpoints to which this tree may be rewound.
pub fn checkpoints(&self) -> &[Checkpoint] {
pub fn checkpoints(&self) -> &VecDeque<Checkpoint> {
&self.checkpoints
}
@ -832,7 +836,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
frontier,
)),
saved: BTreeMap::new(),
checkpoints: vec![],
checkpoints: VecDeque::new(),
max_checkpoints,
}
}
@ -843,7 +847,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
prior_bridges: Vec<MerkleBridge<H>>,
current_bridge: Option<MerkleBridge<H>>,
saved: BTreeMap<Position, usize>,
checkpoints: Vec<Checkpoint>,
checkpoints: VecDeque<Checkpoint>,
max_checkpoints: usize,
) -> Result<Self, BridgeTreeError> {
Self::check_consistency_internal(
@ -876,7 +880,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
prior_bridges: &[MerkleBridge<H>],
current_bridge: &Option<MerkleBridge<H>>,
saved: &BTreeMap<Position, usize>,
checkpoints: &[Checkpoint],
checkpoints: &VecDeque<Checkpoint>,
max_checkpoints: usize,
) -> Result<(), BridgeTreeError> {
// check that saved values correspond to bridges
@ -969,10 +973,10 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
self.current_bridge.as_ref().map(|b| b.current_leaf())
}
/// Marks the current leaf as one for which we're interested in producing
/// a witness. Returns an optional value containing the
/// current position if successful or if the current value was already
/// marked, or None if the tree is empty.
/// Marks the current leaf as one for which we're interested in producing a witness.
///
/// Returns an optional value containing the current position if successful or if the current
/// value was already marked, or None if the tree is empty.
pub fn mark(&mut self) -> Option<Position> {
match self.current_bridge.take() {
Some(mut cur_b) => {
@ -995,15 +999,14 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
self.current_bridge = Some(successor);
}
self.saved
.entry(pos)
.or_insert(self.prior_bridges.len() - 1);
// mark the position as having been marked in the current checkpoint
if let Some(c) = self.checkpoints.last_mut() {
if !c.is_marked {
c.marked.insert(pos);
}
if let std::collections::btree_map::Entry::Vacant(e) = self.saved.entry(pos) {
let c = self
.checkpoints
.back_mut()
.expect("Checkpoints deque must never be empty");
c.marked.insert(pos);
e.insert(self.prior_bridges.len() - 1);
}
Some(pos)
@ -1029,51 +1032,54 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
/// interested in maintaining a mark for. Returns true if successful and
/// false if we were already not maintaining a mark at this position.
pub fn remove_mark(&mut self, position: Position) -> bool {
if let Some(idx) = self.saved.remove(&position) {
// If the position is one that has *not* just been marked since the last checkpoint,
// then add it to the set of those forgotten during the current checkpoint span so that
// it can be restored on rollback.
if let Some(c) = self.checkpoints.last_mut() {
if !c.marked.contains(&position) {
c.forgotten.insert(position, idx);
}
}
if self.saved.contains_key(&position) {
let c = self
.checkpoints
.back_mut()
.expect("Checkpoints deque must never be empty.");
c.forgotten.insert(position);
true
} else {
false
}
}
/// Creates a new checkpoint for the current tree state. It is valid to
/// have multiple checkpoints for the same tree state, and each `rewind`
/// call will remove a single checkpoint.
pub fn checkpoint(&mut self) {
match self.current_bridge.take() {
Some(cur_b) => {
let is_marked = self.get_marked_leaf(cur_b.position()).is_some();
/// Creates a new checkpoint for the current tree state, with the given identifier.
///
/// It is valid to have multiple checkpoints for the same tree state, and each `rewind` call
/// will remove a single checkpoint. Successive checkpoint identifiers must always be provided
/// in increasing order.
pub fn checkpoint(&mut self, id: usize) -> bool {
if Some(id) > self.checkpoints.back().map(|c| c.id) {
match self.current_bridge.take() {
Some(cur_b) => {
// Do not create a duplicate bridge
if self
.prior_bridges
.last()
.map_or(false, |pb| pb.position() == cur_b.position())
{
self.current_bridge = Some(cur_b);
} else {
self.current_bridge = Some(cur_b.successor(false));
self.prior_bridges.push(cur_b);
}
// Do not create a duplicate bridge
if self
.prior_bridges
.last()
.map_or(false, |pb| pb.position() == cur_b.position())
{
self.current_bridge = Some(cur_b);
} else {
self.current_bridge = Some(cur_b.successor(false));
self.prior_bridges.push(cur_b);
self.checkpoints
.push_back(Checkpoint::at_length(self.prior_bridges.len(), id));
}
None => {
self.checkpoints.push_back(Checkpoint::at_length(0, id));
}
self.checkpoints
.push(Checkpoint::at_length(self.prior_bridges.len(), is_marked));
}
None => {
self.checkpoints.push(Checkpoint::at_length(0, false));
}
}
if self.checkpoints.len() > self.max_checkpoints {
self.drop_oldest_checkpoint();
if self.checkpoints.len() > self.max_checkpoints {
self.drop_oldest_checkpoint();
}
true
} else {
false
}
}
@ -1083,80 +1089,72 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
/// at that tree state have been removed using `rewind`. This function
/// return false and leave the tree unmodified if no checkpoints exist.
pub fn rewind(&mut self) -> bool {
match self.checkpoints.pop() {
Some(mut c) => {
// drop marked values at and above the checkpoint height;
// we will re-mark if necessary.
self.saved.append(&mut c.forgotten);
self.saved.retain(|_, i| *i + 1 < c.bridges_len);
self.prior_bridges.truncate(c.bridges_len);
self.current_bridge = self.prior_bridges.last().map(|b| b.successor(c.is_marked));
if c.is_marked {
self.mark();
}
true
if self.checkpoints.len() > 1 {
let c = self
.checkpoints
.pop_back()
.expect("Checkpoints deque is known to be non-empty.");
// Remove marks for positions that were marked during the lifetime of this checkpoint.
for pos in c.marked {
self.saved.remove(&pos);
}
None => false,
self.prior_bridges.truncate(c.bridges_len);
self.current_bridge = self
.prior_bridges
.last()
.map(|b| b.successor(self.saved.contains_key(&b.position())));
true
} else {
false
}
}
/// Obtains a witness to the value at the specified position,
/// as of the tree state corresponding to the given root.
/// Returns `None` if there is no available witness to that
/// position or if the root does not correspond to a checkpointed
/// root of the tree.
pub fn witness(&self, position: Position, as_of_root: &H) -> Option<Vec<H>> {
self.witness_inner(position, as_of_root).ok()
}
fn witness_inner(&self, position: Position, as_of_root: &H) -> Result<Vec<H>, WitnessingError> {
/// Obtains a witness for the value at the specified leaf position, as of the tree state at the
/// given checkpoint depth. Returns `None` if there is no witness information for the requested
/// position or if no checkpoint is available at the specified depth.
pub fn witness(
&self,
position: Position,
checkpoint_depth: usize,
) -> Result<Vec<H>, WitnessingError> {
#[derive(Debug)]
enum AuthBase<'a> {
Current,
Checkpoint(usize, &'a Checkpoint),
NotFound,
}
let max_alt = Level::from(DEPTH);
// Find the earliest checkpoint having a matching root, or the current
// root if it matches and there is no earlier matching checkpoint.
let auth_base = self
.checkpoints
.iter()
.enumerate()
.rev()
.take_while(|(_, c)| c.position(&self.prior_bridges) >= Some(position))
.filter(|(_, c)| &c.root(&self.prior_bridges, max_alt) == as_of_root)
.last()
.map(|(i, c)| AuthBase::Checkpoint(i, c))
.unwrap_or_else(|| {
if self.root(0).as_ref() == Some(as_of_root) {
AuthBase::Current
} else {
AuthBase::NotFound
}
});
let auth_base = if checkpoint_depth == 0 {
Ok(AuthBase::Current)
} else if self.checkpoints.len() >= checkpoint_depth {
let c_idx = self.checkpoints.len() - checkpoint_depth;
if self
.checkpoints
.iter()
.skip(c_idx)
.take_while(|c| {
c.position(&self.prior_bridges)
.iter()
.any(|p| p <= &position)
})
.any(|c| c.marked.contains(&position))
{
// The mark had not yet been established at the point the checkpoint was
// created, so we can't treat it as marked.
Err(WitnessingError::PositionNotMarked(position))
} else {
Ok(AuthBase::Checkpoint(c_idx, &self.checkpoints[c_idx]))
}
} else {
Err(WitnessingError::CheckpointInvalid)
}?;
let saved_idx = self
.saved
.get(&position)
.or_else(|| {
if let AuthBase::Checkpoint(i, _) = auth_base {
// The saved position might have been forgotten since the checkpoint,
// so look for it in each of the subsequent checkpoints' forgotten
// items.
self.checkpoints[i..].iter().find_map(|c| {
// restore the forgotten position, if that position was not also marked
// in the same checkpoint
c.forgotten
.get(&position)
.filter(|_| !c.marked.contains(&position))
})
} else {
None
}
})
.ok_or(WitnessingError::PositionNotMarked(position))?;
let prior_frontier = &self.prior_bridges[*saved_idx].frontier;
@ -1198,10 +1196,6 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
fuse_from - checkpoint.bridges_len,
))
}
AuthBase::NotFound => {
// we didn't find any suitable auth base
Err(WitnessingError::AuthBaseNotFound)
}
}?;
successor.witness(DEPTH, prior_frontier)
@ -1216,17 +1210,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
// checkpoints; we cannot remove information that we might need to restore in
// a rewind.
if self.checkpoints.len() == self.max_checkpoints {
let gc_len = self.checkpoints.first().unwrap().bridges_len;
// Get a list of the leaf positions that we need to retain. This consists of
// all the saved leaves, plus all the leaves that have been forgotten since
// the most distant checkpoint to which we could rewind.
let remember: BTreeSet<Position> = self
.saved
.keys()
.chain(self.checkpoints.iter().flat_map(|c| c.forgotten.keys()))
.cloned()
.collect();
let gc_len = self.checkpoints.front().unwrap().bridges_len;
let mut cur: Option<MerkleBridge<H>> = None;
let mut merged = 0;
let mut ommer_addrs: BTreeSet<Address> = BTreeSet::new();
@ -1236,7 +1220,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
{
if let Some(cur_bridge) = cur {
let pos = cur_bridge.position();
let mut new_cur = if remember.contains(&pos) || i > gc_len {
let mut new_cur = if self.saved.contains_key(&pos) || i > gc_len {
// We need to remember cur_bridge; update its save index & put next_bridge
// on the chopping block
if let Some(idx) = self.saved.get_mut(&pos) {
@ -1300,9 +1284,8 @@ mod tests {
use incrementalmerkletree::{
testing::{
apply_operation, arb_operation, check_checkpoint_rewind, check_operations,
check_rewind_remove_mark, check_rewind_remove_mark_consistency, check_root_hashes,
check_witnesses, complete_tree::CompleteTree, CombinedTree, Frontier, SipHashable,
Tree,
check_remove_mark, check_rewind_remove_mark, check_root_hashes, check_witnesses,
complete_tree::CompleteTree, CombinedTree, Frontier, SipHashable, Tree,
},
Hashable,
};
@ -1317,27 +1300,32 @@ mod tests {
}
}
impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH> {
fn append(&mut self, value: H) -> bool {
BridgeTree::append(self, value)
impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H, usize> for BridgeTree<H, DEPTH> {
fn append(&mut self, value: H, retention: Retention<usize>) -> bool {
let appended = BridgeTree::append(self, value);
if appended {
if retention.is_marked() {
BridgeTree::mark(self);
}
if let Retention::Checkpoint { id, .. } = retention {
BridgeTree::checkpoint(self, id);
}
}
appended
}
fn depth(&self) -> u8 {
DEPTH
}
fn current_position(&self) -> Option<Position> {
BridgeTree::current_position(self)
}
fn current_leaf(&self) -> Option<&H> {
BridgeTree::current_leaf(self)
}
fn get_marked_leaf(&self, position: Position) -> Option<&H> {
BridgeTree::get_marked_leaf(self, position)
}
fn mark(&mut self) -> Option<Position> {
BridgeTree::mark(self)
}
fn marked_positions(&self) -> BTreeSet<Position> {
BridgeTree::marked_positions(self)
}
@ -1346,16 +1334,16 @@ mod tests {
BridgeTree::root(self, checkpoint_depth)
}
fn witness(&self, position: Position, as_of_root: &H) -> Option<Vec<H>> {
BridgeTree::witness(self, position, as_of_root)
fn witness(&self, position: Position, checkpoint_depth: usize) -> Option<Vec<H>> {
BridgeTree::witness(self, position, checkpoint_depth).ok()
}
fn remove_mark(&mut self, position: Position) -> bool {
BridgeTree::remove_mark(self, position)
}
fn checkpoint(&mut self) {
BridgeTree::checkpoint(self)
fn checkpoint(&mut self, id: usize) -> bool {
BridgeTree::checkpoint(self, id)
}
fn rewind(&mut self) -> bool {
@ -1460,13 +1448,29 @@ mod tests {
#[test]
fn tree_depth() {
let mut tree = BridgeTree::<String, 3>::new(100);
let mut tree = BridgeTree::<String, 3>::new(100, 0);
for c in 'a'..'i' {
assert!(tree.append(c.to_string()))
}
assert!(!tree.append('i'.to_string()));
}
fn check_garbage_collect<H: Hashable + Clone + Ord, const DEPTH: u8>(
mut tree: BridgeTree<H, DEPTH>,
) {
// Add checkpoints until we're sure everything that can be gc'ed will be gc'ed
for i in 0..tree.max_checkpoints {
tree.checkpoint(i + 1);
}
let mut tree_mut = tree.clone();
tree_mut.garbage_collect();
for pos in tree.saved.keys() {
assert_eq!(tree.witness(*pos, 0), tree_mut.witness(*pos, 0));
}
}
fn arb_bridgetree<G: Strategy + Clone>(
item_gen: G,
max_count: usize,
@ -1476,9 +1480,9 @@ mod tests {
{
proptest::collection::vec(arb_operation(item_gen, 0..max_count), 0..max_count).prop_map(
|ops| {
let mut tree: BridgeTree<G::Value, 8> = BridgeTree::new(10);
for op in ops {
apply_operation(&mut tree, op);
let mut tree: BridgeTree<G::Value, 8> = BridgeTree::new(10, 0);
for (i, op) in ops.into_iter().enumerate() {
apply_operation(&mut tree, op.map_checkpoint_id(|_| i));
}
tree
},
@ -1506,70 +1510,53 @@ mod tests {
fn prop_garbage_collect(
tree in arb_bridgetree((97u8..123).prop_map(|c| char::from(c).to_string()), 100)
) {
let mut tree_mut = tree.clone();
// ensure we have enough checkpoints to not rewind past the state `tree` is in
for _ in 0..10 {
tree_mut.checkpoint();
}
tree_mut.garbage_collect();
tree_mut.rewind();
for pos in tree.saved.keys() {
assert_eq!(
tree.witness(*pos, &tree.root(0).unwrap()),
tree_mut.witness(*pos, &tree.root(0).unwrap())
);
}
check_garbage_collect(tree);
}
}
#[test]
fn drop_oldest_checkpoint() {
let mut t = BridgeTree::<String, 6>::new(100);
t.checkpoint();
t.append("a".to_string());
t.mark();
t.append("b".to_string());
t.append("c".to_string());
assert!(
t.drop_oldest_checkpoint(),
"Checkpoint drop is expected to succeed"
);
assert!(!t.rewind(), "Rewind is expected to fail.");
}
#[test]
fn root_hashes() {
check_root_hashes(BridgeTree::<String, 4>::new);
check_root_hashes(|max_checkpoints| BridgeTree::<String, 4>::new(max_checkpoints, 0));
}
#[test]
fn witnesss() {
check_witnesses(BridgeTree::<String, 4>::new);
fn witness() {
check_witnesses(|max_checkpoints| BridgeTree::<String, 4>::new(max_checkpoints, 0));
}
#[test]
fn checkpoint_rewind() {
check_checkpoint_rewind(BridgeTree::<String, 4>::new);
check_checkpoint_rewind(|max_checkpoints| BridgeTree::<String, 4>::new(max_checkpoints, 0));
}
#[test]
fn rewind_remove_mark() {
check_rewind_remove_mark(BridgeTree::<String, 4>::new);
check_rewind_remove_mark(|max_checkpoints| {
BridgeTree::<String, 4>::new(max_checkpoints, 0)
});
}
#[test]
fn garbage_collect() {
let mut t = BridgeTree::<String, 7>::new(10);
let mut tree: BridgeTree<String, 7> = BridgeTree::new(1000, 0);
let empty_root = tree.root(0);
tree.append("a".to_string());
for i in 0..100 {
tree.checkpoint(i + 1);
}
tree.garbage_collect();
assert!(tree.root(0) != empty_root);
tree.rewind();
assert!(tree.root(0) != empty_root);
let mut t = BridgeTree::<String, 7>::new(10, 0);
let mut to_unmark = vec![];
let mut has_witness = vec![];
for i in 0usize..100 {
let elem: String = format!("{},", i);
assert!(t.append(elem), "Append should succeed.");
if i % 5 == 0 {
t.checkpoint();
t.checkpoint(i + 1);
}
if i % 7 == 0 {
t.mark();
@ -1586,9 +1573,9 @@ mod tests {
}
// 32 = 20 (checkpointed) + 14 (marked) - 2 (marked & checkpointed)
assert_eq!(t.prior_bridges().len(), 20 + 14 - 2);
let witnesss = has_witness
let witness = has_witness
.iter()
.map(|pos| match t.witness_inner(*pos, &t.root(0).unwrap()) {
.map(|pos| match t.witness(*pos, 0) {
Ok(path) => path,
Err(e) => panic!("Failed to get auth path: {:?}", e),
})
@ -1596,48 +1583,31 @@ mod tests {
t.garbage_collect();
// 20 = 32 - 10 (removed checkpoints) + 1 (not removed due to mark) - 3 (removed marks)
assert_eq!(t.prior_bridges().len(), 32 - 10 + 1 - 3);
let retained_witnesss = has_witness
let retained_witness = has_witness
.iter()
.map(|pos| {
t.witness(*pos, &t.root(0).unwrap())
.expect("Must be able to get auth path")
})
.map(|pos| t.witness(*pos, 0).expect("Must be able to get auth path"))
.collect::<Vec<_>>();
assert_eq!(witnesss, retained_witnesss);
}
#[test]
fn garbage_collect_idx() {
let mut tree: BridgeTree<String, 7> = BridgeTree::new(100);
let empty_root = tree.root(0);
tree.append("a".to_string());
for _ in 0..100 {
tree.checkpoint();
}
tree.garbage_collect();
assert!(tree.root(0) != empty_root);
tree.rewind();
assert!(tree.root(0) != empty_root);
assert_eq!(witness, retained_witness);
}
// Combined tree tests
fn new_combined_tree<H: Hashable + Ord + Clone + Debug>(
max_checkpoints: usize,
) -> CombinedTree<H, CompleteTree<H>, BridgeTree<H, 4>> {
) -> CombinedTree<H, usize, CompleteTree<H, usize, 4>, BridgeTree<H, 4>> {
CombinedTree::new(
CompleteTree::new(4, max_checkpoints),
BridgeTree::<H, 4>::new(max_checkpoints),
CompleteTree::<H, usize, 4>::new(max_checkpoints, 0),
BridgeTree::<H, 4>::new(max_checkpoints, 0),
)
}
#[test]
fn test_rewind_remove_mark() {
check_rewind_remove_mark(new_combined_tree);
fn combined_remove_mark() {
check_remove_mark(new_combined_tree);
}
#[test]
fn test_rewind_remove_mark_consistency() {
check_rewind_remove_mark_consistency(new_combined_tree);
fn combined_rewind_remove_mark() {
check_rewind_remove_mark(new_combined_tree);
}
proptest! {
@ -1651,7 +1621,8 @@ mod tests {
)
) {
let tree = new_combined_tree(100);
check_operations(tree, 4, &ops)?;
let indexed_ops = ops.iter().enumerate().map(|(i, op)| op.map_checkpoint_id(|_| i + 1)).collect::<Vec<_>>();
check_operations(tree, &indexed_ops)?;
}
#[test]
@ -1662,7 +1633,8 @@ mod tests {
)
) {
let tree = new_combined_tree(100);
check_operations(tree, 4, &ops)?;
let indexed_ops = ops.iter().enumerate().map(|(i, op)| op.map_checkpoint_id(|_| i + 1)).collect::<Vec<_>>();
check_operations(tree, &indexed_ops)?;
}
}
}

4
incrementalmerkletree/CHANGELOG.md
View File

@ -41,7 +41,9 @@ is not another good use case for polymorphism over tree implementations.
- `Tree::witnessed_positions` has been renamed to `Tree::marked_positions`
- `Tree::get_witnessed_leaf` has been renamed to `Tree::get_marked_leaf`
- `Tree::remove_witness` has been renamed to `Tree::remove_mark`
- `Tree::authentication_path` has been renamed to `Tree::witness`
- `Tree::authentication_path` has been renamed to `Tree::witness`. Also, this method
now takes a checkpoint depth as its second argument rather than a Merkle root,
to better support future changes.
- `Tree::append` now takes ownership of the value being appended instead of a value passed
by reference.

35
incrementalmerkletree/src/lib.rs
View File

@ -10,6 +10,39 @@ use std::ops::{Add, AddAssign, Range, Sub};
#[cfg(feature = "test-dependencies")]
pub mod testing;
/// A type for metadata that is used to determine when and how a leaf can be pruned from a tree.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub enum Retention<C> {
Ephemeral,
Checkpoint { id: C, is_marked: bool },
Marked,
}
impl<C> Retention<C> {
pub fn is_checkpoint(&self) -> bool {
matches!(self, Retention::Checkpoint { .. })
}
pub fn is_marked(&self) -> bool {
match self {
Retention::Ephemeral => false,
Retention::Checkpoint { is_marked, .. } => *is_marked,
Retention::Marked => true,
}
}
pub fn map<'a, D, F: Fn(&'a C) -> D>(&'a self, f: F) -> Retention<D> {
match self {
Retention::Ephemeral => Retention::Ephemeral,
Retention::Checkpoint { id, is_marked } => Retention::Checkpoint {
id: f(id),
is_marked: *is_marked,
},
Retention::Marked => Retention::Marked,
}
}
}
/// A type representing the position of a leaf in a Merkle tree.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
#[repr(transparent)]
@ -373,7 +406,7 @@ impl<'a> From<&'a Address> for Option<Position> {
/// A trait describing the operations that make a type suitable for use as
/// a leaf or node value in a merkle tree.
pub trait Hashable: Sized {
pub trait Hashable: Sized + core::fmt::Debug {
fn empty_leaf() -> Self;
fn combine(level: Level, a: &Self, b: &Self) -> Self;

753
incrementalmerkletree/src/testing.rs
View File

File diff suppressed because it is too large Load Diff

484
incrementalmerkletree/src/testing/complete_tree.rs
View File

@ -1,13 +1,17 @@
//! Sample implementation of the Tree interface.
use std::collections::BTreeSet;
use std::cmp::min;
use std::collections::{BTreeMap, BTreeSet};
use crate::{
testing::{Frontier, Tree},
Hashable, Level, Position,
};
use crate::{testing::Tree, Hashable, Level, Position, Retention};
pub(crate) fn root<H: Hashable + Clone>(mut leaves: Vec<H>) -> H {
leaves.resize(leaves.len().next_power_of_two(), H::empty_leaf());
pub(crate) fn root<H: Hashable + Clone>(leaves: &[H], depth: u8) -> H {
let empty_leaf = H::empty_leaf();
let mut leaves = leaves
.iter()
.chain(std::iter::repeat(&empty_leaf))
.take(1 << depth)
.cloned()
.collect::<Vec<H>>();
//leaves are always at level zero, so we start there.
let mut level = Level::from(0);
@ -32,214 +36,277 @@ pub(crate) fn root<H: Hashable + Clone>(mut leaves: Vec<H>) -> H {
leaves[0].clone()
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Checkpoint {
/// The number of leaves in the tree when the checkpoint was created.
leaves_len: usize,
/// A set of the positions that have been marked during the period that this
/// checkpoint is the current checkpoint.
marked: BTreeSet<Position>,
/// When a mark is forgotten, we add it to the checkpoint's forgotten set but
/// don't immediately remove it from the `marked` set; that removal occurs when
/// the checkpoint is eventually dropped.
forgotten: BTreeSet<Position>,
}
impl Checkpoint {
fn at_length(leaves_len: usize) -> Self {
Checkpoint {
leaves_len,
marked: BTreeSet::new(),
forgotten: BTreeSet::new(),
}
}
}
#[derive(Clone, Debug)]
pub struct TreeState<H: Hashable> {
leaves: Vec<H>,
current_offset: usize,
pub struct CompleteTree<H, C: Ord, const DEPTH: u8> {
leaves: Vec<Option<H>>,
marks: BTreeSet<Position>,
depth: usize,
checkpoints: BTreeMap<C, Checkpoint>,
max_checkpoints: usize,
}
impl<H: Hashable + Clone> TreeState<H> {
/// Creates a new, empty binary tree of specified depth.
pub fn new(depth: usize) -> Self {
impl<H: Hashable, C: Clone + Ord + core::fmt::Debug, const DEPTH: u8> CompleteTree<H, C, DEPTH> {
/// Creates a new, empty binary tree
pub fn new(max_checkpoints: usize, initial_checkpoint_id: C) -> Self {
Self {
leaves: vec![H::empty_leaf(); 1 << depth],
current_offset: 0,
leaves: vec![],
marks: BTreeSet::new(),
depth,
}
}
}
impl<H: Hashable + Clone> Frontier<H> for TreeState<H> {
fn append(&mut self, value: H) -> bool {
if self.current_offset == (1 << self.depth) {
false
} else {
self.leaves[self.current_offset] = value;
self.current_offset += 1;
true
checkpoints: BTreeMap::from([(initial_checkpoint_id, Checkpoint::at_length(0))]),
max_checkpoints,
}
}
/// Obtains the current root of this Merkle tree.
fn root(&self) -> H {
root(self.leaves.clone())
}
}
/// Appends a new value to the tree at the next available slot.
///
/// Returns true if successful and false if the tree is full or, for values with `Checkpoint`
/// retention, if a checkpoint id would be introduced that is less than or equal to the current
/// maximum checkpoint id.
fn append(&mut self, value: H, retention: Retention<C>) -> Result<(), AppendError<C>> {
fn append<H, C>(
leaves: &mut Vec<Option<H>>,
value: H,
depth: u8,
) -> Result<(), AppendError<C>> {
if leaves.len() < (1 << depth) {
leaves.push(Some(value));
Ok(())
} else {
Err(AppendError::TreeFull)
}
}
match retention {
Retention::Marked => {
append(&mut self.leaves, value, DEPTH)?;
self.mark();
}
Retention::Checkpoint { id, is_marked } => {
let latest_checkpoint = self.checkpoints.keys().rev().next();
if Some(&id) > latest_checkpoint {
append(&mut self.leaves, value, DEPTH)?;
if is_marked {
self.mark();
}
self.checkpoint(id, self.current_position());
} else {
return Err(AppendError::CheckpointOutOfOrder {
current_max: latest_checkpoint.cloned(),
checkpoint: id,
});
}
}
Retention::Ephemeral => {
append(&mut self.leaves, value, DEPTH)?;
}
}
Ok(())
}
impl<H: Hashable + PartialEq + Clone> TreeState<H> {
fn current_position(&self) -> Option<Position> {
if self.current_offset == 0 {
if self.leaves.is_empty() {
None
} else {
Some((self.current_offset - 1).into())
}
}
/// Returns the leaf most recently appended to the tree
fn current_leaf(&self) -> Option<&H> {
self.current_position()
.map(|p| &self.leaves[<usize>::from(p)])
}
/// Returns the leaf at the specified position if the tree can produce
/// a witness for it.
fn get_marked_leaf(&self, position: Position) -> Option<&H> {
if self.marks.contains(&position) {
self.leaves.get(<usize>::from(position))
} else {
None
Some((self.leaves.len() - 1).into())
}
}
/// Marks the current tree state leaf as a value that we're interested in
/// marking. Returns the current position if the tree is non-empty.
fn mark(&mut self) -> Option<Position> {
self.current_position().map(|pos| {
self.marks.insert(pos);
pos
})
}
/// Obtains a witness to the value at the specified position.
/// Returns `None` if there is no available witness to that
/// value.
fn witness(&self, position: Position) -> Option<Vec<H>> {
if Some(position) <= self.current_position() {
let mut path = vec![];
let mut leaf_idx: usize = position.into();
for bit in 0..self.depth {
leaf_idx ^= 1 << bit;
path.push(root::<H>(self.leaves[leaf_idx..][0..(1 << bit)].to_vec()));
leaf_idx &= usize::MAX << (bit + 1);
}
Some(path)
} else {
None
}
}
/// Marks the value at the specified position as a value we're no longer
/// interested in maintaining a mark for. Returns true if successful and
/// false if we were already not maintaining a mark at this position.
fn remove_mark(&mut self, position: Position) -> bool {
self.marks.remove(&position)
}
}
#[derive(Clone, Debug)]
pub struct CompleteTree<H: Hashable> {
tree_state: TreeState<H>,
checkpoints: Vec<TreeState<H>>,
max_checkpoints: usize,
}
impl<H: Hashable + Clone> CompleteTree<H> {
/// Creates a new, empty binary tree of specified depth.
pub fn new(depth: usize, max_checkpoints: usize) -> Self {
Self {
tree_state: TreeState::new(depth),
checkpoints: vec![],
max_checkpoints,
}
}
}
impl<H: Hashable + PartialEq + Clone> CompleteTree<H> {
/// Removes the oldest checkpoint. Returns true if successful and false if
/// there are no checkpoints.
fn drop_oldest_checkpoint(&mut self) -> bool {
if self.checkpoints.is_empty() {
false
} else {
self.checkpoints.remove(0);
true
}
}
/// Retrieve the tree state at the specified checkpoint depth. This
/// is the current tree state if the depth is 0, and this will return
/// None if not enough checkpoints exist to obtain the requested depth.
fn tree_state_at_checkpoint_depth(&self, checkpoint_depth: usize) -> Option<&TreeState<H>> {
if self.checkpoints.len() < checkpoint_depth {
None
} else if checkpoint_depth == 0 {
Some(&self.tree_state)
} else {
self.checkpoints
.get(self.checkpoints.len() - checkpoint_depth)
}
}
}
impl<H: Hashable + PartialEq + Clone + std::fmt::Debug> Tree<H> for CompleteTree<H> {
/// Appends a new value to the tree at the next available slot. Returns true
/// if successful and false if the tree is full.
fn append(&mut self, value: H) -> bool {
self.tree_state.append(value)
}
/// Returns the most recently appended leaf value.
fn current_position(&self) -> Option<Position> {
self.tree_state.current_position()
}
fn current_leaf(&self) -> Option<&H> {
self.tree_state.current_leaf()
}
fn get_marked_leaf(&self, position: Position) -> Option<&H> {
self.tree_state.get_marked_leaf(position)
}
fn mark(&mut self) -> Option<Position> {
self.tree_state.mark()
}
fn marked_positions(&self) -> BTreeSet<Position> {
self.tree_state.marks.clone()
}
fn root(&self, checkpoint_depth: usize) -> Option<H> {
self.tree_state_at_checkpoint_depth(checkpoint_depth)
.map(|s| s.root())
}
fn witness(&self, position: Position, root: &H) -> Option<Vec<H>> {
// Search for the checkpointed state corresponding to the provided root, and if one is
// found, compute the witness as of that root.
self.checkpoints
.iter()
.chain(Some(&self.tree_state))
.rev()
.skip_while(|c| !c.marks.contains(&position))
.find_map(|c| {
if &c.root() == root {
c.witness(position)
} else {
None
match self.current_position() {
Some(pos) => {
if !self.marks.contains(&pos) {
self.marks.insert(pos);
self.checkpoints
.iter_mut()
.rev()
.next()
.unwrap()
.1
.marked
.insert(pos);
}
})
Some(pos)
}
None => None,
}
}
fn remove_mark(&mut self, position: Position) -> bool {
self.tree_state.remove_mark(position)
}
fn checkpoint(&mut self) {
self.checkpoints.push(self.tree_state.clone());
fn checkpoint(&mut self, id: C, pos: Option<Position>) {
self.checkpoints.insert(
id,
Checkpoint::at_length(pos.map_or_else(|| 0, |p| usize::from(p) + 1)),
);
if self.checkpoints.len() > self.max_checkpoints {
self.drop_oldest_checkpoint();
}
}
fn leaves_at_checkpoint_depth(&self, checkpoint_depth: usize) -> Option<usize> {
if checkpoint_depth == 0 {
Some(self.leaves.len())
} else {
self.checkpoints
.iter()
.rev()
.skip(checkpoint_depth - 1)
.map(|(_, c)| c.leaves_len)
.next()
}
}
/// Removes the oldest checkpoint. Returns true if successful and false if
/// there are fewer than `self.max_checkpoints` checkpoints.
fn drop_oldest_checkpoint(&mut self) -> bool {
if self.checkpoints.len() > self.max_checkpoints {
let (id, c) = self.checkpoints.iter().next().unwrap();
for pos in c.forgotten.iter() {
self.marks.remove(pos);
}
let id = id.clone(); // needed to avoid mutable/immutable borrow conflict
self.checkpoints.remove(&id);
true
} else {
false
}
}
}
#[derive(Clone, Debug, PartialEq, Eq)]
enum AppendError<C> {
TreeFull,
CheckpointOutOfOrder {
current_max: Option<C>,
checkpoint: C,
},
}
impl<H: Hashable + PartialEq + Clone, C: Ord + Clone + core::fmt::Debug, const DEPTH: u8> Tree<H, C>
for CompleteTree<H, C, DEPTH>
{
fn depth(&self) -> u8 {
DEPTH
}
fn append(&mut self, value: H, retention: Retention<C>) -> bool {
Self::append(self, value, retention).is_ok()
}
fn current_position(&self) -> Option<Position> {
Self::current_position(self)
}
fn marked_positions(&self) -> BTreeSet<Position> {
self.marks.clone()
}
fn get_marked_leaf(&self, position: Position) -> Option<&H> {
if self.marks.contains(&position) {
self.leaves
.get(usize::from(position))
.and_then(|opt: &Option<H>| opt.as_ref())
} else {
None
}
}
fn root(&self, checkpoint_depth: usize) -> Option<H> {
self.leaves_at_checkpoint_depth(checkpoint_depth)
.and_then(|len| root(&self.leaves[0..len], DEPTH))
}
fn witness(&self, position: Position, checkpoint_depth: usize) -> Option<Vec<H>> {
if self.marks.contains(&position) && checkpoint_depth <= self.checkpoints.len() {
let leaves_len = self.leaves_at_checkpoint_depth(checkpoint_depth)?;
let c_idx = self.checkpoints.len() - checkpoint_depth;
if self
.checkpoints
.iter()
.skip(c_idx)
.any(|(_, c)| c.marked.contains(&position))
{
// The requested position was marked after the checkpoint was created, so we
// cannot create a witness.
None
} else {
let mut path = vec![];
let mut leaf_idx: usize = position.into();
for bit in 0..DEPTH {
leaf_idx ^= 1 << bit;
path.push(if leaf_idx < leaves_len {
let subtree_end = min(leaf_idx + (1 << bit), leaves_len);
root(&self.leaves[leaf_idx..subtree_end], bit)?
} else {
H::empty_root(Level::from(bit))
});
leaf_idx &= usize::MAX << (bit + 1);
}
Some(path)
}
} else {
None
}
}
fn remove_mark(&mut self, position: Position) -> bool {
if self.marks.contains(&position) {
self.checkpoints
.iter_mut()
.rev()
.next()
.unwrap()
.1
.forgotten
.insert(position);
true
} else {
false
}
}
fn checkpoint(&mut self, id: C) -> bool {
if Some(&id) > self.checkpoints.iter().rev().next().map(|(id, _)| id) {
Self::checkpoint(self, id, self.current_position());
true
} else {
false
}
}
fn rewind(&mut self) -> bool {
if let Some(checkpointed_state) = self.checkpoints.pop() {
self.tree_state = checkpointed_state;
if self.checkpoints.len() > 1 {
let (id, c) = self.checkpoints.iter().rev().next().unwrap();
self.leaves.truncate(c.leaves_len);
for pos in c.marked.iter() {
self.marks.remove(pos);
}
let id = id.clone(); // needed to avoid mutable/immutable borrow conflict
self.checkpoints.remove(&id);
true
} else {
false
@ -257,7 +324,7 @@ mod tests {
check_checkpoint_rewind, check_rewind_remove_mark, check_root_hashes, check_witnesses,
compute_root_from_witness, SipHashable, Tree,
},
Hashable, Level, Position,
Hashable, Level, Position, Retention,
};
#[test]
@ -268,20 +335,20 @@ mod tests {
expected = SipHashable::combine(lvl.into(), &expected, &expected);
}
let tree = CompleteTree::<SipHashable>::new(DEPTH as usize, 100);
let tree = CompleteTree::<SipHashable, (), DEPTH>::new(100, ());
assert_eq!(tree.root(0).unwrap(), expected);
}
#[test]
fn correct_root() {
const DEPTH: usize = 3;
const DEPTH: u8 = 3;
let values = (0..(1 << DEPTH)).into_iter().map(SipHashable);
let mut tree = CompleteTree::<SipHashable>::new(DEPTH, 100);
let mut tree = CompleteTree::<SipHashable, (), DEPTH>::new(100, ());
for value in values {
assert!(tree.append(value));
assert!(tree.append(value, Retention::Ephemeral).is_ok());
}
assert!(!tree.append(SipHashable(0)));
assert!(tree.append(SipHashable(0), Retention::Ephemeral).is_err());
let expected = SipHashable::combine(
Level::from(2),
@ -302,25 +369,30 @@ mod tests {
#[test]
fn root_hashes() {
check_root_hashes(|max_c| CompleteTree::<String>::new(4, max_c));
check_root_hashes(|max_checkpoints| {
CompleteTree::<String, usize, 4>::new(max_checkpoints, 0)
});
}
#[test]
fn witnesss() {
check_witnesses(|max_c| CompleteTree::<String>::new(4, max_c));
fn witness() {
check_witnesses(|max_checkpoints| {
CompleteTree::<String, usize, 4>::new(max_checkpoints, 0)
});
}
#[test]
fn correct_witness() {
const DEPTH: usize = 3;
use crate::{testing::Tree, Retention};
const DEPTH: u8 = 3;
let values = (0..(1 << DEPTH)).into_iter().map(SipHashable);
let mut tree = CompleteTree::<SipHashable>::new(DEPTH, 100);
let mut tree = CompleteTree::<SipHashable, (), DEPTH>::new(100, ());
for value in values {
assert!(tree.append(value));
tree.mark();
assert!(Tree::append(&mut tree, value, Retention::Marked));
}
assert!(!tree.append(SipHashable(0)));
assert!(tree.append(SipHashable(0), Retention::Ephemeral).is_err());
let expected = SipHashable::combine(
<Level>::from(2),
@ -340,7 +412,7 @@ mod tests {
for i in 0u64..(1 << DEPTH) {
let position = Position::try_from(i).unwrap();
let path = tree.witness(position, &tree.root(0).unwrap()).unwrap();
let path = tree.witness(position, 0).unwrap();
assert_eq!(
compute_root_from_witness(SipHashable(i), position, &path),
expected
@ -350,11 +422,15 @@ mod tests {
#[test]
fn checkpoint_rewind() {
check_checkpoint_rewind(|max_c| CompleteTree::<String>::new(4, max_c));
check_checkpoint_rewind(|max_checkpoints| {
CompleteTree::<String, usize, 4>::new(max_checkpoints, 0)
});
}
#[test]
fn rewind_remove_mark() {
check_rewind_remove_mark(|max_c| CompleteTree::<String>::new(4, max_c));
check_rewind_remove_mark(|max_checkpoints| {
CompleteTree::<String, usize, 4>::new(max_checkpoints, 0)
});
}
}