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Rename witness->mark
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@nuttycom
nuttycom committed Aug 4, 2022
1 parent 7bd1907 commit ee93cb8
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Showing 3 changed files with 216 additions and 223 deletions.
119 changes: 57 additions & 62 deletions src/bridgetree.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ pub enum FrontierError {

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum PathError {
PositionNotWitnessed(Position),
PositionNotMarked(Position),
BridgeFusionError,
FrontierAddressInvalid(Address),
BridgeAddressInvalid(Address),
Expand Down Expand Up @@ -348,19 +348,19 @@ impl<H> MerkleBridge<H> {
}

impl<'a, H: Hashable + Ord + Clone + 'a> MerkleBridge<H> {
/// Constructs a new bridge to follow this one. If witness_current_leaf is true, the successor
/// Constructs a new bridge to follow this one. If mark_current_leaf is true, the successor
/// will track the information necessary to create an authentication path for the leaf most
/// recently appended to this bridge's frontier.
#[must_use]
pub fn successor(&self, witness_current_leaf: bool) -> Self {
pub fn successor(&self, mark_current_leaf: bool) -> Self {
let mut result = Self {
prior_position: Some(self.frontier.position()),
tracking: self.tracking.clone(),
fragments: BTreeMap::new(),
frontier: self.frontier.clone(),
};

if witness_current_leaf {
if mark_current_leaf {
result.track_current_leaf();
}

Expand Down Expand Up @@ -479,14 +479,14 @@ pub struct Checkpoint {
/// 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 witnessed at the time the checkpoint was created.
is_witnessed: bool,
/// A set of the positions that have been witnessed during the period that this
/// 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.
witnessed: BTreeSet<Position>,
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
/// witnesses to the BridgeTree's "saved" list. If the mark was newly created since the
/// 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>,
Expand All @@ -496,24 +496,24 @@ impl Checkpoint {
/// Creates a new checkpoint from its constituent parts.
pub fn from_parts(
bridges_len: usize,
is_witnessed: bool,
witnessed: BTreeSet<Position>,
is_marked: bool,
marked: BTreeSet<Position>,
forgotten: BTreeMap<Position, usize>,
) -> Self {
Self {
bridges_len,
is_witnessed,
witnessed,
is_marked,
marked,
forgotten,
}
}

/// Creates a new empty checkpoint for the specified [`BridgeTree`] state.
pub fn at_length(bridges_len: usize, is_witnessed: bool) -> Self {
pub fn at_length(bridges_len: usize, is_marked: bool) -> Self {
Checkpoint {
bridges_len,
is_witnessed,
witnessed: BTreeSet::new(),
is_marked,
marked: BTreeSet::new(),
forgotten: BTreeMap::new(),
}
}
Expand All @@ -527,22 +527,22 @@ impl Checkpoint {
self.bridges_len
}

/// Returns whether the current state of the tree had been witnessed at the point that
/// 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_witnessed(&self) -> bool {
self.is_witnessed
pub fn is_marked(&self) -> bool {
self.is_marked
}

/// Returns a set of the positions that have been witnessed during the period that this
/// Returns a set of the positions that have been marked during the period that this
/// checkpoint is the current checkpoint.
pub fn witnessed(&self) -> &BTreeSet<Position> {
&self.witnessed
pub fn marked(&self) -> &BTreeSet<Position> {
&self.marked
}

/// Returns the set of previously-witnessed positions that have had their witnesses removed
/// 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> {
&self.forgotten
Expand Down Expand Up @@ -615,7 +615,7 @@ impl<H: Hashable + Ord + Debug, const DEPTH: u8> Debug for BridgeTree<H, DEPTH>
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum BridgeTreeError {
IncorrectIncompleteIndex,
InvalidWitnessIndex(usize),
InvalidMarkIndex(usize),
PositionMismatch { expected: Position, found: Position },
InvalidSavePoints,
ContinuityError,
Expand Down Expand Up @@ -644,7 +644,7 @@ impl<H: Ord, const DEPTH: u8> BridgeTree<H, DEPTH> {
&self.current_bridge
}

pub fn witnessed_indices(&self) -> &BTreeMap<Position, usize> {
pub fn marked_indices(&self) -> &BTreeMap<Position, usize> {
&self.saved
}

Expand Down Expand Up @@ -686,7 +686,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
// check that saved values correspond to bridges
for (pos, i) in saved {
if i >= &prior_bridges.len() {
return Err(BridgeTreeError::InvalidWitnessIndex(*i));
return Err(BridgeTreeError::InvalidMarkIndex(*i));
}
let found = prior_bridges[*i].position();
if &found != pos {
Expand Down Expand Up @@ -816,17 +816,17 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
// 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 witnessed
// restore the forgotten position, if that position was not also marked
// in the same checkpoint
c.forgotten
.get(&position)
.filter(|_| !c.witnessed.contains(&position))
.filter(|_| !c.marked.contains(&position))
})
} else {
None
}
})
.ok_or(PathError::PositionNotWitnessed(position))?;
.ok_or(PathError::PositionNotMarked(position))?;

let prior_frontier = &self.prior_bridges[*saved_idx].frontier;

Expand Down Expand Up @@ -908,7 +908,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
self.current_bridge.as_ref().map(|b| b.current_leaf())
}

fn witness(&mut self) -> Option<Position> {
fn mark(&mut self) -> Option<Position> {
match self.current_bridge.take() {
Some(mut cur_b) => {
cur_b.track_current_leaf();
Expand All @@ -922,7 +922,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
.map_or(false, |prior_b| prior_b.position() == cur_b.position())
{
// the current bridge has not been advanced, so we just need to make
// sure that we have are tracking the witnessed leaf
// sure that we have are tracking the marked leaf
self.current_bridge = Some(cur_b);
} else {
let successor = cur_b.successor(true);
Expand All @@ -934,10 +934,10 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
.entry(pos)
.or_insert(self.prior_bridges.len() - 1);

// mark the position as having been witnessed in the current checkpoint
// mark the position as having been marked in the current checkpoint
if let Some(c) = self.checkpoints.last_mut() {
if !c.is_witnessed {
c.witnessed.insert(pos);
if !c.is_marked {
c.marked.insert(pos);
}
}

Expand All @@ -947,23 +947,23 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
}
}

fn witnessed_positions(&self) -> BTreeSet<Position> {
fn marked_positions(&self) -> BTreeSet<Position> {
self.saved.keys().cloned().collect()
}

fn get_witnessed_leaf(&self, position: Position) -> Option<&H> {
fn get_marked_leaf(&self, position: Position) -> Option<&H> {
self.saved
.get(&position)
.and_then(|idx| self.prior_bridges.get(*idx).map(|b| b.current_leaf()))
}

fn remove_witness(&mut self, position: Position) -> bool {
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 witnessed since the last checkpoint,
// 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.witnessed.contains(&position) {
if !c.marked.contains(&position) {
c.forgotten.insert(position, idx);
}
}
Expand All @@ -976,7 +976,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
fn checkpoint(&mut self) {
match self.current_bridge.take() {
Some(cur_b) => {
let is_witnessed = self.get_witnessed_leaf(cur_b.position()).is_some();
let is_marked = self.get_marked_leaf(cur_b.position()).is_some();

// Do not create a duplicate bridge
if self
Expand All @@ -990,10 +990,8 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
self.prior_bridges.push(cur_b);
}

self.checkpoints.push(Checkpoint::at_length(
self.prior_bridges.len(),
is_witnessed,
));
self.checkpoints
.push(Checkpoint::at_length(self.prior_bridges.len(), is_marked));
}
None => {
self.checkpoints.push(Checkpoint::at_length(0, false));
Expand All @@ -1008,17 +1006,14 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH
fn rewind(&mut self) -> bool {
match self.checkpoints.pop() {
Some(mut c) => {
// drop witnessed values at and above the checkpoint height;
// 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_witnessed));
if c.is_witnessed {
self.witness();
self.current_bridge = self.prior_bridges.last().map(|b| b.successor(c.is_marked));
if c.is_marked {
self.mark();
}
true
}
Expand Down Expand Up @@ -1245,7 +1240,7 @@ mod tests {
let mut t = BridgeTree::<String, 6>::new(100);
t.checkpoint();
t.append(&"a".to_string());
t.witness();
t.mark();
t.append(&"b".to_string());
t.append(&"c".to_string());
assert!(
Expand All @@ -1271,14 +1266,14 @@ mod tests {
}

#[test]
fn rewind_remove_witness() {
crate::tests::check_rewind_remove_witness(BridgeTree::<String, 4>::new);
fn rewind_remove_mark() {
crate::tests::check_rewind_remove_mark(BridgeTree::<String, 4>::new);
}

#[test]
fn garbage_collect() {
let mut t = BridgeTree::<String, 7>::new(10);
let mut to_unwitness = vec![];
let mut to_unmark = vec![];
let mut has_auth_path = vec![];
for i in 0usize..100 {
let elem: String = format!("{},", i);
Expand All @@ -1287,19 +1282,19 @@ mod tests {
t.checkpoint();
}
if i % 7 == 0 {
t.witness();
t.mark();
if i > 0 && i % 2 == 0 {
to_unwitness.push(Position::from(i));
to_unmark.push(Position::from(i));
} else {
has_auth_path.push(Position::from(i));
}
}
if i % 11 == 0 && !to_unwitness.is_empty() {
let pos = to_unwitness.remove(0);
t.remove_witness(pos);
if i % 11 == 0 && !to_unmark.is_empty() {
let pos = to_unmark.remove(0);
t.remove_mark(pos);
}
}
// 32 = 20 (checkpointed) + 14 (witnessed) - 2 (witnessed & checkpointed)
// 32 = 20 (checkpointed) + 14 (marked) - 2 (marked & checkpointed)
assert_eq!(t.prior_bridges().len(), 20 + 14 - 2);
let auth_paths = has_auth_path
.iter()
Expand All @@ -1311,7 +1306,7 @@ mod tests {
)
.collect::<Vec<_>>();
t.garbage_collect();
// 20 = 32 - 10 (removed checkpoints) + 1 (not removed due to mark) - 3 (removed witnesses)
// 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_auth_paths = has_auth_path
.iter()
Expand Down
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