feat(chain): refactor merge_chains
`merge_chains` now returns a tuple of the resultant checkpoint AND changeset. This is arguably a more readable/understandable setup. To do this, we had to create `CheckPoint::apply_changeset` which is kept as a private method. Thank you @ValuedMammal for the suggestion. Co-authored-by: valuedvalued mammal <valuedmammal@protonmail.com>
This commit is contained in:
parent
2f22987c9e
commit
96a9aa6e63
@ -213,6 +213,46 @@ impl CheckPoint {
|
||||
base.extend(core::iter::once(block_id).chain(tail.into_iter().rev()))
|
||||
.expect("tail is in order")
|
||||
}
|
||||
|
||||
/// Apply `changeset` to the checkpoint.
|
||||
fn apply_changeset(mut self, changeset: &ChangeSet) -> Result<CheckPoint, MissingGenesisError> {
|
||||
if let Some(start_height) = changeset.keys().next().cloned() {
|
||||
// changes after point of agreement
|
||||
let mut extension = BTreeMap::default();
|
||||
// point of agreement
|
||||
let mut base: Option<CheckPoint> = None;
|
||||
|
||||
for cp in self.iter() {
|
||||
if cp.height() >= start_height {
|
||||
extension.insert(cp.height(), cp.hash());
|
||||
} else {
|
||||
base = Some(cp);
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
for (&height, &hash) in changeset {
|
||||
match hash {
|
||||
Some(hash) => {
|
||||
extension.insert(height, hash);
|
||||
}
|
||||
None => {
|
||||
extension.remove(&height);
|
||||
}
|
||||
};
|
||||
}
|
||||
|
||||
let new_tip = match base {
|
||||
Some(base) => base
|
||||
.extend(extension.into_iter().map(BlockId::from))
|
||||
.expect("extension is strictly greater than base"),
|
||||
None => LocalChain::from_blocks(extension)?.tip(),
|
||||
};
|
||||
self = new_tip;
|
||||
}
|
||||
|
||||
Ok(self)
|
||||
}
|
||||
}
|
||||
|
||||
/// Iterates over checkpoints backwards.
|
||||
@ -348,32 +388,22 @@ impl LocalChain {
|
||||
|
||||
/// Applies the given `update` to the chain.
|
||||
///
|
||||
/// The method returns [`ChangeSet`] on success. This represents the applied changes to `self`.
|
||||
/// The method returns [`ChangeSet`] on success. This represents the changes applied to `self`.
|
||||
///
|
||||
/// There must be no ambiguity about which of the existing chain's blocks are still valid and
|
||||
/// which are now invalid. That is, the new chain must implicitly connect to a definite block in
|
||||
/// the existing chain and invalidate the block after it (if it exists) by including a block at
|
||||
/// the same height but with a different hash to explicitly exclude it as a connection point.
|
||||
///
|
||||
/// Additionally, a chain with a single block can have it's block invalidated by an update
|
||||
/// chain with a block at the same height but different hash.
|
||||
///
|
||||
/// # Errors
|
||||
///
|
||||
/// An error will occur if the update does not correctly connect with `self`.
|
||||
///
|
||||
/// [module-level documentation]: crate::local_chain
|
||||
pub fn apply_update(&mut self, update: CheckPoint) -> Result<ChangeSet, CannotConnectError> {
|
||||
let (changeset, can_replace) = merge_chains(self.tip.clone(), update.clone())?;
|
||||
if can_replace {
|
||||
self.tip = update;
|
||||
} else {
|
||||
// `._check_changeset_is_applied` is called in `.apply_changeset`
|
||||
self.apply_changeset(&changeset)
|
||||
.map_err(|_| CannotConnectError {
|
||||
try_include_height: 0,
|
||||
})?;
|
||||
}
|
||||
let (new_tip, changeset) = merge_chains(self.tip.clone(), update)?;
|
||||
self.tip = new_tip;
|
||||
self._check_changeset_is_applied(&changeset);
|
||||
Ok(changeset)
|
||||
}
|
||||
|
||||
@ -465,43 +495,10 @@ impl LocalChain {
|
||||
|
||||
/// Apply the given `changeset`.
|
||||
pub fn apply_changeset(&mut self, changeset: &ChangeSet) -> Result<(), MissingGenesisError> {
|
||||
if let Some(start_height) = changeset.keys().next().cloned() {
|
||||
// changes after point of agreement
|
||||
let mut extension = BTreeMap::default();
|
||||
// point of agreement
|
||||
let mut base: Option<CheckPoint> = None;
|
||||
|
||||
for cp in self.iter_checkpoints() {
|
||||
if cp.height() >= start_height {
|
||||
extension.insert(cp.height(), cp.hash());
|
||||
} else {
|
||||
base = Some(cp);
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
for (&height, &hash) in changeset {
|
||||
match hash {
|
||||
Some(hash) => {
|
||||
extension.insert(height, hash);
|
||||
}
|
||||
None => {
|
||||
extension.remove(&height);
|
||||
}
|
||||
};
|
||||
}
|
||||
|
||||
let new_tip = match base {
|
||||
Some(base) => base
|
||||
.extend(extension.into_iter().map(BlockId::from))
|
||||
.expect("extension is strictly greater than base"),
|
||||
None => LocalChain::from_blocks(extension)?.tip(),
|
||||
};
|
||||
self.tip = new_tip;
|
||||
|
||||
debug_assert!(self._check_changeset_is_applied(changeset));
|
||||
}
|
||||
|
||||
let old_tip = self.tip.clone();
|
||||
let new_tip = old_tip.apply_changeset(changeset)?;
|
||||
self.tip = new_tip;
|
||||
debug_assert!(self._check_changeset_is_applied(changeset));
|
||||
Ok(())
|
||||
}
|
||||
|
||||
@ -731,10 +728,10 @@ impl std::error::Error for ApplyHeaderError {}
|
||||
fn merge_chains(
|
||||
original_tip: CheckPoint,
|
||||
update_tip: CheckPoint,
|
||||
) -> Result<(ChangeSet, bool), CannotConnectError> {
|
||||
) -> Result<(CheckPoint, ChangeSet), CannotConnectError> {
|
||||
let mut changeset = ChangeSet::default();
|
||||
let mut orig = original_tip.into_iter();
|
||||
let mut update = update_tip.into_iter();
|
||||
let mut orig = original_tip.iter();
|
||||
let mut update = update_tip.iter();
|
||||
let mut curr_orig = None;
|
||||
let mut curr_update = None;
|
||||
let mut prev_orig: Option<CheckPoint> = None;
|
||||
@ -743,10 +740,11 @@ fn merge_chains(
|
||||
let mut prev_orig_was_invalidated = false;
|
||||
let mut potentially_invalidated_heights = vec![];
|
||||
|
||||
// Flag to set if heights are removed from original chain. If no heights are removed, and we
|
||||
// have a matching node pointer between the two chains, we can conclude that the update tip can
|
||||
// just replace the original tip.
|
||||
let mut has_removed_heights = false;
|
||||
// If we can, we want to return the update tip as the new tip because this allows checkpoints
|
||||
// in multiple locations to keep the same `Arc` pointers when they are being updated from each
|
||||
// other using this function. We can do this as long as long as the update contains every
|
||||
// block's height of the original chain.
|
||||
let mut is_update_height_superset_of_original = true;
|
||||
|
||||
// To find the difference between the new chain and the original we iterate over both of them
|
||||
// from the tip backwards in tandem. We always dealing with the highest one from either chain
|
||||
@ -773,7 +771,7 @@ fn merge_chains(
|
||||
prev_orig_was_invalidated = false;
|
||||
prev_orig = curr_orig.take();
|
||||
|
||||
has_removed_heights = true;
|
||||
is_update_height_superset_of_original = false;
|
||||
|
||||
// OPTIMIZATION: we have run out of update blocks so we don't need to continue
|
||||
// iterating because there's no possibility of adding anything to changeset.
|
||||
@ -800,7 +798,17 @@ fn merge_chains(
|
||||
// OPTIMIZATION 2 -- if we have the same underlying pointer at this point, we
|
||||
// can guarantee that no older blocks are introduced.
|
||||
if Arc::as_ptr(&o.0) == Arc::as_ptr(&u.0) {
|
||||
return Ok((changeset, !has_removed_heights));
|
||||
if is_update_height_superset_of_original {
|
||||
return Ok((update_tip, changeset));
|
||||
} else {
|
||||
let new_tip =
|
||||
original_tip.apply_changeset(&changeset).map_err(|_| {
|
||||
CannotConnectError {
|
||||
try_include_height: 0,
|
||||
}
|
||||
})?;
|
||||
return Ok((new_tip, changeset));
|
||||
}
|
||||
}
|
||||
} else {
|
||||
// We have an invalidation height so we set the height to the updated hash and
|
||||
@ -834,5 +842,10 @@ fn merge_chains(
|
||||
}
|
||||
}
|
||||
|
||||
Ok((changeset, false))
|
||||
let new_tip = original_tip
|
||||
.apply_changeset(&changeset)
|
||||
.map_err(|_| CannotConnectError {
|
||||
try_include_height: 0,
|
||||
})?;
|
||||
Ok((new_tip, changeset))
|
||||
}
|
||||
|
Loading…
x
Reference in New Issue
Block a user