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Guard reduced tree from errors

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This commit is contained in:
Paul Hauner 2019-08-27 18:09:31 +10:00
parent ed6c39e25a
commit 6bb3a65189
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GPG Key ID: 5E2CFF9B75FA63DF
1 changed files with 57 additions and 50 deletions
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107
eth2/lmd_ghost/src/reduced_tree.rs
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@ -311,51 +311,53 @@ where
/// become redundant and removed from the reduced tree.
fn remove_latest_message(&mut self, validator_index: usize) -> Result<()> {
if let Some(vote) = *self.latest_votes.get(validator_index) {
self.get_mut_node(vote.hash)?.remove_voter(validator_index);
let node = self.get_node(vote.hash)?.clone();
if self.nodes.contains_key(&vote.hash) {
self.get_mut_node(vote.hash)?.remove_voter(validator_index);
let node = self.get_node(vote.hash)?.clone();
if let Some(parent_hash) = node.parent_hash {
if node.has_votes() || node.children.len() > 1 {
// A node with votes or more than one child is never removed.
} else if node.children.len() == 1 {
// A node which has only one child may be removed.
//
// Load the child of the node and set it's parent to be the parent of this
// node (viz., graft the node's child to the node's parent)
let child = self.get_mut_node(node.children[0])?;
child.parent_hash = node.parent_hash;
if let Some(parent_hash) = node.parent_hash {
if node.has_votes() || node.children.len() > 1 {
// A node with votes or more than one child is never removed.
} else if node.children.len() == 1 {
// A node which has only one child may be removed.
//
// Load the child of the node and set it's parent to be the parent of this
// node (viz., graft the node's child to the node's parent)
let child = self.get_mut_node(node.children[0])?;
child.parent_hash = node.parent_hash;
// Graft the parent of this node to it's child.
if let Some(parent_hash) = node.parent_hash {
let parent = self.get_mut_node(parent_hash)?;
parent.replace_child(node.block_hash, node.children[0])?;
// Graft the parent of this node to it's child.
if let Some(parent_hash) = node.parent_hash {
let parent = self.get_mut_node(parent_hash)?;
parent.replace_child(node.block_hash, node.children[0])?;
}
self.nodes.remove(&vote.hash);
} else if node.children.is_empty() {
// Remove the to-be-deleted node from it's parent.
if let Some(parent_hash) = node.parent_hash {
self.get_mut_node(parent_hash)?
.remove_child(node.block_hash)?;
}
self.nodes.remove(&vote.hash);
// A node which has no children may be deleted and potentially it's parent
// too.
self.maybe_delete_node(parent_hash)?;
} else {
// It is impossible for a node to have a number of children that is not 0, 1 or
// greater than one.
//
// This code is strictly unnecessary, however we keep it for readability.
unreachable!();
}
self.nodes.remove(&vote.hash);
} else if node.children.is_empty() {
// Remove the to-be-deleted node from it's parent.
if let Some(parent_hash) = node.parent_hash {
self.get_mut_node(parent_hash)?
.remove_child(node.block_hash)?;
}
self.nodes.remove(&vote.hash);
// A node which has no children may be deleted and potentially it's parent
// too.
self.maybe_delete_node(parent_hash)?;
} else {
// It is impossible for a node to have a number of children that is not 0, 1 or
// greater than one.
//
// This code is strictly unnecessary, however we keep it for readability.
unreachable!();
// A node without a parent is the genesis/finalized node and should never be removed.
}
} else {
// A node without a parent is the genesis/finalized node and should never be removed.
}
self.latest_votes.insert(validator_index, Some(vote));
self.latest_votes.insert(validator_index, Some(vote));
}
}
Ok(())
@ -370,25 +372,30 @@ where
/// - it does not have any votes.
fn maybe_delete_node(&mut self, hash: Hash256) -> Result<()> {
let should_delete = {
let node = self.get_node(hash)?.clone();
if let Ok(node) = self.get_node(hash) {
let node = node.clone();
if let Some(parent_hash) = node.parent_hash {
if (node.children.len() == 1) && !node.has_votes() {
let child_hash = node.children[0];
if let Some(parent_hash) = node.parent_hash {
if (node.children.len() == 1) && !node.has_votes() {
let child_hash = node.children[0];
// Graft the single descendant `node` to the `parent` of node.
self.get_mut_node(child_hash)?.parent_hash = Some(parent_hash);
// Graft the single descendant `node` to the `parent` of node.
self.get_mut_node(child_hash)?.parent_hash = Some(parent_hash);
// Detach `node` from `parent`, replacing it with `child`.
self.get_mut_node(parent_hash)?
.replace_child(hash, child_hash)?;
// Detach `node` from `parent`, replacing it with `child`.
self.get_mut_node(parent_hash)?
.replace_child(hash, child_hash)?;
true
true
} else {
false
}
} else {
// A node without a parent is the genesis node and should not be deleted.
false
}
} else {
// A node without a parent is the genesis node and should not be deleted.
// No need to delete a node that does not exist.
false
}
};