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Merge bitcoindevkit/bdk#1034: Implement linked-list LocalChain and update chain-src crates/examples

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b206a985cf fix: Even more refactoring to code and documentation (志宇)
bea8e5aff4 fix: `TxGraph::missing_blocks` logic (志宇)
db15e03bdc fix: improve more docs and more refactoring (志宇)
95312d4d05 fix: docs and some minor refactoring (志宇)
8bf7a997f7 Refactor `debug_assertions` checks for `LocalChain` (志宇)
315e7e0b4b fix: rm duplicate `bdk_tmp_plan` module (志宇)
af705da1a8 Add exclusion of example cli `*.db` files in `.gitignore` (志宇)
eabeb6ccb1 Implement linked-list `LocalChain` and update chain-src crates/examples (志宇)

Pull request description:

  Fixes #997
  Replaces #1002

  ### Description

  This PR changes the `LocalChain` implementation to have blocks stored as a linked-list. This allows the data-src thread to hold a shared ref to a single checkpoint and have access to the whole history of checkpoints without cloning or keeping a lock on `LocalChain`.

  The APIs of `bdk::Wallet`, `esplora` and `electrum` are also updated to reflect these changes. Note that the `esplora` crate is rewritten to anchor txs in the confirmation block (using the esplora API's tx status block_hash). This guarantees 100% consistency between anchor blocks and their transactions (instead of anchoring txs to the latest tip). `ExploraExt` now has separate methods for updating the `TxGraph` and `LocalChain`.

  A new method `TxGraph::missing_blocks` is introduced for finding "floating anchors" of a `TxGraph` update (given a chain).

  Additional changes:

  * `test_local_chain.rs` is refactored to make test cases easier to write. Additional tests are also added.
  * Examples are updated.
  * Exclude example-cli `*.db` files in `.gitignore`.
  * Rm duplicate `bdk_tmp_plan` module.

  ### Notes to the reviewers

  This is the smallest possible division of #1002 without resulting in PRs that do not compile. Since we have changed the API of `LocalChain`, we also need to change `esplora`, `electrum` crates and examples alongside `bdk::Wallet`.

  ### Changelog notice

  * Implement linked-list `LocalChain`. This allows the data-src thread to hold a shared ref to a single checkpoint and have access to the whole history of checkpoints without cloning or keeping a lock on `LocalChain`.
  * Rewrote `esplora` chain-src crate to anchor txs to their confirmation blocks (using esplora API's tx-status `block_hash`).

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [x] I've added tests for the new feature
  * [x] I've added docs for the new feature

ACKs for top commit:
  LLFourn:
    ACK b206a985cf

Tree-SHA512: a513eecb4f1aae6a5c06a69854e4492961424312a75a42d74377d363b364e3d52415bc81b4aa3fbc3f369ded19bddd07ab895130ebba288e8a43e9d6186e9fcc
This commit is contained in:
志宇
2023-08-03 16:04:30 +08:00
parent 933056706c b206a985cf
commit d73669e8fa
26 changed files with 1723 additions and 1984 deletions
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38
crates/chain/src/keychain.rs
View File

@@ -11,10 +11,7 @@
//! [`SpkTxOutIndex`]: crate::SpkTxOutIndex
use crate::{
collections::BTreeMap,
indexed_tx_graph::IndexedAdditions,
local_chain::{self, LocalChain},
tx_graph::TxGraph,
collections::BTreeMap, indexed_tx_graph::IndexedAdditions, local_chain, tx_graph::TxGraph,
Anchor, Append,
};
@@ -85,24 +82,33 @@ impl<K> AsRef<BTreeMap<K, u32>> for DerivationAdditions<K> {
}
}
/// A structure to update [`KeychainTxOutIndex`], [`TxGraph`] and [`LocalChain`]
/// atomically.
#[derive(Debug, Clone, PartialEq)]
/// A structure to update [`KeychainTxOutIndex`], [`TxGraph`] and [`LocalChain`] atomically.
///
/// [`LocalChain`]: local_chain::LocalChain
#[derive(Debug, Clone)]
pub struct LocalUpdate<K, A> {
/// Last active derivation index per keychain (`K`).
pub keychain: BTreeMap<K, u32>,
/// Contains the last active derivation indices per keychain (`K`), which is used to update the
/// [`KeychainTxOutIndex`].
pub last_active_indices: BTreeMap<K, u32>,
/// Update for the [`TxGraph`].
pub graph: TxGraph<A>,
/// Update for the [`LocalChain`].
pub chain: LocalChain,
///
/// [`LocalChain`]: local_chain::LocalChain
pub chain: local_chain::Update,
}
impl<K, A> Default for LocalUpdate<K, A> {
fn default() -> Self {
impl<K, A> LocalUpdate<K, A> {
/// Construct a [`LocalUpdate`] with a given [`local_chain::Update`].
///
/// [`CheckPoint`]: local_chain::CheckPoint
pub fn new(chain_update: local_chain::Update) -> Self {
Self {
keychain: Default::default(),
graph: Default::default(),
chain: Default::default(),
last_active_indices: BTreeMap::new(),
graph: TxGraph::default(),
chain: chain_update,
}
}
}
@@ -122,6 +128,8 @@ impl<K, A> Default for LocalUpdate<K, A> {
)]
pub struct LocalChangeSet<K, A> {
/// Changes to the [`LocalChain`].
///
/// [`LocalChain`]: local_chain::LocalChain
pub chain_changeset: local_chain::ChangeSet,
/// Additions to [`IndexedTxGraph`].

650
crates/chain/src/local_chain.rs
View File

@@ -2,15 +2,170 @@
use core::convert::Infallible;
use alloc::collections::BTreeMap;
use crate::collections::BTreeMap;
use crate::{BlockId, ChainOracle};
use alloc::sync::Arc;
use bitcoin::BlockHash;
use crate::{BlockId, ChainOracle};
/// A structure that represents changes to [`LocalChain`].
///
/// The key represents the block height, and the value either represents added a new [`CheckPoint`]
/// (if [`Some`]), or removing a [`CheckPoint`] (if [`None`]).
pub type ChangeSet = BTreeMap<u32, Option<BlockHash>>;
/// A [`LocalChain`] checkpoint is used to find the agreement point between two chains and as a
/// transaction anchor.
///
/// Each checkpoint contains the height and hash of a block ([`BlockId`]).
///
/// Internaly, checkpoints are nodes of a reference-counted linked-list. This allows the caller to
/// cheaply clone a [`CheckPoint`] without copying the whole list and to view the entire chain
/// without holding a lock on [`LocalChain`].
#[derive(Debug, Clone)]
pub struct CheckPoint(Arc<CPInner>);
/// The internal contents of [`CheckPoint`].
#[derive(Debug, Clone)]
struct CPInner {
/// Block id (hash and height).
block: BlockId,
/// Previous checkpoint (if any).
prev: Option<Arc<CPInner>>,
}
impl CheckPoint {
/// Construct a new base block at the front of a linked list.
pub fn new(block: BlockId) -> Self {
Self(Arc::new(CPInner { block, prev: None }))
}
/// Puts another checkpoint onto the linked list representing the blockchain.
///
/// Returns an `Err(self)` if the block you are pushing on is not at a greater height that the one you
/// are pushing on to.
pub fn push(self, block: BlockId) -> Result<Self, Self> {
if self.height() < block.height {
Ok(Self(Arc::new(CPInner {
block,
prev: Some(self.0),
})))
} else {
Err(self)
}
}
/// Extends the checkpoint linked list by a iterator of block ids.
///
/// Returns an `Err(self)` if there is block which does not have a greater height than the
/// previous one.
pub fn extend(self, blocks: impl IntoIterator<Item = BlockId>) -> Result<Self, Self> {
let mut curr = self.clone();
for block in blocks {
curr = curr.push(block).map_err(|_| self.clone())?;
}
Ok(curr)
}
/// Get the [`BlockId`] of the checkpoint.
pub fn block_id(&self) -> BlockId {
self.0.block
}
/// Get the height of the checkpoint.
pub fn height(&self) -> u32 {
self.0.block.height
}
/// Get the block hash of the checkpoint.
pub fn hash(&self) -> BlockHash {
self.0.block.hash
}
/// Get the previous checkpoint in the chain
pub fn prev(&self) -> Option<CheckPoint> {
self.0.prev.clone().map(CheckPoint)
}
/// Iterate from this checkpoint in descending height.
pub fn iter(&self) -> CheckPointIter {
self.clone().into_iter()
}
}
/// A structure that iterates over checkpoints backwards.
pub struct CheckPointIter {
current: Option<Arc<CPInner>>,
}
impl Iterator for CheckPointIter {
type Item = CheckPoint;
fn next(&mut self) -> Option<Self::Item> {
let current = self.current.clone()?;
self.current = current.prev.clone();
Some(CheckPoint(current))
}
}
impl IntoIterator for CheckPoint {
type Item = CheckPoint;
type IntoIter = CheckPointIter;
fn into_iter(self) -> Self::IntoIter {
CheckPointIter {
current: Some(self.0),
}
}
}
/// A struct to update [`LocalChain`].
///
/// This is used as input for [`LocalChain::apply_update`]. It contains the update's chain `tip` and
/// a flag `introduce_older_blocks` which signals whether this update intends to introduce missing
/// blocks to the original chain.
///
/// Block-by-block syncing mechanisms would typically create updates that builds upon the previous
/// tip. In this case, `introduce_older_blocks` would be `false`.
///
/// Script-pubkey based syncing mechanisms may not introduce transactions in a chronological order
/// so some updates require introducing older blocks (to anchor older transactions). For
/// script-pubkey based syncing, `introduce_older_blocks` would typically be `true`.
#[derive(Debug, Clone)]
pub struct Update {
/// The update chain's new tip.
pub tip: CheckPoint,
/// Whether the update allows for introducing older blocks.
///
/// Refer to [struct-level documentation] for more.
///
/// [struct-level documentation]: Update
pub introduce_older_blocks: bool,
}
/// This is a local implementation of [`ChainOracle`].
#[derive(Debug, Default, Clone, PartialEq, Eq, PartialOrd, Ord)]
#[derive(Debug, Default, Clone)]
pub struct LocalChain {
blocks: BTreeMap<u32, BlockHash>,
tip: Option<CheckPoint>,
index: BTreeMap<u32, BlockHash>,
}
impl PartialEq for LocalChain {
fn eq(&self, other: &Self) -> bool {
self.index == other.index
}
}
impl From<LocalChain> for BTreeMap<u32, BlockHash> {
fn from(value: LocalChain) -> Self {
value.index
}
}
impl From<BTreeMap<u32, BlockHash>> for LocalChain {
fn from(value: BTreeMap<u32, BlockHash>) -> Self {
Self::from_blocks(value)
}
}
impl ChainOracle for LocalChain {
@@ -19,215 +174,247 @@ impl ChainOracle for LocalChain {
fn is_block_in_chain(
&self,
block: BlockId,
static_block: BlockId,
chain_tip: BlockId,
) -> Result<Option<bool>, Self::Error> {
if block.height > static_block.height {
if block.height > chain_tip.height {
return Ok(None);
}
Ok(
match (
self.blocks.get(&block.height),
self.blocks.get(&static_block.height),
self.index.get(&block.height),
self.index.get(&chain_tip.height),
) {
(Some(&hash), Some(&static_hash)) => {
Some(hash == block.hash && static_hash == static_block.hash)
}
(Some(cp), Some(tip_cp)) => Some(*cp == block.hash && *tip_cp == chain_tip.hash),
_ => None,
},
)
}
fn get_chain_tip(&self) -> Result<Option<BlockId>, Self::Error> {
Ok(self.tip())
}
}
impl AsRef<BTreeMap<u32, BlockHash>> for LocalChain {
fn as_ref(&self) -> &BTreeMap<u32, BlockHash> {
&self.blocks
}
}
impl From<LocalChain> for BTreeMap<u32, BlockHash> {
fn from(value: LocalChain) -> Self {
value.blocks
}
}
impl From<BTreeMap<u32, BlockHash>> for LocalChain {
fn from(value: BTreeMap<u32, BlockHash>) -> Self {
Self { blocks: value }
Ok(self.tip.as_ref().map(|tip| tip.block_id()))
}
}
impl LocalChain {
/// Contruct a [`LocalChain`] from a list of [`BlockId`]s.
pub fn from_blocks<B>(blocks: B) -> Self
where
B: IntoIterator<Item = BlockId>,
{
Self {
blocks: blocks.into_iter().map(|b| (b.height, b.hash)).collect(),
}
/// Construct a [`LocalChain`] from an initial `changeset`.
pub fn from_changeset(changeset: ChangeSet) -> Self {
let mut chain = Self::default();
chain.apply_changeset(&changeset);
debug_assert!(chain._check_index_is_consistent_with_tip());
debug_assert!(chain._check_changeset_is_applied(&changeset));
chain
}
/// Get a reference to a map of block height to hash.
pub fn blocks(&self) -> &BTreeMap<u32, BlockHash> {
&self.blocks
}
/// Get the chain tip.
pub fn tip(&self) -> Option<BlockId> {
self.blocks
.iter()
.last()
.map(|(&height, &hash)| BlockId { height, hash })
}
/// This is like the sparsechain's logic, expect we must guarantee that all invalidated heights
/// are to be re-filled.
pub fn determine_changeset(&self, update: &Self) -> Result<ChangeSet, UpdateNotConnectedError> {
let update = update.as_ref();
let update_tip = match update.keys().last().cloned() {
Some(tip) => tip,
None => return Ok(ChangeSet::default()),
/// Construct a [`LocalChain`] from a given `checkpoint` tip.
pub fn from_tip(tip: CheckPoint) -> Self {
let mut chain = Self {
tip: Some(tip),
..Default::default()
};
chain.reindex(0);
debug_assert!(chain._check_index_is_consistent_with_tip());
chain
}
// this is the latest height where both the update and local chain has the same block hash
let agreement_height = update
.iter()
.rev()
.find(|&(u_height, u_hash)| self.blocks.get(u_height) == Some(u_hash))
.map(|(&height, _)| height);
/// Constructs a [`LocalChain`] from a [`BTreeMap`] of height to [`BlockHash`].
///
/// The [`BTreeMap`] enforces the height order. However, the caller must ensure the blocks are
/// all of the same chain.
pub fn from_blocks(blocks: BTreeMap<u32, BlockHash>) -> Self {
let mut tip: Option<CheckPoint> = None;
// the lower bound of the range to invalidate
let invalidate_lb = match agreement_height {
Some(height) if height == update_tip => u32::MAX,
Some(height) => height + 1,
None => 0,
};
// the first block's height to invalidate in the local chain
let invalidate_from_height = self.blocks.range(invalidate_lb..).next().map(|(&h, _)| h);
// the first block of height to invalidate (if any) should be represented in the update
if let Some(first_invalid_height) = invalidate_from_height {
if !update.contains_key(&first_invalid_height) {
return Err(UpdateNotConnectedError(first_invalid_height));
}
}
let mut changeset: BTreeMap<u32, Option<BlockHash>> = match invalidate_from_height {
Some(first_invalid_height) => {
// the first block of height to invalidate should be represented in the update
if !update.contains_key(&first_invalid_height) {
return Err(UpdateNotConnectedError(first_invalid_height));
for block in &blocks {
match tip {
Some(curr) => {
tip = Some(
curr.push(BlockId::from(block))
.expect("BTreeMap is ordered"),
)
}
self.blocks
.range(first_invalid_height..)
.map(|(height, _)| (*height, None))
.collect()
}
None => BTreeMap::new(),
};
for (height, update_hash) in update {
let original_hash = self.blocks.get(height);
if Some(update_hash) != original_hash {
changeset.insert(*height, Some(*update_hash));
None => tip = Some(CheckPoint::new(BlockId::from(block))),
}
}
Ok(changeset)
let chain = Self { index: blocks, tip };
debug_assert!(chain._check_index_is_consistent_with_tip());
chain
}
/// Applies the given `changeset`.
pub fn apply_changeset(&mut self, changeset: ChangeSet) {
for (height, blockhash) in changeset {
match blockhash {
Some(blockhash) => self.blocks.insert(height, blockhash),
None => self.blocks.remove(&height),
/// Get the highest checkpoint.
pub fn tip(&self) -> Option<CheckPoint> {
self.tip.clone()
}
/// Returns whether the [`LocalChain`] is empty (has no checkpoints).
pub fn is_empty(&self) -> bool {
let res = self.tip.is_none();
debug_assert_eq!(res, self.index.is_empty());
res
}
/// Applies the given `update` to the chain.
///
/// The method returns [`ChangeSet`] on success. This represents the applied changes 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, an empty chain can be updated with any chain, and 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`.
///
/// Refer to [`Update`] for more about the update struct.
///
/// [module-level documentation]: crate::local_chain
pub fn apply_update(&mut self, update: Update) -> Result<ChangeSet, CannotConnectError> {
match self.tip() {
Some(original_tip) => {
let changeset = merge_chains(
original_tip,
update.tip.clone(),
update.introduce_older_blocks,
)?;
self.apply_changeset(&changeset);
// return early as `apply_changeset` already calls `check_consistency`
Ok(changeset)
}
None => {
*self = Self::from_tip(update.tip);
let changeset = self.initial_changeset();
debug_assert!(self._check_index_is_consistent_with_tip());
debug_assert!(self._check_changeset_is_applied(&changeset));
Ok(changeset)
}
}
}
/// Apply the given `changeset`.
pub fn apply_changeset(&mut self, changeset: &ChangeSet) {
if let Some(start_height) = changeset.keys().next().cloned() {
let mut extension = BTreeMap::default();
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) => Some(
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;
self.reindex(start_height);
debug_assert!(self._check_index_is_consistent_with_tip());
debug_assert!(self._check_changeset_is_applied(changeset));
}
}
/// Updates [`LocalChain`] with an update [`LocalChain`].
/// Insert a [`BlockId`].
///
/// This is equivalent to calling [`determine_changeset`] and [`apply_changeset`] in sequence.
/// # Errors
///
/// [`determine_changeset`]: Self::determine_changeset
/// [`apply_changeset`]: Self::apply_changeset
pub fn apply_update(&mut self, update: Self) -> Result<ChangeSet, UpdateNotConnectedError> {
let changeset = self.determine_changeset(&update)?;
self.apply_changeset(changeset.clone());
Ok(changeset)
}
/// Derives a [`ChangeSet`] that assumes that there are no preceding changesets.
///
/// The changeset returned will record additions of all blocks included in [`Self`].
pub fn initial_changeset(&self) -> ChangeSet {
self.blocks
.iter()
.map(|(&height, &hash)| (height, Some(hash)))
.collect()
}
/// Insert a block of [`BlockId`] into the [`LocalChain`].
///
/// # Error
///
/// If the insertion height already contains a block, and the block has a different blockhash,
/// this will result in an [`InsertBlockNotMatchingError`].
pub fn insert_block(
&mut self,
block_id: BlockId,
) -> Result<ChangeSet, InsertBlockNotMatchingError> {
let mut update = Self::from_blocks(self.tip());
if let Some(original_hash) = update.blocks.insert(block_id.height, block_id.hash) {
/// Replacing the block hash of an existing checkpoint will result in an error.
pub fn insert_block(&mut self, block_id: BlockId) -> Result<ChangeSet, InsertBlockError> {
if let Some(&original_hash) = self.index.get(&block_id.height) {
if original_hash != block_id.hash {
return Err(InsertBlockNotMatchingError {
return Err(InsertBlockError {
height: block_id.height,
original_hash,
update_hash: block_id.hash,
});
} else {
return Ok(ChangeSet::default());
}
}
Ok(self.apply_update(update).expect("should always connect"))
let mut changeset = ChangeSet::default();
changeset.insert(block_id.height, Some(block_id.hash));
self.apply_changeset(&changeset);
Ok(changeset)
}
/// Reindex the heights in the chain from (and including) `from` height
fn reindex(&mut self, from: u32) {
let _ = self.index.split_off(&from);
for cp in self.iter_checkpoints() {
if cp.height() < from {
break;
}
self.index.insert(cp.height(), cp.hash());
}
}
/// Derives an initial [`ChangeSet`], meaning that it can be applied to an empty chain to
/// recover the current chain.
pub fn initial_changeset(&self) -> ChangeSet {
self.index.iter().map(|(k, v)| (*k, Some(*v))).collect()
}
/// Iterate over checkpoints in descending height order.
pub fn iter_checkpoints(&self) -> CheckPointIter {
CheckPointIter {
current: self.tip.as_ref().map(|tip| tip.0.clone()),
}
}
/// Get a reference to the internal index mapping the height to block hash.
pub fn blocks(&self) -> &BTreeMap<u32, BlockHash> {
&self.index
}
fn _check_index_is_consistent_with_tip(&self) -> bool {
let tip_history = self
.tip
.iter()
.flat_map(CheckPoint::iter)
.map(|cp| (cp.height(), cp.hash()))
.collect::<BTreeMap<_, _>>();
self.index == tip_history
}
fn _check_changeset_is_applied(&self, changeset: &ChangeSet) -> bool {
for (height, exp_hash) in changeset {
if self.index.get(height) != exp_hash.as_ref() {
return false;
}
}
true
}
}
/// This is the return value of [`determine_changeset`] and represents changes to [`LocalChain`].
///
/// [`determine_changeset`]: LocalChain::determine_changeset
pub type ChangeSet = BTreeMap<u32, Option<BlockHash>>;
/// Represents an update failure of [`LocalChain`] due to the update not connecting to the original
/// chain.
///
/// The update cannot be applied to the chain because the chain suffix it represents did not
/// connect to the existing chain. This error case contains the checkpoint height to include so
/// that the chains can connect.
#[derive(Clone, Debug, PartialEq)]
pub struct UpdateNotConnectedError(pub u32);
impl core::fmt::Display for UpdateNotConnectedError {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(
f,
"the update cannot connect with the chain, try include block at height {}",
self.0
)
}
}
#[cfg(feature = "std")]
impl std::error::Error for UpdateNotConnectedError {}
/// Represents a failure when trying to insert a checkpoint into [`LocalChain`].
#[derive(Clone, Debug, PartialEq)]
pub struct InsertBlockNotMatchingError {
pub struct InsertBlockError {
/// The checkpoints' height.
pub height: u32,
/// Original checkpoint's block hash.
@@ -236,7 +423,7 @@ pub struct InsertBlockNotMatchingError {
pub update_hash: BlockHash,
}
impl core::fmt::Display for InsertBlockNotMatchingError {
impl core::fmt::Display for InsertBlockError {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(
f,
@@ -247,4 +434,129 @@ impl core::fmt::Display for InsertBlockNotMatchingError {
}
#[cfg(feature = "std")]
impl std::error::Error for InsertBlockNotMatchingError {}
impl std::error::Error for InsertBlockError {}
/// Occurs when an update does not have a common checkpoint with the original chain.
#[derive(Clone, Debug, PartialEq)]
pub struct CannotConnectError {
/// The suggested checkpoint to include to connect the two chains.
pub try_include_height: u32,
}
impl core::fmt::Display for CannotConnectError {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(
f,
"introduced chain cannot connect with the original chain, try include height {}",
self.try_include_height,
)
}
}
#[cfg(feature = "std")]
impl std::error::Error for CannotConnectError {}
fn merge_chains(
original_tip: CheckPoint,
update_tip: CheckPoint,
introduce_older_blocks: bool,
) -> Result<ChangeSet, CannotConnectError> {
let mut changeset = ChangeSet::default();
let mut orig = original_tip.into_iter();
let mut update = update_tip.into_iter();
let mut curr_orig = None;
let mut curr_update = None;
let mut prev_orig: Option<CheckPoint> = None;
let mut prev_update: Option<CheckPoint> = None;
let mut point_of_agreement_found = false;
let mut prev_orig_was_invalidated = false;
let mut potentially_invalidated_heights = vec![];
// 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
// first and move to the next highest. The crucial logic is applied when they have blocks at the
// same height.
loop {
if curr_orig.is_none() {
curr_orig = orig.next();
}
if curr_update.is_none() {
curr_update = update.next();
}
match (curr_orig.as_ref(), curr_update.as_ref()) {
// Update block that doesn't exist in the original chain
(o, Some(u)) if Some(u.height()) > o.map(|o| o.height()) => {
changeset.insert(u.height(), Some(u.hash()));
prev_update = curr_update.take();
}
// Original block that isn't in the update
(Some(o), u) if Some(o.height()) > u.map(|u| u.height()) => {
// this block might be gone if an earlier block gets invalidated
potentially_invalidated_heights.push(o.height());
prev_orig_was_invalidated = false;
prev_orig = curr_orig.take();
// OPTIMIZATION: we have run out of update blocks so we don't need to continue
// iterating becuase there's no possibility of adding anything to changeset.
if u.is_none() {
break;
}
}
(Some(o), Some(u)) => {
if o.hash() == u.hash() {
// We have found our point of agreement 🎉 -- we require that the previous (i.e.
// higher because we are iterating backwards) block in the original chain was
// invalidated (if it exists). This ensures that there is an unambigious point of
// connection to the original chain from the update chain (i.e. we know the
// precisely which original blocks are invalid).
if !prev_orig_was_invalidated && !point_of_agreement_found {
if let (Some(prev_orig), Some(_prev_update)) = (&prev_orig, &prev_update) {
return Err(CannotConnectError {
try_include_height: prev_orig.height(),
});
}
}
point_of_agreement_found = true;
prev_orig_was_invalidated = false;
// OPTIMIZATION 1 -- If we know that older blocks cannot be introduced without
// invalidation, we can break after finding the point of agreement.
// OPTIMIZATION 2 -- if we have the same underlying pointer at this point, we
// can guarantee that no older blocks are introduced.
if !introduce_older_blocks || Arc::as_ptr(&o.0) == Arc::as_ptr(&u.0) {
return Ok(changeset);
}
} else {
// We have an invalidation height so we set the height to the updated hash and
// also purge all the original chain block hashes above this block.
changeset.insert(u.height(), Some(u.hash()));
for invalidated_height in potentially_invalidated_heights.drain(..) {
changeset.insert(invalidated_height, None);
}
prev_orig_was_invalidated = true;
}
prev_update = curr_update.take();
prev_orig = curr_orig.take();
}
(None, None) => {
break;
}
_ => {
unreachable!("compiler cannot tell that everything has been covered")
}
}
}
// When we don't have a point of agreement you can imagine it is implicitly the
// genesis block so we need to do the final connectivity check which in this case
// just means making sure the entire original chain was invalidated.
if !prev_orig_was_invalidated && !point_of_agreement_found {
if let Some(prev_orig) = prev_orig {
return Err(CannotConnectError {
try_include_height: prev_orig.height(),
});
}
}
Ok(changeset)
}

2
crates/chain/src/tx_data_traits.rs
View File

@@ -38,6 +38,8 @@ impl ForEachTxOut for Transaction {
/// Trait that "anchors" blockchain data to a specific block of height and hash.
///
/// [`Anchor`] implementations must be [`Ord`] by the anchor block's [`BlockId`] first.
///
/// I.e. If transaction A is anchored in block B, then if block B is in the best chain, we can
/// assume that transaction A is also confirmed in the best chain. This does not necessarily mean
/// that transaction A is confirmed in block B. It could also mean transaction A is confirmed in a

67
crates/chain/src/tx_graph.rs
View File

@@ -56,8 +56,8 @@
//! ```
use crate::{
collections::*, keychain::Balance, Anchor, Append, BlockId, ChainOracle, ChainPosition,
ForEachTxOut, FullTxOut,
collections::*, keychain::Balance, local_chain::LocalChain, Anchor, Append, BlockId,
ChainOracle, ChainPosition, ForEachTxOut, FullTxOut,
};
use alloc::vec::Vec;
use bitcoin::{OutPoint, Script, Transaction, TxOut, Txid};
@@ -598,6 +598,69 @@ impl<A: Clone + Ord> TxGraph<A> {
}
impl<A: Anchor> TxGraph<A> {
/// Find missing block heights of `chain`.
///
/// This works by scanning through anchors, and seeing whether the anchor block of the anchor
/// exists in the [`LocalChain`]. The returned iterator does not output duplicate heights.
pub fn missing_heights<'a>(&'a self, chain: &'a LocalChain) -> impl Iterator<Item = u32> + 'a {
// Map of txids to skip.
//
// Usually, if a height of a tx anchor is missing from the chain, we would want to return
// this height in the iterator. The exception is when the tx is confirmed in chain. All the
// other missing-height anchors of this tx can be skipped.
//
// * Some(true) => skip all anchors of this txid
// * Some(false) => do not skip anchors of this txid
// * None => we do not know whether we can skip this txid
let mut txids_to_skip = HashMap::<Txid, bool>::new();
// Keeps track of the last height emitted so we don't double up.
let mut last_height_emitted = Option::<u32>::None;
self.anchors
.iter()
.filter(move |(_, txid)| {
let skip = *txids_to_skip.entry(*txid).or_insert_with(|| {
let tx_anchors = match self.txs.get(txid) {
Some((_, anchors, _)) => anchors,
None => return true,
};
let mut has_missing_height = false;
for anchor_block in tx_anchors.iter().map(Anchor::anchor_block) {
match chain.blocks().get(&anchor_block.height) {
None => {
has_missing_height = true;
continue;
}
Some(chain_hash) => {
if chain_hash == &anchor_block.hash {
return true;
}
}
}
}
!has_missing_height
});
#[cfg(feature = "std")]
debug_assert!({
println!("txid={} skip={}", txid, skip);
true
});
!skip
})
.filter_map(move |(a, _)| {
let anchor_block = a.anchor_block();
if Some(anchor_block.height) != last_height_emitted
&& !chain.blocks().contains_key(&anchor_block.height)
{
last_height_emitted = Some(anchor_block.height);
Some(anchor_block.height)
} else {
None
}
})
}
/// Get the position of the transaction in `chain` with tip `chain_tip`.
///
/// If the given transaction of `txid` does not exist in the chain of `chain_tip`, `None` is