reth_trie_sparse/arena/
nodes.rs

1use super::{
2    branch_child_idx::{BranchChildIdx, BranchChildIter},
3    ArenaSparseSubtrie, Index, NodeArena,
4};
5use alloc::{boxed::Box, vec::Vec};
6use alloy_primitives::{keccak256, B256};
7use alloy_trie::{BranchNodeCompact, TrieMask};
8use reth_trie_common::{BranchNodeMasks, Nibbles, ProofTrieNodeV2, RlpNode, TrieNodeV2};
9use smallvec::SmallVec;
10use strum::AsRefStr;
11
12use crate::TrieNodeEpoch;
13
14/// Tracks whether a node's RLP encoding is cached or needs recomputation.
15#[derive(Debug, Clone, PartialEq, Eq)]
16pub(super) enum ArenaSparseNodeState {
17    /// The node has been revealed but its RLP encoding is not cached.
18    Revealed,
19    /// The node has a cached RLP encoding that is still valid.
20    Cached {
21        /// The cached RLP-encoded representation of the node.
22        rlp_node: RlpNode,
23        /// The newest tracked modification epoch for this node or its descendants.
24        epoch: TrieNodeEpoch,
25    },
26    /// The node has been modified and its RLP encoding needs recomputation.
27    Dirty,
28}
29
30impl ArenaSparseNodeState {
31    /// Converts into a [`Self::Dirty`] if it's not already.
32    pub(super) const fn to_dirty(&self) -> Self {
33        Self::Dirty
34    }
35
36    /// Returns the [`RlpNode`] cached on the state, if there is one.
37    pub(super) const fn cached_rlp_node(&self) -> Option<&RlpNode> {
38        match self {
39            Self::Cached { rlp_node, .. } => Some(rlp_node),
40            _ => None,
41        }
42    }
43
44    /// Returns the cached epoch, if this node is cached.
45    pub(super) const fn cached_epoch(&self) -> Option<TrieNodeEpoch> {
46        match self {
47            Self::Cached { epoch, .. } => Some(*epoch),
48            _ => None,
49        }
50    }
51}
52
53/// Represents a reference from a branch node to one of its children.
54#[derive(Debug, Clone, PartialEq, Eq)]
55pub(super) enum ArenaSparseNodeBranchChild {
56    /// The child node has been revealed and is present in the arena.
57    Revealed(Index),
58    /// The child node has not been revealed; only its RLP-encoded node is known.
59    Blinded(RlpNode),
60}
61
62impl ArenaSparseNodeBranchChild {
63    /// Returns `true` if this child reference is blinded (not yet revealed in the arena).
64    pub(super) const fn is_blinded(&self) -> bool {
65        matches!(self, Self::Blinded(_))
66    }
67}
68
69/// The branch-specific data stored in an [`ArenaSparseNode::Branch`].
70#[derive(Debug, Clone)]
71pub(super) struct ArenaSparseNodeBranch {
72    /// Cached or dirty state of this node.
73    pub(super) state: ArenaSparseNodeState,
74    /// Revealed or blinded children, packed densely. The `state_mask` tracks which
75    /// nibble positions have entries in this `SmallVec`.
76    pub(super) children: SmallVec<[ArenaSparseNodeBranchChild; 4]>,
77    /// Bitmask indicating which of the 16 child slots are occupied (have an entry
78    /// in `children`).
79    pub(super) state_mask: TrieMask,
80    /// The short key (extension key) for this branch. When non-empty, the node's path is the
81    /// path of the parent extension node with this short key.
82    pub(super) short_key: Nibbles,
83    /// Tree mask and hash mask for database persistence (`TrieUpdates`).
84    pub(super) branch_masks: BranchNodeMasks,
85}
86
87impl ArenaSparseNodeBranch {
88    /// Unsets the bit for `nibble` in `state_mask`, `hash_mask`, and `tree_mask`.
89    pub(super) const fn unset_child_bit(&mut self, nibble: u8) {
90        self.state_mask.unset_bit(nibble);
91    }
92
93    /// Inserts a child at `nibble`, updating the state mask, children array, and marking the
94    /// branch as dirty.
95    pub(super) fn set_child(&mut self, nibble: u8, child: ArenaSparseNodeBranchChild) {
96        let insert_pos = BranchChildIdx::insertion_point(self.state_mask, nibble);
97        self.state_mask.set_bit(nibble);
98        self.children.insert(insert_pos.get(), child);
99        self.state = ArenaSparseNodeState::Dirty;
100    }
101
102    /// Removes the child at `nibble`, updating the state mask, children array, and marking the
103    /// branch as dirty.
104    ///
105    /// # Panics
106    ///
107    /// Panics if `nibble` is not set in the state mask.
108    pub(super) fn remove_child(&mut self, nibble: u8) {
109        let child_idx =
110            BranchChildIdx::new(self.state_mask, nibble).expect("nibble not found in state_mask");
111        self.children.remove(child_idx.get());
112        self.unset_child_bit(nibble);
113        self.state = ArenaSparseNodeState::Dirty;
114    }
115
116    /// Returns a reference to the sibling child in a branch with exactly 2 children.
117    ///
118    /// # Panics
119    ///
120    /// Panics (debug) if the branch does not have exactly 2 children, or if `nibble` is not set.
121    pub(super) fn sibling_child(&self, nibble: u8) -> &ArenaSparseNodeBranchChild {
122        debug_assert_eq!(
123            self.state_mask.count_bits(),
124            2,
125            "sibling_child requires exactly 2 children"
126        );
127        let child_idx =
128            BranchChildIdx::new(self.state_mask, nibble).expect("nibble not found in state_mask");
129        // With exactly 2 children the dense array has indices 0 and 1.
130        &self.children[1 - child_idx.get()]
131    }
132
133    /// Iterates over `(nibble, &ArenaSparseNodeBranchChild)` pairs in nibble order.
134    pub(super) fn child_iter(
135        &self,
136    ) -> impl Iterator<Item = (u8, &ArenaSparseNodeBranchChild)> + '_ {
137        BranchChildIter::new(self.state_mask).map(|(idx, nibble)| (nibble, &self.children[idx]))
138    }
139
140    /// Returns a [`BranchNodeCompact`] from this branch's masks and children hashes.
141    pub(super) fn branch_node_compact(&self, arena: &NodeArena) -> BranchNodeCompact {
142        let mut hashes = Vec::new();
143        for (nibble, child) in self.child_iter() {
144            if self.branch_masks.hash_mask.is_bit_set(nibble) {
145                let hash = match child {
146                    ArenaSparseNodeBranchChild::Blinded(rlp_node) => {
147                        rlp_node.as_hash().expect("blinded child must be a hash")
148                    }
149                    ArenaSparseNodeBranchChild::Revealed(child_idx) => {
150                        arena[*child_idx].cached_hash()
151                    }
152                };
153                hashes.push(hash);
154            }
155        }
156        BranchNodeCompact::new(
157            self.state_mask,
158            self.branch_masks.tree_mask,
159            self.branch_masks.hash_mask,
160            hashes,
161            None,
162        )
163    }
164}
165
166/// A node in the arena-based sparse trie.
167#[derive(Debug, Clone, AsRefStr)]
168pub(super) enum ArenaSparseNode {
169    /// Indicates a trie with no nodes.
170    EmptyRoot {
171        /// Cached or dirty state of this node. Its cached RLP is always the empty root hash.
172        state: ArenaSparseNodeState,
173    },
174    /// A branch node with up to 16 children.
175    Branch(ArenaSparseNodeBranch),
176    /// A leaf node containing a value.
177    Leaf {
178        /// Cached or dirty state of this node.
179        state: ArenaSparseNodeState,
180        /// The RLP-encoded leaf value.
181        value: Vec<u8>,
182        /// The remaining key suffix for this leaf.
183        key: Nibbles,
184    },
185    /// A subtrie that can be taken for parallel processing.
186    Subtrie(Box<ArenaSparseSubtrie>),
187    /// Placeholder for a subtrie that has been temporarily taken for parallel operations.
188    TakenSubtrie,
189}
190
191impl ArenaSparseNode {
192    /// Returns the state of an `EmptyRoot`, `Branch`, `Leaf`, or `Subtrie` root node, or `None` for
193    /// other types.
194    pub(super) fn state_ref(&self) -> Option<&ArenaSparseNodeState> {
195        match self {
196            Self::EmptyRoot { state } | Self::Leaf { state, .. } => Some(state),
197            Self::Branch(b) => Some(&b.state),
198            Self::Subtrie(s) => s.arena[s.root].state_ref(),
199            _ => None,
200        }
201    }
202
203    /// Returns a mutable reference to the state of an `EmptyRoot`, `Branch`, or `Leaf` node.
204    ///
205    /// # Panics
206    ///
207    /// Panics if called on a non-EmptyRoot/Branch/Leaf node.
208    pub(super) fn state_mut(&mut self) -> &mut ArenaSparseNodeState {
209        match self {
210            Self::EmptyRoot { state } | Self::Leaf { state, .. } => state,
211            Self::Branch(b) => &mut b.state,
212            _ => panic!("state_mut called on non-EmptyRoot/Branch/Leaf node"),
213        }
214    }
215
216    /// Returns `true` if this node's RLP encoding is cached.
217    pub(super) fn is_cached(&self) -> bool {
218        self.state_ref().is_some_and(|s| matches!(s, ArenaSparseNodeState::Cached { .. }))
219    }
220
221    /// Returns the short key of the branch or leaf, or None.
222    pub(super) const fn short_key(&self) -> Option<&Nibbles> {
223        match self {
224            Self::Branch(b) => Some(&b.short_key),
225            Self::Leaf { key, .. } => Some(key),
226            _ => None,
227        }
228    }
229
230    /// Returns a reference to the branch data.
231    ///
232    /// # Panics
233    ///
234    /// Panics if this is not a `Branch` node.
235    pub(super) fn branch_ref(&self) -> &ArenaSparseNodeBranch {
236        match self {
237            Self::Branch(b) => b,
238            _ => panic!("branch_ref called on non-Branch node {self:?}"),
239        }
240    }
241
242    /// Returns a mutable reference to the branch data.
243    ///
244    /// # Panics
245    ///
246    /// Panics if this is not a `Branch` node.
247    pub(super) fn branch_mut(&mut self) -> &mut ArenaSparseNodeBranch {
248        match self {
249            Self::Branch(b) => b,
250            _ => panic!("branch_mut called on non-Branch node {self:?}"),
251        }
252    }
253
254    /// Returns a reference to the subtrie if this is a `Subtrie` node, or `None`.
255    #[cfg(debug_assertions)]
256    pub(super) const fn as_subtrie(&self) -> Option<&ArenaSparseSubtrie> {
257        match self {
258            Self::Subtrie(s) => Some(s),
259            _ => None,
260        }
261    }
262
263    /// Returns the branch data if this node (or its subtrie root) is a branch, or `None`.
264    pub(super) fn as_branch(&self) -> Option<&ArenaSparseNodeBranch> {
265        match self {
266            Self::Branch(b) => Some(b),
267            Self::Subtrie(s) => s.arena[s.root].as_branch(),
268            _ => None,
269        }
270    }
271
272    /// Returns `true` if this node should contribute a set bit in its parent's `hash_mask`.
273    ///
274    /// That is, if the node is a branch with no short key (no extension) whose cached
275    /// RLP is a hash (>= 32 bytes). Small branches whose RLP is embedded don't get a
276    /// `hash_mask` bit.
277    pub(super) fn hash_mask_bit(&self) -> bool {
278        self.as_branch().is_some_and(|b| {
279            b.short_key.is_empty() &&
280                b.state.cached_rlp_node().expect("branch's RlpNode must be cached").is_hash()
281        })
282    }
283
284    /// Returns `true` if this node should contribute a set bit in its parent's `tree_mask`.
285    ///
286    /// That is, if the node is a branch with any non-empty `branch_masks`.
287    pub(super) fn tree_mask_bit(&self) -> bool {
288        self.as_branch().is_some_and(|b| !b.branch_masks.is_empty())
289    }
290
291    /// Returns the cached hash of this node. Panics if the node's state is not `Cached`.
292    ///
293    /// If the `RlpNode` is already a hash (>= 32 bytes encoded), returns it directly.
294    /// Otherwise keccak-hashes the RLP encoding to produce the hash. This handles the
295    /// case where a branch's RLP is small enough to be embedded rather than hashed.
296    pub(super) fn cached_hash(&self) -> B256 {
297        let rlp_node = match self {
298            Self::Branch(ArenaSparseNodeBranch { state, .. }) | Self::Leaf { state, .. } => state
299                .cached_rlp_node()
300                .expect("cached_hash called on non-Cached branch or leaf: {self:?}"),
301            Self::Subtrie(s) => return s.arena[s.root].cached_hash(),
302            _ => panic!("cached_hash called on {self:?}"),
303        };
304        rlp_node.as_hash().unwrap_or_else(|| keccak256(rlp_node.as_slice()))
305    }
306}
307
308impl ArenaSparseNode {
309    /// Converts a [`ProofTrieNodeV2`] into an [`ArenaSparseNode`].
310    ///
311    /// # Panics
312    ///
313    /// Panics if the node is an `Extension`, which should have been merged into a branch
314    /// by [`TrieNodeV2`].
315    pub(super) fn from_proof_node(proof_node: ProofTrieNodeV2) -> Self {
316        let ProofTrieNodeV2 { node, masks, .. } = proof_node;
317        match node {
318            TrieNodeV2::EmptyRoot => Self::EmptyRoot { state: ArenaSparseNodeState::Revealed },
319            TrieNodeV2::Leaf(leaf) => Self::Leaf {
320                state: ArenaSparseNodeState::Revealed,
321                key: leaf.key,
322                value: leaf.value,
323            },
324            TrieNodeV2::Branch(branch) => {
325                let children = branch.stack[..branch.state_mask.count_bits() as usize]
326                    .iter()
327                    .map(|rlp| ArenaSparseNodeBranchChild::Blinded(rlp.clone()))
328                    .collect();
329                Self::Branch(ArenaSparseNodeBranch {
330                    state: ArenaSparseNodeState::Revealed,
331                    children,
332                    state_mask: branch.state_mask,
333                    short_key: branch.key,
334                    branch_masks: masks.unwrap_or_default(),
335                })
336            }
337            TrieNodeV2::Extension(_) => {
338                panic!("Extension nodes should be merged into branches by TrieNodeV2")
339            }
340        }
341    }
342}
reth_trie_sparse/arena/nodes.rs

reth_trie_sparse/arena/
nodes.rs
