287 lines
9.8 KiB
Rust
287 lines
9.8 KiB
Rust
//! Contains code that interfaces with the zcash_history crate from
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//! librustzcash.
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// TODO: remove after this module gets to be used
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#![allow(dead_code)]
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mod tests;
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use std::{collections::HashMap, convert::TryInto, io, sync::Arc};
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use crate::{
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block::{Block, ChainHistoryMmrRootHash},
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parameters::{ConsensusBranchId, Network, NetworkUpgrade},
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sapling,
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};
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/// A MMR Tree using zcash_history::Tree.
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///
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/// Currently it should not be used as a long-term data structure because it
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/// may grow without limits.
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pub struct Tree {
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network: Network,
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network_upgrade: NetworkUpgrade,
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inner: zcash_history::Tree<zcash_history::V1>,
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}
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/// An encoded tree node data.
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pub struct NodeData {
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inner: [u8; zcash_history::MAX_NODE_DATA_SIZE],
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}
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impl From<&zcash_history::NodeData> for NodeData {
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/// Convert from librustzcash.
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fn from(inner_node: &zcash_history::NodeData) -> Self {
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let mut node = NodeData {
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inner: [0; zcash_history::MAX_NODE_DATA_SIZE],
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};
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inner_node
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.write(&mut &mut node.inner[..])
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.expect("buffer has the proper size");
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node
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}
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}
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/// An encoded entry in the tree.
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/// Contains the node data and information about its position in the tree.
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pub struct Entry {
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inner: [u8; zcash_history::MAX_ENTRY_SIZE],
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}
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impl From<zcash_history::Entry<zcash_history::V1>> for Entry {
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/// Convert from librustzcash.
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fn from(inner_entry: zcash_history::Entry<zcash_history::V1>) -> Self {
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let mut entry = Entry {
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inner: [0; zcash_history::MAX_ENTRY_SIZE],
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};
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inner_entry
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.write(&mut &mut entry.inner[..])
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.expect("buffer has the proper size");
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entry
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}
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}
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impl Entry {
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/// Create a leaf Entry for the given block, its network, and the root of its
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/// Sapling note commitment tree.
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fn new_leaf(block: Arc<Block>, network: Network, sapling_root: &sapling::tree::Root) -> Self {
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let node_data = block_to_history_node(block, network, sapling_root);
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let inner_entry = zcash_history::Entry::<zcash_history::V1>::new_leaf(node_data);
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inner_entry.into()
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}
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/// Create a node (non-leaf) Entry from the encoded node data and the indices of
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/// its children (in the array representation of the MMR tree).
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fn new_node(
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branch_id: ConsensusBranchId,
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data: NodeData,
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left_idx: u32,
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right_idx: u32,
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) -> Result<Self, io::Error> {
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let node_data = zcash_history::NodeData::from_bytes(branch_id.into(), data.inner)?;
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let inner_entry = zcash_history::Entry::new(
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node_data,
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zcash_history::EntryLink::Stored(left_idx),
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zcash_history::EntryLink::Stored(right_idx),
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);
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Ok(inner_entry.into())
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}
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}
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impl Tree {
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/// Create a MMR tree with the given length from the given cache of nodes.
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///
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/// The `peaks` are the peaks of the MMR tree to build and their position in the
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/// array representation of the tree.
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/// The `extra` are extra nodes that enable removing nodes from the tree, and their position.
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///
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/// Note that the length is usually larger than the length of `peaks` and `extra`, since
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/// you don't need to pass every node, just the peaks of the tree (plus extra).
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///
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/// # Panics
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///
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/// Will panic if `peaks` is empty.
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fn new_from_cache(
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network: Network,
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network_upgrade: NetworkUpgrade,
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length: u32,
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peaks: &HashMap<u32, &Entry>,
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extra: &HashMap<u32, &Entry>,
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) -> Result<Self, io::Error> {
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let branch_id = network_upgrade
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.branch_id()
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.expect("unexpected pre-Overwinter MMR history tree");
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let mut peaks_vec = Vec::new();
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for (idx, entry) in peaks {
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let inner_entry = zcash_history::Entry::from_bytes(branch_id.into(), entry.inner)?;
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peaks_vec.push((*idx, inner_entry));
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}
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let mut extra_vec = Vec::new();
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for (idx, entry) in extra {
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let inner_entry = zcash_history::Entry::from_bytes(branch_id.into(), entry.inner)?;
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extra_vec.push((*idx, inner_entry));
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}
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let inner = zcash_history::Tree::new(length, peaks_vec, extra_vec);
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Ok(Tree {
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network,
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network_upgrade,
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inner,
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})
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}
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/// Create a single-node MMR tree for the given block.
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///
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/// `sapling_root` is the root of the Sapling note commitment tree of the block.
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fn new_from_block(
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network: Network,
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block: Arc<Block>,
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sapling_root: &sapling::tree::Root,
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) -> Result<Self, io::Error> {
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let height = block
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.coinbase_height()
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.expect("block must have coinbase height during contextual verification");
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let network_upgrade = NetworkUpgrade::current(network, height);
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let entry0 = Entry::new_leaf(block, network, sapling_root);
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let mut peaks = HashMap::new();
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peaks.insert(0u32, &entry0);
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Tree::new_from_cache(network, network_upgrade, 1, &peaks, &HashMap::new())
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}
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/// Append a new block to the tree, as a new leaf.
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///
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/// `sapling_root` is the root of the Sapling note commitment tree of the block.
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///
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/// Returns a vector of nodes added to the tree (leaf + internal nodes).
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///
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/// # Panics
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///
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/// Panics if the network upgrade of the given block is different from
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/// the network upgrade of the other blocks in the tree.
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fn append_leaf(
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&mut self,
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block: Arc<Block>,
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sapling_root: &sapling::tree::Root,
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) -> Result<Vec<NodeData>, zcash_history::Error> {
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let height = block
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.coinbase_height()
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.expect("block must have coinbase height during contextual verification");
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let network_upgrade = NetworkUpgrade::current(self.network, height);
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if self.network_upgrade != network_upgrade {
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panic!(
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"added block from network upgrade {:?} but MMR tree is restricted to {:?}",
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network_upgrade, self.network_upgrade
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);
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}
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let node_data = block_to_history_node(block, self.network, sapling_root);
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let appended = self.inner.append_leaf(node_data)?;
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let mut new_nodes = Vec::new();
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for entry in appended {
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let mut node = NodeData {
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inner: [0; zcash_history::MAX_NODE_DATA_SIZE],
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};
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self.inner
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.resolve_link(entry)
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.expect("entry was just generated so it must be valid")
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.data()
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.write(&mut &mut node.inner[..])
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.expect("buffer was created with enough capacity");
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new_nodes.push(node);
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}
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Ok(new_nodes)
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}
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/// Append multiple blocks to the tree.
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fn append_leaf_iter(
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&mut self,
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vals: impl Iterator<Item = (Arc<Block>, sapling::tree::Root)>,
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) -> Result<Vec<NodeData>, zcash_history::Error> {
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let mut new_nodes = Vec::new();
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for (block, root) in vals {
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new_nodes.append(&mut self.append_leaf(block, &root)?);
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}
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Ok(new_nodes)
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}
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/// Remove the last leaf (block) from the tree.
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///
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/// Returns the number of nodes removed from the tree after the operation.
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fn truncate_leaf(&mut self) -> Result<u32, zcash_history::Error> {
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self.inner.truncate_leaf()
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}
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/// Return the root hash of the tree, i.e. `hashChainHistoryRoot`.
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fn hash(&self) -> ChainHistoryMmrRootHash {
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// Both append_leaf() and truncate_leaf() leave a root node, so it should
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// always exist.
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self.inner
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.root_node()
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.expect("must have root node")
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.data()
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.hash()
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.into()
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}
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}
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/// Convert a Block into a zcash_history::NodeData used in the MMR tree.
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///
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/// `sapling_root` is the root of the Sapling note commitment tree of the block.
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fn block_to_history_node(
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block: Arc<Block>,
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network: Network,
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sapling_root: &sapling::tree::Root,
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) -> zcash_history::NodeData {
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let height = block
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.coinbase_height()
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.expect("block must have coinbase height during contextual verification");
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let branch_id = ConsensusBranchId::current(network, height)
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.expect("must have branch ID for chain history network upgrades");
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let block_hash = block.hash().0;
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let time: u32 = block
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.header
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.time
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.timestamp()
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.try_into()
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.expect("deserialized and generated timestamps are u32 values");
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let target = block.header.difficulty_threshold.0;
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let sapling_root: [u8; 32] = sapling_root.into();
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let work = block
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.header
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.difficulty_threshold
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.to_work()
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.expect("work must be valid during contextual verification");
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// There is no direct `std::primitive::u128` to `bigint::U256` conversion
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let work = bigint::U256::from_big_endian(&work.as_u128().to_be_bytes());
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let sapling_tx_count = count_sapling_transactions(block);
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zcash_history::NodeData {
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consensus_branch_id: branch_id.into(),
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subtree_commitment: block_hash,
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start_time: time,
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end_time: time,
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start_target: target,
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end_target: target,
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start_sapling_root: sapling_root,
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end_sapling_root: sapling_root,
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subtree_total_work: work,
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start_height: height.0 as u64,
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end_height: height.0 as u64,
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sapling_tx: sapling_tx_count,
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}
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}
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/// Count how many Sapling transactions exist in a block,
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/// i.e. transactions "where either of vSpendsSapling or vOutputsSapling is non-empty"
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/// (https://zips.z.cash/zip-0221#tree-node-specification).
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fn count_sapling_transactions(block: Arc<Block>) -> u64 {
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block
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.transactions
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.iter()
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.filter(|tx| tx.has_sapling_shielded_data())
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.count()
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.try_into()
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.expect("number of transactions must fit u64")
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}
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