243 lines
8.2 KiB
Rust
243 lines
8.2 KiB
Rust
//! Equihash Solution and related items.
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use std::{fmt, io};
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use serde_big_array::BigArray;
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use crate::{
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block::Header,
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serialization::{
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zcash_serialize_bytes, SerializationError, ZcashDeserialize, ZcashDeserializeInto,
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ZcashSerialize,
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},
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};
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#[cfg(feature = "internal-miner")]
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use crate::serialization::AtLeastOne;
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/// The error type for Equihash validation.
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#[non_exhaustive]
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#[derive(Debug, thiserror::Error)]
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#[error("invalid equihash solution for BlockHeader")]
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pub struct Error(#[from] equihash::Error);
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/// The error type for Equihash solving.
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#[derive(Copy, Clone, Debug, Eq, PartialEq, thiserror::Error)]
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#[error("solver was cancelled")]
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pub struct SolverCancelled;
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/// The size of an Equihash solution in bytes (always 1344).
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pub(crate) const SOLUTION_SIZE: usize = 1344;
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/// Equihash Solution in compressed format.
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///
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/// A wrapper around [u8; 1344] because Rust doesn't implement common
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/// traits like `Debug`, `Clone`, etc for collections like array
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/// beyond lengths 0 to 32.
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///
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/// The size of an Equihash solution in bytes is always 1344 so the
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/// length of this type is fixed.
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#[derive(Deserialize, Serialize)]
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pub struct Solution(#[serde(with = "BigArray")] pub [u8; SOLUTION_SIZE]);
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impl Solution {
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/// The length of the portion of the header used as input when verifying
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/// equihash solutions, in bytes.
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///
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/// Excludes the 32-byte nonce, which is passed as a separate argument
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/// to the verification function.
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pub const INPUT_LENGTH: usize = 4 + 32 * 3 + 4 * 2;
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/// Returns `Ok(())` if `EquihashSolution` is valid for `header`
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#[allow(clippy::unwrap_in_result)]
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pub fn check(&self, header: &Header) -> Result<(), Error> {
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let n = 200;
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let k = 9;
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let nonce = &header.nonce;
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let solution = &self.0;
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let mut input = Vec::new();
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header
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.zcash_serialize(&mut input)
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.expect("serialization into a vec can't fail");
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// The part of the header before the nonce and solution.
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// This data is kept constant during solver runs, so the verifier API takes it separately.
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let input = &input[0..Solution::INPUT_LENGTH];
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equihash::is_valid_solution(n, k, input, nonce.as_ref(), solution)?;
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Ok(())
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}
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/// Returns a [`Solution`] containing the bytes from `solution`.
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/// Returns an error if `solution` is the wrong length.
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pub fn from_bytes(solution: &[u8]) -> Result<Self, SerializationError> {
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if solution.len() != SOLUTION_SIZE {
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return Err(SerializationError::Parse(
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"incorrect equihash solution size",
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));
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}
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let mut bytes = [0; SOLUTION_SIZE];
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// Won't panic, because we just checked the length.
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bytes.copy_from_slice(solution);
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Ok(Self(bytes))
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}
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/// Returns a [`Solution`] of `[0; SOLUTION_SIZE]` to be used in block proposals.
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#[cfg(feature = "getblocktemplate-rpcs")]
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pub fn for_proposal() -> Self {
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Self([0; SOLUTION_SIZE])
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}
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/// Mines and returns one or more [`Solution`]s based on a template `header`.
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/// The returned header contains a valid `nonce` and `solution`.
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///
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/// If `cancel_fn()` returns an error, returns early with `Err(SolverCancelled)`.
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///
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/// The `nonce` in the header template is taken as the starting nonce. If you are running multiple
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/// solvers at the same time, start them with different nonces.
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/// The `solution` in the header template is ignored.
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///
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/// This method is CPU and memory-intensive. It uses 144 MB of RAM and one CPU core while running.
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/// It can run for minutes or hours if the network difficulty is high.
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#[cfg(feature = "internal-miner")]
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#[allow(clippy::unwrap_in_result)]
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pub fn solve<F>(
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mut header: Header,
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mut cancel_fn: F,
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) -> Result<AtLeastOne<Header>, SolverCancelled>
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where
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F: FnMut() -> Result<(), SolverCancelled>,
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{
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use crate::shutdown::is_shutting_down;
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let mut input = Vec::new();
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header
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.zcash_serialize(&mut input)
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.expect("serialization into a vec can't fail");
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// Take the part of the header before the nonce and solution.
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// This data is kept constant for this solver run.
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let input = &input[0..Solution::INPUT_LENGTH];
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while !is_shutting_down() {
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// Don't run the solver if we'd just cancel it anyway.
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cancel_fn()?;
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let solutions = equihash_solver::tromp::solve_200_9_compressed(input, || {
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// Cancel the solver if we have a new template.
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if cancel_fn().is_err() {
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return None;
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}
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// This skips the first nonce, which doesn't matter in practice.
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Self::next_nonce(&mut header.nonce);
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Some(*header.nonce)
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});
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let mut valid_solutions = Vec::new();
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// If we got any solutions, try submitting them, because the new template might just
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// contain some extra transactions. Mining extra transactions is optional.
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for solution in &solutions {
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header.solution = Self::from_bytes(solution)
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.expect("unexpected invalid solution: incorrect length");
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// TODO: work out why we sometimes get invalid solutions here
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if let Err(error) = header.solution.check(&header) {
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info!(?error, "found invalid solution for header");
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continue;
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}
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if Self::difficulty_is_valid(&header) {
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valid_solutions.push(header);
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}
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}
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match valid_solutions.try_into() {
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Ok(at_least_one_solution) => return Ok(at_least_one_solution),
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Err(_is_empty_error) => debug!(
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solutions = ?solutions.len(),
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"found valid solutions which did not pass the validity or difficulty checks"
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),
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}
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}
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Err(SolverCancelled)
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}
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/// Modifies `nonce` to be the next integer in big-endian order.
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/// Wraps to zero if the next nonce would overflow.
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#[cfg(feature = "internal-miner")]
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fn next_nonce(nonce: &mut [u8; 32]) {
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let _ignore_overflow = crate::primitives::byte_array::increment_big_endian(&mut nonce[..]);
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}
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/// Returns `true` if the `nonce` and `solution` in `header` meet the difficulty threshold.
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///
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/// Assumes that the difficulty threshold in the header is valid.
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#[cfg(feature = "internal-miner")]
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fn difficulty_is_valid(header: &Header) -> bool {
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// Simplified from zebra_consensus::block::check::difficulty_is_valid().
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let difficulty_threshold = header
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.difficulty_threshold
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.to_expanded()
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.expect("unexpected invalid header template: invalid difficulty threshold");
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// TODO: avoid calculating this hash multiple times
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let hash = header.hash();
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// Note: this comparison is a u256 integer comparison, like zcashd and bitcoin. Greater
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// values represent *less* work.
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hash <= difficulty_threshold
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}
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}
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impl PartialEq<Solution> for Solution {
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fn eq(&self, other: &Solution) -> bool {
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self.0.as_ref() == other.0.as_ref()
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}
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}
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impl fmt::Debug for Solution {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_tuple("EquihashSolution")
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.field(&hex::encode(&self.0[..]))
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.finish()
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}
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}
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// These impls all only exist because of array length restrictions.
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impl Copy for Solution {}
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impl Clone for Solution {
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fn clone(&self) -> Self {
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*self
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}
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}
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impl Eq for Solution {}
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#[cfg(any(test, feature = "proptest-impl"))]
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impl Default for Solution {
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fn default() -> Self {
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Self([0; SOLUTION_SIZE])
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}
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}
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impl ZcashSerialize for Solution {
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fn zcash_serialize<W: io::Write>(&self, writer: W) -> Result<(), io::Error> {
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zcash_serialize_bytes(&self.0.to_vec(), writer)
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}
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}
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impl ZcashDeserialize for Solution {
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fn zcash_deserialize<R: io::Read>(mut reader: R) -> Result<Self, SerializationError> {
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let solution: Vec<u8> = (&mut reader).zcash_deserialize_into()?;
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Self::from_bytes(&solution)
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}
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}
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