Makes `equihash::Solution` an enum to support Regtest solutions, adds a test for validating and committing the Regtest genesis block

zebra-chain/src/block/genesis.rs

@@ -1,16 +1,19 @@
 //! Regtest genesis block
 
+use std::sync::Arc;
+
 use hex::FromHex;
 
 use crate::{block::Block, serialization::ZcashDeserializeInto};
 
 /// Genesis block for Regtest, copied from zcashd via `getblock 0 0` RPC method
-pub fn regtest_genesis_block() -> Block {
+pub fn regtest_genesis_block() -> Arc<Block> {
     let regtest_genesis_block_bytes =
         <Vec<u8>>::from_hex(include_str!("genesis/block-regtest-0-000-000.txt").trim())
             .expect("Block bytes are in valid hex representation");
 
     regtest_genesis_block_bytes
         .zcash_deserialize_into()
+        .map(Arc::new)
         .expect("hard-coded Regtest genesis block data must deserialize successfully")
 }

zebra-chain/src/parameters/network_upgrade.rs

@@ -340,6 +340,9 @@ impl NetworkUpgrade {
                 self.next_upgrade()
                     .and_then(|next_nu| next_nu.activation_height(network))
             })
+            // TODO: Remove `.expect()` calls on the return value of this function (except for Genesis), or
+            //       update this method's return type
+            .or(Some(block::Height::MAX))
     }
 
     /// Returns `true` if `height` is the activation height of any network upgrade

zebra-chain/src/work/arbitrary.rs

@@ -10,7 +10,7 @@ impl Arbitrary for equihash::Solution {
             .prop_map(|v| {
                 let mut bytes = [0; equihash::SOLUTION_SIZE];
                 bytes.copy_from_slice(v.as_slice());
-                Self(bytes)
+                Self::Common(bytes)
             })
             .boxed()
     }

zebra-chain/src/work/equihash.rs

@@ -29,16 +29,26 @@ pub struct SolverCancelled;
 /// The size of an Equihash solution in bytes (always 1344).
 pub(crate) const SOLUTION_SIZE: usize = 1344;
 
+/// The size of an Equihash solution in bytes on Regtest (always 36).
+pub(crate) const REGTEST_SOLUTION_SIZE: usize = 36;
+
 /// Equihash Solution in compressed format.
 ///
 /// A wrapper around [u8; 1344] because Rust doesn't implement common
 /// traits like `Debug`, `Clone`, etc for collections like array
 /// beyond lengths 0 to 32.
 ///
-/// The size of an Equihash solution in bytes is always 1344 so the
-/// length of this type is fixed.
+/// The size of an Equihash solution in bytes is always 1344 on Mainnet and Testnet, and
+/// is always 36 on Regtest so the length of this type is fixed.
 #[derive(Deserialize, Serialize)]
-pub struct Solution(#[serde(with = "BigArray")] pub [u8; SOLUTION_SIZE]);
+// It's okay to use the extra space on Regtest
+#[allow(clippy::large_enum_variant)]
+pub enum Solution {
+    /// Equihash solution on Mainnet or Testnet
+    Common(#[serde(with = "BigArray")] [u8; SOLUTION_SIZE]),
+    /// Equihash solution on Regtest
+    Regtest(#[serde(with = "BigArray")] [u8; REGTEST_SOLUTION_SIZE]),
+}
 
 impl Solution {
     /// The length of the portion of the header used as input when verifying
@@ -48,15 +58,24 @@ impl Solution {
     /// to the verification function.
     pub const INPUT_LENGTH: usize = 4 + 32 * 3 + 4 * 2;
 
+    /// Returns the inner value of the [`Solution`] as a byte slice.
+    fn value(&self) -> &[u8] {
+        match self {
+            Solution::Common(solution) => solution.as_slice(),
+            Solution::Regtest(solution) => solution.as_slice(),
+        }
+    }
+
     /// Returns `Ok(())` if `EquihashSolution` is valid for `header`
     #[allow(clippy::unwrap_in_result)]
     pub fn check(&self, header: &Header) -> Result<(), Error> {
-        let n = 200;
-        let k = 9;
         let nonce = &header.nonce;
-        let solution = &self.0;
-        let mut input = Vec::new();
+        let (solution, n, k) = match self {
+            Solution::Common(solution) => (solution.as_slice(), 200, 9),
+            Solution::Regtest(solution) => (solution.as_slice(), 48, 5),
+        };
 
+        let mut input = Vec::new();
         header
             .zcash_serialize(&mut input)
             .expect("serialization into a vec can't fail");
@@ -73,23 +92,29 @@ impl Solution {
     /// Returns a [`Solution`] containing the bytes from `solution`.
     /// Returns an error if `solution` is the wrong length.
     pub fn from_bytes(solution: &[u8]) -> Result<Self, SerializationError> {
-        if solution.len() != SOLUTION_SIZE {
-            return Err(SerializationError::Parse(
+        match solution.len() {
+            // Won't panic, because we just checked the length.
+            SOLUTION_SIZE => {
+                let mut bytes = [0; SOLUTION_SIZE];
+                bytes.copy_from_slice(solution);
+                Ok(Self::Common(bytes))
+            }
+            REGTEST_SOLUTION_SIZE => {
+                let mut bytes = [0; REGTEST_SOLUTION_SIZE];
+                bytes.copy_from_slice(solution);
+                Ok(Self::Regtest(bytes))
+            }
+            _unexpected_len => Err(SerializationError::Parse(
                 "incorrect equihash solution size",
-            ));
+            )),
         }
-
-        let mut bytes = [0; SOLUTION_SIZE];
-        // Won't panic, because we just checked the length.
-        bytes.copy_from_slice(solution);
-
-        Ok(Self(bytes))
     }
 
     /// Returns a [`Solution`] of `[0; SOLUTION_SIZE]` to be used in block proposals.
     #[cfg(feature = "getblocktemplate-rpcs")]
     pub fn for_proposal() -> Self {
-        Self([0; SOLUTION_SIZE])
+        // TODO: Accept network as an argument, and if it's Regtest, return the shorter null solution.
+        Self::Common([0; SOLUTION_SIZE])
     }
 
     /// Mines and returns one or more [`Solution`]s based on a template `header`.
@@ -126,14 +151,14 @@ impl Solution {
 
 impl PartialEq<Solution> for Solution {
     fn eq(&self, other: &Solution) -> bool {
-        self.0.as_ref() == other.0.as_ref()
+        self.value() == other.value()
     }
 }
 
 impl fmt::Debug for Solution {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_tuple("EquihashSolution")
-            .field(&hex::encode(&self.0[..]))
+            .field(&hex::encode(self.value()))
             .finish()
     }
 }
@@ -153,13 +178,13 @@ impl Eq for Solution {}
 #[cfg(any(test, feature = "proptest-impl"))]
 impl Default for Solution {
     fn default() -> Self {
-        Self([0; SOLUTION_SIZE])
+        Self::Common([0; SOLUTION_SIZE])
     }
 }
 
 impl ZcashSerialize for Solution {
     fn zcash_serialize<W: io::Write>(&self, writer: W) -> Result<(), io::Error> {
-        zcash_serialize_bytes(&self.0.to_vec(), writer)
+        zcash_serialize_bytes(&self.value().to_vec(), writer)
     }
 }
 

zebrad/tests/acceptance.rs

@@ -161,10 +161,12 @@ use color_eyre::{
 use semver::Version;
 use serde_json::Value;
 
+use tower::ServiceExt;
 use zebra_chain::{
-    block::{self, Height},
+    block::{self, genesis::regtest_genesis_block, Height},
     parameters::Network::{self, *},
 };
+use zebra_consensus::ParameterCheckpoint;
 use zebra_network::constants::PORT_IN_USE_ERROR;
 use zebra_node_services::rpc_client::RpcRequestClient;
 use zebra_state::{constants::LOCK_FILE_ERROR, state_database_format_version_in_code};
@@ -3098,3 +3100,29 @@ fn scan_start_where_left() -> Result<()> {
 async fn scan_task_commands() -> Result<()> {
     common::shielded_scan::scan_task_commands::run().await
 }
+
+/// Checks that the Regtest genesis block can be validated.
+#[tokio::test]
+async fn validate_regtest_genesis_block() {
+    let _init_guard = zebra_test::init();
+
+    let network = Network::new_regtest(Default::default());
+    let state = zebra_state::init_test(&network);
+    let (
+        block_verifier_router,
+        _transaction_verifier,
+        _parameter_download_task_handle,
+        _max_checkpoint_height,
+    ) = zebra_consensus::router::init(zebra_consensus::Config::default(), &network, state).await;
+
+    let genesis_hash = block_verifier_router
+        .oneshot(zebra_consensus::Request::Commit(regtest_genesis_block()))
+        .await
+        .expect("should validate Regtest genesis block");
+
+    assert_eq!(
+        genesis_hash,
+        network.genesis_hash(),
+        "validated block hash should match network genesis hash"
+    )
+}