feat(trie): noop hashed cursors (paradigmxyz#11627)

crates/trie/trie/src/hashed_cursor/mod.rs

@@ -6,6 +6,9 @@ use reth_storage_errors::db::DatabaseError;
 mod post_state;
 pub use post_state::*;
 
+/// Implementation of noop hashed state cursor.
+pub mod noop;
+
 /// The factory trait for creating cursors over the hashed state.
 pub trait HashedCursorFactory {
     /// The hashed account cursor type.

crates/trie/trie/src/hashed_cursor/noop.rs

@@ -0,0 +1,65 @@
+use super::{HashedCursor, HashedCursorFactory, HashedStorageCursor};
+use alloy_primitives::{B256, U256};
+use reth_primitives::Account;
+use reth_storage_errors::db::DatabaseError;
+
+/// Noop hashed cursor factory.
+#[derive(Default, Debug)]
+#[non_exhaustive]
+pub struct NoopHashedCursorFactory;
+
+impl HashedCursorFactory for NoopHashedCursorFactory {
+    type AccountCursor = NoopHashedAccountCursor;
+    type StorageCursor = NoopHashedStorageCursor;
+
+    fn hashed_account_cursor(&self) -> Result<Self::AccountCursor, DatabaseError> {
+        Ok(NoopHashedAccountCursor::default())
+    }
+
+    fn hashed_storage_cursor(
+        &self,
+        _hashed_address: B256,
+    ) -> Result<Self::StorageCursor, DatabaseError> {
+        Ok(NoopHashedStorageCursor::default())
+    }
+}
+
+/// Noop account hashed cursor.
+#[derive(Default, Debug)]
+#[non_exhaustive]
+pub struct NoopHashedAccountCursor;
+
+impl HashedCursor for NoopHashedAccountCursor {
+    type Value = Account;
+
+    fn next(&mut self) -> Result<Option<(B256, Self::Value)>, DatabaseError> {
+        Ok(None)
+    }
+
+    fn seek(&mut self, _key: B256) -> Result<Option<(B256, Self::Value)>, DatabaseError> {
+        Ok(None)
+    }
+}
+
+/// Noop account hashed cursor.
+#[derive(Default, Debug)]
+#[non_exhaustive]
+pub struct NoopHashedStorageCursor;
+
+impl HashedCursor for NoopHashedStorageCursor {
+    type Value = U256;
+
+    fn next(&mut self) -> Result<Option<(B256, Self::Value)>, DatabaseError> {
+        Ok(None)
+    }
+
+    fn seek(&mut self, _key: B256) -> Result<Option<(B256, Self::Value)>, DatabaseError> {
+        Ok(None)
+    }
+}
+
+impl HashedStorageCursor for NoopHashedStorageCursor {
+    fn is_storage_empty(&mut self) -> Result<bool, DatabaseError> {
+        Ok(true)
+    }
+}