zcash_client_sqlite: Add `FsBlockDb::find_block`

zcash_client_sqlite/CHANGELOG.md

@@ -6,19 +6,16 @@ and this library adheres to Rust's notion of
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
-
 ### Added 
 - `zcash_client_sqlite::FsBlockDb::rewind_to_height` rewinds the BlockMeta Db
  to the specified height following the same logic as homonymous functions on 
  `WalletDb`. This function does not delete the files referenced by the rows
  that might be present and are deleted by this function call.
-- `zcash_client_sqlite::chain::blockmetadb_rewind_to_height` implementation
- of the function above.
+- `zcash_client_sqlite::FsBlockDb::find_block`
 
 ### Changed
 - MSRV is now 1.60.0.
 
-
 ## [0.4.2] - 2022-12-13
 ### Fixed
 - `zcash_client_sqlite::WalletDb::get_transparent_balances` no longer returns an

zcash_client_sqlite/src/chain.rs

@@ -161,6 +161,32 @@ pub(crate) fn blockmetadb_get_max_cached_height(
     })
 }
 
+/// Returns the metadata for the block with the given height, if it exists in the database.
+#[cfg(feature = "unstable")]
+pub(crate) fn blockmetadb_find_block(
+    conn: &Connection,
+    height: BlockHeight,
+) -> Result<Option<BlockMeta>, rusqlite::Error> {
+    use rusqlite::OptionalExtension;
+
+    conn.query_row(
+        "SELECT blockhash, time, sapling_outputs_count, orchard_actions_count
+        FROM compactblocks_meta
+        WHERE height = ?",
+        [u32::from(height)],
+        |row| {
+            Ok(BlockMeta {
+                height,
+                block_hash: BlockHash::from_slice(&row.get::<_, Vec<_>>(0)?),
+                block_time: row.get(1)?,
+                sapling_outputs_count: row.get(2)?,
+                orchard_actions_count: row.get(3)?,
+            })
+        },
+    )
+    .optional()
+}
+
 /// Implements a traversal of `limit` blocks of the filesystem-backed
 /// block cache.
 ///

zcash_client_sqlite/src/lib.rs

@@ -929,6 +929,13 @@ impl FsBlockDb {
 
         Ok(chain::blockmetadb_insert(&self.conn, block_meta)?)
     }
+
+    /// Returns the metadata for the block with the given height, if it exists in the
+    /// database.
+    pub fn find_block(&self, height: BlockHeight) -> Result<Option<BlockMeta>, FsBlockDbError> {
+        Ok(chain::blockmetadb_find_block(&self.conn, height)?)
+    }
+
     /// Rewinds the BlockMeta Db to the `block_height` provided.
     ///
     /// This doesn't delete any files referenced by the records