use extend_from_slice when appending multiple hashes to hash file (#3497)

* use extend_from_slice when appending multiple hashes to hash file

* bump

core/src/core/pmmr/backend.rs

@@ -27,7 +27,7 @@ pub trait Backend<T: PMMRable> {
 	/// associated data element to flatfile storage (for leaf nodes only). The
 	/// position of the first element of the Vec in the MMR is provided to
 	/// help the implementation.
-	fn append(&mut self, data: &T, hashes: Vec<Hash>) -> Result<(), String>;
+	fn append(&mut self, data: &T, hashes: &[Hash]) -> Result<(), String>;
 
 	/// Rewind the backend state to a previous position, as if all append
 	/// operations after that had been canceled. Expects a position in the PMMR

core/src/core/pmmr/pmmr.rs

@@ -237,7 +237,7 @@ where
 		}
 
 		// append all the new nodes and update the MMR index
-		self.backend.append(elmt, hashes)?;
+		self.backend.append(elmt, &hashes)?;
 		self.last_pos = pos;
 		Ok(elmt_pos)
 	}

core/src/core/pmmr/vec_backend.rs

@@ -35,11 +35,11 @@ pub struct VecBackend<T: PMMRable> {
 }
 
 impl<T: PMMRable> Backend<T> for VecBackend<T> {
-	fn append(&mut self, elmt: &T, hashes: Vec<Hash>) -> Result<(), String> {
+	fn append(&mut self, elmt: &T, hashes: &[Hash]) -> Result<(), String> {
 		if let Some(data) = &mut self.data {
 			data.push(elmt.clone());
 		}
-		self.hashes.append(&mut hashes.clone());
+		self.hashes.extend_from_slice(hashes);
 		Ok(())
 	}
 

store/src/pmmr.rs

@@ -66,17 +66,15 @@ impl<T: PMMRable> Backend<T> for PMMRBackend<T> {
 	/// Append the provided data and hashes to the backend storage.
 	/// Add the new leaf pos to our leaf_set if this is a prunable MMR.
 	#[allow(unused_variables)]
-	fn append(&mut self, data: &T, hashes: Vec<Hash>) -> Result<(), String> {
+	fn append(&mut self, data: &T, hashes: &[Hash]) -> Result<(), String> {
 		let size = self
 			.data_file
 			.append(&data.as_elmt())
 			.map_err(|e| format!("Failed to append data to file. {}", e))?;
 
-		for h in &hashes {
+		self.hash_file
-			self.hash_file
+			.extend_from_slice(hashes)
-				.append(h)
+			.map_err(|e| format!("Failed to append hash to file. {}", e))?;
-				.map_err(|e| format!("Failed to append hash to file. {}", e))?;
-		}
 
 		if self.prunable {
 			// (Re)calculate the latest pos given updated size of data file

store/src/types.rs

@@ -99,6 +99,14 @@ where
 		Ok(self.size_unsync())
 	}
 
+	/// Append a slice of multiple elements to the file.
+	/// Will not be written to disk until flush() is subsequently called.
+	/// Alternatively discard() may be called to discard any pending changes.
+	pub fn extend_from_slice(&mut self, data: &[T]) -> io::Result<u64> {
+		self.file.append_elmts(data)?;
+		Ok(self.size_unsync())
+	}
+
 	/// Read an element from the file by position.
 	/// Assumes we have already "shifted" the position to account for pruned data.
 	/// Note: PMMR API is 1-indexed, but backend storage is 0-indexed.
@@ -280,6 +288,14 @@ where
 		Ok(())
 	}
 
+	/// Iterate over the slice and append each element.
+	fn append_elmts(&mut self, data: &[T]) -> io::Result<()> {
+		for x in data {
+			self.append_elmt(x)?;
+		}
+		Ok(())
+	}
+
 	/// Append data to the file. Until the append-only file is synced, data is
 	/// only written to memory.
 	pub fn append(&mut self, bytes: &mut [u8]) -> io::Result<()> {