optimize Vec<T>::parse(), for Streeamable, by pre-allocating its size

Chia-Network · Nov 4, 2023 · 54249e2 · 54249e2
1 parent 1517f0f
commit 54249e2
Showing 1 changed file with 2 additions and 3 deletions.
diff --git a/chia-traits/src/streamable.rs b/chia-traits/src/streamable.rs
@@ -115,9 +115,8 @@ impl<T: Streamable> Streamable for Vec<T> {
     fn parse(input: &mut Cursor<&[u8]>) -> Result<Self> {
         let len = u32::parse(input)?;
 
-        // TODO: pre-allocate capacity, but we'd need safe-guards for overflow
-        // attacks
-        let mut ret = Vec::<T>::new();
+        let limit = 2 * 1024 * 1024 / std::mem::size_of::<T>();
+        let mut ret = Vec::<T>::with_capacity(std::cmp::min(limit, len as usize));
         for _ in 0..len {
             ret.push(T::parse(input)?);
         }