From e4c6b70e8ee124ad91cbad84e36b5018da2d07a7 Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Sat, 4 Nov 2023 21:01:18 +0000 Subject: [PATCH] Pre-allocate the full `Vec` prior to serializing as a `Vec` We end up generating a substantial amount of allocations just doubling `Vec`s when serializing to them, and our `serialized_length` method is generally rather effecient, so we just rely on it and allocate correctly up front. --- lightning/src/util/ser.rs | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/lightning/src/util/ser.rs b/lightning/src/util/ser.rs index 85b991c61..64d59da0d 100644 --- a/lightning/src/util/ser.rs +++ b/lightning/src/util/ser.rs @@ -199,8 +199,14 @@ pub trait Writeable { /// Writes `self` out to a `Vec`. fn encode(&self) -> Vec { - let mut msg = VecWriter(Vec::new()); + let len = self.serialized_length(); + let mut msg = VecWriter(Vec::with_capacity(len)); self.write(&mut msg).unwrap(); + // Note that objects with interior mutability may change size between when we called + // serialized_length and when we called write. That's okay, but shouldn't happen during + // testing as most of our tests are not threaded. + #[cfg(test)] + debug_assert_eq!(len, msg.0.len()); msg.0 } @@ -211,6 +217,7 @@ pub trait Writeable { 0u16.write(&mut msg).unwrap(); self.write(&mut msg).unwrap(); let len = msg.0.len(); + debug_assert_eq!(len - 2, self.serialized_length()); msg.0[..2].copy_from_slice(&(len as u16 - 2).to_be_bytes()); msg.0 } -- 2.39.5