perf(serde_v8): remove Mutex from ZeroCopyBuf (denoland#15888)

serde_v8/magic/buffer.rs

@@ -3,7 +3,6 @@
 use std::fmt::Debug;
 use std::ops::Deref;
 use std::ops::DerefMut;
-use std::sync::Mutex;
 
 use super::transl8::FromV8;
 use super::transl8::ToV8;
@@ -14,7 +13,7 @@ use crate::magic::transl8::impl_magic;
 // allowing us to use a single type for familiarity
 pub enum ZeroCopyBuf {
  FromV8(V8Slice),
- ToV8(Mutex<Option<Box<[u8]>>>),
+ ToV8(Option<Box<[u8]>>),
  // Variant of the ZeroCopyBuf than is never exposed to the JS.
  // Generally used to pass Vec<u8> backed buffers to resource methods.
  Temp(Vec<u8>),
@@ -30,7 +29,7 @@ impl Debug for ZeroCopyBuf {
 
 impl ZeroCopyBuf {
  pub fn empty() -> Self {
- ZeroCopyBuf::ToV8(Mutex::new(Some(vec![0_u8; 0].into_boxed_slice())))
+ ZeroCopyBuf::ToV8(Some(vec![0_u8; 0].into_boxed_slice()))
  }
 
  pub fn new_temp(vec: Vec<u8>) -> Self {
@@ -91,7 +90,7 @@ impl DerefMut for ZeroCopyBuf {
 
 impl From<Box<[u8]>> for ZeroCopyBuf {
  fn from(buf: Box<[u8]>) -> Self {
- ZeroCopyBuf::ToV8(Mutex::new(Some(buf)))
+ ZeroCopyBuf::ToV8(Some(buf))
  }
 }
 
@@ -112,9 +111,7 @@ impl ToV8 for ZeroCopyBuf {
  value.into()
  }
  Self::Temp(_) => unreachable!(),
- Self::ToV8(x) => {
- x.get_mut().unwrap().take().expect("ZeroCopyBuf was empty")
- }
+ Self::ToV8(ref mut x) => x.take().expect("ZeroCopyBuf was empty"),
  };
 
  if buf.is_empty() {
@@ -151,13 +148,9 @@ impl From<ZeroCopyBuf> for bytes::Bytes {
  fn from(zbuf: ZeroCopyBuf) -> bytes::Bytes {
  match zbuf {
  ZeroCopyBuf::FromV8(v) => v.into(),
- // WARNING(AaronO): potential footgun, but will disappear in future ZeroCopyBuf refactor
- ZeroCopyBuf::ToV8(v) => v
- .lock()
- .unwrap()
- .take()
- .expect("ZeroCopyBuf was empty")
- .into(),
+ ZeroCopyBuf::ToV8(mut v) => {
+ v.take().expect("ZeroCopyBuf was empty").into()
+ }
  ZeroCopyBuf::Temp(v) => v.into(),
  }
  }