From 5f2a83f56346ccbbce906513f9fe56ebc42cd2e6 Mon Sep 17 00:00:00 2001
From: Aaron O'Mullan <aaron.omullan@gmail.com>
Date: Sun, 4 Apr 2021 15:04:35 +0200
Subject: perf(serde_v8): preallocate vector when serializing arrays (#9955)

---
 serde_v8/src/ser.rs | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

(limited to 'serde_v8/src')

diff --git a/serde_v8/src/ser.rs b/serde_v8/src/ser.rs
index 16b6447b9..126657c6b 100644
--- a/serde_v8/src/ser.rs
+++ b/serde_v8/src/ser.rs
@@ -103,13 +103,12 @@ pub struct ArraySerializer<'a, 'b, 'c> {
 }
 
 impl<'a, 'b, 'c> ArraySerializer<'a, 'b, 'c> {
-  pub fn new(scope: ScopePtr<'a, 'b, 'c>) -> Self {
-    // let serializer = Serializer::new(scope);
-    Self {
-      scope,
-      // serializer,
-      pending: vec![],
-    }
+  pub fn new(scope: ScopePtr<'a, 'b, 'c>, len: Option<usize>) -> Self {
+    let pending = match len {
+      Some(len) => Vec::with_capacity(len),
+      None => vec![],
+    };
+    Self { scope, pending }
   }
 }
 
@@ -421,8 +420,8 @@ impl<'a, 'b, 'c> ser::Serializer for Serializer<'a, 'b, 'c> {
   }
 
   /// Serialises any Rust iterable into a JS Array
-  fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq> {
-    Ok(ArraySerializer::new(self.scope))
+  fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq> {
+    Ok(ArraySerializer::new(self.scope, len))
   }
 
   fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
-- 
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