From 2eafbf2b98e56ef992ba0ea47886e97c9567886e Mon Sep 17 00:00:00 2001
From: Aaron O'Mullan <aaron.omullan@gmail.com>
Date: Mon, 12 Apr 2021 23:38:26 +0200
Subject: perf(core/ops): avoid allocs when returning primitives (#10149)

---
 core/minvalue.rs | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 core/minvalue.rs

(limited to 'core/minvalue.rs')

diff --git a/core/minvalue.rs b/core/minvalue.rs
new file mode 100644
index 000000000..1c9059c12
--- /dev/null
+++ b/core/minvalue.rs
@@ -0,0 +1,95 @@
+use rusty_v8 as v8;
+use std::any::TypeId;
+
+/// SerializablePkg exists to provide a fast path for op returns,
+/// allowing them to avoid boxing primtives (ints/floats/bool/unit/...)
+pub enum SerializablePkg {
+  MinValue(MinValue),
+  Serializable(Box<dyn serde_v8::Serializable>),
+}
+
+impl SerializablePkg {
+  pub fn to_v8<'a>(
+    &self,
+    scope: &mut v8::HandleScope<'a>,
+  ) -> Result<v8::Local<'a, v8::Value>, serde_v8::Error> {
+    match &*self {
+      Self::MinValue(x) => serde_v8::to_v8(scope, x),
+      Self::Serializable(x) => x.to_v8(scope),
+    }
+  }
+}
+
+/// MinValue serves as a lightweight serializable wrapper around primitives
+/// so that we can use them for async values
+#[derive(Clone, Copy)]
+pub enum MinValue {
+  Unit(()),
+  Bool(bool),
+  Int8(i8),
+  Int16(i16),
+  Int32(i32),
+  Int64(i64),
+  UInt8(u8),
+  UInt16(u16),
+  UInt32(u32),
+  UInt64(u64),
+  Float32(f32),
+  Float64(f64),
+}
+
+impl serde::Serialize for MinValue {
+  fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+  where
+    S: serde::Serializer,
+  {
+    match *self {
+      Self::Unit(_) => serializer.serialize_unit(),
+      Self::Bool(x) => serializer.serialize_bool(x),
+      Self::Int8(x) => serializer.serialize_i8(x),
+      Self::Int16(x) => serializer.serialize_i16(x),
+      Self::Int32(x) => serializer.serialize_i32(x),
+      Self::Int64(x) => serializer.serialize_i64(x),
+      Self::UInt8(x) => serializer.serialize_u8(x),
+      Self::UInt16(x) => serializer.serialize_u16(x),
+      Self::UInt32(x) => serializer.serialize_u32(x),
+      Self::UInt64(x) => serializer.serialize_u64(x),
+      Self::Float32(x) => serializer.serialize_f32(x),
+      Self::Float64(x) => serializer.serialize_f64(x),
+    }
+  }
+}
+
+impl<T: serde::Serialize + 'static> From<T> for SerializablePkg {
+  fn from(x: T) -> Self {
+    let tid = TypeId::of::<T>();
+
+    if tid == TypeId::of::<()>() {
+      Self::MinValue(MinValue::Unit(()))
+    } else if tid == TypeId::of::<bool>() {
+      Self::MinValue(MinValue::Bool(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<i8>() {
+      Self::MinValue(MinValue::Int8(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<i16>() {
+      Self::MinValue(MinValue::Int16(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<i32>() {
+      Self::MinValue(MinValue::Int32(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<i64>() {
+      Self::MinValue(MinValue::Int64(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<u8>() {
+      Self::MinValue(MinValue::UInt8(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<u16>() {
+      Self::MinValue(MinValue::UInt16(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<u32>() {
+      Self::MinValue(MinValue::UInt32(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<u64>() {
+      Self::MinValue(MinValue::UInt64(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<f32>() {
+      Self::MinValue(MinValue::Float32(unsafe { std::mem::transmute_copy(&x) }))
+    } else if tid == TypeId::of::<f64>() {
+      Self::MinValue(MinValue::Float64(unsafe { std::mem::transmute_copy(&x) }))
+    } else {
+      Self::Serializable(Box::new(x))
+    }
+  }
+}
-- 
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