[GitHub] [arrow] wesm commented on a change in pull request #7506: ARROW-9197: [C++] Overhaul integer/floating point casting: vectorize truncation checks, reduce binary size

[GitBox <gi...@apache.org>]

wesm commented on a change in pull request #7506:
URL: https://github.com/apache/arrow/pull/7506#discussion_r443244978



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File path: cpp/src/arrow/compute/kernels/codegen_internal.h
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@@ -215,27 +215,23 @@ template <typename Type>
 struct BoxScalar<Type, enable_if_has_c_type<Type>> {
   using T = typename GetOutputType<Type>::T;
   using ScalarType = typename TypeTraits<Type>::ScalarType;
-  static std::shared_ptr<Scalar> Box(T val, const std::shared_ptr<DataType>& type) {
-    return std::make_shared<ScalarType>(val, type);
-  }
+  static void Box(T val, Scalar* out) { checked_cast<ScalarType*>(out)->value = val; }
 };
 
 template <typename Type>
 struct BoxScalar<Type, enable_if_base_binary<Type>> {
   using T = typename GetOutputType<Type>::T;
   using ScalarType = typename TypeTraits<Type>::ScalarType;
-  static std::shared_ptr<Scalar> Box(T val, const std::shared_ptr<DataType>&) {
-    return std::make_shared<ScalarType>(val);
+  static void Box(T val, Scalar* out) {
+    checked_cast<ScalarType*>(out)->value = std::make_shared<Buffer>(val);
   }
 };
 
 template <>
 struct BoxScalar<Decimal128Type> {
   using T = Decimal128;
   using ScalarType = Decimal128Scalar;
-  static std::shared_ptr<Scalar> Box(T val, const std::shared_ptr<DataType>& type) {
-    return std::make_shared<ScalarType>(val, type);
-  }
+  static void Box(T val, Scalar* out) { checked_cast<ScalarType*>(out)->value = val; }

Review comment:
       The prior implementation was causing a lot of compiled code to be generated for some reason, FYI




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