Re: [PR] GH-44194: [C++] Avoid repeated ArrayData::offset lookups [arrow]

[via GitHub]

mapleFU commented on code in PR #44190:
URL: https://github.com/apache/arrow/pull/44190#discussion_r1818534498


##########
cpp/src/arrow/array/array_primitive.h:
##########
@@ -90,26 +90,25 @@ class NumericArray : public PrimitiveArray {
   using value_type = typename TypeClass::c_type;
   using IteratorType = stl::ArrayIterator<NumericArray<TYPE>>;
 
-  explicit NumericArray(const std::shared_ptr<ArrayData>& data) : 
PrimitiveArray(data) {}
+  explicit NumericArray(const std::shared_ptr<ArrayData>& data) { 
SetData(data); }
 
   // Only enable this constructor without a type argument for types without 
additional
   // metadata
   template <typename T1 = TYPE>
   NumericArray(enable_if_parameter_free<T1, int64_t> length,
                const std::shared_ptr<Buffer>& data,
                const std::shared_ptr<Buffer>& null_bitmap = NULLPTR,
-               int64_t null_count = kUnknownNullCount, int64_t offset = 0)
-      : PrimitiveArray(TypeTraits<T1>::type_singleton(), length, data, 
null_bitmap,
-                       null_count, offset) {}
-
-  const value_type* raw_values() const {
-    return reinterpret_cast<const value_type*>(raw_values_) + data_->offset;
+               int64_t null_count = kUnknownNullCount, int64_t offset = 0) {
+    SetData(ArrayData::Make(TypeTraits<T1>::type_singleton(), length, 
{null_bitmap, data},

Review Comment:
   Would be fixed with 
   
   ```
   diff --git a/cpp/src/arrow/array/array_primitive.h 
b/cpp/src/arrow/array/array_primitive.h
   index 3e2893b7dd..410e8516da 100644
   --- a/cpp/src/arrow/array/array_primitive.h
   +++ b/cpp/src/arrow/array/array_primitive.h
   @@ -103,6 +103,15 @@ class NumericArray : public PrimitiveArray {
                                null_count, offset));
      }
    
   +  NumericArray(const std::shared_ptr<DataType>& type, int64_t length,
   +                 const std::shared_ptr<Buffer>& data,
   +                 const std::shared_ptr<Buffer>& null_bitmap = NULLPTR,
   +                 int64_t null_count = kUnknownNullCount, int64_t offset = 
0): PrimitiveArray(type, length, data, null_bitmap, null_count, offset) {
   +      values_ = raw_values_
   +                    ? (reinterpret_cast<const value_type*>(raw_values_) + 
data_->offset)
   +                    : NULLPTR;
   +  }
   +
      const value_type* raw_values() const { return values_; }
    
      value_type Value(int64_t i) const { return values_[i]; }
   ```
   
   For `NumericArray`



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