Function: add method to create shallow copy of virtual array

Creating a shallow copy is sometimes useful to get a unique ptr
for a virtual array when one only has a reference. It shouldn't
be used usually, but sometimes its the fastest way to do correct
ownership handling.

1 files changed, 51 insertions, 0 deletions

diff --git a/source/blender/functions/intern/generic_virtual_array.cc b/source/blender/functions/intern/generic_virtual_array.cc
index 754a2156a65..ca2bd0f806f 100644
--- a/source/blender/functions/intern/generic_virtual_array.cc
+++ b/source/blender/functions/intern/generic_virtual_array.cc
@@ -19,6 +19,37 @@
 namespace blender::fn {
 
 /* --------------------------------------------------------------------
+ * GVArray_For_ShallowCopy.
+ */
+
+class GVArray_For_ShallowCopy : public GVArray {
+ private:
+  const GVArray &varray_;
+
+ public:
+  GVArray_For_ShallowCopy(const GVArray &varray)
+      : GVArray(varray.type(), varray.size()), varray_(varray)
+  {
+  }
+
+ private:
+  void get_impl(const int64_t index, void *r_value) const override
+  {
+    varray_.get(index, r_value);
+  }
+
+  void get_to_uninitialized_impl(const int64_t index, void *r_value) const override
+  {
+    varray_.get_to_uninitialized(index, r_value);
+  }
+
+  void materialize_to_uninitialized_impl(const IndexMask mask, void *dst) const override
+  {
+    varray_.materialize_to_uninitialized(mask, dst);
+  }
+};
+
+/* --------------------------------------------------------------------
  * GVArray.
  */
 
@@ -73,6 +104,26 @@ const void *GVArray::try_get_internal_varray_impl() const
   return nullptr;
 }
 
+/**
+ * Creates a new `std::unique_ptr<GVArray>` based on this `GVArray`.
+ * The lifetime of the returned virtual array must not be longer than the lifetime of this virtual
+ * array.
+ */
+GVArrayPtr GVArray::shallow_copy() const
+{
+  if (this->is_span()) {
+    return std::make_unique<GVArray_For_GSpan>(this->get_internal_span());
+  }
+  if (this->is_single()) {
+    BUFFER_FOR_CPP_TYPE_VALUE(*type_, buffer);
+    this->get_internal_single(buffer);
+    std::unique_ptr new_varray = std::make_unique<GVArray_For_SingleValue>(*type_, size_, buffer);
+    type_->destruct(buffer);
+    return new_varray;
+  }
+  return std::make_unique<GVArray_For_ShallowCopy>(*this);
+}
+
 /* --------------------------------------------------------------------
  * GVMutableArray.
  */