Extend the Const accessor to support proxy references

alpaka-group · Nov 29, 2022 · 5aa4048 · 5aa4048
1 parent d87e08e
commit 5aa4048
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diff --git a/include/llama/Accessors.hpp b/include/llama/Accessors.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "Concepts.hpp"
+#include "ProxyRefOpMixin.hpp"
 #include "macros.hpp"
 
 #include <atomic>
@@ -34,11 +35,40 @@ namespace llama::accessor
     /// Allows only read access by qualifying the references to memory with const. Only works on l-value references.
     struct Const
     {
+        // for l-value references
         template<typename T>
         LLAMA_FN_HOST_ACC_INLINE auto operator()(T& r) const -> const T&
         {
             return r;
         }
+
+        template<typename Ref>
+        struct Reference : ProxyRefOpMixin<Reference<Ref>, typename Ref::value_type>
+        {
+            using value_type = typename Ref::value_type;
+
+            Ref ref;
+
+            // NOLINTNEXTLINE(google-explicit-constructor,hicpp-explicit-conversions)
+            operator value_type() const
+            {
+                return static_cast<value_type>(ref);
+            }
+
+            template<typename T>
+            auto operator=(T) -> Reference&
+            {
+                static_assert(sizeof(T) == 0, "You cannot write through a Const accessor");
+                return *this;
+            }
+        };
+
+        // for proxy references
+        template<typename ProxyReference, std::enable_if_t<llama::isProxyReference<ProxyReference>, int> = 0>
+        LLAMA_FN_HOST_ACC_INLINE auto operator()(ProxyReference r) const
+        {
+            return Reference<ProxyReference>{{}, std::move(r)};
+        }
     };
 
     /// Qualifies references to memory with __restrict. Only works on l-value references.

diff --git a/tests/accessor.cpp b/tests/accessor.cpp
@@ -76,6 +76,25 @@ TEMPLATE_TEST_CASE(
     iotaCheckView(view);
 }
 
+TEST_CASE("view.withAccessor.shallowCopy.Const")
+{
+    auto view
+        = llama::allocView(llama::mapping::AoS{llama::ArrayExtents{4, 4}, Vec3I{}}, llama::bloballoc::SharedPtr{});
+    iotaFillView(view);
+    auto view2 = llama::withAccessor<llama::accessor::Const>(llama::shallowCopy(view));
+    iotaCheckView(view2);
+}
+
+TEST_CASE("view.withAccessor.shallowCopy.Const.ProxyRef")
+{
+    auto view = llama::allocView(
+        llama::mapping::Byteswap<llama::ArrayExtents<int, 4, 4>, Vec3I, llama::mapping::BindAoS<>::fn>{{}},
+        llama::bloballoc::SharedPtr{});
+    iotaFillView(view);
+    auto view2 = llama::withAccessor<llama::accessor::Const>(llama::shallowCopy(view));
+    iotaCheckView(view2);
+}
+
 #ifdef __cpp_lib_atomic_ref
 TEMPLATE_TEST_CASE(
     "view.withAccessor.shallowCopy.Atomic",