From 067ed0672a530ba6525475f0e719dd670f4c0737 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franz=20P=C3=B6schel?= <franz.poeschel@gmail.com>
Date: Fri, 24 May 2024 13:34:28 +0200
Subject: [PATCH] Add variant-based loadChunk

---
 include/openPMD/LoadStoreChunk.hpp |  4 ++++
 src/LoadStoreChunk.cpp             | 23 +++++++++++++++++++++++
 test/SerialIOTest.cpp              | 16 ++++++++++------
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/include/openPMD/LoadStoreChunk.hpp b/include/openPMD/LoadStoreChunk.hpp
index 7818ce0137..197e3459fc 100644
--- a/include/openPMD/LoadStoreChunk.hpp
+++ b/include/openPMD/LoadStoreChunk.hpp
@@ -121,6 +121,10 @@ class ConfigureLoadStore : protected internal::ConfigureLoadStoreData
 
     template <typename T>
     [[nodiscard]] auto enqueueLoad() -> std::shared_ptr<T>;
+
+    using shared_ptr_dataset_types = auxiliary::detail::
+        map_variant<auxiliary::detail::as_shared_pointer, dataset_types>::type;
+    [[nodiscard]] auto enqueueLoadVariant() -> shared_ptr_dataset_types;
 };
 
 template <typename Ptr_Type, typename ChildClass = void>
diff --git a/src/LoadStoreChunk.cpp b/src/LoadStoreChunk.cpp
index c229844dab..4d81371604 100644
--- a/src/LoadStoreChunk.cpp
+++ b/src/LoadStoreChunk.cpp
@@ -133,6 +133,29 @@ auto ConfigureLoadStore<ChildClass>::enqueueLoad() -> std::shared_ptr<T>
     return m_rc.loadChunkAllocate_impl<T>(storeChunkConfig());
 }
 
+namespace
+{
+    template <typename ConfigureLoadStore_t>
+    struct VisitorEnqueueLoadVariant
+    {
+        template <typename T>
+        static auto call(RecordComponent const &, ConfigureLoadStore_t &cfg) ->
+            typename ConfigureLoadStore_t::shared_ptr_dataset_types
+        {
+            return cfg.template enqueueLoad<T>();
+        }
+    };
+} // namespace
+
+template <typename ChildClass>
+auto ConfigureLoadStore<ChildClass>::enqueueLoadVariant()
+    -> shared_ptr_dataset_types
+{
+    return m_rc
+        .visit<VisitorEnqueueLoadVariant<ConfigureLoadStore<ChildClass>>>(
+            *this);
+}
+
 template <typename Ptr_Type, typename ChildClass>
 ConfigureStoreChunkFromBuffer<Ptr_Type, ChildClass>::
     ConfigureStoreChunkFromBuffer(Ptr_Type buffer, parent_t &&parent)
diff --git a/test/SerialIOTest.cpp b/test/SerialIOTest.cpp
index bbb8225d4a..1e201580e2 100644
--- a/test/SerialIOTest.cpp
+++ b/test/SerialIOTest.cpp
@@ -1659,13 +1659,17 @@ inline void write_test(const std::string &backend)
     auto opaqueTypeDataset = rc.visit<ReadFromAnyType>();
 
     auto variantTypeDataset = rc.loadChunkVariant();
+    auto variantTypeDataset2 = rc.prepareLoadStore().enqueueLoadVariant();
     rc.seriesFlush();
-    std::visit(
-        [](auto &&shared_ptr) {
-            std::cout << "First value in loaded chunk: '" << shared_ptr.get()[0]
-                      << '\'' << std::endl;
-        },
-        variantTypeDataset);
+    for (auto ptr : {&variantTypeDataset, &variantTypeDataset2})
+    {
+        std::visit(
+            [](auto &&shared_ptr) {
+                std::cout << "First value in loaded chunk: '"
+                          << shared_ptr.get()[0] << '\'' << std::endl;
+            },
+            *ptr);
+    }
 }
 
 TEST_CASE("write_test", "[serial]")