Variant: add inplace constructor (project-chip#13232)

Author: kghost

src/credentials/FabricTable.h

@@ -21,6 +21,8 @@
 
 #pragma once
 
+#include <algorithm>
+
 #include <app/util/basic-types.h>
 #include <credentials/CHIPCert.h>
 #include <crypto/CHIPCryptoPAL.h>

src/credentials/GroupDataProvider.h

@@ -16,12 +16,14 @@
  */
 #pragma once
 
+#include <algorithm>
+#include <stdint.h>
+#include <sys/types.h>
+
 #include <app-common/zap-generated/cluster-objects.h>
 #include <app/util/basic-types.h>
 #include <crypto/CHIPCryptoPAL.h>
 #include <lib/core/CHIPError.h>
-#include <stdint.h>
-#include <sys/types.h>
 #include <transport/raw/MessageHeader.h>
 
 namespace chip {

src/darwin/Framework/CHIP/CHIPOperationalCredentialsDelegate.h

@@ -15,6 +15,8 @@
  *    limitations under the License.
  */
 
+#include <memory>
+
 #import <Foundation/Foundation.h>
 #import <Security/Security.h>
 

src/darwin/Framework/CHIP/CHIPOperationalCredentialsDelegate.mm

@@ -15,6 +15,8 @@
  *    limitations under the License.
  */
 
+#include <algorithm>
+
 #import "CHIPOperationalCredentialsDelegate.h"
 
 #import <Security/Security.h>

src/lib/core/InPlace.h

@@ -33,4 +33,12 @@ struct InPlaceType
 };
 constexpr InPlaceType InPlace{};
 
+template <class T>
+struct InPlaceTemplateType
+{
+    explicit InPlaceTemplateType() = default;
+};
+template <class T>
+constexpr InPlaceTemplateType<T> InPlaceTemplate{};
+
 } // namespace chip

src/lib/core/Optional.h

@@ -23,9 +23,10 @@
  */
 #pragma once
 
+#include <new>
+
 #include <lib/core/CHIPCore.h>
 #include <lib/core/InPlace.h>
-#include <lib/support/Variant.h>
 
 namespace chip {
 

src/lib/support/Variant.h

@@ -27,6 +27,8 @@
 #include <typeinfo>
 #include <utility>
 
+#include <lib/core/InPlace.h>
+
 namespace chip {
 
 namespace VariantInternal {
@@ -148,6 +150,13 @@ struct Variant
 public:
     Variant() : mTypeId(kInvalidType) {}
 
+    template <typename T, class... Args>
+    constexpr explicit Variant(InPlaceTemplateType<T>, Args &&... args) :
+        mTypeId(VariantInternal::TupleIndexOfType<T, std::tuple<Ts...>>::value)
+    {
+        new (&mData) T(std::forward<Args>(args)...);
+    }
+
     Variant(const Variant<Ts...> & that) : mTypeId(that.mTypeId) { Curry::Copy(that.mTypeId, &that.mData, &mData); }
 
     Variant(Variant<Ts...> && that) : mTypeId(that.mTypeId)
@@ -193,9 +202,7 @@ struct Variant
     template <typename T, typename... Args>
     static Variant<Ts...> Create(Args &&... args)
     {
-        Variant<Ts...> instance;
-        instance.template Set<T>(std::forward<Args>(args)...);
-        return instance;
+        return Variant<Ts...>(InPlaceTemplate<T>, std::forward<Args>(args)...);
     }
 
     template <typename T, typename... Args>

src/lib/support/tests/TestVariant.cpp

@@ -16,6 +16,8 @@
  *    limitations under the License.
  */
 
+#include <functional>
+
 #include <lib/support/UnitTestRegistration.h>
 #include <lib/support/Variant.h>
 
@@ -208,6 +210,21 @@ void TestVariantMoveAssign(nlTestSuite * inSuite, void * inContext)
     NL_TEST_ASSERT(inSuite, v2.Get<Pod>().m2 == 10);
 }
 
+void TestVariantInPlace(nlTestSuite * inSuite, void * inContext)
+{
+    int i = 0;
+
+    Variant<std::reference_wrapper<int>> v1 = Variant<std::reference_wrapper<int>>(InPlaceTemplate<std::reference_wrapper<int>>, i);
+    NL_TEST_ASSERT(inSuite, v1.Valid());
+    NL_TEST_ASSERT(inSuite, v1.Is<std::reference_wrapper<int>>());
+    NL_TEST_ASSERT(inSuite, &v1.Get<std::reference_wrapper<int>>().get() == &i);
+
+    Variant<std::reference_wrapper<int>> v2 = Variant<std::reference_wrapper<int>>::Create<std::reference_wrapper<int>>(i);
+    NL_TEST_ASSERT(inSuite, v2.Valid());
+    NL_TEST_ASSERT(inSuite, v2.Is<std::reference_wrapper<int>>());
+    NL_TEST_ASSERT(inSuite, &v2.Get<std::reference_wrapper<int>>().get() == &i);
+}
+
 void TestVariantCompare(nlTestSuite * inSuite, void * inContext)
 {
     Variant<Simple, Pod> v0;
@@ -268,11 +285,11 @@ int Teardown(void * inContext)
 /**
  *   Test Suite. It lists all the test functions.
  */
-static const nlTest sTests[] = {
-    NL_TEST_DEF_FN(TestVariantSimple),     NL_TEST_DEF_FN(TestVariantMovable), NL_TEST_DEF_FN(TestVariantCtorDtor),
-    NL_TEST_DEF_FN(TestVariantCopy),       NL_TEST_DEF_FN(TestVariantMove),    NL_TEST_DEF_FN(TestVariantCopyAssign),
-    NL_TEST_DEF_FN(TestVariantMoveAssign), NL_TEST_DEF_FN(TestVariantCompare), NL_TEST_SENTINEL()
-};
+static const nlTest sTests[] = { NL_TEST_DEF_FN(TestVariantSimple),     NL_TEST_DEF_FN(TestVariantMovable),
+                                 NL_TEST_DEF_FN(TestVariantCtorDtor),   NL_TEST_DEF_FN(TestVariantCopy),
+                                 NL_TEST_DEF_FN(TestVariantMove),       NL_TEST_DEF_FN(TestVariantCopyAssign),
+                                 NL_TEST_DEF_FN(TestVariantMoveAssign), NL_TEST_DEF_FN(TestVariantInPlace),
+                                 NL_TEST_DEF_FN(TestVariantCompare),    NL_TEST_SENTINEL() };
 
 int TestVariant()
 {