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Add C++20 compatible versions of
InvocableMap and QueryableMap.
Sadly, the syntax the clang extension offers cannot be reproduced with standard C++20. These new map types will allow for C++20 support on non-clang compilers. #42 PiperOrigin-RevId: 710765161
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright 2024 Google LLC | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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|
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| #ifndef JNI_BIND_METAPROGRAMMING_INVOCABLE_MAP_20_H | ||
| #define JNI_BIND_METAPROGRAMMING_INVOCABLE_MAP_20_H | ||
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| #include <cstddef> | ||
| #include <string_view> | ||
| #include <tuple> | ||
| #include <type_traits> | ||
| #include <utility> | ||
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| #include "modified_max.h" | ||
| #include "string_literal.h" | ||
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| namespace jni::metaprogramming { | ||
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| // This class enables compile time lookup that perfectly forward arguments | ||
| // to a method named `Call`. This is a C++ 20 version of InvocableMap. | ||
| // | ||
| // This is an interface that can be inherited from to expose a method named | ||
| // `Call`. It provides compile time string index lookup with no macros. | ||
| // | ||
| // To use this API, inherit from this class using template types as follows: | ||
| // | ||
| // |CrtpBase|: The name of the class inheriting from the map. This class | ||
| // will inherit an operator(). It must implement this exact signature: | ||
| // | ||
| // template <std::size_t I, StringLiteral key_literal, typename... Args> | ||
| // auto InvocableMap20Call(Args&&... args); | ||
| // | ||
| // If i is the index where |tup_container_v.*nameable_member|.name_ == key, | ||
| // then InvocableMap20Call will forward the args from operator() with the | ||
| // same args. Static memory can be used in this function call and it will | ||
| // be unique because of the I non-type template parameter. | ||
| // | ||
| // |tup_container_v| is a static instance of an object whose |nameable_member| | ||
| // contains a public field called name_. It might seem strange not to | ||
| // directly pass a const auto&, however, this prevents accessing subobjects. | ||
| // | ||
| // The motivation for using inheritance as opposed to a simple member is that | ||
| // the the const char cannot be propagated without losing its constexpr-ness, | ||
| // and so the clang extension can no longer restrict function candidates. | ||
| template <typename CrtpBase, const auto& tup_container_v, | ||
| typename TupContainerT, const auto TupContainerT::* nameable_member> | ||
| class InvocableMap20 { | ||
| #if __cplusplus >= 202002L | ||
| public: | ||
| template <StringLiteral key_literal, std::size_t Idx, typename... Args> | ||
| constexpr auto Do(Args&&... args) { | ||
| return (*static_cast<CrtpBase*>(this)) | ||
| .template InvocableMap20Call<Idx, key_literal, Args...>( | ||
| std::forward<Args>(args)...); | ||
| } | ||
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| template <std::size_t N, std::size_t... Is> | ||
| static constexpr std::size_t SelectCandidate(StringLiteral<N> string_literal, | ||
| std::index_sequence<Is...>) { | ||
| return ModifiedMax( | ||
| {((std::get<Is>(tup_container_v.*nameable_member).name_ == | ||
| std::string_view{string_literal.value}) | ||
| ? std::size_t{Is} | ||
| : kNegativeOne)..., | ||
| kNegativeOne}); | ||
| } | ||
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| template <StringLiteral string_literal, typename... Args> | ||
| constexpr auto Call(Args&&... args) { | ||
| return Do<string_literal, | ||
| SelectCandidate( | ||
| string_literal, | ||
| std::make_index_sequence<std::tuple_size_v<std::decay_t< | ||
| decltype(tup_container_v.*nameable_member)>>>())>( | ||
| std::forward<Args>(args)...); | ||
| } | ||
| #endif // __cplusplus >= 202002L | ||
| }; | ||
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| template <typename CrtpBase, const auto& tup_container_v, | ||
| const auto std::decay_t<decltype(tup_container_v)>::* nameable_member> | ||
| using InvocableMap20_t = | ||
| InvocableMap20<CrtpBase, tup_container_v, | ||
| std::decay_t<decltype(tup_container_v)>, nameable_member>; | ||
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| } // namespace jni::metaprogramming | ||
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| #endif // JNI_BIND_METAPROGRAMMING_INVOCABLE_MAP_20_H |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| /* | ||
| * Copyright 2024 Google LLC | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| #include "invocable_map_20.h" | ||
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| #include <cstddef> | ||
| #include <string_view> | ||
| #include <tuple> | ||
| #include <type_traits> | ||
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| #include "string_literal.h" | ||
| #include <gtest/gtest.h> | ||
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| using jni::metaprogramming::InvocableMap20_t; | ||
| using jni::metaprogramming::StringLiteral; | ||
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| struct Str { | ||
| const char* name_; | ||
| constexpr Str(const char* name) : name_(name) {} | ||
| }; | ||
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| struct NameContainer { | ||
| std::tuple<Str, Str, Str> container1_; | ||
| std::tuple<Str, Str, Str> container2_; | ||
| }; | ||
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| constexpr NameContainer name_container{ | ||
| {{"Foo"}, {"Bar"}, {"Baz"}}, | ||
| {{"Fizz"}, {"Buzz"}, {"Bang"}}, | ||
| }; | ||
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| //////////////////////////////////////////////////////////////////////////////// | ||
| class SampleClassNowExposingCallOperator1 | ||
| : public InvocableMap20_t<SampleClassNowExposingCallOperator1, | ||
| name_container, &NameContainer::container1_> { | ||
| protected: | ||
| friend InvocableMap20_t<SampleClassNowExposingCallOperator1, name_container, | ||
| &NameContainer::container1_>; | ||
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| template <size_t I, StringLiteral key_literal, typename... Args> | ||
| auto InvocableMap20Call(Args&&... ts) { | ||
| if (std::string_view(key_literal.value) == "Foo") { | ||
| EXPECT_TRUE(I == 0); | ||
| EXPECT_TRUE((std::is_same_v<std::tuple<Args...>, std::tuple<int>>)); | ||
| } else if (std::string_view(key_literal.value) == "Bar") { | ||
| EXPECT_TRUE(I == 1); | ||
| EXPECT_TRUE( | ||
| (std::is_same_v<std::tuple<Args...>, std::tuple<float, float>>)); | ||
| } else if (std::string_view(key_literal.value) == "Baz") { | ||
| EXPECT_TRUE(I == 2); | ||
| EXPECT_TRUE(( | ||
| std::is_same_v<std::tuple<Args...>, std::tuple<int, float, double>>)); | ||
| } else { | ||
| FAIL(); | ||
| } | ||
| } | ||
| }; | ||
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| TEST(InvocableMapTest1, HasCorrectTypesAndForwardsCalls) { | ||
| SampleClassNowExposingCallOperator1 val; | ||
| val.Call<"Foo">(1); | ||
| val.Call<"Bar">(2.f, 3.f); | ||
| val.Call<"Baz">(4, 5.f, double{6}); | ||
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| // By design, doesn't compile. | ||
| // val("BazNar", 7, 8, 9); | ||
| } |
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