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Fr4nz D13trich 2025-11-22 14:04:28 +01:00
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// Copyright 2023 The Abseil Authors
//
// 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
//
// https://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.
// The IfConstexpr and IfConstexprElse utilities in this file are meant to be
// used to emulate `if constexpr` in pre-C++17 mode in library implementation.
// The motivation is to allow for avoiding complex SFINAE.
//
// The functions passed in must depend on the type(s) of the object(s) that
// require SFINAE. For example:
// template<typename T>
// int MaybeFoo(T& t) {
// if constexpr (HasFoo<T>::value) return t.foo();
// return 0;
// }
//
// can be written in pre-C++17 as:
//
// template<typename T>
// int MaybeFoo(T& t) {
// int i = 0;
// absl::utility_internal::IfConstexpr<HasFoo<T>::value>(
// [&](const auto& fooer) { i = fooer.foo(); }, t);
// return i;
// }
#ifndef ABSL_UTILITY_INTERNAL_IF_CONSTEXPR_H_
#define ABSL_UTILITY_INTERNAL_IF_CONSTEXPR_H_
#include <tuple>
#include <utility>
#include "absl/base/config.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace utility_internal {
template <bool condition, typename TrueFunc, typename FalseFunc,
typename... Args>
auto IfConstexprElse(TrueFunc&& true_func, FalseFunc&& false_func,
Args&&... args) {
return std::get<condition>(std::forward_as_tuple(
std::forward<FalseFunc>(false_func), std::forward<TrueFunc>(true_func)))(
std::forward<Args>(args)...);
}
template <bool condition, typename Func, typename... Args>
void IfConstexpr(Func&& func, Args&&... args) {
IfConstexprElse<condition>(std::forward<Func>(func), [](auto&&...){},
std::forward<Args>(args)...);
}
} // namespace utility_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_UTILITY_INTERNAL_IF_CONSTEXPR_H_

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// Copyright 2023 The Abseil Authors
//
// 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
//
// https://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.
#include "absl/utility/internal/if_constexpr.h"
#include <utility>
#include "gtest/gtest.h"
namespace {
struct Empty {};
struct HasFoo {
int foo() const { return 1; }
};
TEST(IfConstexpr, Basic) {
int i = 0;
absl::utility_internal::IfConstexpr<false>(
[&](const auto& t) { i = t.foo(); }, Empty{});
EXPECT_EQ(i, 0);
absl::utility_internal::IfConstexpr<false>(
[&](const auto& t) { i = t.foo(); }, HasFoo{});
EXPECT_EQ(i, 0);
absl::utility_internal::IfConstexpr<true>(
[&](const auto& t) { i = t.foo(); }, HasFoo{});
EXPECT_EQ(i, 1);
}
TEST(IfConstexprElse, Basic) {
EXPECT_EQ(absl::utility_internal::IfConstexprElse<false>(
[&](const auto& t) { return t.foo(); }, [&](const auto&) { return 2; },
Empty{}), 2);
EXPECT_EQ(absl::utility_internal::IfConstexprElse<false>(
[&](const auto& t) { return t.foo(); }, [&](const auto&) { return 2; },
HasFoo{}), 2);
EXPECT_EQ(absl::utility_internal::IfConstexprElse<true>(
[&](const auto& t) { return t.foo(); }, [&](const auto&) { return 2; },
HasFoo{}), 1);
}
struct HasFooRValue {
int foo() && { return 1; }
};
struct RValueFunc {
void operator()(HasFooRValue&& t) && { *i = std::move(t).foo(); }
int* i = nullptr;
};
TEST(IfConstexpr, RValues) {
int i = 0;
RValueFunc func = {&i};
absl::utility_internal::IfConstexpr<false>(
std::move(func), HasFooRValue{});
EXPECT_EQ(i, 0);
func = RValueFunc{&i};
absl::utility_internal::IfConstexpr<true>(
std::move(func), HasFooRValue{});
EXPECT_EQ(i, 1);
}
} // namespace

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// Copyright 2017 The Abseil Authors.
//
// 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
//
// https://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.
//
// This header file contains C++14 versions of standard <utility> header
// abstractions available within C++17, and are designed to be drop-in
// replacement for code compliant with C++14 and C++17.
//
// The following abstractions are defined:
//
// * apply<Functor, Tuple> == std::apply<Functor, Tuple>
// * exchange<T> == std::exchange<T>
// * make_from_tuple<T> == std::make_from_tuple<T>
//
// This header file also provides the tag types `in_place_t`, `in_place_type_t`,
// and `in_place_index_t`, as well as the constant `in_place`, and
// `constexpr` `std::move()` and `std::forward()` implementations in C++11.
//
// References:
//
// https://en.cppreference.com/w/cpp/utility/apply
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html
#ifndef ABSL_UTILITY_UTILITY_H_
#define ABSL_UTILITY_UTILITY_H_
#include <cstddef>
#include <cstdlib>
#include <tuple>
#include <utility>
#include "absl/base/config.h"
#include "absl/base/internal/inline_variable.h"
#include "absl/base/internal/invoke.h"
#include "absl/meta/type_traits.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
// Historical note: Abseil once provided implementations of these
// abstractions for platforms that had not yet provided them. Those
// platforms are no longer supported. New code should simply use the
// the ones from std directly.
using std::exchange;
using std::forward;
using std::index_sequence;
using std::index_sequence_for;
using std::integer_sequence;
using std::make_index_sequence;
using std::make_integer_sequence;
using std::move;
namespace utility_internal {
template <typename T>
struct InPlaceTypeTag {
explicit InPlaceTypeTag() = delete;
InPlaceTypeTag(const InPlaceTypeTag&) = delete;
InPlaceTypeTag& operator=(const InPlaceTypeTag&) = delete;
};
template <size_t I>
struct InPlaceIndexTag {
explicit InPlaceIndexTag() = delete;
InPlaceIndexTag(const InPlaceIndexTag&) = delete;
InPlaceIndexTag& operator=(const InPlaceIndexTag&) = delete;
};
} // namespace utility_internal
// Tag types
#ifdef ABSL_USES_STD_OPTIONAL
using std::in_place_t;
using std::in_place;
#else // ABSL_USES_STD_OPTIONAL
// in_place_t
//
// Tag type used to specify in-place construction, such as with
// `absl::optional`, designed to be a drop-in replacement for C++17's
// `std::in_place_t`.
struct in_place_t {};
ABSL_INTERNAL_INLINE_CONSTEXPR(in_place_t, in_place, {});
#endif // ABSL_USES_STD_OPTIONAL
#if defined(ABSL_USES_STD_ANY) || defined(ABSL_USES_STD_VARIANT)
using std::in_place_type;
using std::in_place_type_t;
#else
// in_place_type_t
//
// Tag type used for in-place construction when the type to construct needs to
// be specified, such as with `absl::any`, designed to be a drop-in replacement
// for C++17's `std::in_place_type_t`.
template <typename T>
using in_place_type_t = void (*)(utility_internal::InPlaceTypeTag<T>);
template <typename T>
void in_place_type(utility_internal::InPlaceTypeTag<T>) {}
#endif // ABSL_USES_STD_ANY || ABSL_USES_STD_VARIANT
#ifdef ABSL_USES_STD_VARIANT
using std::in_place_index;
using std::in_place_index_t;
#else
// in_place_index_t
//
// Tag type used for in-place construction when the type to construct needs to
// be specified, such as with `absl::any`, designed to be a drop-in replacement
// for C++17's `std::in_place_index_t`.
template <size_t I>
using in_place_index_t = void (*)(utility_internal::InPlaceIndexTag<I>);
template <size_t I>
void in_place_index(utility_internal::InPlaceIndexTag<I>) {}
#endif // ABSL_USES_STD_VARIANT
namespace utility_internal {
// Helper method for expanding tuple into a called method.
template <typename Functor, typename Tuple, std::size_t... Indexes>
auto apply_helper(Functor&& functor, Tuple&& t, index_sequence<Indexes...>)
-> decltype(absl::base_internal::invoke(
absl::forward<Functor>(functor),
std::get<Indexes>(absl::forward<Tuple>(t))...)) {
return absl::base_internal::invoke(
absl::forward<Functor>(functor),
std::get<Indexes>(absl::forward<Tuple>(t))...);
}
} // namespace utility_internal
// apply
//
// Invokes a Callable using elements of a tuple as its arguments.
// Each element of the tuple corresponds to an argument of the call (in order).
// Both the Callable argument and the tuple argument are perfect-forwarded.
// For member-function Callables, the first tuple element acts as the `this`
// pointer. `absl::apply` is designed to be a drop-in replacement for C++17's
// `std::apply`. Unlike C++17's `std::apply`, this is not currently `constexpr`.
//
// Example:
//
// class Foo {
// public:
// void Bar(int);
// };
// void user_function1(int, std::string);
// void user_function2(std::unique_ptr<Foo>);
// auto user_lambda = [](int, int) {};
//
// int main()
// {
// std::tuple<int, std::string> tuple1(42, "bar");
// // Invokes the first user function on int, std::string.
// absl::apply(&user_function1, tuple1);
//
// std::tuple<std::unique_ptr<Foo>> tuple2(absl::make_unique<Foo>());
// // Invokes the user function that takes ownership of the unique
// // pointer.
// absl::apply(&user_function2, std::move(tuple2));
//
// auto foo = absl::make_unique<Foo>();
// std::tuple<Foo*, int> tuple3(foo.get(), 42);
// // Invokes the method Bar on foo with one argument, 42.
// absl::apply(&Foo::Bar, tuple3);
//
// std::tuple<int, int> tuple4(8, 9);
// // Invokes a lambda.
// absl::apply(user_lambda, tuple4);
// }
template <typename Functor, typename Tuple>
auto apply(Functor&& functor, Tuple&& t)
-> decltype(utility_internal::apply_helper(
absl::forward<Functor>(functor), absl::forward<Tuple>(t),
absl::make_index_sequence<std::tuple_size<
typename std::remove_reference<Tuple>::type>::value>{})) {
return utility_internal::apply_helper(
absl::forward<Functor>(functor), absl::forward<Tuple>(t),
absl::make_index_sequence<std::tuple_size<
typename std::remove_reference<Tuple>::type>::value>{});
}
namespace utility_internal {
template <typename T, typename Tuple, size_t... I>
T make_from_tuple_impl(Tuple&& tup, absl::index_sequence<I...>) {
return T(std::get<I>(std::forward<Tuple>(tup))...);
}
} // namespace utility_internal
// make_from_tuple
//
// Given the template parameter type `T` and a tuple of arguments
// `std::tuple(arg0, arg1, ..., argN)` constructs an object of type `T` as if by
// calling `T(arg0, arg1, ..., argN)`.
//
// Example:
//
// std::tuple<const char*, size_t> args("hello world", 5);
// auto s = absl::make_from_tuple<std::string>(args);
// assert(s == "hello");
//
template <typename T, typename Tuple>
constexpr T make_from_tuple(Tuple&& tup) {
return utility_internal::make_from_tuple_impl<T>(
std::forward<Tuple>(tup),
absl::make_index_sequence<
std::tuple_size<absl::decay_t<Tuple>>::value>{});
}
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_UTILITY_UTILITY_H_

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// Copyright 2022 The Abseil Authors.
//
// 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
//
// https://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.
#include "absl/utility/utility.h"
#include <memory>
#include <sstream>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/base/attributes.h"
#include "absl/memory/memory.h"
#include "absl/strings/str_cat.h"
namespace {
using ::testing::ElementsAre;
using ::testing::Pointee;
using ::testing::StaticAssertTypeEq;
int Function(int a, int b) { return a - b; }
int Sink(std::unique_ptr<int> p) { return *p; }
std::unique_ptr<int> Factory(int n) { return absl::make_unique<int>(n); }
void NoOp() {}
struct ConstFunctor {
int operator()(int a, int b) const { return a - b; }
};
struct MutableFunctor {
int operator()(int a, int b) { return a - b; }
};
struct EphemeralFunctor {
EphemeralFunctor() {}
EphemeralFunctor(const EphemeralFunctor&) {}
EphemeralFunctor(EphemeralFunctor&&) {}
int operator()(int a, int b) && { return a - b; }
};
struct OverloadedFunctor {
OverloadedFunctor() {}
OverloadedFunctor(const OverloadedFunctor&) {}
OverloadedFunctor(OverloadedFunctor&&) {}
template <typename... Args>
std::string operator()(const Args&... args) & {
return absl::StrCat("&", args...);
}
template <typename... Args>
std::string operator()(const Args&... args) const& {
return absl::StrCat("const&", args...);
}
template <typename... Args>
std::string operator()(const Args&... args) && {
return absl::StrCat("&&", args...);
}
};
struct Class {
int Method(int a, int b) { return a - b; }
int ConstMethod(int a, int b) const { return a - b; }
int member;
};
struct FlipFlop {
int ConstMethod() const { return member; }
FlipFlop operator*() const { return {-member}; }
int member;
};
TEST(ApplyTest, Function) {
EXPECT_EQ(1, absl::apply(Function, std::make_tuple(3, 2)));
EXPECT_EQ(1, absl::apply(&Function, std::make_tuple(3, 2)));
}
TEST(ApplyTest, NonCopyableArgument) {
EXPECT_EQ(42, absl::apply(Sink, std::make_tuple(absl::make_unique<int>(42))));
}
TEST(ApplyTest, NonCopyableResult) {
EXPECT_THAT(absl::apply(Factory, std::make_tuple(42)), Pointee(42));
}
TEST(ApplyTest, VoidResult) { absl::apply(NoOp, std::tuple<>()); }
TEST(ApplyTest, ConstFunctor) {
EXPECT_EQ(1, absl::apply(ConstFunctor(), std::make_tuple(3, 2)));
}
TEST(ApplyTest, MutableFunctor) {
MutableFunctor f;
EXPECT_EQ(1, absl::apply(f, std::make_tuple(3, 2)));
EXPECT_EQ(1, absl::apply(MutableFunctor(), std::make_tuple(3, 2)));
}
TEST(ApplyTest, EphemeralFunctor) {
EphemeralFunctor f;
EXPECT_EQ(1, absl::apply(std::move(f), std::make_tuple(3, 2)));
EXPECT_EQ(1, absl::apply(EphemeralFunctor(), std::make_tuple(3, 2)));
}
TEST(ApplyTest, OverloadedFunctor) {
OverloadedFunctor f;
const OverloadedFunctor& cf = f;
EXPECT_EQ("&", absl::apply(f, std::tuple<>{}));
EXPECT_EQ("& 42", absl::apply(f, std::make_tuple(" 42")));
EXPECT_EQ("const&", absl::apply(cf, std::tuple<>{}));
EXPECT_EQ("const& 42", absl::apply(cf, std::make_tuple(" 42")));
EXPECT_EQ("&&", absl::apply(std::move(f), std::tuple<>{}));
OverloadedFunctor f2;
EXPECT_EQ("&& 42", absl::apply(std::move(f2), std::make_tuple(" 42")));
}
TEST(ApplyTest, ReferenceWrapper) {
ConstFunctor cf;
MutableFunctor mf;
EXPECT_EQ(1, absl::apply(std::cref(cf), std::make_tuple(3, 2)));
EXPECT_EQ(1, absl::apply(std::ref(cf), std::make_tuple(3, 2)));
EXPECT_EQ(1, absl::apply(std::ref(mf), std::make_tuple(3, 2)));
}
TEST(ApplyTest, MemberFunction) {
std::unique_ptr<Class> p(new Class);
std::unique_ptr<const Class> cp(new Class);
EXPECT_EQ(
1, absl::apply(&Class::Method,
std::tuple<std::unique_ptr<Class>&, int, int>(p, 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::Method,
std::tuple<Class*, int, int>(p.get(), 3, 2)));
EXPECT_EQ(
1, absl::apply(&Class::Method, std::tuple<Class&, int, int>(*p, 3, 2)));
EXPECT_EQ(
1, absl::apply(&Class::ConstMethod,
std::tuple<std::unique_ptr<Class>&, int, int>(p, 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
std::tuple<Class*, int, int>(p.get(), 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
std::tuple<Class&, int, int>(*p, 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
std::tuple<std::unique_ptr<const Class>&, int, int>(
cp, 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
std::tuple<const Class*, int, int>(cp.get(), 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
std::tuple<const Class&, int, int>(*cp, 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::Method,
std::make_tuple(absl::make_unique<Class>(), 3, 2)));
EXPECT_EQ(1, absl::apply(&Class::ConstMethod,
std::make_tuple(absl::make_unique<Class>(), 3, 2)));
EXPECT_EQ(
1, absl::apply(&Class::ConstMethod,
std::make_tuple(absl::make_unique<const Class>(), 3, 2)));
}
TEST(ApplyTest, DataMember) {
std::unique_ptr<Class> p(new Class{42});
std::unique_ptr<const Class> cp(new Class{42});
EXPECT_EQ(
42, absl::apply(&Class::member, std::tuple<std::unique_ptr<Class>&>(p)));
EXPECT_EQ(42, absl::apply(&Class::member, std::tuple<Class&>(*p)));
EXPECT_EQ(42, absl::apply(&Class::member, std::tuple<Class*>(p.get())));
absl::apply(&Class::member, std::tuple<std::unique_ptr<Class>&>(p)) = 42;
absl::apply(&Class::member, std::tuple<Class*>(p.get())) = 42;
absl::apply(&Class::member, std::tuple<Class&>(*p)) = 42;
EXPECT_EQ(42, absl::apply(&Class::member,
std::tuple<std::unique_ptr<const Class>&>(cp)));
EXPECT_EQ(42, absl::apply(&Class::member, std::tuple<const Class&>(*cp)));
EXPECT_EQ(42,
absl::apply(&Class::member, std::tuple<const Class*>(cp.get())));
}
TEST(ApplyTest, FlipFlop) {
FlipFlop obj = {42};
// This call could resolve to (obj.*&FlipFlop::ConstMethod)() or
// ((*obj).*&FlipFlop::ConstMethod)(). We verify that it's the former.
EXPECT_EQ(42, absl::apply(&FlipFlop::ConstMethod, std::make_tuple(obj)));
EXPECT_EQ(42, absl::apply(&FlipFlop::member, std::make_tuple(obj)));
}
TEST(MakeFromTupleTest, String) {
EXPECT_EQ(
absl::make_from_tuple<std::string>(std::make_tuple("hello world", 5)),
"hello");
}
TEST(MakeFromTupleTest, MoveOnlyParameter) {
struct S {
S(std::unique_ptr<int> n, std::unique_ptr<int> m) : value(*n + *m) {}
int value = 0;
};
auto tup =
std::make_tuple(absl::make_unique<int>(3), absl::make_unique<int>(4));
auto s = absl::make_from_tuple<S>(std::move(tup));
EXPECT_EQ(s.value, 7);
}
TEST(MakeFromTupleTest, NoParameters) {
struct S {
S() : value(1) {}
int value = 2;
};
EXPECT_EQ(absl::make_from_tuple<S>(std::make_tuple()).value, 1);
}
TEST(MakeFromTupleTest, Pair) {
EXPECT_EQ(
(absl::make_from_tuple<std::pair<bool, int>>(std::make_tuple(true, 17))),
std::make_pair(true, 17));
}
} // namespace