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-rw-r--r--absl/utility/BUILD.bazel3
-rw-r--r--absl/utility/utility.h79
-rw-r--r--absl/utility/utility_test.cc178
3 files changed, 240 insertions, 20 deletions
diff --git a/absl/utility/BUILD.bazel b/absl/utility/BUILD.bazel
index 396b05f8..62984626 100644
--- a/absl/utility/BUILD.bazel
+++ b/absl/utility/BUILD.bazel
@@ -14,6 +14,7 @@ cc_library(
hdrs = ["utility.h"],
copts = ABSL_DEFAULT_COPTS,
deps = [
+ "//absl/base:base_internal",
"//absl/base:config",
"//absl/meta:type_traits",
],
@@ -26,6 +27,8 @@ cc_test(
deps = [
":utility",
"//absl/base:core_headers",
+ "//absl/memory",
+ "//absl/strings",
"@com_google_googletest//:gtest_main",
],
)
diff --git a/absl/utility/utility.h b/absl/utility/utility.h
index 732cd4c5..d37f4c30 100644
--- a/absl/utility/utility.h
+++ b/absl/utility/utility.h
@@ -23,6 +23,7 @@
// * make_integer_sequence<T, N> == std::make_integer_sequence<T, N>
// * make_index_sequence<N> == std::make_index_sequence<N>
// * index_sequence_for<Ts...> == std::index_sequence_for<Ts...>
+// * apply<Functor, Tuple> == std::apply<Functor, Tuple>
//
// 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
@@ -31,34 +32,20 @@
// References:
//
// http://en.cppreference.com/w/cpp/utility/integer_sequence
+// http://en.cppreference.com/w/cpp/utility/apply
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html
//
-//
-// Example:
-// // Unpack a tuple for use as a function call's argument list.
-//
-// template <typename F, typename Tup, size_t... Is>
-// auto Impl(F f, const Tup& tup, absl::index_sequence<Is...>)
-// -> decltype(f(std::get<Is>(tup) ...)) {
-// return f(std::get<Is>(tup) ...);
-// }
-//
-// template <typename Tup>
-// using TupIdxSeq = absl::make_index_sequence<std::tuple_size<Tup>::value>;
-//
-// template <typename F, typename Tup>
-// auto ApplyFromTuple(F f, const Tup& tup)
-// -> decltype(Impl(f, tup, TupIdxSeq<Tup>{})) {
-// return Impl(f, tup, TupIdxSeq<Tup>{});
-// }
+
#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/invoke.h"
#include "absl/meta/type_traits.h"
namespace absl {
@@ -214,6 +201,62 @@ constexpr T&& forward(
return static_cast<T&&>(t);
}
+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{void Bar(int);};
+// void user_function(int, std::string);
+// void user_function(std::unique_ptr<Foo>);
+//
+// int main()
+// {
+// std::tuple<int, std::string> tuple1(42, "bar");
+// // Invokes the user function overload on int, std::string.
+// absl::apply(&user_function, tuple1);
+//
+// auto foo = absl::make_unique<Foo>();
+// std::tuple<Foo*, int> tuple2(foo.get(), 42);
+// // Invokes the method Bar on foo with one argument 42.
+// absl::apply(&Foo::Bar, foo.get(), 42);
+//
+// std::tuple<std::unique_ptr<Foo>> tuple3(absl::make_unique<Foo>());
+// // Invokes the user function that takes ownership of the unique
+// // pointer.
+// absl::apply(&user_function, std::move(tuple));
+// }
+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 absl
#endif // ABSL_UTILITY_UTILITY_H_
diff --git a/absl/utility/utility_test.cc b/absl/utility/utility_test.cc
index 62cb46f4..342165ed 100644
--- a/absl/utility/utility_test.cc
+++ b/absl/utility/utility_test.cc
@@ -23,6 +23,8 @@
#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 {
@@ -38,8 +40,9 @@ namespace {
#pragma warning( disable : 4101 ) // unreferenced local variable
#endif // _MSC_VER
-using testing::StaticAssertTypeEq;
-using testing::ElementsAre;
+using ::testing::ElementsAre;
+using ::testing::Pointee;
+using ::testing::StaticAssertTypeEq;
TEST(IntegerSequenceTest, ValueType) {
StaticAssertTypeEq<int, absl::integer_sequence<int>::value_type>();
@@ -159,5 +162,176 @@ TEST(IndexSequenceForTest, Example) {
ElementsAre("12", "abc", "3.14"));
}
+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)),
+ ::testing::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)));
+}
+
} // namespace
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-14 01:46:29 +0000