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+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+// Adapted from donated nonius code.
+
+#ifndef CATCH_BENCHMARK_FUNCTION_HPP_INCLUDED
+#define CATCH_BENCHMARK_FUNCTION_HPP_INCLUDED
+
+#include <catch2/benchmark/catch_chronometer.hpp>
+#include <catch2/internal/catch_meta.hpp>
+#include <catch2/internal/catch_unique_ptr.hpp>
+#include <catch2/internal/catch_move_and_forward.hpp>
+
+#include <type_traits>
+
+namespace Catch {
+    namespace Benchmark {
+        namespace Detail {
+            template <typename T, typename U>
+            struct is_related
+                : std::is_same<std::decay_t<T>, std::decay_t<U>> {};
+
+            /// We need to reinvent std::function because every piece of code that might add overhead
+            /// in a measurement context needs to have consistent performance characteristics so that we
+            /// can account for it in the measurement.
+            /// Implementations of std::function with optimizations that aren't always applicable, like
+            /// small buffer optimizations, are not uncommon.
+            /// This is effectively an implementation of std::function without any such optimizations;
+            /// it may be slow, but it is consistently slow.
+            struct BenchmarkFunction {
+            private:
+                struct callable {
+                    virtual void call(Chronometer meter) const = 0;
+                    virtual ~callable(); // = default;
+
+                    callable() = default;
+                    callable(callable&&) = default;
+                    callable& operator=(callable&&) = default;
+                };
+                template <typename Fun>
+                struct model : public callable {
+                    model(Fun&& fun_) : fun(CATCH_MOVE(fun_)) {}
+                    model(Fun const& fun_) : fun(fun_) {}
+
+                    void call(Chronometer meter) const override {
+                        call(meter, is_callable<Fun(Chronometer)>());
+                    }
+                    void call(Chronometer meter, std::true_type) const {
+                        fun(meter);
+                    }
+                    void call(Chronometer meter, std::false_type) const {
+                        meter.measure(fun);
+                    }
+
+                    Fun fun;
+                };
+
+            public:
+                BenchmarkFunction();
+
+                template <typename Fun,
+                    std::enable_if_t<!is_related<Fun, BenchmarkFunction>::value, int> = 0>
+                    BenchmarkFunction(Fun&& fun)
+                    : f(new model<std::decay_t<Fun>>(CATCH_FORWARD(fun))) {}
+
+                BenchmarkFunction( BenchmarkFunction&& that ) noexcept:
+                    f( CATCH_MOVE( that.f ) ) {}
+
+                BenchmarkFunction&
+                operator=( BenchmarkFunction&& that ) noexcept {
+                    f = CATCH_MOVE( that.f );
+                    return *this;
+                }
+
+                void operator()(Chronometer meter) const { f->call(meter); }
+
+            private:
+                Catch::Detail::unique_ptr<callable> f;
+            };
+        } // namespace Detail
+    } // namespace Benchmark
+} // namespace Catch
+
+#endif // CATCH_BENCHMARK_FUNCTION_HPP_INCLUDED