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.venv/Lib/site-packages/pyarrow/include/arrow/util/functional.h

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+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#pragma once
+
+#include <memory>
+#include <tuple>
+#include <type_traits>
+
+#include "arrow/result.h"
+#include "arrow/util/macros.h"
+
+namespace arrow {
+namespace internal {
+
+struct Empty {
+  static Result<Empty> ToResult(Status s) {
+    if (ARROW_PREDICT_TRUE(s.ok())) {
+      return Empty{};
+    }
+    return s;
+  }
+};
+
+/// Helper struct for examining lambdas and other callables.
+/// TODO(ARROW-12655) support function pointers
+struct call_traits {
+ public:
+  template <typename R, typename... A>
+  static std::false_type is_overloaded_impl(R(A...));
+
+  template <typename F>
+  static std::false_type is_overloaded_impl(decltype(&F::operator())*);
+
+  template <typename F>
+  static std::true_type is_overloaded_impl(...);
+
+  template <typename F, typename R, typename... A>
+  static R return_type_impl(R (F::*)(A...));
+
+  template <typename F, typename R, typename... A>
+  static R return_type_impl(R (F::*)(A...) const);
+
+  template <std::size_t I, typename F, typename R, typename... A>
+  static typename std::tuple_element<I, std::tuple<A...>>::type argument_type_impl(
+      R (F::*)(A...));
+
+  template <std::size_t I, typename F, typename R, typename... A>
+  static typename std::tuple_element<I, std::tuple<A...>>::type argument_type_impl(
+      R (F::*)(A...) const);
+
+  template <std::size_t I, typename F, typename R, typename... A>
+  static typename std::tuple_element<I, std::tuple<A...>>::type argument_type_impl(
+      R (F::*)(A...) &&);
+
+  template <typename F, typename R, typename... A>
+  static std::integral_constant<int, sizeof...(A)> argument_count_impl(R (F::*)(A...));
+
+  template <typename F, typename R, typename... A>
+  static std::integral_constant<int, sizeof...(A)> argument_count_impl(R (F::*)(A...)
+                                                                           const);
+
+  template <typename F, typename R, typename... A>
+  static std::integral_constant<int, sizeof...(A)> argument_count_impl(R (F::*)(A...) &&);
+
+  /// bool constant indicating whether F is a callable with more than one possible
+  /// signature. Will be true_type for objects which define multiple operator() or which
+  /// define a template operator()
+  template <typename F>
+  using is_overloaded =
+      decltype(is_overloaded_impl<typename std::decay<F>::type>(NULLPTR));
+
+  template <typename F, typename T = void>
+  using enable_if_overloaded = typename std::enable_if<is_overloaded<F>::value, T>::type;
+
+  template <typename F, typename T = void>
+  using disable_if_overloaded =
+      typename std::enable_if<!is_overloaded<F>::value, T>::type;
+
+  /// If F is not overloaded, the argument types of its call operator can be
+  /// extracted via call_traits::argument_type<Index, F>
+  template <std::size_t I, typename F>
+  using argument_type = decltype(argument_type_impl<I>(&std::decay<F>::type::operator()));
+
+  template <typename F>
+  using argument_count = decltype(argument_count_impl(&std::decay<F>::type::operator()));
+
+  template <typename F>
+  using return_type = decltype(return_type_impl(&std::decay<F>::type::operator()));
+
+  template <typename F, typename T, typename RT = T>
+  using enable_if_return =
+      typename std::enable_if<std::is_same<return_type<F>, T>::value, RT>;
+
+  template <typename T, typename R = void>
+  using enable_if_empty = typename std::enable_if<std::is_same<T, Empty>::value, R>::type;
+
+  template <typename T, typename R = void>
+  using enable_if_not_empty =
+      typename std::enable_if<!std::is_same<T, Empty>::value, R>::type;
+};
+
+/// A type erased callable object which may only be invoked once.
+/// It can be constructed from any lambda which matches the provided call signature.
+/// Invoking it results in destruction of the lambda, freeing any state/references
+/// immediately. Invoking a default constructed FnOnce or one which has already been
+/// invoked will segfault.
+template <typename Signature>
+class FnOnce;
+
+template <typename R, typename... A>
+class FnOnce<R(A...)> {
+ public:
+  FnOnce() = default;
+
+  template <typename Fn,
+            typename = typename std::enable_if<std::is_convertible<
+                decltype(std::declval<Fn&&>()(std::declval<A>()...)), R>::value>::type>
+  FnOnce(Fn fn) : impl_(new FnImpl<Fn>(std::move(fn))) {  // NOLINT runtime/explicit
+  }
+
+  explicit operator bool() const { return impl_ != NULLPTR; }
+
+  R operator()(A... a) && {
+    auto bye = std::move(impl_);
+    return bye->invoke(std::forward<A&&>(a)...);
+  }
+
+ private:
+  struct Impl {
+    virtual ~Impl() = default;
+    virtual R invoke(A&&... a) = 0;
+  };
+
+  template <typename Fn>
+  struct FnImpl : Impl {
+    explicit FnImpl(Fn fn) : fn_(std::move(fn)) {}
+    R invoke(A&&... a) override { return std::move(fn_)(std::forward<A&&>(a)...); }
+    Fn fn_;
+  };
+
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace internal
+}  // namespace arrow