mirror of
https://github.com/aykhans/AzSuicideDataVisualization.git
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161 lines
5.5 KiB
C++
161 lines
5.5 KiB
C++
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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#pragma once
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#include <memory>
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#include <tuple>
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#include <type_traits>
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#include "arrow/result.h"
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#include "arrow/util/macros.h"
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namespace arrow {
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namespace internal {
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struct Empty {
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static Result<Empty> ToResult(Status s) {
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if (ARROW_PREDICT_TRUE(s.ok())) {
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return Empty{};
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}
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return s;
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}
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};
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/// Helper struct for examining lambdas and other callables.
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/// TODO(ARROW-12655) support function pointers
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struct call_traits {
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public:
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template <typename R, typename... A>
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static std::false_type is_overloaded_impl(R(A...));
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template <typename F>
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static std::false_type is_overloaded_impl(decltype(&F::operator())*);
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template <typename F>
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static std::true_type is_overloaded_impl(...);
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template <typename F, typename R, typename... A>
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static R return_type_impl(R (F::*)(A...));
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template <typename F, typename R, typename... A>
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static R return_type_impl(R (F::*)(A...) const);
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template <std::size_t I, typename F, typename R, typename... A>
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static typename std::tuple_element<I, std::tuple<A...>>::type argument_type_impl(
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R (F::*)(A...));
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template <std::size_t I, typename F, typename R, typename... A>
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static typename std::tuple_element<I, std::tuple<A...>>::type argument_type_impl(
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R (F::*)(A...) const);
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template <std::size_t I, typename F, typename R, typename... A>
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static typename std::tuple_element<I, std::tuple<A...>>::type argument_type_impl(
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R (F::*)(A...) &&);
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template <typename F, typename R, typename... A>
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static std::integral_constant<int, sizeof...(A)> argument_count_impl(R (F::*)(A...));
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template <typename F, typename R, typename... A>
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static std::integral_constant<int, sizeof...(A)> argument_count_impl(R (F::*)(A...)
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const);
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template <typename F, typename R, typename... A>
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static std::integral_constant<int, sizeof...(A)> argument_count_impl(R (F::*)(A...) &&);
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/// bool constant indicating whether F is a callable with more than one possible
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/// signature. Will be true_type for objects which define multiple operator() or which
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/// define a template operator()
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template <typename F>
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using is_overloaded =
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decltype(is_overloaded_impl<typename std::decay<F>::type>(NULLPTR));
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template <typename F, typename T = void>
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using enable_if_overloaded = typename std::enable_if<is_overloaded<F>::value, T>::type;
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template <typename F, typename T = void>
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using disable_if_overloaded =
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typename std::enable_if<!is_overloaded<F>::value, T>::type;
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/// If F is not overloaded, the argument types of its call operator can be
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/// extracted via call_traits::argument_type<Index, F>
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template <std::size_t I, typename F>
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using argument_type = decltype(argument_type_impl<I>(&std::decay<F>::type::operator()));
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template <typename F>
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using argument_count = decltype(argument_count_impl(&std::decay<F>::type::operator()));
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template <typename F>
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using return_type = decltype(return_type_impl(&std::decay<F>::type::operator()));
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template <typename F, typename T, typename RT = T>
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using enable_if_return =
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typename std::enable_if<std::is_same<return_type<F>, T>::value, RT>;
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template <typename T, typename R = void>
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using enable_if_empty = typename std::enable_if<std::is_same<T, Empty>::value, R>::type;
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template <typename T, typename R = void>
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using enable_if_not_empty =
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typename std::enable_if<!std::is_same<T, Empty>::value, R>::type;
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};
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/// A type erased callable object which may only be invoked once.
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/// It can be constructed from any lambda which matches the provided call signature.
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/// Invoking it results in destruction of the lambda, freeing any state/references
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/// immediately. Invoking a default constructed FnOnce or one which has already been
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/// invoked will segfault.
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template <typename Signature>
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class FnOnce;
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template <typename R, typename... A>
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class FnOnce<R(A...)> {
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public:
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FnOnce() = default;
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template <typename Fn,
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typename = typename std::enable_if<std::is_convertible<
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decltype(std::declval<Fn&&>()(std::declval<A>()...)), R>::value>::type>
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FnOnce(Fn fn) : impl_(new FnImpl<Fn>(std::move(fn))) { // NOLINT runtime/explicit
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}
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explicit operator bool() const { return impl_ != NULLPTR; }
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R operator()(A... a) && {
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auto bye = std::move(impl_);
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return bye->invoke(std::forward<A&&>(a)...);
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}
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private:
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struct Impl {
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virtual ~Impl() = default;
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virtual R invoke(A&&... a) = 0;
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};
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template <typename Fn>
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struct FnImpl : Impl {
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explicit FnImpl(Fn fn) : fn_(std::move(fn)) {}
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R invoke(A&&... a) override { return std::move(fn_)(std::forward<A&&>(a)...); }
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Fn fn_;
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};
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std::unique_ptr<Impl> impl_;
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};
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} // namespace internal
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} // namespace arrow
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