From 2125e6444a9de9e41f21ecdc674dd7d8759c149d Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Wed, 1 Aug 2018 04:34:12 -0700 Subject: Export of internal Abseil changes. -- ac7508120c60dfe689c40929e416b6a486f83ee3 by Gennadiy Rozental : Internal change PiperOrigin-RevId: 206912089 -- bd709faba88565367b6d337466e6456481b5f3e8 by Matt Calabrese : Implement `std::experimental::is_detected` in type_traits internals and move `is_detected_convertible` from variant's internals to type_traits internals. This is in preparation of creating workarounds for broken standard traits. PiperOrigin-RevId: 206825598 -- 0dbddea569370eb9b6348cee172d1874f9046eb4 by Jorg Brown : Support users who turn on floating-point conversion warnings PiperOrigin-RevId: 206813209 -- 30991f757c8f0100584619d8a9c41897d029f112 by Jorg Brown : Speed up the absl::Seconds() function for floating-point values, roughly by 4.5x, since we can take advantage of the fact that we're just taking a floating-point number and splitting it into its integral and fractional parts. PiperOrigin-RevId: 206806270 -- 6883837176838aa5a517e7a8cb4c99afd24c0d12 by Jon Cohen : Remove the DISABLE_INSTALL from absl_container. It doesn't do anything. PiperOrigin-RevId: 206802544 -- 92ab14fed06e6dd1f01a0284bd7f95d3e2c0c3d8 by Jon Cohen : Internal change PiperOrigin-RevId: 206776244 -- 17b76c7f364ac562d9e0faeca0320f63aa3fdb85 by Jorg Brown : Fix absl/strings:numbers_test flakiness due to exceeding the 1-minute timeout PiperOrigin-RevId: 206763175 -- 6637843f2e198b8efd90e5577fbc86bdea43b2cc by Abseil Team : Adds templated allocator to absl::FixedArray with corresponding tests PiperOrigin-RevId: 206354178 -- bced22f81add828c9b4c60eb45554d36c22e2f96 by Abseil Team : Adds templated allocator to absl::FixedArray with corresponding tests PiperOrigin-RevId: 206347377 -- 75be14a71d2d5e335812d5b7670120271fb5bd79 by Abseil Team : Internal change. PiperOrigin-RevId: 206326935 -- 6929e43f4c7898b1f51e441911a19092a06fbf97 by Abseil Team : Adds templated allocator to absl::FixedArray with corresponding tests PiperOrigin-RevId: 206326368 -- 55ae34b75ff029eb267f9519e577bab8a575b487 by Abseil Team : Internal change. PiperOrigin-RevId: 206233448 -- 6950a8ccddf35d451eec2d02cd28a797c8b7cf6a by Matt Kulukundis : Internal change PiperOrigin-RevId: 206035613 GitOrigin-RevId: ac7508120c60dfe689c40929e416b6a486f83ee3 Change-Id: I675605abbedab6b3ac9aa82195cbd059ff7c82b1 --- absl/container/internal/compressed_tuple.h | 175 +++++++++++++++++++++++++++++ 1 file changed, 175 insertions(+) create mode 100644 absl/container/internal/compressed_tuple.h (limited to 'absl/container/internal/compressed_tuple.h') diff --git a/absl/container/internal/compressed_tuple.h b/absl/container/internal/compressed_tuple.h new file mode 100644 index 0000000..cc52614 --- /dev/null +++ b/absl/container/internal/compressed_tuple.h @@ -0,0 +1,175 @@ +// Copyright 2018 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 +// +// 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. +// +// Helper class to perform the Empty Base Optimization. +// Ts can contain classes and non-classes, empty or not. For the ones that +// are empty classes, we perform the optimization. If all types in Ts are empty +// classes, then CompressedTuple is itself an empty class. +// +// To access the members, use member get() function. +// +// Eg: +// absl::container_internal::CompressedTuple value(7, t1, t2, +// t3); +// assert(value.get<0>() == 7); +// T1& t1 = value.get<1>(); +// const T2& t2 = value.get<2>(); +// ... +// +// http://en.cppreference.com/w/cpp/language/ebo + +#ifndef ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_ +#define ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_ + +#include +#include +#include + +#include "absl/utility/utility.h" + +#ifdef _MSC_VER +// We need to mark these classes with this declspec to ensure that +// CompressedTuple happens. +#define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC __declspec(empty_bases) +#else // _MSC_VER +#define ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC +#endif // _MSC_VER + +namespace absl { +namespace container_internal { + +template +class CompressedTuple; + +namespace internal_compressed_tuple { + +template +struct Elem; +template +struct Elem, I> + : std::tuple_element> {}; +template +using ElemT = typename Elem::type; + +// Use the __is_final intrinsic if available. Where it's not available, classes +// declared with the 'final' specifier cannot be used as CompressedTuple +// elements. +// TODO(sbenza): Replace this with std::is_final in C++14. +template +constexpr bool IsFinal() { +#if defined(__clang__) || defined(__GNUC__) + return __is_final(T); +#else + return false; +#endif +} + +template +constexpr bool ShouldUseBase() { + return std::is_class::value && std::is_empty::value && !IsFinal(); +} + +// The storage class provides two specializations: +// - For empty classes, it stores T as a base class. +// - For everything else, it stores T as a member. +template >()> +struct Storage { + using T = ElemT; + T value; + constexpr Storage() = default; + explicit constexpr Storage(T&& v) : value(absl::forward(v)) {} + constexpr const T& get() const { return value; } + T& get() { return value; } +}; + +template +struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC Storage + : ElemT { + using T = internal_compressed_tuple::ElemT; + constexpr Storage() = default; + explicit constexpr Storage(T&& v) : T(absl::forward(v)) {} + constexpr const T& get() const { return *this; } + T& get() { return *this; } +}; + +template +struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTupleImpl; + +template +struct ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC + CompressedTupleImpl, absl::index_sequence> + // We use the dummy identity function through std::integral_constant to + // convince MSVC of accepting and expanding I in that context. Without it + // you would get: + // error C3548: 'I': parameter pack cannot be used in this context + : Storage, + std::integral_constant::value>... { + constexpr CompressedTupleImpl() = default; + explicit constexpr CompressedTupleImpl(Ts&&... args) + : Storage, I>(absl::forward(args))... {} +}; + +} // namespace internal_compressed_tuple + +// Helper class to perform the Empty Base Class Optimization. +// Ts can contain classes and non-classes, empty or not. For the ones that +// are empty classes, we perform the CompressedTuple. If all types in Ts are +// empty classes, then CompressedTuple is itself an empty class. +// +// To access the members, use member .get() function. +// +// Eg: +// absl::container_internal::CompressedTuple value(7, t1, t2, +// t3); +// assert(value.get<0>() == 7); +// T1& t1 = value.get<1>(); +// const T2& t2 = value.get<2>(); +// ... +// +// http://en.cppreference.com/w/cpp/language/ebo +template +class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple + : private internal_compressed_tuple::CompressedTupleImpl< + CompressedTuple, absl::index_sequence_for> { + private: + template + using ElemT = internal_compressed_tuple::ElemT; + + public: + constexpr CompressedTuple() = default; + explicit constexpr CompressedTuple(Ts... base) + : CompressedTuple::CompressedTupleImpl(absl::forward(base)...) {} + + template + ElemT& get() { + return internal_compressed_tuple::Storage::get(); + } + + template + constexpr const ElemT& get() const { + return internal_compressed_tuple::Storage::get(); + } +}; + +// Explicit specialization for a zero-element tuple +// (needed to avoid ambiguous overloads for the default constructor). +template <> +class ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC CompressedTuple<> {}; + +} // namespace container_internal +} // namespace absl + +#undef ABSL_INTERNAL_COMPRESSED_TUPLE_DECLSPEC + +#endif // ABSL_CONTAINER_INTERNAL_COMPRESSED_TUPLE_H_ -- cgit v1.2.3