Abseil Common Libraries (C++) (grcp 依赖)
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469 lines
17 KiB
469 lines
17 KiB
// Copyright 2018 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://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, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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#ifndef ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_ |
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#define ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_ |
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#include <cassert> |
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#include <cstddef> |
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#include <memory> |
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#include <new> |
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#include <tuple> |
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#include <type_traits> |
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#include <utility> |
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#include "absl/base/config.h" |
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#include "absl/memory/memory.h" |
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#include "absl/meta/type_traits.h" |
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#include "absl/utility/utility.h" |
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#ifdef ABSL_HAVE_ADDRESS_SANITIZER |
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#include <sanitizer/asan_interface.h> |
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#endif |
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#ifdef ABSL_HAVE_MEMORY_SANITIZER |
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#include <sanitizer/msan_interface.h> |
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#endif |
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namespace absl { |
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ABSL_NAMESPACE_BEGIN |
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namespace container_internal { |
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template <size_t Alignment> |
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struct alignas(Alignment) AlignedType {}; |
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// Allocates at least n bytes aligned to the specified alignment. |
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// Alignment must be a power of 2. It must be positive. |
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// |
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// Note that many allocators don't honor alignment requirements above certain |
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// threshold (usually either alignof(std::max_align_t) or alignof(void*)). |
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// Allocate() doesn't apply alignment corrections. If the underlying allocator |
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// returns insufficiently alignment pointer, that's what you are going to get. |
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template <size_t Alignment, class Alloc> |
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void* Allocate(Alloc* alloc, size_t n) { |
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static_assert(Alignment > 0, ""); |
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assert(n && "n must be positive"); |
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using M = AlignedType<Alignment>; |
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using A = typename absl::allocator_traits<Alloc>::template rebind_alloc<M>; |
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using AT = typename absl::allocator_traits<Alloc>::template rebind_traits<M>; |
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// On macOS, "mem_alloc" is a #define with one argument defined in |
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// rpc/types.h, so we can't name the variable "mem_alloc" and initialize it |
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// with the "foo(bar)" syntax. |
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A my_mem_alloc(*alloc); |
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void* p = AT::allocate(my_mem_alloc, (n + sizeof(M) - 1) / sizeof(M)); |
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assert(reinterpret_cast<uintptr_t>(p) % Alignment == 0 && |
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"allocator does not respect alignment"); |
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return p; |
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} |
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// The pointer must have been previously obtained by calling |
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// Allocate<Alignment>(alloc, n). |
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template <size_t Alignment, class Alloc> |
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void Deallocate(Alloc* alloc, void* p, size_t n) { |
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static_assert(Alignment > 0, ""); |
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assert(n && "n must be positive"); |
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using M = AlignedType<Alignment>; |
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using A = typename absl::allocator_traits<Alloc>::template rebind_alloc<M>; |
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using AT = typename absl::allocator_traits<Alloc>::template rebind_traits<M>; |
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// On macOS, "mem_alloc" is a #define with one argument defined in |
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// rpc/types.h, so we can't name the variable "mem_alloc" and initialize it |
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// with the "foo(bar)" syntax. |
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A my_mem_alloc(*alloc); |
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AT::deallocate(my_mem_alloc, static_cast<M*>(p), |
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(n + sizeof(M) - 1) / sizeof(M)); |
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} |
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namespace memory_internal { |
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// Constructs T into uninitialized storage pointed by `ptr` using the args |
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// specified in the tuple. |
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template <class Alloc, class T, class Tuple, size_t... I> |
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void ConstructFromTupleImpl(Alloc* alloc, T* ptr, Tuple&& t, |
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absl::index_sequence<I...>) { |
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absl::allocator_traits<Alloc>::construct( |
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*alloc, ptr, std::get<I>(std::forward<Tuple>(t))...); |
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} |
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template <class T, class F> |
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struct WithConstructedImplF { |
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template <class... Args> |
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decltype(std::declval<F>()(std::declval<T>())) operator()( |
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Args&&... args) const { |
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return std::forward<F>(f)(T(std::forward<Args>(args)...)); |
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} |
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F&& f; |
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}; |
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template <class T, class Tuple, size_t... Is, class F> |
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decltype(std::declval<F>()(std::declval<T>())) WithConstructedImpl( |
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Tuple&& t, absl::index_sequence<Is...>, F&& f) { |
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return WithConstructedImplF<T, F>{std::forward<F>(f)}( |
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std::get<Is>(std::forward<Tuple>(t))...); |
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} |
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template <class T, size_t... Is> |
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auto TupleRefImpl(T&& t, absl::index_sequence<Is...>) |
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-> decltype(std::forward_as_tuple(std::get<Is>(std::forward<T>(t))...)) { |
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return std::forward_as_tuple(std::get<Is>(std::forward<T>(t))...); |
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} |
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// Returns a tuple of references to the elements of the input tuple. T must be a |
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// tuple. |
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template <class T> |
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auto TupleRef(T&& t) -> decltype( |
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TupleRefImpl(std::forward<T>(t), |
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absl::make_index_sequence< |
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std::tuple_size<typename std::decay<T>::type>::value>())) { |
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return TupleRefImpl( |
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std::forward<T>(t), |
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absl::make_index_sequence< |
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std::tuple_size<typename std::decay<T>::type>::value>()); |
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} |
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template <class F, class K, class V> |
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decltype(std::declval<F>()(std::declval<const K&>(), std::piecewise_construct, |
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std::declval<std::tuple<K>>(), std::declval<V>())) |
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DecomposePairImpl(F&& f, std::pair<std::tuple<K>, V> p) { |
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const auto& key = std::get<0>(p.first); |
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return std::forward<F>(f)(key, std::piecewise_construct, std::move(p.first), |
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std::move(p.second)); |
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} |
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} // namespace memory_internal |
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// Constructs T into uninitialized storage pointed by `ptr` using the args |
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// specified in the tuple. |
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template <class Alloc, class T, class Tuple> |
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void ConstructFromTuple(Alloc* alloc, T* ptr, Tuple&& t) { |
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memory_internal::ConstructFromTupleImpl( |
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alloc, ptr, std::forward<Tuple>(t), |
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absl::make_index_sequence< |
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std::tuple_size<typename std::decay<Tuple>::type>::value>()); |
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} |
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// Constructs T using the args specified in the tuple and calls F with the |
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// constructed value. |
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template <class T, class Tuple, class F> |
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decltype(std::declval<F>()(std::declval<T>())) WithConstructed( |
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Tuple&& t, F&& f) { |
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return memory_internal::WithConstructedImpl<T>( |
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std::forward<Tuple>(t), |
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absl::make_index_sequence< |
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std::tuple_size<typename std::decay<Tuple>::type>::value>(), |
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std::forward<F>(f)); |
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} |
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// Given arguments of an std::pair's consructor, PairArgs() returns a pair of |
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// tuples with references to the passed arguments. The tuples contain |
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// constructor arguments for the first and the second elements of the pair. |
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// |
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// The following two snippets are equivalent. |
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// |
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// 1. std::pair<F, S> p(args...); |
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// |
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// 2. auto a = PairArgs(args...); |
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// std::pair<F, S> p(std::piecewise_construct, |
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// std::move(a.first), std::move(a.second)); |
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inline std::pair<std::tuple<>, std::tuple<>> PairArgs() { return {}; } |
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template <class F, class S> |
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std::pair<std::tuple<F&&>, std::tuple<S&&>> PairArgs(F&& f, S&& s) { |
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return {std::piecewise_construct, std::forward_as_tuple(std::forward<F>(f)), |
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std::forward_as_tuple(std::forward<S>(s))}; |
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} |
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template <class F, class S> |
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std::pair<std::tuple<const F&>, std::tuple<const S&>> PairArgs( |
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const std::pair<F, S>& p) { |
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return PairArgs(p.first, p.second); |
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} |
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template <class F, class S> |
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std::pair<std::tuple<F&&>, std::tuple<S&&>> PairArgs(std::pair<F, S>&& p) { |
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return PairArgs(std::forward<F>(p.first), std::forward<S>(p.second)); |
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} |
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template <class F, class S> |
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auto PairArgs(std::piecewise_construct_t, F&& f, S&& s) |
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-> decltype(std::make_pair(memory_internal::TupleRef(std::forward<F>(f)), |
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memory_internal::TupleRef(std::forward<S>(s)))) { |
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return std::make_pair(memory_internal::TupleRef(std::forward<F>(f)), |
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memory_internal::TupleRef(std::forward<S>(s))); |
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} |
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// A helper function for implementing apply() in map policies. |
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template <class F, class... Args> |
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auto DecomposePair(F&& f, Args&&... args) |
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-> decltype(memory_internal::DecomposePairImpl( |
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std::forward<F>(f), PairArgs(std::forward<Args>(args)...))) { |
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return memory_internal::DecomposePairImpl( |
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std::forward<F>(f), PairArgs(std::forward<Args>(args)...)); |
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} |
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// A helper function for implementing apply() in set policies. |
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template <class F, class Arg> |
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decltype(std::declval<F>()(std::declval<const Arg&>(), std::declval<Arg>())) |
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DecomposeValue(F&& f, Arg&& arg) { |
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const auto& key = arg; |
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return std::forward<F>(f)(key, std::forward<Arg>(arg)); |
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} |
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// Helper functions for asan and msan. |
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inline void SanitizerPoisonMemoryRegion(const void* m, size_t s) { |
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#ifdef ABSL_HAVE_ADDRESS_SANITIZER |
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ASAN_POISON_MEMORY_REGION(m, s); |
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#endif |
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#ifdef ABSL_HAVE_MEMORY_SANITIZER |
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__msan_poison(m, s); |
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#endif |
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(void)m; |
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(void)s; |
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} |
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inline void SanitizerUnpoisonMemoryRegion(const void* m, size_t s) { |
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#ifdef ABSL_HAVE_ADDRESS_SANITIZER |
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ASAN_UNPOISON_MEMORY_REGION(m, s); |
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#endif |
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#ifdef ABSL_HAVE_MEMORY_SANITIZER |
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__msan_unpoison(m, s); |
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#endif |
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(void)m; |
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(void)s; |
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} |
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template <typename T> |
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inline void SanitizerPoisonObject(const T* object) { |
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SanitizerPoisonMemoryRegion(object, sizeof(T)); |
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} |
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template <typename T> |
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inline void SanitizerUnpoisonObject(const T* object) { |
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SanitizerUnpoisonMemoryRegion(object, sizeof(T)); |
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} |
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namespace memory_internal { |
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// If Pair is a standard-layout type, OffsetOf<Pair>::kFirst and |
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// OffsetOf<Pair>::kSecond are equivalent to offsetof(Pair, first) and |
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// offsetof(Pair, second) respectively. Otherwise they are -1. |
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// |
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// The purpose of OffsetOf is to avoid calling offsetof() on non-standard-layout |
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// type, which is non-portable. |
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template <class Pair, class = std::true_type> |
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struct OffsetOf { |
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static constexpr size_t kFirst = static_cast<size_t>(-1); |
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static constexpr size_t kSecond = static_cast<size_t>(-1); |
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}; |
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template <class Pair> |
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struct OffsetOf<Pair, typename std::is_standard_layout<Pair>::type> { |
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static constexpr size_t kFirst = offsetof(Pair, first); |
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static constexpr size_t kSecond = offsetof(Pair, second); |
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}; |
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template <class K, class V> |
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struct IsLayoutCompatible { |
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private: |
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struct Pair { |
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K first; |
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V second; |
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}; |
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// Is P layout-compatible with Pair? |
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template <class P> |
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static constexpr bool LayoutCompatible() { |
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return std::is_standard_layout<P>() && sizeof(P) == sizeof(Pair) && |
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alignof(P) == alignof(Pair) && |
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memory_internal::OffsetOf<P>::kFirst == |
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memory_internal::OffsetOf<Pair>::kFirst && |
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memory_internal::OffsetOf<P>::kSecond == |
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memory_internal::OffsetOf<Pair>::kSecond; |
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} |
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public: |
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// Whether pair<const K, V> and pair<K, V> are layout-compatible. If they are, |
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// then it is safe to store them in a union and read from either. |
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static constexpr bool value = std::is_standard_layout<K>() && |
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std::is_standard_layout<Pair>() && |
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memory_internal::OffsetOf<Pair>::kFirst == 0 && |
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LayoutCompatible<std::pair<K, V>>() && |
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LayoutCompatible<std::pair<const K, V>>(); |
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}; |
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} // namespace memory_internal |
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// The internal storage type for key-value containers like flat_hash_map. |
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// |
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// It is convenient for the value_type of a flat_hash_map<K, V> to be |
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// pair<const K, V>; the "const K" prevents accidental modification of the key |
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// when dealing with the reference returned from find() and similar methods. |
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// However, this creates other problems; we want to be able to emplace(K, V) |
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// efficiently with move operations, and similarly be able to move a |
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// pair<K, V> in insert(). |
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// |
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// The solution is this union, which aliases the const and non-const versions |
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// of the pair. This also allows flat_hash_map<const K, V> to work, even though |
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// that has the same efficiency issues with move in emplace() and insert() - |
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// but people do it anyway. |
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// |
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// If kMutableKeys is false, only the value member can be accessed. |
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// |
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// If kMutableKeys is true, key can be accessed through all slots while value |
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// and mutable_value must be accessed only via INITIALIZED slots. Slots are |
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// created and destroyed via mutable_value so that the key can be moved later. |
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// |
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// Accessing one of the union fields while the other is active is safe as |
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// long as they are layout-compatible, which is guaranteed by the definition of |
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// kMutableKeys. For C++11, the relevant section of the standard is |
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// https://timsong-cpp.github.io/cppwp/n3337/class.mem#19 (9.2.19) |
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template <class K, class V> |
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union map_slot_type { |
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map_slot_type() {} |
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~map_slot_type() = delete; |
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using value_type = std::pair<const K, V>; |
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using mutable_value_type = |
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std::pair<absl::remove_const_t<K>, absl::remove_const_t<V>>; |
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value_type value; |
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mutable_value_type mutable_value; |
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absl::remove_const_t<K> key; |
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}; |
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template <class K, class V> |
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struct map_slot_policy { |
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using slot_type = map_slot_type<K, V>; |
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using value_type = std::pair<const K, V>; |
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using mutable_value_type = std::pair<K, V>; |
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private: |
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static void emplace(slot_type* slot) { |
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// The construction of union doesn't do anything at runtime but it allows us |
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// to access its members without violating aliasing rules. |
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new (slot) slot_type; |
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} |
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// If pair<const K, V> and pair<K, V> are layout-compatible, we can accept one |
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// or the other via slot_type. We are also free to access the key via |
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// slot_type::key in this case. |
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using kMutableKeys = memory_internal::IsLayoutCompatible<K, V>; |
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public: |
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static value_type& element(slot_type* slot) { return slot->value; } |
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static const value_type& element(const slot_type* slot) { |
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return slot->value; |
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} |
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// When C++17 is available, we can use std::launder to provide mutable |
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// access to the key for use in node handle. |
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#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606 |
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static K& mutable_key(slot_type* slot) { |
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// Still check for kMutableKeys so that we can avoid calling std::launder |
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// unless necessary because it can interfere with optimizations. |
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return kMutableKeys::value ? slot->key |
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: *std::launder(const_cast<K*>( |
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std::addressof(slot->value.first))); |
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} |
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#else // !(defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606) |
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static const K& mutable_key(slot_type* slot) { return key(slot); } |
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#endif |
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static const K& key(const slot_type* slot) { |
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return kMutableKeys::value ? slot->key : slot->value.first; |
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} |
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template <class Allocator, class... Args> |
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static void construct(Allocator* alloc, slot_type* slot, Args&&... args) { |
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emplace(slot); |
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if (kMutableKeys::value) { |
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absl::allocator_traits<Allocator>::construct(*alloc, &slot->mutable_value, |
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std::forward<Args>(args)...); |
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} else { |
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absl::allocator_traits<Allocator>::construct(*alloc, &slot->value, |
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std::forward<Args>(args)...); |
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} |
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} |
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// Construct this slot by moving from another slot. |
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template <class Allocator> |
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static void construct(Allocator* alloc, slot_type* slot, slot_type* other) { |
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emplace(slot); |
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if (kMutableKeys::value) { |
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absl::allocator_traits<Allocator>::construct( |
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*alloc, &slot->mutable_value, std::move(other->mutable_value)); |
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} else { |
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absl::allocator_traits<Allocator>::construct(*alloc, &slot->value, |
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std::move(other->value)); |
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} |
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} |
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// Construct this slot by copying from another slot. |
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template <class Allocator> |
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static void construct(Allocator* alloc, slot_type* slot, |
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const slot_type* other) { |
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emplace(slot); |
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absl::allocator_traits<Allocator>::construct(*alloc, &slot->value, |
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other->value); |
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} |
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template <class Allocator> |
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static void destroy(Allocator* alloc, slot_type* slot) { |
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if (kMutableKeys::value) { |
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absl::allocator_traits<Allocator>::destroy(*alloc, &slot->mutable_value); |
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} else { |
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absl::allocator_traits<Allocator>::destroy(*alloc, &slot->value); |
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} |
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} |
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template <class Allocator> |
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static void transfer(Allocator* alloc, slot_type* new_slot, |
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slot_type* old_slot) { |
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emplace(new_slot); |
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if (kMutableKeys::value) { |
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absl::allocator_traits<Allocator>::construct( |
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*alloc, &new_slot->mutable_value, std::move(old_slot->mutable_value)); |
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} else { |
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absl::allocator_traits<Allocator>::construct(*alloc, &new_slot->value, |
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std::move(old_slot->value)); |
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} |
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destroy(alloc, old_slot); |
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} |
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template <class Allocator> |
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static void swap(Allocator* alloc, slot_type* a, slot_type* b) { |
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if (kMutableKeys::value) { |
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using std::swap; |
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swap(a->mutable_value, b->mutable_value); |
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} else { |
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value_type tmp = std::move(a->value); |
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absl::allocator_traits<Allocator>::destroy(*alloc, &a->value); |
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absl::allocator_traits<Allocator>::construct(*alloc, &a->value, |
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std::move(b->value)); |
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absl::allocator_traits<Allocator>::destroy(*alloc, &b->value); |
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absl::allocator_traits<Allocator>::construct(*alloc, &b->value, |
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std::move(tmp)); |
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} |
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} |
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template <class Allocator> |
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static void move(Allocator* alloc, slot_type* src, slot_type* dest) { |
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if (kMutableKeys::value) { |
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dest->mutable_value = std::move(src->mutable_value); |
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} else { |
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absl::allocator_traits<Allocator>::destroy(*alloc, &dest->value); |
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absl::allocator_traits<Allocator>::construct(*alloc, &dest->value, |
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std::move(src->value)); |
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} |
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} |
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}; |
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} // namespace container_internal |
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ABSL_NAMESPACE_END |
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} // namespace absl |
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#endif // ABSL_CONTAINER_INTERNAL_CONTAINER_MEMORY_H_
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