208 lines
5.5 KiB
C
208 lines
5.5 KiB
C
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// 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_H_
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#define ABSL_CONTAINER_INTERNAL_CONTAINER_H_
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#include <cassert>
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#include <type_traits>
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#include "absl/meta/type_traits.h"
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#include "absl/types/optional.h"
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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 <class, class = void>
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struct IsTransparent : std::false_type {};
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template <class T>
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struct IsTransparent<T, absl::void_t<typename T::is_transparent>>
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: std::true_type {};
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template <bool is_transparent>
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struct KeyArg {
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// Transparent. Forward `K`.
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template <typename K, typename key_type>
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using type = K;
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};
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template <>
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struct KeyArg<false> {
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// Not transparent. Always use `key_type`.
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template <typename K, typename key_type>
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using type = key_type;
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};
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// The node_handle concept from C++17.
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// We specialize node_handle for sets and maps. node_handle_base holds the
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// common API of both.
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template <typename PolicyTraits, typename Alloc>
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class node_handle_base {
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protected:
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using slot_type = typename PolicyTraits::slot_type;
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public:
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using allocator_type = Alloc;
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constexpr node_handle_base() = default;
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node_handle_base(node_handle_base&& other) noexcept {
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*this = std::move(other);
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}
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~node_handle_base() { destroy(); }
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node_handle_base& operator=(node_handle_base&& other) noexcept {
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destroy();
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if (!other.empty()) {
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alloc_ = other.alloc_;
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PolicyTraits::transfer(alloc(), slot(), other.slot());
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other.reset();
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}
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return *this;
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}
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bool empty() const noexcept { return !alloc_; }
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explicit operator bool() const noexcept { return !empty(); }
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allocator_type get_allocator() const { return *alloc_; }
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protected:
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friend struct CommonAccess;
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struct transfer_tag_t {};
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node_handle_base(transfer_tag_t, const allocator_type& a, slot_type* s)
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: alloc_(a) {
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PolicyTraits::transfer(alloc(), slot(), s);
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}
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struct construct_tag_t {};
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template <typename... Args>
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node_handle_base(construct_tag_t, const allocator_type& a, Args&&... args)
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: alloc_(a) {
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PolicyTraits::construct(alloc(), slot(), std::forward<Args>(args)...);
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}
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void destroy() {
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if (!empty()) {
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PolicyTraits::destroy(alloc(), slot());
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reset();
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}
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}
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void reset() {
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assert(alloc_.has_value());
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alloc_ = absl::nullopt;
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}
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slot_type* slot() const {
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assert(!empty());
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return reinterpret_cast<slot_type*>(std::addressof(slot_space_));
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}
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allocator_type* alloc() { return std::addressof(*alloc_); }
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private:
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absl::optional<allocator_type> alloc_ = {};
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alignas(slot_type) mutable unsigned char slot_space_[sizeof(slot_type)] = {};
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};
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// For sets.
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template <typename Policy, typename PolicyTraits, typename Alloc,
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typename = void>
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class node_handle : public node_handle_base<PolicyTraits, Alloc> {
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using Base = node_handle_base<PolicyTraits, Alloc>;
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public:
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using value_type = typename PolicyTraits::value_type;
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constexpr node_handle() {}
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value_type& value() const { return PolicyTraits::element(this->slot()); }
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private:
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friend struct CommonAccess;
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using Base::Base;
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};
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// For maps.
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template <typename Policy, typename PolicyTraits, typename Alloc>
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class node_handle<Policy, PolicyTraits, Alloc,
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absl::void_t<typename Policy::mapped_type>>
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: public node_handle_base<PolicyTraits, Alloc> {
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using Base = node_handle_base<PolicyTraits, Alloc>;
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using slot_type = typename PolicyTraits::slot_type;
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public:
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using key_type = typename Policy::key_type;
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using mapped_type = typename Policy::mapped_type;
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constexpr node_handle() {}
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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. Otherwise, we provide const access.
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auto key() const
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-> decltype(PolicyTraits::mutable_key(std::declval<slot_type*>())) {
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return PolicyTraits::mutable_key(this->slot());
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}
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mapped_type& mapped() const {
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return PolicyTraits::value(&PolicyTraits::element(this->slot()));
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}
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private:
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friend struct CommonAccess;
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using Base::Base;
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};
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// Provide access to non-public node-handle functions.
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struct CommonAccess {
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template <typename Node>
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static auto GetSlot(const Node& node) -> decltype(node.slot()) {
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return node.slot();
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}
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template <typename Node>
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static void Destroy(Node* node) {
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node->destroy();
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}
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template <typename Node>
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static void Reset(Node* node) {
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node->reset();
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}
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template <typename T, typename... Args>
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static T Transfer(Args&&... args) {
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return T(typename T::transfer_tag_t{}, std::forward<Args>(args)...);
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}
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template <typename T, typename... Args>
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static T Construct(Args&&... args) {
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return T(typename T::construct_tag_t{}, std::forward<Args>(args)...);
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}
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};
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// Implement the insert_return_type<> concept of C++17.
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template <class Iterator, class NodeType>
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struct InsertReturnType {
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Iterator position;
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bool inserted;
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NodeType node;
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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_H_
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