Abseil Common Libraries (C++) (grcp 依赖)
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89 lines
2.7 KiB
89 lines
2.7 KiB
6 years ago
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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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// 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, 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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//
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// Adapts a policy for nodes.
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//
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// The node policy should model:
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//
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// struct Policy {
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// // Returns a new node allocated and constructed using the allocator, using
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// // the specified arguments.
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// template <class Alloc, class... Args>
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// value_type* new_element(Alloc* alloc, Args&&... args) const;
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//
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// // Destroys and deallocates node using the allocator.
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// template <class Alloc>
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// void delete_element(Alloc* alloc, value_type* node) const;
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// };
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//
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// It may also optionally define `value()` and `apply()`. For documentation on
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// these, see hash_policy_traits.h.
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#ifndef ABSL_CONTAINER_INTERNAL_NODE_HASH_POLICY_H_
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#define ABSL_CONTAINER_INTERNAL_NODE_HASH_POLICY_H_
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#include <cassert>
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#include <cstddef>
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#include <memory>
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#include <type_traits>
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#include <utility>
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namespace absl {
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namespace container_internal {
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template <class Reference, class Policy>
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struct node_hash_policy {
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static_assert(std::is_lvalue_reference<Reference>::value, "");
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using slot_type = typename std::remove_cv<
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typename std::remove_reference<Reference>::type>::type*;
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template <class Alloc, class... Args>
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static void construct(Alloc* alloc, slot_type* slot, Args&&... args) {
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*slot = Policy::new_element(alloc, std::forward<Args>(args)...);
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}
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template <class Alloc>
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static void destroy(Alloc* alloc, slot_type* slot) {
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Policy::delete_element(alloc, *slot);
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}
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template <class Alloc>
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static void transfer(Alloc*, slot_type* new_slot, slot_type* old_slot) {
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*new_slot = *old_slot;
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}
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static size_t space_used(const slot_type* slot) {
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if (slot == nullptr) return Policy::element_space_used(nullptr);
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return Policy::element_space_used(*slot);
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}
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static Reference element(slot_type* slot) { return **slot; }
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template <class T, class P = Policy>
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static auto value(T* elem) -> decltype(P::value(elem)) {
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return P::value(elem);
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}
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template <class... Ts, class P = Policy>
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static auto apply(Ts&&... ts) -> decltype(P::apply(std::forward<Ts>(ts)...)) {
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return P::apply(std::forward<Ts>(ts)...);
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}
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};
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} // namespace container_internal
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} // namespace absl
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#endif // ABSL_CONTAINER_INTERNAL_NODE_HASH_POLICY_H_
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