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