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// Copyright 2023 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
//
//
// 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.
// Common code shared between absl/hash/hash_test.cc and
// absl/hash/hash_instantiated_test.cc.
#ifndef ABSL_HASH_INTERNAL_HASH_TEST_H_
#define ABSL_HASH_INTERNAL_HASH_TEST_H_
#include <type_traits>
#include <utility>
#include "absl/base/config.h"
#include "absl/hash/hash.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace hash_test_internal {
// Utility wrapper of T for the purposes of testing the `AbslHash` type erasure
// mechanism. `TypeErasedValue<T>` can be constructed with a `T`, and can
// be compared and hashed. However, all hashing goes through the hashing
// type-erasure framework.
template <typename T>
class TypeErasedValue {
public:
TypeErasedValue() = default;
TypeErasedValue(const TypeErasedValue&) = default;
TypeErasedValue(TypeErasedValue&&) = default;
explicit TypeErasedValue(const T& n) : n_(n) {}
template <typename H>
friend H AbslHashValue(H hash_state, const TypeErasedValue& v) {
v.HashValue(absl::HashState::Create(&hash_state));
return hash_state;
}
void HashValue(absl::HashState state) const {
absl::HashState::combine(std::move(state), n_);
}
bool operator==(const TypeErasedValue& rhs) const { return n_ == rhs.n_; }
bool operator!=(const TypeErasedValue& rhs) const { return !(*this == rhs); }
private:
T n_;
};
// A TypeErasedValue refinement, for containers. It exposes the wrapped
// `value_type` and is constructible from an initializer list.
template <typename T>
class TypeErasedContainer : public TypeErasedValue<T> {
public:
using value_type = typename T::value_type;
TypeErasedContainer() = default;
TypeErasedContainer(const TypeErasedContainer&) = default;
TypeErasedContainer(TypeErasedContainer&&) = default;
explicit TypeErasedContainer(const T& n) : TypeErasedValue<T>(n) {}
TypeErasedContainer(std::initializer_list<value_type> init_list)
: TypeErasedContainer(T(init_list.begin(), init_list.end())) {}
// one-argument constructor of value type T, to appease older toolchains that
// get confused by one-element initializer lists in some contexts
explicit TypeErasedContainer(const value_type& v)
: TypeErasedContainer(T(&v, &v + 1)) {}
};
// Helper trait to verify if T is hashable. We use absl::Hash's poison status to
// detect it.
template <typename T>
using is_hashable = std::is_default_constructible<absl::Hash<T>>;
} // namespace hash_test_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_HASH_INTERNAL_HASH_TEST_H_