Abseil Common Libraries (C++) (grcp 依赖)
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95 lines
3.5 KiB
95 lines
3.5 KiB
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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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// |
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#ifndef ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_ |
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#define ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_ |
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#include <utility> |
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#include <type_traits> |
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#include "absl/base/config.h" |
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#include "absl/base/internal/fast_type_id.h" |
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#include "absl/utility/utility.h" |
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namespace absl { |
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ABSL_NAMESPACE_BEGIN |
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namespace random_internal { |
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// DistributionCaller provides an opportunity to overload the general |
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// mechanism for calling a distribution, allowing for mock-RNG classes |
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// to intercept such calls. |
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template <typename URBG> |
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struct DistributionCaller { |
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static_assert(!std::is_pointer<URBG>::value, |
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"You must pass a reference, not a pointer."); |
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// SFINAE to detect whether the URBG type includes a member matching |
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// bool InvokeMock(base_internal::FastTypeIdType, void*, void*). |
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// |
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// These live inside BitGenRef so that they have friend access |
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// to MockingBitGen. (see similar methods in DistributionCaller). |
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template <template <class...> class Trait, class AlwaysVoid, class... Args> |
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struct detector : std::false_type {}; |
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template <template <class...> class Trait, class... Args> |
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struct detector<Trait, absl::void_t<Trait<Args...>>, Args...> |
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: std::true_type {}; |
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template <class T> |
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using invoke_mock_t = decltype(std::declval<T*>()->InvokeMock( |
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std::declval<::absl::base_internal::FastTypeIdType>(), |
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std::declval<void*>(), std::declval<void*>())); |
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using HasInvokeMock = typename detector<invoke_mock_t, void, URBG>::type; |
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// Default implementation of distribution caller. |
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template <typename DistrT, typename... Args> |
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static typename DistrT::result_type Impl(std::false_type, URBG* urbg, |
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Args&&... args) { |
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DistrT dist(std::forward<Args>(args)...); |
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return dist(*urbg); |
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} |
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// Mock implementation of distribution caller. |
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// The underlying KeyT must match the KeyT constructed by MockOverloadSet. |
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template <typename DistrT, typename... Args> |
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static typename DistrT::result_type Impl(std::true_type, URBG* urbg, |
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Args&&... args) { |
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using ResultT = typename DistrT::result_type; |
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using ArgTupleT = std::tuple<absl::decay_t<Args>...>; |
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using KeyT = ResultT(DistrT, ArgTupleT); |
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ArgTupleT arg_tuple(std::forward<Args>(args)...); |
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ResultT result; |
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if (!urbg->InvokeMock(::absl::base_internal::FastTypeId<KeyT>(), &arg_tuple, |
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&result)) { |
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auto dist = absl::make_from_tuple<DistrT>(arg_tuple); |
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result = dist(*urbg); |
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} |
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return result; |
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} |
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// Default implementation of distribution caller. |
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template <typename DistrT, typename... Args> |
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static typename DistrT::result_type Call(URBG* urbg, Args&&... args) { |
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return Impl<DistrT, Args...>(HasInvokeMock{}, urbg, |
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std::forward<Args>(args)...); |
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} |
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}; |
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} // namespace random_internal |
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ABSL_NAMESPACE_END |
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} // namespace absl |
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#endif // ABSL_RANDOM_INTERNAL_DISTRIBUTION_CALLER_H_
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