Abseil Common Libraries (C++) (grcp 依赖)
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185 lines
6.8 KiB
185 lines
6.8 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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// ----------------------------------------------------------------------------- |
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// File: bit_gen_ref.h |
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// ----------------------------------------------------------------------------- |
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// |
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// This header defines a bit generator "reference" class, for use in interfaces |
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// that take both Abseil (e.g. `absl::BitGen`) and standard library (e.g. |
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// `std::mt19937`) bit generators. |
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#ifndef ABSL_RANDOM_BIT_GEN_REF_H_ |
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#define ABSL_RANDOM_BIT_GEN_REF_H_ |
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#include <limits> |
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#include <type_traits> |
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#include <utility> |
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#include "absl/base/internal/fast_type_id.h" |
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#include "absl/base/macros.h" |
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#include "absl/meta/type_traits.h" |
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#include "absl/random/internal/distribution_caller.h" |
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#include "absl/random/internal/fast_uniform_bits.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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template <typename URBG, typename = void, typename = void, typename = void> |
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struct is_urbg : std::false_type {}; |
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template <typename URBG> |
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struct is_urbg< |
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URBG, |
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absl::enable_if_t<std::is_same< |
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typename URBG::result_type, |
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typename std::decay<decltype((URBG::min)())>::type>::value>, |
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absl::enable_if_t<std::is_same< |
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typename URBG::result_type, |
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typename std::decay<decltype((URBG::max)())>::type>::value>, |
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absl::enable_if_t<std::is_same< |
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typename URBG::result_type, |
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typename std::decay<decltype(std::declval<URBG>()())>::type>::value>> |
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: std::true_type {}; |
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template <typename> |
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struct DistributionCaller; |
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class MockHelpers; |
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} // namespace random_internal |
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// ----------------------------------------------------------------------------- |
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// absl::BitGenRef |
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// ----------------------------------------------------------------------------- |
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// |
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// `absl::BitGenRef` is a type-erasing class that provides a generator-agnostic |
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// non-owning "reference" interface for use in place of any specific uniform |
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// random bit generator (URBG). This class may be used for both Abseil |
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// (e.g. `absl::BitGen`, `absl::InsecureBitGen`) and Standard library (e.g |
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// `std::mt19937`, `std::minstd_rand`) bit generators. |
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// |
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// Like other reference classes, `absl::BitGenRef` does not own the |
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// underlying bit generator, and the underlying instance must outlive the |
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// `absl::BitGenRef`. |
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// |
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// `absl::BitGenRef` is particularly useful when used with an |
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// `absl::MockingBitGen` to test specific paths in functions which use random |
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// values. |
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// |
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// Example: |
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// void TakesBitGenRef(absl::BitGenRef gen) { |
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// int x = absl::Uniform<int>(gen, 0, 1000); |
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// } |
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// |
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class BitGenRef { |
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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<base_internal::FastTypeIdType>(), std::declval<void*>(), |
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std::declval<void*>())); |
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template <typename T> |
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using HasInvokeMock = typename detector<invoke_mock_t, void, T>::type; |
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public: |
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BitGenRef(const BitGenRef&) = default; |
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BitGenRef(BitGenRef&&) = default; |
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BitGenRef& operator=(const BitGenRef&) = default; |
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BitGenRef& operator=(BitGenRef&&) = default; |
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template <typename URBG, typename absl::enable_if_t< |
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(!std::is_same<URBG, BitGenRef>::value && |
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random_internal::is_urbg<URBG>::value && |
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!HasInvokeMock<URBG>::value)>* = nullptr> |
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BitGenRef(URBG& gen) // NOLINT |
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: t_erased_gen_ptr_(reinterpret_cast<uintptr_t>(&gen)), |
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mock_call_(NotAMock), |
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generate_impl_fn_(ImplFn<URBG>) {} |
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template <typename URBG, |
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typename absl::enable_if_t<(!std::is_same<URBG, BitGenRef>::value && |
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random_internal::is_urbg<URBG>::value && |
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HasInvokeMock<URBG>::value)>* = nullptr> |
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BitGenRef(URBG& gen) // NOLINT |
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: t_erased_gen_ptr_(reinterpret_cast<uintptr_t>(&gen)), |
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mock_call_(&MockCall<URBG>), |
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generate_impl_fn_(ImplFn<URBG>) {} |
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using result_type = uint64_t; |
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static constexpr result_type(min)() { |
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return (std::numeric_limits<result_type>::min)(); |
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} |
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static constexpr result_type(max)() { |
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return (std::numeric_limits<result_type>::max)(); |
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} |
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result_type operator()() { return generate_impl_fn_(t_erased_gen_ptr_); } |
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private: |
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using impl_fn = result_type (*)(uintptr_t); |
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using mock_call_fn = bool (*)(uintptr_t, base_internal::FastTypeIdType, void*, |
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void*); |
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template <typename URBG> |
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static result_type ImplFn(uintptr_t ptr) { |
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// Ensure that the return values from operator() fill the entire |
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// range promised by result_type, min() and max(). |
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absl::random_internal::FastUniformBits<result_type> fast_uniform_bits; |
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return fast_uniform_bits(*reinterpret_cast<URBG*>(ptr)); |
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} |
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// Get a type-erased InvokeMock pointer. |
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template <typename URBG> |
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static bool MockCall(uintptr_t gen_ptr, base_internal::FastTypeIdType type, |
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void* result, void* arg_tuple) { |
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return reinterpret_cast<URBG*>(gen_ptr)->InvokeMock(type, result, |
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arg_tuple); |
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} |
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static bool NotAMock(uintptr_t, base_internal::FastTypeIdType, void*, void*) { |
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return false; |
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} |
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inline bool InvokeMock(base_internal::FastTypeIdType type, void* args_tuple, |
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void* result) { |
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if (mock_call_ == NotAMock) return false; // avoids an indirect call. |
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return mock_call_(t_erased_gen_ptr_, type, args_tuple, result); |
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} |
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uintptr_t t_erased_gen_ptr_; |
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mock_call_fn mock_call_; |
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impl_fn generate_impl_fn_; |
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template <typename> |
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friend struct ::absl::random_internal::DistributionCaller; // for InvokeMock |
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friend class ::absl::random_internal::MockHelpers; // for InvokeMock |
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}; |
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ABSL_NAMESPACE_END |
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} // namespace absl |
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#endif // ABSL_RANDOM_BIT_GEN_REF_H_
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