Abseil Common Libraries (C++) (grcp 依赖)
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92 lines
2.8 KiB
92 lines
2.8 KiB
// Copyright 2017 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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#ifndef ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_ |
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#define ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_ |
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#include <algorithm> |
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#include <cstddef> |
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#include <cstdint> |
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#include <initializer_list> |
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#include <iterator> |
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#include <vector> |
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#include "absl/base/config.h" |
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#include "absl/base/internal/endian.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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// This class conforms to the C++ Standard "Seed Sequence" concept |
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// [rand.req.seedseq]. |
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// |
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// An "ExplicitSeedSeq" is meant to provide a conformant interface for |
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// forwarding pre-computed seed material to the constructor of a class |
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// conforming to the "Uniform Random Bit Generator" concept. This class makes no |
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// attempt to mutate the state provided by its constructor, and returns it |
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// directly via ExplicitSeedSeq::generate(). |
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// |
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// If this class is asked to generate more seed material than was provided to |
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// the constructor, then the remaining bytes will be filled with deterministic, |
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// nonrandom data. |
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class ExplicitSeedSeq { |
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public: |
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using result_type = uint32_t; |
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ExplicitSeedSeq() : state_() {} |
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// Copy and move both allowed. |
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ExplicitSeedSeq(const ExplicitSeedSeq& other) = default; |
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ExplicitSeedSeq& operator=(const ExplicitSeedSeq& other) = default; |
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ExplicitSeedSeq(ExplicitSeedSeq&& other) = default; |
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ExplicitSeedSeq& operator=(ExplicitSeedSeq&& other) = default; |
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template <typename Iterator> |
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ExplicitSeedSeq(Iterator begin, Iterator end) { |
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for (auto it = begin; it != end; it++) { |
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state_.push_back(*it & 0xffffffff); |
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} |
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} |
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template <typename T> |
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ExplicitSeedSeq(std::initializer_list<T> il) |
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: ExplicitSeedSeq(il.begin(), il.end()) {} |
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size_t size() const { return state_.size(); } |
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template <typename OutIterator> |
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void param(OutIterator out) const { |
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std::copy(std::begin(state_), std::end(state_), out); |
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} |
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template <typename OutIterator> |
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void generate(OutIterator begin, OutIterator end) { |
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for (size_t index = 0; begin != end; begin++) { |
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*begin = state_.empty() ? 0 : little_endian::FromHost32(state_[index++]); |
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if (index >= state_.size()) { |
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index = 0; |
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} |
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} |
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} |
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protected: |
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std::vector<uint32_t> state_; |
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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_EXPLICIT_SEED_SEQ_H_
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