93 lines
2.8 KiB
C
93 lines
2.8 KiB
C
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// 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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