// Copyright 2017 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 // // https://www.apache.org/licenses/LICENSE-2.0 // // 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. #ifndef ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_ #define ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_ #include <algorithm> #include <cstddef> #include <cstdint> #include <initializer_list> #include <iterator> #include <vector> #include "absl/base/config.h" #include "absl/base/internal/endian.h" namespace absl { ABSL_NAMESPACE_BEGIN namespace random_internal { // This class conforms to the C++ Standard "Seed Sequence" concept // [rand.req.seedseq]. // // An "ExplicitSeedSeq" is meant to provide a conformant interface for // forwarding pre-computed seed material to the constructor of a class // conforming to the "Uniform Random Bit Generator" concept. This class makes no // attempt to mutate the state provided by its constructor, and returns it // directly via ExplicitSeedSeq::generate(). // // If this class is asked to generate more seed material than was provided to // the constructor, then the remaining bytes will be filled with deterministic, // nonrandom data. class ExplicitSeedSeq { public: using result_type = uint32_t; ExplicitSeedSeq() : state_() {} // Copy and move both allowed. ExplicitSeedSeq(const ExplicitSeedSeq& other) = default; ExplicitSeedSeq& operator=(const ExplicitSeedSeq& other) = default; ExplicitSeedSeq(ExplicitSeedSeq&& other) = default; ExplicitSeedSeq& operator=(ExplicitSeedSeq&& other) = default; template <typename Iterator> ExplicitSeedSeq(Iterator begin, Iterator end) { for (auto it = begin; it != end; it++) { state_.push_back(*it & 0xffffffff); } } template <typename T> ExplicitSeedSeq(std::initializer_list<T> il) : ExplicitSeedSeq(il.begin(), il.end()) {} size_t size() const { return state_.size(); } template <typename OutIterator> void param(OutIterator out) const { std::copy(std::begin(state_), std::end(state_), out); } template <typename OutIterator> void generate(OutIterator begin, OutIterator end) { for (size_t index = 0; begin != end; begin++) { *begin = state_.empty() ? 0 : state_[index++]; if (index >= state_.size()) { index = 0; } } } protected: std::vector<uint32_t> state_; }; } // namespace random_internal ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_RANDOM_INTERNAL_EXPLICIT_SEED_SEQ_H_