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// 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_
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