151 lines
4.9 KiB
C++
151 lines
4.9 KiB
C++
// 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_NONSECURE_BASE_H_
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#define ABSL_RANDOM_INTERNAL_NONSECURE_BASE_H_
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#include <algorithm>
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#include <cstdint>
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#include <iostream>
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#include <iterator>
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#include <random>
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#include <string>
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#include <type_traits>
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#include <vector>
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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/pool_urbg.h"
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#include "absl/random/internal/salted_seed_seq.h"
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#include "absl/random/internal/seed_material.h"
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#include "absl/types/optional.h"
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#include "absl/types/span.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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// Each instance of NonsecureURBGBase<URBG> will be seeded by variates produced
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// by a thread-unique URBG-instance.
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template <typename URBG>
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class NonsecureURBGBase {
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public:
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using result_type = typename URBG::result_type;
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// Default constructor
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NonsecureURBGBase() : urbg_(ConstructURBG()) {}
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// Copy disallowed, move allowed.
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NonsecureURBGBase(const NonsecureURBGBase&) = delete;
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NonsecureURBGBase& operator=(const NonsecureURBGBase&) = delete;
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NonsecureURBGBase(NonsecureURBGBase&&) = default;
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NonsecureURBGBase& operator=(NonsecureURBGBase&&) = default;
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// Constructor using a seed
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template <class SSeq, typename = typename absl::enable_if_t<
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!std::is_same<SSeq, NonsecureURBGBase>::value>>
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explicit NonsecureURBGBase(SSeq&& seq)
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: urbg_(ConstructURBG(std::forward<SSeq>(seq))) {}
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// Note: on MSVC, min() or max() can be interpreted as MIN() or MAX(), so we
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// enclose min() or max() in parens as (min)() and (max)().
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// Additionally, clang-format requires no space before this construction.
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// NonsecureURBGBase::min()
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static constexpr result_type(min)() { return (URBG::min)(); }
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// NonsecureURBGBase::max()
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static constexpr result_type(max)() { return (URBG::max)(); }
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// NonsecureURBGBase::operator()()
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result_type operator()() { return urbg_(); }
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// NonsecureURBGBase::discard()
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void discard(unsigned long long values) { // NOLINT(runtime/int)
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urbg_.discard(values);
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}
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bool operator==(const NonsecureURBGBase& other) const {
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return urbg_ == other.urbg_;
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}
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bool operator!=(const NonsecureURBGBase& other) const {
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return !(urbg_ == other.urbg_);
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}
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private:
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// Seeder is a custom seed sequence type where generate() fills the provided
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// buffer via the RandenPool entropy source.
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struct Seeder {
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using result_type = uint32_t;
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size_t size() { return 0; }
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template <typename OutIterator>
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void param(OutIterator) const {}
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template <typename RandomAccessIterator>
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void generate(RandomAccessIterator begin, RandomAccessIterator end) {
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if (begin != end) {
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// begin, end must be random access iterators assignable from uint32_t.
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generate_impl(
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std::integral_constant<bool, sizeof(*begin) == sizeof(uint32_t)>{},
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begin, end);
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}
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}
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// Commonly, generate is invoked with a pointer to a buffer which
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// can be cast to a uint32_t.
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template <typename RandomAccessIterator>
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void generate_impl(std::integral_constant<bool, true>,
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RandomAccessIterator begin, RandomAccessIterator end) {
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auto buffer = absl::MakeSpan(begin, end);
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auto target = absl::MakeSpan(reinterpret_cast<uint32_t*>(buffer.data()),
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buffer.size());
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RandenPool<uint32_t>::Fill(target);
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}
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// The non-uint32_t case should be uncommon, and involves an extra copy,
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// filling the uint32_t buffer and then mixing into the output.
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template <typename RandomAccessIterator>
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void generate_impl(std::integral_constant<bool, false>,
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RandomAccessIterator begin, RandomAccessIterator end) {
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const size_t n = std::distance(begin, end);
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absl::InlinedVector<uint32_t, 8> data(n, 0);
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RandenPool<uint32_t>::Fill(absl::MakeSpan(data.begin(), data.end()));
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std::copy(std::begin(data), std::end(data), begin);
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}
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};
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static URBG ConstructURBG() {
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Seeder seeder;
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return URBG(seeder);
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}
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template <typename SSeq>
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static URBG ConstructURBG(SSeq&& seq) { // NOLINT(runtime/references)
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auto salted_seq =
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random_internal::MakeSaltedSeedSeq(std::forward<SSeq>(seq));
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return URBG(salted_seq);
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}
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URBG urbg_;
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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_NONSECURE_BASE_H_
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