--- /dev/null
+// 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_SALTED_SEED_SEQ_H_
+#define ABSL_RANDOM_INTERNAL_SALTED_SEED_SEQ_H_
+
+#include <cstdint>
+#include <cstdlib>
+#include <initializer_list>
+#include <iterator>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/meta/type_traits.h"
+#include "absl/random/internal/seed_material.h"
+#include "absl/types/optional.h"
+#include "absl/types/span.h"
+
+namespace absl {
+namespace random_internal {
+
+// This class conforms to the C++ Standard "Seed Sequence" concept
+// [rand.req.seedseq].
+//
+// A `SaltedSeedSeq` is meant to wrap an existing seed sequence and modify
+// generated sequence by mixing with extra entropy. This entropy may be
+// build-dependent or process-dependent. The implementation may change to be
+// have either or both kinds of entropy. If salt is not available sequence is
+// not modified.
+template <typename SSeq>
+class SaltedSeedSeq {
+ public:
+ using inner_sequence_type = SSeq;
+ using result_type = typename SSeq::result_type;
+
+ SaltedSeedSeq() : seq_(absl::make_unique<SSeq>()) {}
+
+ template <typename Iterator>
+ SaltedSeedSeq(Iterator begin, Iterator end)
+ : seq_(absl::make_unique<SSeq>(begin, end)) {}
+
+ template <typename T>
+ SaltedSeedSeq(std::initializer_list<T> il)
+ : SaltedSeedSeq(il.begin(), il.end()) {}
+
+ SaltedSeedSeq(const SaltedSeedSeq& other) = delete;
+ SaltedSeedSeq& operator=(const SaltedSeedSeq& other) = delete;
+
+ SaltedSeedSeq(SaltedSeedSeq&& other) = default;
+ SaltedSeedSeq& operator=(SaltedSeedSeq&& other) = default;
+
+ template <typename RandomAccessIterator>
+ void generate(RandomAccessIterator begin, RandomAccessIterator end) {
+ if (begin != end) {
+ generate_impl(
+ std::integral_constant<bool, sizeof(*begin) == sizeof(uint32_t)>{},
+ begin, end);
+ }
+ }
+
+ template <typename OutIterator>
+ void param(OutIterator out) const {
+ seq_->param(out);
+ }
+
+ size_t size() const { return seq_->size(); }
+
+ private:
+ // The common case for generate is that it is called with iterators over a
+ // 32-bit value buffer. These can be reinterpreted to a uint32_t and we can
+ // operate on them as such.
+ template <typename RandomAccessIterator>
+ void generate_impl(std::integral_constant<bool, true> /*is_32bit*/,
+ RandomAccessIterator begin, RandomAccessIterator end) {
+ seq_->generate(begin, end);
+ const uint32_t salt = absl::random_internal::GetSaltMaterial().value_or(0);
+ auto buffer = absl::MakeSpan(begin, end);
+ MixIntoSeedMaterial(
+ absl::MakeConstSpan(&salt, 1),
+ absl::MakeSpan(reinterpret_cast<uint32_t*>(buffer.data()),
+ buffer.size()));
+ }
+
+ // The uncommon case for generate is that it is called with iterators over
+ // some other buffer type which is assignable from a 32-bit value. In this
+ // case we allocate a temporary 32-bit buffer and then copy-assign back
+ // to the initial inputs.
+ template <typename RandomAccessIterator>
+ void generate_impl(std::integral_constant<bool, false> /*is_32bit*/,
+ RandomAccessIterator begin, RandomAccessIterator end) {
+ // Allocate a temporary buffer, seed, and then copy.
+ absl::InlinedVector<uint32_t, 8> data(std::distance(begin, end), 0);
+ generate_impl(std::integral_constant<bool, true>{}, data.begin(),
+ data.end());
+ std::copy(data.begin(), data.end(), begin);
+ }
+
+ // Because [rand.req.seedseq] is not copy-constructible, copy-assignable nor
+ // movable so we wrap it with unique pointer to be able to move SaltedSeedSeq.
+ std::unique_ptr<SSeq> seq_;
+};
+
+// is_salted_seed_seq indicates whether the type is a SaltedSeedSeq.
+template <typename T, typename = void>
+struct is_salted_seed_seq : public std::false_type {};
+
+template <typename T>
+struct is_salted_seed_seq<
+ T, typename std::enable_if<std::is_same<
+ T, SaltedSeedSeq<typename T::inner_sequence_type>>::value>::type>
+ : public std::true_type {};
+
+// MakeSaltedSeedSeq returns a salted variant of the seed sequence.
+// When provided with an existing SaltedSeedSeq, returns the input parameter,
+// otherwise constructs a new SaltedSeedSeq which embodies the original
+// non-salted seed parameters.
+template <
+ typename SSeq, //
+ typename EnableIf = absl::enable_if_t<is_salted_seed_seq<SSeq>::value>>
+SSeq MakeSaltedSeedSeq(SSeq&& seq) {
+ return SSeq(std::forward<SSeq>(seq));
+}
+
+template <
+ typename SSeq, //
+ typename EnableIf = absl::enable_if_t<!is_salted_seed_seq<SSeq>::value>>
+SaltedSeedSeq<typename std::decay<SSeq>::type> MakeSaltedSeedSeq(SSeq&& seq) {
+ using sseq_type = typename std::decay<SSeq>::type;
+ using result_type = typename sseq_type::result_type;
+
+ absl::InlinedVector<result_type, 8> data;
+ seq.param(std::back_inserter(data));
+ return SaltedSeedSeq<sseq_type>(data.begin(), data.end());
+}
+
+} // namespace random_internal
+} // namespace absl
+
+#endif // ABSL_RANDOM_INTERNAL_SALTED_SEED_SEQ_H_
git://repos.xcallymotion.com / motion2.git / blobdiff