diff options
Diffstat (limited to 'abseil-cpp/absl/random/internal/salted_seed_seq.h')
-rw-r--r-- | abseil-cpp/absl/random/internal/salted_seed_seq.h | 50 |
1 files changed, 24 insertions, 26 deletions
diff --git a/abseil-cpp/absl/random/internal/salted_seed_seq.h b/abseil-cpp/absl/random/internal/salted_seed_seq.h index 5953a09..0629186 100644 --- a/abseil-cpp/absl/random/internal/salted_seed_seq.h +++ b/abseil-cpp/absl/random/internal/salted_seed_seq.h @@ -22,6 +22,7 @@ #include <memory> #include <type_traits> #include <utility> +#include <vector> #include "absl/container/inlined_vector.h" #include "absl/meta/type_traits.h" @@ -65,15 +66,19 @@ class SaltedSeedSeq { template <typename RandomAccessIterator> void generate(RandomAccessIterator begin, RandomAccessIterator end) { + using U = typename std::iterator_traits<RandomAccessIterator>::value_type; + // The common case is that generate is called with ContiguousIterators // to uint arrays. Such contiguous memory regions may be optimized, // which we detect here. - using tag = absl::conditional_t< - (std::is_pointer<RandomAccessIterator>::value && - std::is_same<absl::decay_t<decltype(*begin)>, uint32_t>::value), + using TagType = absl::conditional_t< + (std::is_same<U, uint32_t>::value && + (std::is_pointer<RandomAccessIterator>::value || + std::is_same<RandomAccessIterator, + typename std::vector<U>::iterator>::value)), ContiguousAndUint32Tag, DefaultTag>; if (begin != end) { - generate_impl(begin, end, tag{}); + generate_impl(TagType{}, begin, end, std::distance(begin, end)); } } @@ -89,8 +94,15 @@ class SaltedSeedSeq { struct DefaultTag {}; // Generate which requires the iterators are contiguous pointers to uint32_t. - void generate_impl(uint32_t* begin, uint32_t* end, ContiguousAndUint32Tag) { - generate_contiguous(absl::MakeSpan(begin, end)); + // Fills the initial seed buffer the underlying SSeq::generate() call, + // then mixes in the salt material. + template <typename Contiguous> + void generate_impl(ContiguousAndUint32Tag, Contiguous begin, Contiguous end, + size_t n) { + seq_->generate(begin, end); + const uint32_t salt = absl::random_internal::GetSaltMaterial().value_or(0); + auto span = absl::Span<uint32_t>(&*begin, n); + MixIntoSeedMaterial(absl::MakeConstSpan(&salt, 1), span); } // The uncommon case for generate is that it is called with iterators over @@ -98,27 +110,13 @@ class SaltedSeedSeq { // case we allocate a temporary 32-bit buffer and then copy-assign back // to the initial inputs. template <typename RandomAccessIterator> - void generate_impl(RandomAccessIterator begin, RandomAccessIterator end, - DefaultTag) { - return generate_and_copy(std::distance(begin, end), begin); - } - - // Fills the initial seed buffer the underlying SSeq::generate() call, - // mixing in the salt material. - void generate_contiguous(absl::Span<uint32_t> buffer) { - seq_->generate(buffer.begin(), buffer.end()); - const uint32_t salt = absl::random_internal::GetSaltMaterial().value_or(0); - MixIntoSeedMaterial(absl::MakeConstSpan(&salt, 1), buffer); - } - - // Allocates a seed buffer of `n` elements, generates the seed, then - // copies the result into the `out` iterator. - template <typename Iterator> - void generate_and_copy(size_t n, Iterator out) { - // Allocate a temporary buffer, generate, and then copy. + void generate_impl(DefaultTag, RandomAccessIterator begin, + RandomAccessIterator, size_t n) { + // Allocates a seed buffer of `n` elements, generates the seed, then + // copies the result into the `out` iterator. absl::InlinedVector<uint32_t, 8> data(n, 0); - generate_contiguous(absl::MakeSpan(data.data(), data.size())); - std::copy(data.begin(), data.end(), out); + generate_impl(ContiguousAndUint32Tag{}, data.begin(), data.end(), n); + std::copy(data.begin(), data.end(), begin); } // Because [rand.req.seedseq] is not required to be copy-constructible, |