From e9324d926a9189e222741fce6e676f0944661a72 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 21 Jun 2019 13:11:42 -0700 Subject: Export of internal Abseil changes. -- 7a6ff16a85beb730c172d5d25cf1b5e1be885c56 by Laramie Leavitt : Internal change. PiperOrigin-RevId: 254454546 -- ff8f9bafaefc26d451f576ea4a06d150aed63f6f by Andy Soffer : Internal changes PiperOrigin-RevId: 254451562 -- deefc5b651b479ce36f0b4ef203e119c0c8936f2 by CJ Johnson : Account for subtracting unsigned values from the size of InlinedVector PiperOrigin-RevId: 254450625 -- 3c677316a27bcadc17e41957c809ca472d5fef14 by Andy Soffer : Add C++17's std::make_from_tuple to absl/utility/utility.h PiperOrigin-RevId: 254411573 -- 4ee3536a918830eeec402a28fc31a62c7c90b940 by CJ Johnson : Adds benchmark for the rest of the InlinedVector public API PiperOrigin-RevId: 254408378 -- e5a21a00700ee83498ff1efbf649169756463ee4 by CJ Johnson : Updates the definition of InlinedVector::shrink_to_fit() to be exception safe and adds exception safety tests for it. PiperOrigin-RevId: 254401387 -- 2ea82e72b86d82d78b4e4712a63a55981b53c64b by Laramie Leavitt : Use absl::InsecureBitGen in place of std::mt19937 in tests absl/random/...distribution_test.cc PiperOrigin-RevId: 254289444 -- fa099e02c413a7ffda732415e8105cad26a90337 by Andy Soffer : Internal changes PiperOrigin-RevId: 254286334 -- ce34b7f36933b30cfa35b9c9a5697a792b5666e4 by Andy Soffer : Internal changes PiperOrigin-RevId: 254273059 -- 6f9c473da7c2090c2e85a37c5f00622e8a912a89 by Jorg Brown : Change absl::container_internal::CompressedTuple to instantiate its internal Storage class with the name of the type it's holding, rather than the name of the Tuple. This is not an externally-visible change, other than less compiler memory is used and less debug information is generated. PiperOrigin-RevId: 254269285 -- 8bd3c186bf2fc0c55d8a2dd6f28a5327502c9fba by Andy Soffer : Adding short-hand IntervalClosed for IntervalClosedClosed and IntervalOpen for IntervalOpenOpen. PiperOrigin-RevId: 254252419 -- ea957f99b6a04fccd42aa05605605f3b44b1ecfd by Abseil Team : Do not directly use __SIZEOF_INT128__. In order to avoid linker errors when building with clang-cl (__fixunsdfti, __udivti3 and __fixunssfti are undefined), this CL uses ABSL_HAVE_INTRINSIC_INT128 which is not defined for clang-cl. PiperOrigin-RevId: 254250739 -- 89ab385cd26b34d64130bce856253aaba96d2345 by Andy Soffer : Internal changes PiperOrigin-RevId: 254242321 -- cffc793d93eca6d6bdf7de733847b6ab4a255ae9 by CJ Johnson : Adds benchmark for InlinedVector::reserve(size_type) PiperOrigin-RevId: 254199226 -- c90c7a9fa3c8f0c9d5114036979548b055ea2f2a by Gennadiy Rozental : Import of CCTZ from GitHub. PiperOrigin-RevId: 254072387 -- c4c388beae016c9570ab54ffa1d52660e4a85b7b by Laramie Leavitt : Internal cleanup. PiperOrigin-RevId: 254062381 -- d3c992e221cc74e5372d0c8fa410170b6a43c062 by Tom Manshreck : Update distributions.h to Abseil standards PiperOrigin-RevId: 254054946 -- d15ad0035c34ef11b14fadc5a4a2d3ec415f5518 by CJ Johnson : Removes functions with only one caller from the implementation details of InlinedVector by manually inlining the definitions PiperOrigin-RevId: 254005427 -- 2f37e807efc3a8ef1f4b539bdd379917d4151520 by Andy Soffer : Initial release of Abseil Random PiperOrigin-RevId: 253999861 -- 24ed1694b6430791d781ed533a8f8ccf6cac5856 by CJ Johnson : Updates the definition of InlinedVector::assign(...)/InlinedVector::operator=(...) to new, exception-safe implementations with exception safety tests to boot PiperOrigin-RevId: 253993691 -- 5613d95f5a7e34a535cfaeadce801441e990843e by CJ Johnson : Adds benchmarks for InlinedVector::shrink_to_fit() PiperOrigin-RevId: 253989647 -- 2a96ddfdac40bbb8cb6a7f1aeab90917067c6e63 by Abseil Team : Initial release of Abseil Random PiperOrigin-RevId: 253927497 -- bf1aff8fc9ffa921ad74643e9525ecf25b0d8dc1 by Andy Soffer : Initial release of Abseil Random PiperOrigin-RevId: 253920512 -- bfc03f4a3dcda3cf3a4b84bdb84cda24e3394f41 by Laramie Leavitt : Internal change. PiperOrigin-RevId: 253886486 -- 05036cfcc078ca7c5f581a00dfb0daed568cbb69 by Eric Fiselier : Don't include `winsock2.h` because it drags in `windows.h` and friends, and they define awful macros like OPAQUE, ERROR, and more. This has the potential to break abseil users. Instead we only forward declare `timeval` and require Windows users include `winsock2.h` themselves. This is both inconsistent and poor QoI, but so including 'windows.h' is bad too. PiperOrigin-RevId: 253852615 GitOrigin-RevId: 7a6ff16a85beb730c172d5d25cf1b5e1be885c56 Change-Id: Icd6aff87da26f29ec8915da856f051129987cef6 --- absl/random/internal/randen_engine.h | 228 +++++++++++++++++++++++++++++++++++ 1 file changed, 228 insertions(+) create mode 100644 absl/random/internal/randen_engine.h (limited to 'absl/random/internal/randen_engine.h') diff --git a/absl/random/internal/randen_engine.h b/absl/random/internal/randen_engine.h new file mode 100644 index 000000000000..02212a137c36 --- /dev/null +++ b/absl/random/internal/randen_engine.h @@ -0,0 +1,228 @@ +// 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_RANDEN_ENGINE_H_ +#define ABSL_RANDOM_INTERNAL_RANDEN_ENGINE_H_ + +#include +#include +#include +#include +#include +#include +#include + +#include "absl/meta/type_traits.h" +#include "absl/random/internal/iostream_state_saver.h" +#include "absl/random/internal/randen.h" + +namespace absl { +namespace random_internal { + +// Deterministic pseudorandom byte generator with backtracking resistance +// (leaking the state does not compromise prior outputs). Based on Reverie +// (see "A Robust and Sponge-Like PRNG with Improved Efficiency") instantiated +// with an improved Simpira-like permutation. +// Returns values of type "T" (must be a built-in unsigned integer type). +// +// RANDen = RANDom generator or beetroots in Swiss High German. +// 'Strong' (well-distributed, unpredictable, backtracking-resistant) random +// generator, faster in some benchmarks than std::mt19937_64 and pcg64_c32. +template +class alignas(16) randen_engine { + public: + // C++11 URBG interface: + using result_type = T; + static_assert(std::is_unsigned::value, + "randen_engine template argument must be a built-in unsigned " + "integer type"); + + static constexpr result_type(min)() { + return (std::numeric_limits::min)(); + } + + static constexpr result_type(max)() { + return (std::numeric_limits::max)(); + } + + explicit randen_engine(result_type seed_value = 0) { seed(seed_value); } + + template ::value>> + explicit randen_engine(SeedSequence&& seq) { + seed(seq); + } + + randen_engine(const randen_engine&) = default; + + // Returns random bits from the buffer in units of result_type. + result_type operator()() { + // Refill the buffer if needed (unlikely). + if (next_ >= kStateSizeT) { + next_ = kCapacityT; + impl_.Generate(state_); + } + + return state_[next_++]; + } + + template + typename absl::enable_if_t< + !std::is_convertible::value> + seed(SeedSequence&& seq) { + // Zeroes the state. + seed(); + reseed(seq); + } + + void seed(result_type seed_value = 0) { + next_ = kStateSizeT; + // Zeroes the inner state and fills the outer state with seed_value to + // mimics behaviour of reseed + std::fill(std::begin(state_), std::begin(state_) + kCapacityT, 0); + std::fill(std::begin(state_) + kCapacityT, std::end(state_), seed_value); + } + + // Inserts entropy into (part of) the state. Calling this periodically with + // sufficient entropy ensures prediction resistance (attackers cannot predict + // future outputs even if state is compromised). + template + void reseed(SeedSequence& seq) { + using sequence_result_type = typename SeedSequence::result_type; + static_assert(sizeof(sequence_result_type) == 4, + "SeedSequence::result_type must be 32-bit"); + + constexpr size_t kBufferSize = + Randen::kSeedBytes / sizeof(sequence_result_type); + alignas(16) sequence_result_type buffer[kBufferSize]; + + // Randen::Absorb XORs the seed into state, which is then mixed by a call + // to Randen::Generate. Seeding with only the provided entropy is preferred + // to using an arbitrary generate() call, so use [rand.req.seed_seq] + // size as a proxy for the number of entropy units that can be generated + // without relying on seed sequence mixing... + const size_t entropy_size = seq.size(); + if (entropy_size < kBufferSize) { + // ... and only request that many values, or 256-bits, when unspecified. + const size_t requested_entropy = (entropy_size == 0) ? 8u : entropy_size; + std::fill(std::begin(buffer) + requested_entropy, std::end(buffer), 0); + seq.generate(std::begin(buffer), std::begin(buffer) + requested_entropy); + // The Randen paper suggests preferentially initializing even-numbered + // 128-bit vectors of the randen state (there are 16 such vectors). + // The seed data is merged into the state offset by 128-bits, which + // implies prefering seed bytes [16..31, ..., 208..223]. Since the + // buffer is 32-bit values, we swap the corresponding buffer positions in + // 128-bit chunks. + size_t dst = kBufferSize; + while (dst > 7) { + // leave the odd bucket as-is. + dst -= 4; + size_t src = dst >> 1; + // swap 128-bits into the even bucket + std::swap(buffer[--dst], buffer[--src]); + std::swap(buffer[--dst], buffer[--src]); + std::swap(buffer[--dst], buffer[--src]); + std::swap(buffer[--dst], buffer[--src]); + } + } else { + seq.generate(std::begin(buffer), std::end(buffer)); + } + impl_.Absorb(buffer, state_); + + // Generate will be called when operator() is called + next_ = kStateSizeT; + } + + void discard(uint64_t count) { + uint64_t step = std::min(kStateSizeT - next_, count); + count -= step; + + constexpr uint64_t kRateT = kStateSizeT - kCapacityT; + while (count > 0) { + next_ = kCapacityT; + impl_.Generate(state_); + step = std::min(kRateT, count); + count -= step; + } + next_ += step; + } + + bool operator==(const randen_engine& other) const { + return next_ == other.next_ && + std::equal(std::begin(state_), std::end(state_), + std::begin(other.state_)); + } + + bool operator!=(const randen_engine& other) const { + return !(*this == other); + } + + template + friend std::basic_ostream& operator<<( + std::basic_ostream& os, // NOLINT(runtime/references) + const randen_engine& engine) { // NOLINT(runtime/references) + using numeric_type = + typename random_internal::stream_format_type::type; + auto saver = random_internal::make_ostream_state_saver(os); + for (const auto& elem : engine.state_) { + // In the case that `elem` is `uint8_t`, it must be cast to something + // larger so that it prints as an integer rather than a character. For + // simplicity, apply the cast all circumstances. + os << static_cast(elem) << os.fill(); + } + os << engine.next_; + return os; + } + + template + friend std::basic_istream& operator>>( + std::basic_istream& is, // NOLINT(runtime/references) + randen_engine& engine) { // NOLINT(runtime/references) + using numeric_type = + typename random_internal::stream_format_type::type; + result_type state[kStateSizeT]; + size_t next; + for (auto& elem : state) { + // It is not possible to read uint8_t from wide streams, so it is + // necessary to read a wider type and then cast it to uint8_t. + numeric_type value; + is >> value; + elem = static_cast(value); + } + is >> next; + if (is.fail()) { + return is; + } + std::memcpy(engine.state_, state, sizeof(engine.state_)); + engine.next_ = next; + return is; + } + + private: + static constexpr size_t kStateSizeT = + Randen::kStateBytes / sizeof(result_type); + static constexpr size_t kCapacityT = + Randen::kCapacityBytes / sizeof(result_type); + + // First kCapacityT are `inner', the others are accessible random bits. + alignas(16) result_type state_[kStateSizeT]; + size_t next_; // index within state_ + Randen impl_; +}; + +} // namespace random_internal +} // namespace absl + +#endif // ABSL_RANDOM_INTERNAL_RANDEN_ENGINE_H_ -- cgit 1.4.1