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Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
// 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 <algorithm>
#include <cinttypes>
#include <cstdlib>
#include <iostream>
#include <iterator>
#include <limits>
#include <type_traits>
#include "absl/base/internal/endian.h"
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
#include "absl/meta/type_traits.h"
#include "absl/random/internal/iostream_state_saver.h"
#include "absl/random/internal/randen.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
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 <typename T>
class alignas(16) randen_engine {
public:
// C++11 URBG interface:
using result_type = T;
static_assert(std::is_unsigned<result_type>::value,
"randen_engine template argument must be a built-in unsigned "
"integer type");
static constexpr result_type(min)() {
return (std::numeric_limits<result_type>::min)();
}
static constexpr result_type(max)() {
return (std::numeric_limits<result_type>::max)();
}
explicit randen_engine(result_type seed_value = 0) { seed(seed_value); }
template <class SeedSequence,
typename = typename absl::enable_if_t<
!std::is_same<SeedSequence, randen_engine>::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 little_endian::ToHost(state_[next_++]);
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
}
template <class SeedSequence>
typename absl::enable_if_t<
!std::is_convertible<SeedSequence, result_type>::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 <class SeedSequence>
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);
#ifdef ABSL_IS_BIG_ENDIAN
// Randen expects the seed buffer to be in Little Endian; reverse it on
// Big Endian platforms.
for (sequence_result_type& e : buffer) {
e = absl::little_endian::FromHost(e);
}
#endif
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
// 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<uint64_t>(kStateSizeT - next_, count);
count -= step;
constexpr uint64_t kRateT = kStateSizeT - kCapacityT;
while (count > 0) {
next_ = kCapacityT;
impl_.Generate(state_);
step = std::min<uint64_t>(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 <class CharT, class Traits>
friend std::basic_ostream<CharT, Traits>& operator<<(
std::basic_ostream<CharT, Traits>& os, // NOLINT(runtime/references)
const randen_engine<T>& engine) { // NOLINT(runtime/references)
using numeric_type =
typename random_internal::stream_format_type<result_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<numeric_type>(little_endian::FromHost(elem))
<< os.fill();
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
}
os << engine.next_;
return os;
}
template <class CharT, class Traits>
friend std::basic_istream<CharT, Traits>& operator>>(
std::basic_istream<CharT, Traits>& is, // NOLINT(runtime/references)
randen_engine<T>& engine) { // NOLINT(runtime/references)
using numeric_type =
typename random_internal::stream_format_type<result_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 = little_endian::ToHost(static_cast<result_type>(value));
Export of internal Abseil changes -- f012012ef78234a6a4585321b67d7b7c92ebc266 by Laramie Leavitt <lar@google.com>: Slight restructuring of absl/random/internal randen implementation. Convert round-keys.inc into randen_round_keys.cc file. Consistently use a 128-bit pointer type for internal method parameters. This allows simpler pointer arithmetic in C++ & permits removal of some constants and casts. Remove some redundancy in comments & constexpr variables. Specifically, all references to Randen algorithm parameters use RandenTraits; duplication in RandenSlow removed. PiperOrigin-RevId: 312190313 -- dc8b42e054046741e9ed65335bfdface997c6063 by Abseil Team <absl-team@google.com>: Internal change. PiperOrigin-RevId: 312167304 -- f13d248fafaf206492c1362c3574031aea3abaf7 by Matthew Brown <matthewbr@google.com>: Cleanup StrFormat extensions a little. PiperOrigin-RevId: 312166336 -- 9d9117589667afe2332bb7ad42bc967ca7c54502 by Derek Mauro <dmauro@google.com>: Internal change PiperOrigin-RevId: 312105213 -- 9a12b9b3aa0e59b8ee6cf9408ed0029045543a9b by Abseil Team <absl-team@google.com>: Complete IGNORE_TYPE macro renaming. PiperOrigin-RevId: 311999699 -- 64756f20d61021d999bd0d4c15e9ad3857382f57 by Gennadiy Rozental <rogeeff@google.com>: Switch to fixed bytes specific default value. This fixes the Abseil Flags for big endian platforms. PiperOrigin-RevId: 311844448 -- bdbe6b5b29791dbc3816ada1828458b3010ff1e9 by Laramie Leavitt <lar@google.com>: Change many distribution tests to use pcg_engine as a deterministic source of entropy. It's reasonable to test that the BitGen itself has good entropy, however when testing the cross product of all random distributions x all the architecture variations x all submitted changes results in a large number of tests. In order to account for these failures while still using good entropy requires that our allowed sigma need to account for all of these independent tests. Our current sigma values are too restrictive, and we see a lot of failures, so we have to either relax the sigma values or convert some of the statistical tests to use deterministic values. This changelist does the latter. PiperOrigin-RevId: 311840096 GitOrigin-RevId: f012012ef78234a6a4585321b67d7b7c92ebc266 Change-Id: Ic84886f38ff30d7d72c126e9b63c9a61eb729a1a
5 years ago
}
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
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_RANDOM_INTERNAL_RANDEN_ENGINE_H_