Abseil Common Libraries (C++) (grcp 依赖) https://abseil.io/
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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_POOL_URBG_H_
#define ABSL_RANDOM_INTERNAL_POOL_URBG_H_
#include <cinttypes>
#include <limits>
#include "absl/random/internal/traits.h"
#include "absl/types/span.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace random_internal {
// RandenPool is a thread-safe random number generator [random.req.urbg] that
// uses an underlying pool of Randen generators to generate values. Each thread
// has affinity to one instance of the underlying pool generators. Concurrent
// access is guarded by a spin-lock.
template <typename T>
class RandenPool {
public:
using result_type = T;
static_assert(std::is_unsigned<result_type>::value,
"RandenPool 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)();
}
RandenPool() {}
// Returns a single value.
inline result_type operator()() { return Generate(); }
// Fill data with random values.
static void Fill(absl::Span<result_type> data);
protected:
// Generate returns a single value.
static result_type Generate();
};
extern template class RandenPool<uint8_t>;
extern template class RandenPool<uint16_t>;
extern template class RandenPool<uint32_t>;
extern template class RandenPool<uint64_t>;
// PoolURBG uses an underlying pool of random generators to implement a
// thread-compatible [random.req.urbg] interface with an internal cache of
// values.
template <typename T, size_t kBufferSize>
class PoolURBG {
// Inheritance to access the protected static members of RandenPool.
using unsigned_type = typename make_unsigned_bits<T>::type;
using PoolType = RandenPool<unsigned_type>;
using SpanType = absl::Span<unsigned_type>;
static constexpr size_t kInitialBuffer = kBufferSize + 1;
static constexpr size_t kHalfBuffer = kBufferSize / 2;
public:
using result_type = T;
static_assert(std::is_unsigned<result_type>::value,
"PoolURBG must be parameterized by an unsigned integer type");
static_assert(kBufferSize > 1,
"PoolURBG must be parameterized by a buffer-size > 1");
static_assert(kBufferSize <= 256,
"PoolURBG must be parameterized by a buffer-size <= 256");
static constexpr result_type(min)() {
return (std::numeric_limits<result_type>::min)();
}
static constexpr result_type(max)() {
return (std::numeric_limits<result_type>::max)();
}
PoolURBG() : next_(kInitialBuffer) {}
// copy-constructor does not copy cache.
PoolURBG(const PoolURBG&) : next_(kInitialBuffer) {}
const PoolURBG& operator=(const PoolURBG&) {
next_ = kInitialBuffer;
return *this;
}
// move-constructor does move cache.
PoolURBG(PoolURBG&&) = default;
PoolURBG& operator=(PoolURBG&&) = default;
inline result_type operator()() {
if (next_ >= kBufferSize) {
next_ = (kBufferSize > 2 && next_ > kBufferSize) ? kHalfBuffer : 0;
PoolType::Fill(SpanType(reinterpret_cast<unsigned_type*>(state_ + next_),
kBufferSize - next_));
}
return state_[next_++];
}
private:
// Buffer size.
size_t next_; // index within state_
result_type state_[kBufferSize];
};
} // namespace random_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_RANDOM_INTERNAL_POOL_URBG_H_