186 lines
6.8 KiB
C++
186 lines
6.8 KiB
C++
//
|
|
// Copyright 2018 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.
|
|
//
|
|
// -----------------------------------------------------------------------------
|
|
// File: bit_gen_ref.h
|
|
// -----------------------------------------------------------------------------
|
|
//
|
|
// This header defines a bit generator "reference" class, for use in interfaces
|
|
// that take both Abseil (e.g. `absl::BitGen`) and standard library (e.g.
|
|
// `std::mt19937`) bit generators.
|
|
|
|
#ifndef ABSL_RANDOM_BIT_GEN_REF_H_
|
|
#define ABSL_RANDOM_BIT_GEN_REF_H_
|
|
|
|
#include <limits>
|
|
#include <type_traits>
|
|
#include <utility>
|
|
|
|
#include "absl/base/internal/fast_type_id.h"
|
|
#include "absl/base/macros.h"
|
|
#include "absl/meta/type_traits.h"
|
|
#include "absl/random/internal/distribution_caller.h"
|
|
#include "absl/random/internal/fast_uniform_bits.h"
|
|
|
|
namespace absl {
|
|
ABSL_NAMESPACE_BEGIN
|
|
namespace random_internal {
|
|
|
|
template <typename URBG, typename = void, typename = void, typename = void>
|
|
struct is_urbg : std::false_type {};
|
|
|
|
template <typename URBG>
|
|
struct is_urbg<
|
|
URBG,
|
|
absl::enable_if_t<std::is_same<
|
|
typename URBG::result_type,
|
|
typename std::decay<decltype((URBG::min)())>::type>::value>,
|
|
absl::enable_if_t<std::is_same<
|
|
typename URBG::result_type,
|
|
typename std::decay<decltype((URBG::max)())>::type>::value>,
|
|
absl::enable_if_t<std::is_same<
|
|
typename URBG::result_type,
|
|
typename std::decay<decltype(std::declval<URBG>()())>::type>::value>>
|
|
: std::true_type {};
|
|
|
|
template <typename>
|
|
struct DistributionCaller;
|
|
class MockHelpers;
|
|
|
|
} // namespace random_internal
|
|
|
|
// -----------------------------------------------------------------------------
|
|
// absl::BitGenRef
|
|
// -----------------------------------------------------------------------------
|
|
//
|
|
// `absl::BitGenRef` is a type-erasing class that provides a generator-agnostic
|
|
// non-owning "reference" interface for use in place of any specific uniform
|
|
// random bit generator (URBG). This class may be used for both Abseil
|
|
// (e.g. `absl::BitGen`, `absl::InsecureBitGen`) and Standard library (e.g
|
|
// `std::mt19937`, `std::minstd_rand`) bit generators.
|
|
//
|
|
// Like other reference classes, `absl::BitGenRef` does not own the
|
|
// underlying bit generator, and the underlying instance must outlive the
|
|
// `absl::BitGenRef`.
|
|
//
|
|
// `absl::BitGenRef` is particularly useful when used with an
|
|
// `absl::MockingBitGen` to test specific paths in functions which use random
|
|
// values.
|
|
//
|
|
// Example:
|
|
// void TakesBitGenRef(absl::BitGenRef gen) {
|
|
// int x = absl::Uniform<int>(gen, 0, 1000);
|
|
// }
|
|
//
|
|
class BitGenRef {
|
|
// SFINAE to detect whether the URBG type includes a member matching
|
|
// bool InvokeMock(base_internal::FastTypeIdType, void*, void*).
|
|
//
|
|
// These live inside BitGenRef so that they have friend access
|
|
// to MockingBitGen. (see similar methods in DistributionCaller).
|
|
template <template <class...> class Trait, class AlwaysVoid, class... Args>
|
|
struct detector : std::false_type {};
|
|
template <template <class...> class Trait, class... Args>
|
|
struct detector<Trait, absl::void_t<Trait<Args...>>, Args...>
|
|
: std::true_type {};
|
|
|
|
template <class T>
|
|
using invoke_mock_t = decltype(std::declval<T*>()->InvokeMock(
|
|
std::declval<base_internal::FastTypeIdType>(), std::declval<void*>(),
|
|
std::declval<void*>()));
|
|
|
|
template <typename T>
|
|
using HasInvokeMock = typename detector<invoke_mock_t, void, T>::type;
|
|
|
|
public:
|
|
BitGenRef(const BitGenRef&) = default;
|
|
BitGenRef(BitGenRef&&) = default;
|
|
BitGenRef& operator=(const BitGenRef&) = default;
|
|
BitGenRef& operator=(BitGenRef&&) = default;
|
|
|
|
template <typename URBG, typename absl::enable_if_t<
|
|
(!std::is_same<URBG, BitGenRef>::value &&
|
|
random_internal::is_urbg<URBG>::value &&
|
|
!HasInvokeMock<URBG>::value)>* = nullptr>
|
|
BitGenRef(URBG& gen) // NOLINT
|
|
: t_erased_gen_ptr_(reinterpret_cast<uintptr_t>(&gen)),
|
|
mock_call_(NotAMock),
|
|
generate_impl_fn_(ImplFn<URBG>) {}
|
|
|
|
template <typename URBG,
|
|
typename absl::enable_if_t<(!std::is_same<URBG, BitGenRef>::value &&
|
|
random_internal::is_urbg<URBG>::value &&
|
|
HasInvokeMock<URBG>::value)>* = nullptr>
|
|
BitGenRef(URBG& gen) // NOLINT
|
|
: t_erased_gen_ptr_(reinterpret_cast<uintptr_t>(&gen)),
|
|
mock_call_(&MockCall<URBG>),
|
|
generate_impl_fn_(ImplFn<URBG>) {}
|
|
|
|
using result_type = uint64_t;
|
|
|
|
static constexpr result_type(min)() {
|
|
return (std::numeric_limits<result_type>::min)();
|
|
}
|
|
|
|
static constexpr result_type(max)() {
|
|
return (std::numeric_limits<result_type>::max)();
|
|
}
|
|
|
|
result_type operator()() { return generate_impl_fn_(t_erased_gen_ptr_); }
|
|
|
|
private:
|
|
using impl_fn = result_type (*)(uintptr_t);
|
|
using mock_call_fn = bool (*)(uintptr_t, base_internal::FastTypeIdType, void*,
|
|
void*);
|
|
|
|
template <typename URBG>
|
|
static result_type ImplFn(uintptr_t ptr) {
|
|
// Ensure that the return values from operator() fill the entire
|
|
// range promised by result_type, min() and max().
|
|
absl::random_internal::FastUniformBits<result_type> fast_uniform_bits;
|
|
return fast_uniform_bits(*reinterpret_cast<URBG*>(ptr));
|
|
}
|
|
|
|
// Get a type-erased InvokeMock pointer.
|
|
template <typename URBG>
|
|
static bool MockCall(uintptr_t gen_ptr, base_internal::FastTypeIdType type,
|
|
void* result, void* arg_tuple) {
|
|
return reinterpret_cast<URBG*>(gen_ptr)->InvokeMock(type, result,
|
|
arg_tuple);
|
|
}
|
|
static bool NotAMock(uintptr_t, base_internal::FastTypeIdType, void*, void*) {
|
|
return false;
|
|
}
|
|
|
|
inline bool InvokeMock(base_internal::FastTypeIdType type, void* args_tuple,
|
|
void* result) {
|
|
if (mock_call_ == NotAMock) return false; // avoids an indirect call.
|
|
return mock_call_(t_erased_gen_ptr_, type, args_tuple, result);
|
|
}
|
|
|
|
uintptr_t t_erased_gen_ptr_;
|
|
mock_call_fn mock_call_;
|
|
impl_fn generate_impl_fn_;
|
|
|
|
template <typename>
|
|
friend struct ::absl::random_internal::DistributionCaller; // for InvokeMock
|
|
friend class ::absl::random_internal::MockHelpers; // for InvokeMock
|
|
};
|
|
|
|
ABSL_NAMESPACE_END
|
|
} // namespace absl
|
|
|
|
#endif // ABSL_RANDOM_BIT_GEN_REF_H_
|