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// 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.
#include "absl/random/internal/fast_uniform_bits.h"
#include <random>
#include "gtest/gtest.h"
namespace {
template <typename IntType>
class FastUniformBitsTypedTest : public ::testing::Test {};
using IntTypes = ::testing::Types<uint8_t, uint16_t, uint32_t, uint64_t>;
TYPED_TEST_SUITE(FastUniformBitsTypedTest, IntTypes);
TYPED_TEST(FastUniformBitsTypedTest, BasicTest) {
using Limits = std::numeric_limits<TypeParam>;
using FastBits = absl::random_internal::FastUniformBits<TypeParam>;
EXPECT_EQ(0, FastBits::min());
EXPECT_EQ(Limits::max(), FastBits::max());
constexpr int kIters = 10000;
std::random_device rd;
std::mt19937 gen(rd());
FastBits fast;
for (int i = 0; i < kIters; i++) {
const auto v = fast(gen);
EXPECT_LE(v, FastBits::max());
EXPECT_GE(v, FastBits::min());
}
}
class UrngOddbits {
public:
using result_type = uint8_t;
static constexpr result_type min() { return 1; }
static constexpr result_type max() { return 0xfe; }
result_type operator()() { return 2; }
};
class Urng4bits {
public:
using result_type = uint8_t;
static constexpr result_type min() { return 1; }
static constexpr result_type max() { return 0xf + 1; }
result_type operator()() { return 2; }
};
class Urng32bits {
public:
using result_type = uint32_t;
static constexpr result_type min() { return 0; }
static constexpr result_type max() { return 0xffffffff; }
result_type operator()() { return 1; }
};
// Compile-time test to validate the helper classes used by FastUniformBits
TEST(FastUniformBitsTest, FastUniformBitsDetails) {
using absl::random_internal::FastUniformBitsLoopingConstants;
using absl::random_internal::FastUniformBitsURBGConstants;
// 4-bit URBG
{
using constants = FastUniformBitsURBGConstants<Urng4bits>;
static_assert(constants::kPowerOfTwo == true,
"constants::kPowerOfTwo == false");
static_assert(constants::kRange == 16, "constants::kRange == false");
static_assert(constants::kRangeBits == 4, "constants::kRangeBits == false");
static_assert(constants::kRangeMask == 0x0f,
"constants::kRangeMask == false");
}
// ~7-bit URBG
{
using constants = FastUniformBitsURBGConstants<UrngOddbits>;
static_assert(constants::kPowerOfTwo == false,
"constants::kPowerOfTwo == false");
static_assert(constants::kRange == 0xfe, "constants::kRange == 0xfe");
static_assert(constants::kRangeBits == 7, "constants::kRangeBits == 7");
static_assert(constants::kRangeMask == 0x7f,
"constants::kRangeMask == 0x7f");
}
}
TEST(FastUniformBitsTest, Urng4_VariousOutputs) {
// Tests that how values are composed; the single-bit deltas should be spread
// across each invocation.
Urng4bits urng4;
Urng32bits urng32;
// 8-bit types
{
absl::random_internal::FastUniformBits<uint8_t> fast8;
EXPECT_EQ(0x11, fast8(urng4));
EXPECT_EQ(0x1, fast8(urng32));
}
// 16-bit types
{
absl::random_internal::FastUniformBits<uint16_t> fast16;
EXPECT_EQ(0x1111, fast16(urng4));
EXPECT_EQ(0x1, fast16(urng32));
}
// 32-bit types
{
absl::random_internal::FastUniformBits<uint32_t> fast32;
EXPECT_EQ(0x11111111, fast32(urng4));
EXPECT_EQ(0x1, fast32(urng32));
}
// 64-bit types
{
absl::random_internal::FastUniformBits<uint64_t> fast64;
EXPECT_EQ(0x1111111111111111, fast64(urng4));
EXPECT_EQ(0x0000000100000001, fast64(urng32));
}
}
} // namespace
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