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123 lines
3.8 KiB
123 lines
3.8 KiB
// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_random/xor_shift.h"
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#include <cinttypes>
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#include <cstddef>
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#include <cstdint>
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#include <cstdio>
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#include "gtest/gtest.h"
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namespace pw::random {
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namespace {
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constexpr uint64_t seed1 = 5;
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constexpr uint64_t result1[] = {
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0x423212e85fb37474u,
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0x96051f25a1aadc74u,
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0x8ac1f520f5595a79u,
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0x7587fe57095b7c11u,
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};
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constexpr int result1_count = sizeof(result1) / sizeof(result1[0]);
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constexpr uint64_t seed2 = 0x21feabcd5fb37474u;
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constexpr uint64_t result2[] = {
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0x568ea260a4f3e793u,
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0x5ea87d669ab04d36u,
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0x77a8675eec48ae8bu,
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};
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constexpr int result2_count = sizeof(result2) / sizeof(result2[0]);
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TEST(XorShiftStarRng64, ValidateSeries1) {
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XorShiftStarRng64 rng(seed1);
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for (size_t i = 0; i < result1_count; ++i) {
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uint64_t val = 0;
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EXPECT_EQ(rng.GetInt(val).status(), OkStatus());
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EXPECT_EQ(val, result1[i]);
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}
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}
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TEST(XorShiftStarRng64, ValidateSeries2) {
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XorShiftStarRng64 rng(seed2);
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for (size_t i = 0; i < result2_count; ++i) {
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uint64_t val = 0;
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EXPECT_EQ(rng.GetInt(val).status(), OkStatus());
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EXPECT_EQ(val, result2[i]);
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}
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}
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TEST(XorShiftStarRng64, InjectEntropyBits) {
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XorShiftStarRng64 rng(seed1);
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uint64_t val = 0;
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rng.InjectEntropyBits(0x1, 1);
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EXPECT_EQ(rng.GetInt(val).status(), OkStatus());
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EXPECT_NE(val, result1[0]);
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}
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// Ensure injecting the same entropy integer, but different bit counts causes
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// the randomly generated number to differ.
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TEST(XorShiftStarRng64, EntropyBitCount) {
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XorShiftStarRng64 rng_1(seed1);
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uint64_t first_val = 0;
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rng_1.InjectEntropyBits(0x1, 1);
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EXPECT_EQ(rng_1.GetInt(first_val).status(), OkStatus());
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// Use the same starting seed.
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XorShiftStarRng64 rng_2(seed1);
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uint64_t second_val = 0;
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// Use a different number of entropy bits.
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rng_2.InjectEntropyBits(0x1, 2);
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EXPECT_EQ(rng_2.GetInt(second_val).status(), OkStatus());
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EXPECT_NE(first_val, second_val);
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}
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// Ensure injecting the same integer bit-by-bit applies the same transformation
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// as all in one call. This lets applications decide which is more convenient
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// without worrying about algorithmic changes.
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TEST(XorShiftStarRng64, IncrementalEntropy) {
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XorShiftStarRng64 rng_1(seed1);
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uint64_t first_val = 0;
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rng_1.InjectEntropyBits(0x6, 3);
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EXPECT_EQ(rng_1.GetInt(first_val).status(), OkStatus());
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// Use the same starting seed.
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XorShiftStarRng64 rng_2(seed1);
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uint64_t second_val = 0;
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// Use a different number of injection calls. 6 = 0b110
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rng_2.InjectEntropyBits(0x1, 1);
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rng_2.InjectEntropyBits(0x1, 1);
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rng_2.InjectEntropyBits(0x0, 1);
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EXPECT_EQ(rng_2.GetInt(second_val).status(), OkStatus());
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EXPECT_EQ(first_val, second_val);
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}
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TEST(XorShiftStarRng64, InjectEntropy) {
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XorShiftStarRng64 rng(seed1);
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uint64_t val = 0;
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constexpr std::array<const std::byte, 5> entropy{std::byte(0xaf),
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std::byte(0x9b),
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std::byte(0x33),
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std::byte(0x17),
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std::byte(0x02)};
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rng.InjectEntropy(entropy);
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EXPECT_EQ(rng.GetInt(val).status(), OkStatus());
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EXPECT_NE(val, result1[0]);
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}
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} // namespace
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} // namespace pw::random
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