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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/seed_sequences.h"
+
+#include <iterator>
+#include <random>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/random/internal/nonsecure_base.h"
+#include "absl/random/random.h"
+namespace {
+
+TEST(SeedSequences, Examples) {
+ {
+ absl::SeedSeq seed_seq({1, 2, 3});
+ absl::BitGen bitgen(seed_seq);
+
+ EXPECT_NE(0, bitgen());
+ }
+ {
+ absl::BitGen engine;
+ auto seed_seq = absl::CreateSeedSeqFrom(&engine);
+ absl::BitGen bitgen(seed_seq);
+
+ EXPECT_NE(engine(), bitgen());
+ }
+ {
+ auto seed_seq = absl::MakeSeedSeq();
+ std::mt19937 random(seed_seq);
+
+ EXPECT_NE(0, random());
+ }
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithStdTypes) {
+ using ExampleNonsecureURBG =
+ absl::random_internal::NonsecureURBGBase<std::minstd_rand0>;
+
+ // Construct a URBG instance.
+ ExampleNonsecureURBG rng;
+
+ // Construct a Seed Sequence from its variates.
+ auto seq_from_rng = absl::CreateSeedSeqFrom(&rng);
+
+ // Ensure that another URBG can be validly constructed from the Seed Sequence.
+ std::mt19937_64{seq_from_rng};
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithBitGenerator) {
+ // Construct a URBG instance.
+ absl::BitGen rng;
+
+ // Construct a Seed Sequence from its variates.
+ auto seq_from_rng = absl::CreateSeedSeqFrom(&rng);
+
+ // Ensure that another URBG can be validly constructed from the Seed Sequence.
+ std::mt19937_64{seq_from_rng};
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithInsecureBitGen) {
+ // Construct a URBG instance.
+ absl::InsecureBitGen rng;
+
+ // Construct a Seed Sequence from its variates.
+ auto seq_from_rng = absl::CreateSeedSeqFrom(&rng);
+
+ // Ensure that another URBG can be validly constructed from the Seed Sequence.
+ std::mt19937_64{seq_from_rng};
+}
+
+TEST(CreateSeedSeqFrom, CompatibleWithRawURBG) {
+ // Construct a URBG instance.
+ std::random_device urandom;
+
+ // Construct a Seed Sequence from its variates, using 64b of seed-material.
+ auto seq_from_rng = absl::CreateSeedSeqFrom(&urandom);
+
+ // Ensure that another URBG can be validly constructed from the Seed Sequence.
+ std::mt19937_64{seq_from_rng};
+}
+
+template <typename URBG>
+void TestReproducibleVariateSequencesForNonsecureURBG() {
+ const size_t kNumVariates = 1000;
+
+ // Master RNG instance.
+ URBG rng;
+ // Reused for both RNG instances.
+ auto reusable_seed = absl::CreateSeedSeqFrom(&rng);
+
+ typename URBG::result_type variates[kNumVariates];
+ {
+ URBG child(reusable_seed);
+ for (auto& variate : variates) {
+ variate = child();
+ }
+ }
+ // Ensure that variate-sequence can be "replayed" by identical RNG.
+ {
+ URBG child(reusable_seed);
+ for (auto& variate : variates) {
+ ASSERT_EQ(variate, child());
+ }
+ }
+}
+
+TEST(CreateSeedSeqFrom, ReproducesVariateSequencesForInsecureBitGen) {
+ TestReproducibleVariateSequencesForNonsecureURBG<absl::InsecureBitGen>();
+}
+
+TEST(CreateSeedSeqFrom, ReproducesVariateSequencesForBitGenerator) {
+ TestReproducibleVariateSequencesForNonsecureURBG<absl::BitGen>();
+}
+} // namespace