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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.
+
+#ifndef ABSL_RANDOM_INTERNAL_RANDEN_H_
+#define ABSL_RANDOM_INTERNAL_RANDEN_H_
+
+#include <cstddef>
+
+#include "absl/random/internal/platform.h"
+#include "absl/random/internal/randen_hwaes.h"
+#include "absl/random/internal/randen_slow.h"
+#include "absl/random/internal/randen_traits.h"
+
+namespace absl {
+inline namespace lts_2019_08_08 {
+namespace random_internal {
+
+// RANDen = RANDom generator or beetroots in Swiss German.
+// 'Strong' (well-distributed, unpredictable, backtracking-resistant) random
+// generator, faster in some benchmarks than std::mt19937_64 and pcg64_c32.
+//
+// Randen implements the basic state manipulation methods.
+class Randen {
+ public:
+  static constexpr size_t kStateBytes = RandenTraits::kStateBytes;
+  static constexpr size_t kCapacityBytes = RandenTraits::kCapacityBytes;
+  static constexpr size_t kSeedBytes = RandenTraits::kSeedBytes;
+
+  ~Randen() = default;
+
+  Randen();
+
+  // Generate updates the randen sponge. The outer portion of the sponge
+  // (kCapacityBytes .. kStateBytes) may be consumed as PRNG state.
+  template <typename T, size_t N>
+  void Generate(T (&state)[N]) const {
+    static_assert(N * sizeof(T) == kStateBytes,
+                  "Randen::Generate() requires kStateBytes of state");
+#if ABSL_RANDOM_INTERNAL_AES_DISPATCH
+    // HW AES Dispatch.
+    if (has_crypto_) {
+      RandenHwAes::Generate(keys_, state);
+    } else {
+      RandenSlow::Generate(keys_, state);
+    }
+#elif ABSL_HAVE_ACCELERATED_AES
+    // HW AES is enabled.
+    RandenHwAes::Generate(keys_, state);
+#else
+    // HW AES is disabled.
+    RandenSlow::Generate(keys_, state);
+#endif
+  }
+
+  // Absorb incorporates additional seed material into the randen sponge.  After
+  // absorb returns, Generate must be called before the state may be consumed.
+  template <typename S, size_t M, typename T, size_t N>
+  void Absorb(const S (&seed)[M], T (&state)[N]) const {
+    static_assert(M * sizeof(S) == RandenTraits::kSeedBytes,
+                  "Randen::Absorb() requires kSeedBytes of seed");
+
+    static_assert(N * sizeof(T) == RandenTraits::kStateBytes,
+                  "Randen::Absorb() requires kStateBytes of state");
+#if ABSL_RANDOM_INTERNAL_AES_DISPATCH
+    // HW AES Dispatch.
+    if (has_crypto_) {
+      RandenHwAes::Absorb(seed, state);
+    } else {
+      RandenSlow::Absorb(seed, state);
+    }
+#elif ABSL_HAVE_ACCELERATED_AES
+    // HW AES is enabled.
+    RandenHwAes::Absorb(seed, state);
+#else
+    // HW AES is disabled.
+    RandenSlow::Absorb(seed, state);
+#endif
+  }
+
+ private:
+  const void* keys_;
+#if ABSL_RANDOM_INTERNAL_AES_DISPATCH
+  bool has_crypto_;
+#endif
+};
+
+}  // namespace random_internal
+}  // inline namespace lts_2019_08_08
+}  // namespace absl
+
+#endif  // ABSL_RANDOM_INTERNAL_RANDEN_H_