text: // 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 {
  ABSL_NAMESPACE_BEGIN
  namespace random_internal {
  
  // RANDen = RANDom generator or beetroots in Swiss High 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
  ABSL_NAMESPACE_END
  }  // namespace absl
  
  #endif  // ABSL_RANDOM_INTERNAL_RANDEN_H_
  