/*

* (C) 2016,2019,2020 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_RNG_PROCESSOR_RNG_H_

#define BOTAN_RNG_PROCESSOR_RNG_H_

#include <botan/rng.h>

namespace Botan {

/**

* Directly invokes a CPU specific instruction to generate random numbers.

* On x86, the RDRAND instruction is used.

* on POWER, the DARN instruction is used.

*/

class BOTAN_PUBLIC_API(2, 15) Processor_RNG final : public Hardware_RNG {

   public:

      /**

      * Constructor will throw if CPU does not have RDRAND bit set

      */

      Processor_RNG();

      /**

      * Return true if RNG instruction is available on the current processor

      */

      static bool available();

      bool accepts_input() const override { return false; }

      bool is_seeded() const override { return true; }

      /*

      * No way to reseed processor provided generator, so reseed is ignored

      */

      size_t reseed(Entropy_Sources&, size_t, std::chrono::milliseconds) override;

      std::string name() const override;

   private:

      void fill_bytes_with_input(std::span<uint8_t> out, std::span<const uint8_t> in) override;

};

}  // namespace Botan

#endif