/*

* RDRAND RNG

* (C) 2016,2019 Jack Lloyd

*

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

*/

#ifndef BOTAN_RNG_RDRAND_H_

#define BOTAN_RNG_RDRAND_H_

#include <botan/rng.h>

namespace Botan {

class BOTAN_PUBLIC_API(2,0) RDRAND_RNG final : public Hardware_RNG

   {

   public:

      /**

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

      */

      RDRAND_RNG();

      /**

      * Return true if RDRAND is available on the current processor

      */

      static bool available();

      bool accepts_input() const override { return false; }

      /**

      * Uses RDRAND to produce output

      */

      void randomize(uint8_t out[], size_t out_len) override;

      /*

      * No way to provide entropy to RDRAND generator, so add_entropy is ignored

      */

      void add_entropy(const uint8_t[], size_t) override

         { /* no op */ }

      /*

      * No way to reseed RDRAND generator, so reseed is ignored

      */

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

         { return 0; /* no op */ }

      std::string name() const override { return "RDRAND"; }

      bool is_seeded() const override { return true; }

      /**

      * On correctly working hardware, RDRAND is always supposed to

      * succeed within a set number of retries. If after that many

      * retries RDRAND has still not suceeded, sets ok = false and

      * returns 0.

      */

      static uint32_t BOTAN_DEPRECATED("Use RDRAND_RNG::randomize") rdrand_status(bool& ok);

      /*

      * Calls RDRAND until it succeeds, this could hypothetically

      * loop forever on broken hardware.

      */

      static uint32_t BOTAN_DEPRECATED("Use RDRAND_RNG::randomize") rdrand();

   };

}

#endif