/*

* BigInt Random Generation

* (C) 1999-2007 Jack Lloyd

*

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

*/

#include <botan/bigint.h>

#include <botan/rng.h>

#include <botan/internal/rounding.h>

namespace Botan {

/*

* Randomize this number

*/

void BigInt::randomize(RandomNumberGenerator& rng,

                       size_t bitsize, bool set_high_bit)

   {

   set_sign(Positive);

   if(bitsize == 0)

      {

      clear();

      }

   else

      {

      secure_vector<uint8_t> array = rng.random_vec(round_up(bitsize, 8) / 8);

      // Always cut unwanted bits

      if(bitsize % 8)

         array[0] &= 0xFF >> (8 - (bitsize % 8));

      // Set the highest bit if wanted

      if (set_high_bit)

         array[0] |= 0x80 >> ((bitsize % 8) ? (8 - bitsize % 8) : 0);

      binary_decode(array);

      }

   }

/*

* Generate a random integer within given range

*/

BigInt BigInt::random_integer(RandomNumberGenerator& rng,

                              const BigInt& min, const BigInt& max)

   {

   if(min.is_negative() || max.is_negative() || max <= min)

      throw Invalid_Argument("BigInt::random_integer invalid range");

   BigInt r;

   const size_t bits = max.bits();

   do

      {

      r.randomize(rng, bits, false);

      }

   while(r < min || r >= max);

   return r;

   }

}