/*
* (C) 2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/internal/poly_dbl.h>
#include <botan/loadstor.h>
#include <botan/exceptn.h>

namespace Botan {

namespace {

template<size_t LIMBS, uint64_t POLY>
void poly_double(uint8_t out[], const uint8_t in[])
   {
   uint64_t W[LIMBS];
   load_be(W, in, LIMBS);

   const uint64_t carry = POLY * (W[0] >> 63);
   for(size_t i = 0; i != LIMBS - 1; ++i)
      W[i] = (W[i] << 1) ^ (W[i+1] >> 63);
   W[LIMBS-1] = (W[LIMBS-1] << 1) ^ carry;

   copy_out_be(out, LIMBS*8, W);
   }

template<size_t LIMBS, uint64_t POLY>
void poly_double_le(uint8_t out[], const uint8_t in[])
   {
   uint64_t W[LIMBS];
   load_le(W, in, LIMBS);

   const uint64_t carry = POLY * (W[LIMBS-1] >> 63);
   for(size_t i = 0; i != LIMBS - 1; ++i)
      W[LIMBS-1-i] = (W[LIMBS-1-i] << 1) ^ (W[LIMBS-2-i] >> 63);
   W[0] = (W[0] << 1) ^ carry;

   copy_out_le(out, LIMBS*8, W);
   }

}

void poly_double_n(uint8_t out[], const uint8_t in[], size_t n)
   {
   switch(n)
      {
      case 8:
         return poly_double<1, 0x1B>(out, in);
      case 16:
         return poly_double<2, 0x87>(out, in);
      case 24:
         return poly_double<3, 0x87>(out, in);
      case 32:
         return poly_double<4, 0x425>(out, in);
      case 64:
         return poly_double<8, 0x125>(out, in);
      default:
         throw Invalid_Argument("Unsupported size for poly_double_n");
      }
   }

void poly_double_n_le(uint8_t out[], const uint8_t in[], size_t n)
   {
   switch(n)
      {
      case 8:
         return poly_double_le<1, 0x1B>(out, in);
      case 16:
         return poly_double_le<2, 0x87>(out, in);
      case 24:
         return poly_double_le<3, 0x87>(out, in);
      case 32:
         return poly_double_le<4, 0x425>(out, in);
      case 64:
         return poly_double_le<8, 0x125>(out, in);
      default:
         throw Invalid_Argument("Unsupported size for poly_double_n_le");
      }
   }

}
