/*

* BigInt Binary Operators

* (C) 1999-2007,2018 Jack Lloyd

*     2016 Matthias Gierlings

*

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

*/

#include <botan/bigint.h>

#include <botan/internal/divide.h>

#include <botan/internal/mp_core.h>

#include <botan/internal/bit_ops.h>

#include <algorithm>

namespace Botan {

//static

BigInt BigInt::add2(const BigInt& x, const word y[], size_t y_words, BigInt::Sign y_sign)

   {

   const size_t x_sw = x.sig_words();

   BigInt z(x.sign(), std::max(x_sw, y_words) + 1);

   if(x.sign() == y_sign)

      {

      bigint_add3(z.mutable_data(), x.data(), x_sw, y, y_words);

      }

   else

      {

      const int32_t relative_size = bigint_sub_abs(z.mutable_data(), x.data(), x_sw, y, y_words);

      //z.sign_fixup(relative_size, y_sign);

      if(relative_size < 0)

         z.set_sign(y_sign);

      else if(relative_size == 0)

         z.set_sign(BigInt::Positive);

      }

   return z;

   }

/*

* Multiplication Operator

*/

BigInt operator*(const BigInt& x, const BigInt& y)

   {

   const size_t x_sw = x.sig_words();

   const size_t y_sw = y.sig_words();

   BigInt z(BigInt::Positive, x.size() + y.size());

   if(x_sw == 1 && y_sw)

      bigint_linmul3(z.mutable_data(), y.data(), y_sw, x.word_at(0));

   else if(y_sw == 1 && x_sw)

      bigint_linmul3(z.mutable_data(), x.data(), x_sw, y.word_at(0));

   else if(x_sw && y_sw)

      {

      secure_vector<word> workspace(z.size());

      bigint_mul(z.mutable_data(), z.size(),

                 x.data(), x.size(), x_sw,

                 y.data(), y.size(), y_sw,

                 workspace.data(), workspace.size());

      }

   z.cond_flip_sign(x_sw > 0 && y_sw > 0 && x.sign() != y.sign());

   return z;

   }

/*

* Multiplication Operator

*/

BigInt operator*(const BigInt& x, word y)

   {

   const size_t x_sw = x.sig_words();

   BigInt z(BigInt::Positive, x_sw + 1);

   if(x_sw && y)

      {

      bigint_linmul3(z.mutable_data(), x.data(), x_sw, y);

      z.set_sign(x.sign());

      }

   return z;

   }

/*

* Division Operator

*/

BigInt operator/(const BigInt& x, const BigInt& y)

   {

   if(y.sig_words() == 1)

      {

      return x / y.word_at(0);

      }

   BigInt q, r;

   vartime_divide(x, y, q, r);

   return q;

   }

/*

* Division Operator

*/

BigInt operator/(const BigInt& x, word y)

   {

   if(y == 0)

      throw Invalid_Argument("BigInt::operator/ divide by zero");

   else if(y == 1)

      return x;

   else if(y == 2)

      return (x >> 1);

   else if(y <= 255)

      {

      BigInt q;

      uint8_t r;

      ct_divide_u8(x, static_cast<uint8_t>(y), q, r);

      return q;

      }

   BigInt q, r;

   vartime_divide(x, y, q, r);

   return q;

   }

/*

* Modulo Operator

*/

BigInt operator%(const BigInt& n, const BigInt& mod)

   {

   if(mod.is_zero())

      throw Invalid_Argument("BigInt::operator% divide by zero");

   if(mod.is_negative())

      throw Invalid_Argument("BigInt::operator% modulus must be > 0");

   if(n.is_positive() && mod.is_positive() && n < mod)

      return n;

   if(mod.sig_words() == 1)

      {

      return n % mod.word_at(0);

      }

   BigInt q, r;

   vartime_divide(n, mod, q, r);

   return r;

   }

/*

* Modulo Operator

*/

word operator%(const BigInt& n, word mod)

   {

   if(mod == 0)

      throw Invalid_Argument("BigInt::operator% divide by zero");

   if(mod == 1)

      return 0;

   word remainder = 0;

   if(is_power_of_2(mod))

      {

      remainder = (n.word_at(0) & (mod - 1));

      }

   else

      {

      const size_t sw = n.sig_words();

      for(size_t i = sw; i > 0; --i)

         {

         remainder = bigint_modop(remainder, n.word_at(i-1), mod);

         }

      }

   if(remainder && n.sign() == BigInt::Negative)

      return mod - remainder;

   return remainder;

   }

/*

* Left Shift Operator

*/

BigInt operator<<(const BigInt& x, size_t shift)

   {

   const size_t shift_words = shift / BOTAN_MP_WORD_BITS,

                shift_bits  = shift % BOTAN_MP_WORD_BITS;

   const size_t x_sw = x.sig_words();

   BigInt y(x.sign(), x_sw + shift_words + (shift_bits ? 1 : 0));

   bigint_shl2(y.mutable_data(), x.data(), x_sw, shift_words, shift_bits);

   return y;

   }

/*

* Right Shift Operator

*/

BigInt operator>>(const BigInt& x, size_t shift)

   {

   const size_t shift_words = shift / BOTAN_MP_WORD_BITS;

   const size_t shift_bits  = shift % BOTAN_MP_WORD_BITS;

   const size_t x_sw = x.sig_words();

   BigInt y(x.sign(), x_sw - shift_words);

   bigint_shr2(y.mutable_data(), x.data(), x_sw, shift_words, shift_bits);

   if(x.is_negative() && y.is_zero())

      y.set_sign(BigInt::Positive);

   return y;

   }

}