/*

* (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/mp_core.h>

#include <botan/internal/bit_ops.h>

#include <algorithm>

namespace Botan {

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

   {

   const size_t x_sw = sig_words();

   grow_to(std::max(x_sw, y_words) + 1);

   if(sign() == y_sign)

      {

      bigint_add2(mutable_data(), size() - 1, y, y_words);

      }

   else

      {

      const int32_t relative_size = bigint_cmp(data(), x_sw, y, y_words);

      if(relative_size >= 0)

         {

         // *this >= y

         bigint_sub2(mutable_data(), x_sw, y, y_words);

         }

      else

         {

         // *this < y

         bigint_sub2_rev(mutable_data(), y, y_words);

         }

      //this->sign_fixup(relative_size, y_sign);

      if(relative_size < 0)

         set_sign(y_sign);

      else if(relative_size == 0)

         set_sign(Positive);

      }

   return (*this);

   }

BigInt& BigInt::mod_add(const BigInt& s, const BigInt& mod, secure_vector<word>& ws)

   {

   if(this->is_negative() || s.is_negative() || mod.is_negative())

      throw Invalid_Argument("BigInt::mod_add expects all arguments are positive");

   BOTAN_DEBUG_ASSERT(*this < mod);

   BOTAN_DEBUG_ASSERT(s < mod);

   /*

   t + s or t + s - p == t - (p - s)

   So first compute ws = p - s

   Then compute t + s and t - ws

   If t - ws does not borrow, then that is the correct valued

   */

   const size_t mod_sw = mod.sig_words();

   BOTAN_ARG_CHECK(mod_sw > 0, "BigInt::mod_add modulus must be positive");

   this->grow_to(mod_sw);

   s.grow_to(mod_sw);

   // First mod_sw for p - s, 2*mod_sw for bigint_addsub workspace

   if(ws.size() < 3*mod_sw)

      ws.resize(3*mod_sw);

   word borrow = bigint_sub3(&ws[0], mod.data(), mod_sw, s.data(), mod_sw);

   BOTAN_DEBUG_ASSERT(borrow == 0);

   // Compute t - ws

   borrow = bigint_sub3(&ws[mod_sw], this->data(), mod_sw, &ws[0], mod_sw);

   // Compute t + s

   bigint_add3_nc(&ws[mod_sw*2], this->data(), mod_sw, s.data(), mod_sw);

   CT::conditional_copy_mem(borrow, &ws[0], &ws[mod_sw*2], &ws[mod_sw], mod_sw);

   set_words(&ws[0], mod_sw);

   return (*this);

   }

BigInt& BigInt::mod_sub(const BigInt& s, const BigInt& mod, secure_vector<word>& ws)

   {

   if(this->is_negative() || s.is_negative() || mod.is_negative())

      throw Invalid_Argument("BigInt::mod_sub expects all arguments are positive");

   // We are assuming in this function that *this and s are no more than mod_sw words long

   BOTAN_DEBUG_ASSERT(*this < mod);

   BOTAN_DEBUG_ASSERT(s < mod);

   const size_t mod_sw = mod.sig_words();

   this->grow_to(mod_sw);

   s.grow_to(mod_sw);

   if(ws.size() < mod_sw)

      ws.resize(mod_sw);

#if 0

   //Faster but not const time:

   // Compute t - s

   word borrow = bigint_sub3(ws.data(), data(), mod_sw, s.data(), mod_sw);

   if(borrow)

      {

      // If t < s, instead compute p - (s - t)

      bigint_sub2_rev(mutable_data(), s.data(), mod_sw);

      bigint_sub2_rev(mutable_data(), mod.data(), mod_sw);

      }

   else

      {

      // No borrow so we already have the result we need

      swap_reg(ws);

      }

#else

   if(mod_sw == 4)

      bigint_mod_sub_n<4>(mutable_data(), s.data(), mod.data(), ws.data());

   else if(mod_sw == 6)

      bigint_mod_sub_n<6>(mutable_data(), s.data(), mod.data(), ws.data());

   else

      bigint_mod_sub(mutable_data(), s.data(), mod.data(), mod_sw, ws.data());

#endif

   return (*this);

   }

BigInt& BigInt::mod_mul(uint8_t y, const BigInt& mod, secure_vector<word>& ws)

   {

   BOTAN_ARG_CHECK(this->is_negative() == false, "*this must be positive");

   BOTAN_ARG_CHECK(y < 16, "y too large");

   BOTAN_DEBUG_ASSERT(*this < mod);

   *this *= static_cast<word>(y);

   this->reduce_below(mod, ws);

   return (*this);

   }

BigInt& BigInt::rev_sub(const word y[], size_t y_sw, secure_vector<word>& ws)

   {

   if(this->sign() != BigInt::Positive)

      throw Invalid_State("BigInt::sub_rev requires this is positive");

   const size_t x_sw = this->sig_words();

   ws.resize(std::max(x_sw, y_sw));

   clear_mem(ws.data(), ws.size());

   const int32_t relative_size = bigint_sub_abs(ws.data(), data(), x_sw, y, y_sw);

   this->cond_flip_sign(relative_size > 0);

   this->swap_reg(ws);

   return (*this);

   }

/*

* Multiplication Operator

*/

BigInt& BigInt::operator*=(const BigInt& y)

   {

   secure_vector<word> ws;

   return this->mul(y, ws);

   }

BigInt& BigInt::mul(const BigInt& y, secure_vector<word>& ws)

   {

   const size_t x_sw = sig_words();

   const size_t y_sw = y.sig_words();

   set_sign((sign() == y.sign()) ? Positive : Negative);

   if(x_sw == 0 || y_sw == 0)

      {

      clear();

      set_sign(Positive);

      }

   else if(x_sw == 1 && y_sw)

      {

      grow_to(y_sw + 1);

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

      }

   else if(y_sw == 1 && x_sw)

      {

      word carry = bigint_linmul2(mutable_data(), x_sw, y.word_at(0));

      set_word_at(x_sw, carry);

      }

   else

      {

      const size_t new_size = x_sw + y_sw + 1;

      ws.resize(new_size);

      secure_vector<word> z_reg(new_size);

      bigint_mul(z_reg.data(), z_reg.size(),

                 data(), size(), x_sw,

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

                 ws.data(), ws.size());

      this->swap_reg(z_reg);

      }

   return (*this);

   }

BigInt& BigInt::square(secure_vector<word>& ws)

   {

   const size_t sw = sig_words();

   secure_vector<word> z(2*sw);

   ws.resize(z.size());

   bigint_sqr(z.data(), z.size(),

              data(), size(), sw,

              ws.data(), ws.size());

   swap_reg(z);

   set_sign(BigInt::Positive);

   return (*this);

   }

BigInt& BigInt::operator*=(word y)

   {

   if(y == 0)

      {

      clear();

      set_sign(Positive);

      }

   const word carry = bigint_linmul2(mutable_data(), size(), y);

   set_word_at(size(), carry);

   return (*this);

   }

/*

* Division Operator

*/

BigInt& BigInt::operator/=(const BigInt& y)

   {

   if(y.sig_words() == 1 && is_power_of_2(y.word_at(0)))

      (*this) >>= (y.bits() - 1);

   else

      (*this) = (*this) / y;

   return (*this);

   }

/*

* Modulo Operator

*/

BigInt& BigInt::operator%=(const BigInt& mod)

   {

   return (*this = (*this) % mod);

   }

/*

* Modulo Operator

*/

word BigInt::operator%=(word mod)

   {

   if(mod == 0)

      throw BigInt::DivideByZero();

   word remainder = 0;

   if(is_power_of_2(mod))

       {

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

       }

   else

      {

      const size_t sw = sig_words();

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

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

      }

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

      remainder = mod - remainder;

   m_data.set_to_zero();

   m_data.set_word_at(0, remainder);

   set_sign(BigInt::Positive);

   return remainder;

   }

/*

* Left Shift Operator

*/

BigInt& BigInt::operator<<=(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 size = sig_words();

   const size_t bits_free = top_bits_free();

   const size_t new_size = size + shift_words + (bits_free < shift_bits);

   m_data.grow_to(new_size);

   bigint_shl1(m_data.mutable_data(), new_size, size, shift_words, shift_bits);

   return (*this);

   }

/*

* Right Shift Operator

*/

BigInt& BigInt::operator>>=(size_t shift)

   {

   const size_t shift_words = shift / BOTAN_MP_WORD_BITS;

   const size_t shift_bits  = shift % BOTAN_MP_WORD_BITS;

   bigint_shr1(m_data.mutable_data(), m_data.size(), shift_words, shift_bits);

   if(is_negative() && is_zero())

      set_sign(Positive);

   return (*this);

   }

}