/*
* Lowest Level MPI Algorithms
* (C) 1999-2010 Jack Lloyd
*     2006 Luca Piccarreta
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/internal/mp_core.h>
#include <botan/internal/mp_asmi.h>
#include <botan/internal/mp_core.h>
#include <botan/exceptn.h>
#include <botan/mem_ops.h>

namespace Botan {

/*
* Two Operand Addition, No Carry
*/
word bigint_add2_nc(word x[], size_t x_size, const word y[], size_t y_size)
   {
   word carry = 0;

   BOTAN_ASSERT(x_size >= y_size, "Expected sizes");

   const size_t blocks = y_size - (y_size % 8);

   for(size_t i = 0; i != blocks; i += 8)
      carry = word8_add2(x + i, y + i, carry);

   for(size_t i = blocks; i != y_size; ++i)
      x[i] = word_add(x[i], y[i], &carry);

   for(size_t i = y_size; i != x_size; ++i)
      x[i] = word_add(x[i], 0, &carry);

   return carry;
   }

/*
* Three Operand Addition, No Carry
*/
word bigint_add3_nc(word z[], const word x[], size_t x_size,
                              const word y[], size_t y_size)
   {
   if(x_size < y_size)
      { return bigint_add3_nc(z, y, y_size, x, x_size); }

   word carry = 0;

   const size_t blocks = y_size - (y_size % 8);

   for(size_t i = 0; i != blocks; i += 8)
      carry = word8_add3(z + i, x + i, y + i, carry);

   for(size_t i = blocks; i != y_size; ++i)
      z[i] = word_add(x[i], y[i], &carry);

   for(size_t i = y_size; i != x_size; ++i)
      z[i] = word_add(x[i], 0, &carry);

   return carry;
   }

/*
* Two Operand Addition
*/
void bigint_add2(word x[], size_t x_size, const word y[], size_t y_size)
   {
   if(bigint_add2_nc(x, x_size, y, y_size))
      x[x_size] += 1;
   }

/*
* Three Operand Addition
*/
void bigint_add3(word z[], const word x[], size_t x_size,
                           const word y[], size_t y_size)
   {
   z[(x_size > y_size ? x_size : y_size)] +=
      bigint_add3_nc(z, x, x_size, y, y_size);
   }

/*
* Two Operand Subtraction
*/
word bigint_sub2(word x[], size_t x_size, const word y[], size_t y_size)
   {
   word borrow = 0;

   BOTAN_ASSERT(x_size >= y_size, "Expected sizes");

   const size_t blocks = y_size - (y_size % 8);

   for(size_t i = 0; i != blocks; i += 8)
      borrow = word8_sub2(x + i, y + i, borrow);

   for(size_t i = blocks; i != y_size; ++i)
      x[i] = word_sub(x[i], y[i], &borrow);

   for(size_t i = y_size; i != x_size; ++i)
      x[i] = word_sub(x[i], 0, &borrow);

   return borrow;
   }

/*
* Two Operand Subtraction x = y - x
*/
void bigint_sub2_rev(word x[],  const word y[], size_t y_size)
   {
   word borrow = 0;

   const size_t blocks = y_size - (y_size % 8);

   for(size_t i = 0; i != blocks; i += 8)
      borrow = word8_sub2_rev(x + i, y + i, borrow);

   for(size_t i = blocks; i != y_size; ++i)
      x[i] = word_sub(y[i], x[i], &borrow);

   BOTAN_ASSERT(!borrow, "y must be greater than x");
   }

/*
* Three Operand Subtraction
*/
word bigint_sub3(word z[], const word x[], size_t x_size,
                           const word y[], size_t y_size)
   {
   word borrow = 0;

   BOTAN_ASSERT(x_size >= y_size, "Expected sizes");

   const size_t blocks = y_size - (y_size % 8);

   for(size_t i = 0; i != blocks; i += 8)
      borrow = word8_sub3(z + i, x + i, y + i, borrow);

   for(size_t i = blocks; i != y_size; ++i)
      z[i] = word_sub(x[i], y[i], &borrow);

   for(size_t i = y_size; i != x_size; ++i)
      z[i] = word_sub(x[i], 0, &borrow);

   return borrow;
   }

/*
* Two Operand Linear Multiply
*/
void bigint_linmul2(word x[], size_t x_size, word y)
   {
   const size_t blocks = x_size - (x_size % 8);

   word carry = 0;

   for(size_t i = 0; i != blocks; i += 8)
      carry = word8_linmul2(x + i, y, carry);

   for(size_t i = blocks; i != x_size; ++i)
      x[i] = word_madd2(x[i], y, &carry);

   x[x_size] = carry;
   }

/*
* Three Operand Linear Multiply
*/
void bigint_linmul3(word z[], const word x[], size_t x_size, word y)
   {
   const size_t blocks = x_size - (x_size % 8);

   word carry = 0;

   for(size_t i = 0; i != blocks; i += 8)
      carry = word8_linmul3(z + i, x + i, y, carry);

   for(size_t i = blocks; i != x_size; ++i)
      z[i] = word_madd2(x[i], y, &carry);

   z[x_size] = carry;
   }

}