1  /* mpn_mul_1 -- Multiply a limb vector with a single limb and
       2     store the product in a second limb vector.
       3  
       4  Copyright (C) 1991-2023 Free Software Foundation, Inc.
       5  
       6  This file is part of the GNU MP Library.
       7  
       8  The GNU MP Library is free software; you can redistribute it and/or modify
       9  it under the terms of the GNU Lesser General Public License as published by
      10  the Free Software Foundation; either version 2.1 of the License, or (at your
      11  option) any later version.
      12  
      13  The GNU MP Library is distributed in the hope that it will be useful, but
      14  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      15  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
      16  License for more details.
      17  
      18  You should have received a copy of the GNU Lesser General Public License
      19  along with the GNU MP Library; see the file COPYING.LIB.  If not, see
      20  <https://www.gnu.org/licenses/>.  */
      21  
      22  #include <gmp.h>
      23  #include "gmp-impl.h"
      24  #include "longlong.h"
      25  
      26  mp_limb_t
      27  mpn_mul_1 (register mp_ptr res_ptr, register mp_srcptr s1_ptr,
      28  	   mp_size_t s1_size, register mp_limb_t s2_limb)
      29  {
      30    register mp_limb_t cy_limb;
      31    register mp_size_t j;
      32    register mp_limb_t prod_high, prod_low;
      33  
      34    /* The loop counter and index J goes from -S1_SIZE to -1.  This way
      35       the loop becomes faster.  */
      36    j = -s1_size;
      37  
      38    /* Offset the base pointers to compensate for the negative indices.  */
      39    s1_ptr -= j;
      40    res_ptr -= j;
      41  
      42    cy_limb = 0;
      43    do
      44      {
      45        umul_ppmm (prod_high, prod_low, s1_ptr[j], s2_limb);
      46  
      47        prod_low += cy_limb;
      48        cy_limb = (prod_low < cy_limb) + prod_high;
      49  
      50        res_ptr[j] = prod_low;
      51      }
      52    while (++j != 0);
      53  
      54    return cy_limb;
      55  }