1  /* mpn_bdiv_q_1, mpn_pi1_bdiv_q_1 -- schoolbook Hensel division by 1-limb
       2     divisor, returning quotient only.
       3  
       4     THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY.  THEY'RE ALMOST
       5     CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN
       6     FUTURE GNU MP RELEASES.
       7  
       8  Copyright 2000-2003, 2005, 2009, 2017 Free Software Foundation, Inc.
       9  
      10  This file is part of the GNU MP Library.
      11  
      12  The GNU MP Library is free software; you can redistribute it and/or modify
      13  it under the terms of either:
      14  
      15    * the GNU Lesser General Public License as published by the Free
      16      Software Foundation; either version 3 of the License, or (at your
      17      option) any later version.
      18  
      19  or
      20  
      21    * the GNU General Public License as published by the Free Software
      22      Foundation; either version 2 of the License, or (at your option) any
      23      later version.
      24  
      25  or both in parallel, as here.
      26  
      27  The GNU MP Library is distributed in the hope that it will be useful, but
      28  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      29  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      30  for more details.
      31  
      32  You should have received copies of the GNU General Public License and the
      33  GNU Lesser General Public License along with the GNU MP Library.  If not,
      34  see https://www.gnu.org/licenses/.  */
      35  
      36  #include "gmp-impl.h"
      37  #include "longlong.h"
      38  
      39  mp_limb_t
      40  mpn_pi1_bdiv_q_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t d,
      41  		  mp_limb_t di, int shift)
      42  {
      43    mp_size_t  i;
      44    mp_limb_t  c, h, l, u, u_next, dummy;
      45  
      46    ASSERT (n >= 1);
      47    ASSERT (d != 0);
      48    ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
      49    ASSERT_MPN (up, n);
      50    ASSERT_LIMB (d);
      51  
      52    d <<= GMP_NAIL_BITS;
      53  
      54    if (shift != 0)
      55      {
      56        c = 0;
      57  
      58        u = up[0];
      59        rp--;
      60        for (i = 1; i < n; i++)
      61  	{
      62  	  u_next = up[i];
      63  	  u = ((u >> shift) | (u_next << (GMP_NUMB_BITS-shift))) & GMP_NUMB_MASK;
      64  
      65  	  SUBC_LIMB (c, l, u, c);
      66  
      67  	  l = (l * di) & GMP_NUMB_MASK;
      68  	  rp[i] = l;
      69  
      70  	  umul_ppmm (h, dummy, l, d);
      71  	  c += h;
      72  	  u = u_next;
      73  	}
      74  
      75        u = u >> shift;
      76        SUBC_LIMB (c, l, u, c);
      77  
      78        l = (l * di) & GMP_NUMB_MASK;
      79        rp[n] = l;
      80      }
      81    else
      82      {
      83        u = up[0];
      84        l = (u * di) & GMP_NUMB_MASK;
      85        rp[0] = l;
      86        c = 0;
      87  
      88        for (i = 1; i < n; i++)
      89  	{
      90  	  umul_ppmm (h, dummy, l, d);
      91  	  c += h;
      92  
      93  	  u = up[i];
      94  	  SUBC_LIMB (c, l, u, c);
      95  
      96  	  l = (l * di) & GMP_NUMB_MASK;
      97  	  rp[i] = l;
      98  	}
      99      }
     100  
     101    return c;
     102  }
     103  
     104  mp_limb_t
     105  mpn_bdiv_q_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t d)
     106  {
     107    mp_limb_t di;
     108    int shift;
     109  
     110    ASSERT (n >= 1);
     111    ASSERT (d != 0);
     112    ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
     113    ASSERT_MPN (up, n);
     114    ASSERT_LIMB (d);
     115  
     116    count_trailing_zeros (shift, d);
     117    d >>= shift;
     118  
     119    binvert_limb (di, d);
     120    return mpn_pi1_bdiv_q_1 (rp, up, n, d, di, shift);
     121  }