source/libs/gmp/gmp-src/mpn/generic/bdiv_q_1.c

   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 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.h"
  37 #include "gmp-impl.h"
  38 #include "longlong.h"
  39
  40 mp_limb_t
  41 mpn_pi1_bdiv_q_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t d,
  42                   mp_limb_t di, int shift)
  43 {
  44   mp_size_t  i;
  45   mp_limb_t  c, h, l, u, u_next, dummy;
  46
  47   ASSERT (n >= 1);
  48   ASSERT (d != 0);
  49   ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
  50   ASSERT_MPN (up, n);
  51   ASSERT_LIMB (d);
  52
  53   d <<= GMP_NAIL_BITS;
  54
  55   if (shift != 0)
  56     {
  57       c = 0;
  58
  59       u = up[0];
  60       rp--;
  61       for (i = 1; i < n; i++)
  62         {
  63           u_next = up[i];
  64           u = ((u >> shift) | (u_next << (GMP_NUMB_BITS-shift))) & GMP_NUMB_MASK;
  65
  66           SUBC_LIMB (c, l, u, c);
  67
  68           l = (l * di) & GMP_NUMB_MASK;
  69           rp[i] = l;
  70
  71           umul_ppmm (h, dummy, l, d);
  72           c += h;
  73           u = u_next;
  74         }
  75
  76       u = u >> shift;
  77       l = u - c;
  78       l = (l * di) & GMP_NUMB_MASK;
  79       rp[i] = 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   if ((d & 1) == 0)
 117     {
 118       count_trailing_zeros (shift, d);
 119       d >>= shift;
 120     }
 121   else
 122     shift = 0;
 123
 124   binvert_limb (di, d);
 125   return mpn_pi1_bdiv_q_1 (rp, up, n, d, di, shift);
 126 }