bdiv_q_1.c revision 1.1.1.3 
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
8Copyright 2000-2003, 2005, 2009, 2017 Free Software Foundation, Inc.
9
10This file is part of the GNU MP Library.
11
12The GNU MP Library is free software; you can redistribute it and/or modify
13it 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
19or
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
25or both in parallel, as here.
26
27The GNU MP Library is distributed in the hope that it will be useful, but
28WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
29or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
30for more details.
31
32You should have received copies of the GNU General Public License and the
33GNU Lesser General Public License along with the GNU MP Library.  If not,
34see https://www.gnu.org/licenses/.  */
35
36#include "gmp-impl.h"
37#include "longlong.h"
38
39mp_limb_t
40mpn_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
104mp_limb_t
105mpn_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}
122