bdiv_q_1.c revision 1.1.1.2 
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 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.h"
37#include "gmp-impl.h"
38#include "longlong.h"
39
40mp_limb_t
41mpn_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
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  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}
127