source: trunk/third/gmp/mpz/tdiv_r_2exp.c @ 15294

Revision 15294, 2.2 KB checked in by ghudson, 24 years ago (diff)
This commit was generated by cvs2svn to compensate for changes in r15293, which included commits to RCS files with non-trunk default branches.
Line 
1/* mpz_tdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder.
2
3Copyright (C) 1991, 1993, 1994, 1995 Free Software Foundation, Inc.
4
5This file is part of the GNU MP Library.
6
7The GNU MP Library is free software; you can redistribute it and/or modify
8it under the terms of the GNU Lesser General Public License as published by
9the Free Software Foundation; either version 2.1 of the License, or (at your
10option) any later version.
11
12The GNU MP Library is distributed in the hope that it will be useful, but
13WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
15License for more details.
16
17You should have received a copy of the GNU Lesser General Public License
18along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
19the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20MA 02111-1307, USA. */
21
22#include "gmp.h"
23#include "gmp-impl.h"
24
25void
26#if __STDC__
27mpz_tdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt)
28#else
29mpz_tdiv_r_2exp (res, in, cnt)
30     mpz_ptr res;
31     mpz_srcptr in;
32     unsigned long int cnt;
33#endif
34{
35  mp_size_t in_size = ABS (in->_mp_size);
36  mp_size_t res_size;
37  mp_size_t limb_cnt = cnt / BITS_PER_MP_LIMB;
38  mp_srcptr in_ptr = in->_mp_d;
39
40  if (in_size > limb_cnt)
41    {
42      /* The input operand is (probably) greater than 2**CNT.  */
43      mp_limb_t x;
44
45      x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % BITS_PER_MP_LIMB) - 1);
46      if (x != 0)
47        {
48          res_size = limb_cnt + 1;
49          if (res->_mp_alloc < res_size)
50            _mpz_realloc (res, res_size);
51
52          res->_mp_d[limb_cnt] = x;
53        }
54      else
55        {
56          res_size = limb_cnt;
57          MPN_NORMALIZE (in_ptr, res_size);
58
59          if (res->_mp_alloc < res_size)
60            _mpz_realloc (res, res_size);
61
62          limb_cnt = res_size;
63        }
64    }
65  else
66    {
67      /* The input operand is smaller than 2**CNT.  We perform a no-op,
68         apart from that we might need to copy IN to RES.  */
69      res_size = in_size;
70      if (res->_mp_alloc < res_size)
71        _mpz_realloc (res, res_size);
72
73      limb_cnt = res_size;
74    }
75
76  if (res != in)
77    MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt);
78  res->_mp_size = in->_mp_size >= 0 ? res_size : -res_size;
79}
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