1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
/* mpf_div_2exp -- Divide a float by 2^n.
Copyright (C) 1993, 1994, 1996 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
void
#if __STDC__
mpf_div_2exp (mpf_ptr r, mpf_srcptr u, unsigned long int exp)
#else
mpf_div_2exp (r, u, exp)
mpf_ptr r;
mpf_srcptr u;
unsigned long int exp;
#endif
{
mp_srcptr up;
mp_ptr rp = r->_mp_d;
mp_size_t usize;
mp_size_t abs_usize;
mp_size_t prec = r->_mp_prec;
mp_exp_t uexp = u->_mp_exp;
usize = u->_mp_size;
if (usize == 0)
{
r->_mp_size = 0;
r->_mp_exp = 0;
return;
}
abs_usize = ABS (usize);
up = u->_mp_d;
if (abs_usize > prec)
{
up += abs_usize - prec;
abs_usize = prec;
}
if (exp % BITS_PER_MP_LIMB == 0)
{
if (rp != up)
MPN_COPY (rp, up, abs_usize);
r->_mp_exp = uexp - exp / BITS_PER_MP_LIMB;
}
else
{
/* Use mpn_lshift since mpn_rshift operates upwards, and we therefore
would clobber part of U before using that part, when R == U. */
mp_limb_t cy_limb;
cy_limb = mpn_lshift (rp, up, abs_usize, -exp % BITS_PER_MP_LIMB);
rp[abs_usize] = cy_limb;
cy_limb = cy_limb != 0;
abs_usize += cy_limb;
r->_mp_exp = uexp - exp / BITS_PER_MP_LIMB - 1 + cy_limb;
}
r->_mp_size = usize >= 0 ? abs_usize : -abs_usize;
}
|
