80 lines
2.1 KiB
C
80 lines
2.1 KiB
C
|
/* 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;
|
||
|
|
}
|