freebsd-dev/contrib/libgmp/mpz/fdiv_q_2exp.c
Mark Murray aa9bc17601 Clean import of libgmp 2.0.2, with only the non-x86 bits removed.
BMakefiles and other bits will follow.

Requested by:	Andrey Chernov
Made world by:	Chuck Robey
1996-10-20 08:49:26 +00:00

95 lines
2.5 KiB
C

/* mpz_fdiv_q_2exp -- Divide an integer by 2**CNT. Round the quotient
towards -infinity.
Copyright (C) 1991, 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__
mpz_fdiv_q_2exp (mpz_ptr w, mpz_srcptr u, unsigned long int cnt)
#else
mpz_fdiv_q_2exp (w, u, cnt)
mpz_ptr w;
mpz_srcptr u;
unsigned long int cnt;
#endif
{
mp_size_t usize = u->_mp_size;
mp_size_t wsize;
mp_size_t abs_usize = ABS (usize);
mp_size_t limb_cnt;
mp_ptr wp;
mp_limb_t round = 0;
limb_cnt = cnt / BITS_PER_MP_LIMB;
wsize = abs_usize - limb_cnt;
if (wsize <= 0)
{
wp = w->_mp_d;
wsize = 0;
/* Set ROUND since we know we skip some non-zero words in this case.
Well, if U is zero, we don't, but then this will be taken care of
below, since rounding only really takes place for negative U. */
round = 1;
wp[0] = 1;
w->_mp_size = -(usize < 0);
return;
}
else
{
mp_size_t i;
mp_ptr up;
/* Make sure there is enough space. We make an extra limb
here to account for possible rounding at the end. */
if (w->_mp_alloc < wsize + 1)
_mpz_realloc (w, wsize + 1);
wp = w->_mp_d;
up = u->_mp_d;
/* Set ROUND if we are about skip some non-zero limbs. */
for (i = 0; i < limb_cnt && round == 0; i++)
round = up[i];
cnt %= BITS_PER_MP_LIMB;
if (cnt != 0)
{
round |= mpn_rshift (wp, up + limb_cnt, wsize, cnt);
wsize -= wp[wsize - 1] == 0;
}
else
{
MPN_COPY_INCR (wp, up + limb_cnt, wsize);
}
}
if (usize < 0 && round != 0)
{
mp_limb_t cy;
cy = mpn_add_1 (wp, wp, wsize, 1);
wp[wsize] = cy;
wsize += cy;
}
w->_mp_size = usize >= 0 ? wsize : -wsize;
}