mirror of
https://sourceware.org/git/glibc.git
synced 2025-11-03 20:53:13 +03:00
89 lines
2.3 KiB
C
89 lines
2.3 KiB
C
/* mpn_rshift -- Shift right a low-level natural-number integer.
|
|
|
|
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"
|
|
|
|
/* Shift U (pointed to by UP and USIZE limbs long) CNT bits to the right
|
|
and store the USIZE least significant limbs of the result at WP.
|
|
The bits shifted out to the right are returned.
|
|
|
|
Argument constraints:
|
|
1. 0 < CNT < BITS_PER_MP_LIMB
|
|
2. If the result is to be written over the input, WP must be <= UP.
|
|
*/
|
|
|
|
mp_limb_t
|
|
#if __STDC__
|
|
mpn_rshift (register mp_ptr wp,
|
|
register mp_srcptr up, mp_size_t usize,
|
|
register unsigned int cnt)
|
|
#else
|
|
mpn_rshift (wp, up, usize, cnt)
|
|
register mp_ptr wp;
|
|
register mp_srcptr up;
|
|
mp_size_t usize;
|
|
register unsigned int cnt;
|
|
#endif
|
|
{
|
|
register mp_limb_t high_limb, low_limb;
|
|
register unsigned sh_1, sh_2;
|
|
register mp_size_t i;
|
|
mp_limb_t retval;
|
|
|
|
#ifdef DEBUG
|
|
if (usize == 0 || cnt == 0)
|
|
abort ();
|
|
#endif
|
|
|
|
sh_1 = cnt;
|
|
|
|
#if 0
|
|
if (sh_1 == 0)
|
|
{
|
|
if (wp != up)
|
|
{
|
|
/* Copy from low end to high end, to allow specified input/output
|
|
overlapping. */
|
|
for (i = 0; i < usize; i++)
|
|
wp[i] = up[i];
|
|
}
|
|
return usize;
|
|
}
|
|
#endif
|
|
|
|
wp -= 1;
|
|
sh_2 = BITS_PER_MP_LIMB - sh_1;
|
|
high_limb = up[0];
|
|
retval = high_limb << sh_2;
|
|
low_limb = high_limb;
|
|
|
|
for (i = 1; i < usize; i++)
|
|
{
|
|
high_limb = up[i];
|
|
wp[i] = (low_limb >> sh_1) | (high_limb << sh_2);
|
|
low_limb = high_limb;
|
|
}
|
|
wp[i] = low_limb >> sh_1;
|
|
|
|
return retval;
|
|
}
|