version 1.1.1.1, 2000/01/10 15:35:23 |
version 1.1.1.3, 2003/08/25 16:06:20 |
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/* mpn_rshift -- Shift right a low-level natural-number integer. |
/* mpn_rshift -- Shift right low level. |
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Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc. |
Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2002 Free Software Foundation, |
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Inc. |
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This file is part of the GNU MP Library. |
This file is part of the GNU MP Library. |
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The GNU MP Library is free software; you can redistribute it and/or modify |
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 |
it under the terms of the GNU Lesser General Public License as published by |
the Free Software Foundation; either version 2 of the License, or (at your |
the Free Software Foundation; either version 2.1 of the License, or (at your |
option) any later version. |
option) any later version. |
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The GNU MP Library is distributed in the hope that it will be useful, but |
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 |
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
License for more details. |
License for more details. |
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You should have received a copy of the GNU Library General Public License |
You should have received a copy of the GNU Lesser General Public License |
along with the GNU MP Library; see the file COPYING.LIB. If not, write to |
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, |
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
MA 02111-1307, USA. */ |
MA 02111-1307, USA. */ |
Line 22 MA 02111-1307, USA. */ |
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Line 23 MA 02111-1307, USA. */ |
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#include "gmp.h" |
#include "gmp.h" |
#include "gmp-impl.h" |
#include "gmp-impl.h" |
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/* Shift U (pointed to by UP and USIZE limbs long) CNT bits to the right |
/* Shift U (pointed to by up and N limbs long) cnt bits to the right |
and store the USIZE least significant limbs of the result at WP. |
and store the n least significant limbs of the result at rp. |
The bits shifted out to the right are returned. |
The bits shifted out to the right are returned. |
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Argument constraints: |
Argument constraints: |
1. 0 < CNT < BITS_PER_MP_LIMB |
1. 0 < cnt < GMP_NUMB_BITS. |
2. If the result is to be written over the input, WP must be <= UP. |
2. If the result is to be written over the input, rp must be <= up. |
*/ |
*/ |
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mp_limb_t |
mp_limb_t |
#if __STDC__ |
mpn_rshift (mp_ptr rp, mp_srcptr up, mp_size_t n, unsigned int cnt) |
mpn_rshift (register mp_ptr wp, |
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register mp_srcptr up, mp_size_t usize, |
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register unsigned int cnt) |
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#else |
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mpn_rshift (wp, up, usize, cnt) |
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register mp_ptr wp; |
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register mp_srcptr up; |
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mp_size_t usize; |
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register unsigned int cnt; |
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#endif |
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{ |
{ |
register mp_limb_t high_limb, low_limb; |
mp_limb_t high_limb, low_limb; |
register unsigned sh_1, sh_2; |
unsigned int tnc; |
register mp_size_t i; |
mp_size_t i; |
mp_limb_t retval; |
mp_limb_t retval; |
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#ifdef DEBUG |
ASSERT (n >= 1); |
if (usize == 0 || cnt == 0) |
ASSERT (cnt >= 1); |
abort (); |
ASSERT (cnt < GMP_NUMB_BITS); |
#endif |
ASSERT (MPN_SAME_OR_INCR_P (rp, up, n)); |
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sh_1 = cnt; |
tnc = GMP_NUMB_BITS - cnt; |
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high_limb = *up++; |
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retval = (high_limb << tnc) & GMP_NUMB_MASK; |
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low_limb = high_limb >> cnt; |
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#if 0 |
for (i = n - 1; i != 0; i--) |
if (sh_1 == 0) |
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{ |
{ |
if (wp != up) |
high_limb = *up++; |
{ |
*rp++ = low_limb | ((high_limb << tnc) & GMP_NUMB_MASK); |
/* Copy from low end to high end, to allow specified input/output |
low_limb = high_limb >> cnt; |
overlapping. */ |
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for (i = 0; i < usize; i++) |
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wp[i] = up[i]; |
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} |
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return usize; |
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} |
} |
#endif |
*rp = low_limb; |
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wp -= 1; |
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sh_2 = BITS_PER_MP_LIMB - sh_1; |
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high_limb = up[0]; |
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retval = high_limb << sh_2; |
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low_limb = high_limb; |
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for (i = 1; i < usize; i++) |
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{ |
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high_limb = up[i]; |
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wp[i] = (low_limb >> sh_1) | (high_limb << sh_2); |
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low_limb = high_limb; |
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} |
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wp[i] = low_limb >> sh_1; |
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return retval; |
return retval; |
} |
} |