Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpz/mul_2exp.c, Revision 1.1.1.1
1.1 takayama 1: /* mpz_mul_2exp -- Multiply a bignum by 2**CNT
2:
3: Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
4:
5: This file is part of the GNU MP Library.
6:
7: The GNU MP Library is free software; you can redistribute it and/or modify
8: it under the terms of the GNU Library General Public License as published by
9: the Free Software Foundation; either version 2 of the License, or (at your
10: option) any later version.
11:
12: The GNU MP Library is distributed in the hope that it will be useful, but
13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
15: License for more details.
16:
17: You should have received a copy of the GNU Library General Public License
18: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20: MA 02111-1307, USA. */
21:
22: #include "gmp.h"
23: #include "gmp-impl.h"
24:
25: void
26: #if __STDC__
27: mpz_mul_2exp (mpz_ptr w, mpz_srcptr u, unsigned long int cnt)
28: #else
29: mpz_mul_2exp (w, u, cnt)
30: mpz_ptr w;
31: mpz_srcptr u;
32: unsigned long int cnt;
33: #endif
34: {
35: mp_size_t usize = u->_mp_size;
36: mp_size_t abs_usize = ABS (usize);
37: mp_size_t wsize;
38: mp_size_t limb_cnt;
39: mp_ptr wp;
40: mp_limb_t wlimb;
41:
42: if (usize == 0)
43: {
44: w->_mp_size = 0;
45: return;
46: }
47:
48: limb_cnt = cnt / BITS_PER_MP_LIMB;
49: wsize = abs_usize + limb_cnt + 1;
50: if (w->_mp_alloc < wsize)
51: _mpz_realloc (w, wsize);
52:
53: wp = w->_mp_d;
54: wsize = abs_usize + limb_cnt;
55:
56: cnt %= BITS_PER_MP_LIMB;
57: if (cnt != 0)
58: {
59: wlimb = mpn_lshift (wp + limb_cnt, u->_mp_d, abs_usize, cnt);
60: if (wlimb != 0)
61: {
62: wp[wsize] = wlimb;
63: wsize++;
64: }
65: }
66: else
67: {
68: MPN_COPY_DECR (wp + limb_cnt, u->_mp_d, abs_usize);
69: }
70:
71: /* Zero all whole limbs at low end. Do it here and not before calling
72: mpn_lshift, not to lose for U == W. */
73: MPN_ZERO (wp, limb_cnt);
74:
75: w->_mp_size = usize >= 0 ? wsize : -wsize;
76: }
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