Annotation of OpenXM/src/kan96xx/gmp-2.0.2/mpz/fdiv_r_2exp.c, Revision 1.1.1.1
1.1 maekawa 1: /* mpz_fdiv_r_2exp -- Divide a integer by 2**CNT and produce a remainder.
2:
3: Copyright (C) 1991, 1993, 1994, 1995 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_fdiv_r_2exp (mpz_ptr res, mpz_srcptr in, unsigned long int cnt)
28: #else
29: mpz_fdiv_r_2exp (res, in, cnt)
30: mpz_ptr res;
31: mpz_srcptr in;
32: unsigned long int cnt;
33: #endif
34: {
35: mp_size_t in_size = ABS (in->_mp_size);
36: mp_size_t res_size;
37: mp_size_t limb_cnt = cnt / BITS_PER_MP_LIMB;
38: mp_srcptr in_ptr = in->_mp_d;
39:
40: if (in_size > limb_cnt)
41: {
42: /* The input operand is (probably) greater than 2**CNT. */
43: mp_limb_t x;
44:
45: x = in_ptr[limb_cnt] & (((mp_limb_t) 1 << cnt % BITS_PER_MP_LIMB) - 1);
46: if (x != 0)
47: {
48: res_size = limb_cnt + 1;
49: if (res->_mp_alloc < res_size)
50: _mpz_realloc (res, res_size);
51:
52: res->_mp_d[limb_cnt] = x;
53: }
54: else
55: {
56: res_size = limb_cnt;
57: MPN_NORMALIZE (in_ptr, res_size);
58:
59: if (res->_mp_alloc < res_size)
60: _mpz_realloc (res, res_size);
61:
62: limb_cnt = res_size;
63: }
64: }
65: else
66: {
67: /* The input operand is smaller than 2**CNT. We perform a no-op,
68: apart from that we might need to copy IN to RES. */
69: res_size = in_size;
70: if (res->_mp_alloc < res_size)
71: _mpz_realloc (res, res_size);
72:
73: limb_cnt = res_size;
74: }
75:
76: if (res != in)
77: MPN_COPY (res->_mp_d, in->_mp_d, limb_cnt);
78: res->_mp_size = res_size;
79: if (in->_mp_size < 0 && res_size != 0)
80: {
81: /* Result should be 2^CNT - RES */
82: mpz_t tmp;
83: MPZ_TMP_INIT (tmp, limb_cnt + 1);
84: mpz_set_ui (tmp, 1L);
85: mpz_mul_2exp (tmp, tmp, cnt);
86: mpz_sub (res, tmp, res);
87: }
88: }
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