Annotation of OpenXM/src/kan96xx/gmp-2.0.2/mpz/com.c, Revision 1.1.1.1
1.1 maekawa 1: /* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
2: SRC to DST.
3:
4: Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
5:
6: This file is part of the GNU MP Library.
7:
8: The GNU MP Library is free software; you can redistribute it and/or modify
9: it under the terms of the GNU Library General Public License as published by
10: the Free Software Foundation; either version 2 of the License, or (at your
11: option) any later version.
12:
13: The GNU MP Library is distributed in the hope that it will be useful, but
14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
16: License for more details.
17:
18: You should have received a copy of the GNU Library General Public License
19: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
21: MA 02111-1307, USA. */
22:
23: #include "gmp.h"
24: #include "gmp-impl.h"
25:
26: void
27: #if __STDC__
28: mpz_com (mpz_ptr dst, mpz_srcptr src)
29: #else
30: mpz_com (dst, src)
31: mpz_ptr dst;
32: mpz_srcptr src;
33: #endif
34: {
35: mp_size_t size = src->_mp_size;
36: mp_srcptr src_ptr;
37: mp_ptr dst_ptr;
38:
39: if (size >= 0)
40: {
41: /* As with infinite precision: one's complement, two's complement.
42: But this can be simplified using the identity -x = ~x + 1.
43: So we're going to compute (~~x) + 1 = x + 1! */
44:
45: if (dst->_mp_alloc < size + 1)
46: _mpz_realloc (dst, size + 1);
47:
48: src_ptr = src->_mp_d;
49: dst_ptr = dst->_mp_d;
50:
51: if (size == 0)
52: {
53: /* Special case, as mpn_add wants the first arg's size >= the
54: second arg's size. */
55: dst_ptr[0] = 1;
56: dst->_mp_size = -1;
57: return;
58: }
59:
60: {
61: mp_limb_t cy;
62:
63: cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
64: if (cy)
65: {
66: dst_ptr[size] = cy;
67: size++;
68: }
69: }
70:
71: /* Store a negative size, to indicate ones-extension. */
72: dst->_mp_size = -size;
73: }
74: else
75: {
76: /* As with infinite precision: two's complement, then one's complement.
77: But that can be simplified using the identity -x = ~(x - 1).
78: So we're going to compute ~~(x - 1) = x - 1! */
79: size = -size;
80:
81: if (dst->_mp_alloc < size)
82: _mpz_realloc (dst, size);
83:
84: src_ptr = src->_mp_d;
85: dst_ptr = dst->_mp_d;
86:
87: mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
88: size -= dst_ptr[size - 1] == 0;
89:
90: /* Store a positive size, to indicate zero-extension. */
91: dst->_mp_size = size;
92: }
93: }
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