Annotation of OpenXM_contrib/gmp/mpz/com.c, Revision 1.1.1.3
1.1 maekawa 1: /* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
2: SRC to DST.
3:
1.1.1.3 ! ohara 4: Copyright 1991, 1993, 1994, 1996, 2001 Free Software Foundation, Inc.
1.1 maekawa 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
1.1.1.2 maekawa 9: it under the terms of the GNU Lesser General Public License as published by
10: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1 maekawa 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
1.1.1.2 maekawa 15: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
1.1 maekawa 16: License for more details.
17:
1.1.1.2 maekawa 18: You should have received a copy of the GNU Lesser General Public License
1.1 maekawa 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: mpz_com (mpz_ptr dst, mpz_srcptr src)
28: {
29: mp_size_t size = src->_mp_size;
30: mp_srcptr src_ptr;
31: mp_ptr dst_ptr;
32:
33: if (size >= 0)
34: {
35: /* As with infinite precision: one's complement, two's complement.
36: But this can be simplified using the identity -x = ~x + 1.
37: So we're going to compute (~~x) + 1 = x + 1! */
38:
39: if (dst->_mp_alloc < size + 1)
40: _mpz_realloc (dst, size + 1);
41:
42: src_ptr = src->_mp_d;
43: dst_ptr = dst->_mp_d;
44:
45: if (size == 0)
46: {
47: /* Special case, as mpn_add wants the first arg's size >= the
48: second arg's size. */
49: dst_ptr[0] = 1;
50: dst->_mp_size = -1;
51: return;
52: }
53:
54: {
55: mp_limb_t cy;
56:
57: cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
58: if (cy)
59: {
60: dst_ptr[size] = cy;
61: size++;
62: }
63: }
64:
65: /* Store a negative size, to indicate ones-extension. */
66: dst->_mp_size = -size;
67: }
68: else
69: {
70: /* As with infinite precision: two's complement, then one's complement.
71: But that can be simplified using the identity -x = ~(x - 1).
72: So we're going to compute ~~(x - 1) = x - 1! */
73: size = -size;
74:
75: if (dst->_mp_alloc < size)
76: _mpz_realloc (dst, size);
77:
78: src_ptr = src->_mp_d;
79: dst_ptr = dst->_mp_d;
80:
81: mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
82: size -= dst_ptr[size - 1] == 0;
83:
84: /* Store a positive size, to indicate zero-extension. */
85: dst->_mp_size = size;
86: }
87: }
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