Annotation of OpenXM_contrib/gmp/mpz/setbit.c, Revision 1.1.1.2
1.1 maekawa 1: /* mpz_setbit -- set a specified bit.
2:
1.1.1.2 ! maekawa 3: Copyright (C) 1991, 1993, 1994, 1995, 1997, 1999 Free Software Foundation,
! 4: 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: #if __STDC__
28: mpz_setbit (mpz_ptr d, unsigned long int bit_index)
29: #else
30: mpz_setbit (d, bit_index)
31: mpz_ptr d;
32: unsigned long int bit_index;
33: #endif
34: {
35: mp_size_t dsize = d->_mp_size;
36: mp_ptr dp = d->_mp_d;
37: mp_size_t limb_index;
38:
39: limb_index = bit_index / BITS_PER_MP_LIMB;
40: if (dsize >= 0)
41: {
42: if (limb_index < dsize)
43: {
44: dp[limb_index] |= (mp_limb_t) 1 << (bit_index % BITS_PER_MP_LIMB);
45: d->_mp_size = dsize;
46: }
47: else
48: {
49: /* Ugh. The bit should be set outside of the end of the
50: number. We have to increase the size of the number. */
51: if (d->_mp_alloc < limb_index + 1)
52: {
53: _mpz_realloc (d, limb_index + 1);
54: dp = d->_mp_d;
55: }
56: MPN_ZERO (dp + dsize, limb_index - dsize);
57: dp[limb_index] = (mp_limb_t) 1 << (bit_index % BITS_PER_MP_LIMB);
58: d->_mp_size = limb_index + 1;
59: }
60: }
61: else
62: {
63: mp_size_t zero_bound;
64:
65: /* Simulate two's complement arithmetic, i.e. simulate
66: 1. Set OP = ~(OP - 1) [with infinitely many leading ones].
1.1.1.2 ! maekawa 67: 2. Set the bit.
1.1 maekawa 68: 3. Set OP = ~OP + 1. */
69:
70: dsize = -dsize;
71:
72: /* No upper bound on this loop, we're sure there's a non-zero limb
73: sooner ot later. */
74: for (zero_bound = 0; ; zero_bound++)
75: if (dp[zero_bound] != 0)
76: break;
77:
78: if (limb_index > zero_bound)
79: {
80: if (limb_index < dsize)
81: dp[limb_index] &= ~((mp_limb_t) 1 << (bit_index % BITS_PER_MP_LIMB));
82: else
83: ;
84: }
85: else if (limb_index == zero_bound)
86: {
87: dp[limb_index] = ((dp[limb_index] - 1)
88: & ~((mp_limb_t) 1 << (bit_index % BITS_PER_MP_LIMB))) + 1;
89: if (dp[limb_index] == 0)
90: {
91: mp_size_t i;
92: for (i = limb_index + 1; i < dsize; i++)
93: {
94: dp[i] += 1;
95: if (dp[i] != 0)
96: goto fin;
97: }
98: /* We got carry all way out beyond the end of D. Increase
99: its size (and allocation if necessary). */
100: dsize++;
101: if (d->_mp_alloc < dsize)
102: {
103: _mpz_realloc (d, dsize);
104: dp = d->_mp_d;
105: }
106: dp[i] = 1;
107: d->_mp_size = -dsize;
108: fin:;
109: }
110: }
111: else
1.1.1.2 ! maekawa 112: {
! 113: mpn_decr_u (dp + limb_index,
! 114: (mp_limb_t) 1 << (bit_index % BITS_PER_MP_LIMB));
! 115: dsize -= dp[dsize - 1] == 0;
! 116: d->_mp_size = -dsize;
! 117: }
1.1 maekawa 118: }
119: }
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