Annotation of OpenXM_contrib/gmp/mpz/clrbit.c, Revision 1.1.1.3
1.1 maekawa 1: /* mpz_clrbit -- clear a specified bit.
2:
1.1.1.3 ! ohara 3: Copyright 1991, 1993, 1994, 1995, 2001, 2002 Free Software Foundation, Inc.
1.1 maekawa 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
1.1.1.2 maekawa 8: it under the terms of the GNU Lesser General Public License as published by
9: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1 maekawa 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
1.1.1.2 maekawa 14: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
1.1 maekawa 15: License for more details.
16:
1.1.1.2 maekawa 17: You should have received a copy of the GNU Lesser General Public License
1.1 maekawa 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: mpz_clrbit (mpz_ptr d, unsigned long int bit_index)
27: {
28: mp_size_t dsize = d->_mp_size;
29: mp_ptr dp = d->_mp_d;
30: mp_size_t limb_index;
31:
1.1.1.3 ! ohara 32: limb_index = bit_index / GMP_NUMB_BITS;
1.1 maekawa 33: if (dsize >= 0)
34: {
35: if (limb_index < dsize)
36: {
1.1.1.3 ! ohara 37: dp[limb_index] &= ~((mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS));
1.1 maekawa 38: MPN_NORMALIZE (dp, dsize);
39: d->_mp_size = dsize;
40: }
41: else
42: ;
43: }
44: else
45: {
46: mp_size_t zero_bound;
47:
48: /* Simulate two's complement arithmetic, i.e. simulate
49: 1. Set OP = ~(OP - 1) [with infinitely many leading ones].
50: 2. clear the bit.
51: 3. Set OP = ~OP + 1. */
52:
53: dsize = -dsize;
54:
55: /* No upper bound on this loop, we're sure there's a non-zero limb
56: sooner ot later. */
57: for (zero_bound = 0; ; zero_bound++)
58: if (dp[zero_bound] != 0)
59: break;
60:
61: if (limb_index > zero_bound)
62: {
63: if (limb_index < dsize)
1.1.1.3 ! ohara 64: dp[limb_index] |= (mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS);
1.1 maekawa 65: else
66: {
67: /* Ugh. The bit should be cleared outside of the end of the
68: number. We have to increase the size of the number. */
69: if (d->_mp_alloc < limb_index + 1)
70: {
71: _mpz_realloc (d, limb_index + 1);
72: dp = d->_mp_d;
73: }
74: MPN_ZERO (dp + dsize, limb_index - dsize);
1.1.1.3 ! ohara 75: dp[limb_index] = (mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS);
1.1 maekawa 76: d->_mp_size = -(limb_index + 1);
77: }
78: }
79: else if (limb_index == zero_bound)
80: {
1.1.1.3 ! ohara 81: dp[limb_index] = ((((dp[limb_index] - 1)
! 82: | ((mp_limb_t) 1 << (bit_index % GMP_NUMB_BITS))) + 1)
! 83: & GMP_NUMB_MASK);
1.1 maekawa 84: if (dp[limb_index] == 0)
85: {
86: mp_size_t i;
87: for (i = limb_index + 1; i < dsize; i++)
88: {
1.1.1.3 ! ohara 89: dp[i] = (dp[i] + 1) & GMP_NUMB_MASK;
1.1 maekawa 90: if (dp[i] != 0)
91: goto fin;
92: }
93: /* We got carry all way out beyond the end of D. Increase
94: its size (and allocation if necessary). */
95: dsize++;
96: if (d->_mp_alloc < dsize)
97: {
98: _mpz_realloc (d, dsize);
99: dp = d->_mp_d;
100: }
101: dp[i] = 1;
102: d->_mp_size = -dsize;
103: fin:;
104: }
105: }
106: else
107: ;
108: }
109: }
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