Line | Count | Source (jump to first uncovered line) |
1 | | /* mpz_clrbit -- clear a specified bit. |
2 | | |
3 | | Copyright 1991, 1993-1995, 2001, 2002, 2012 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 either: |
9 | | |
10 | | * the GNU Lesser General Public License as published by the Free |
11 | | Software Foundation; either version 3 of the License, or (at your |
12 | | option) any later version. |
13 | | |
14 | | or |
15 | | |
16 | | * the GNU General Public License as published by the Free Software |
17 | | Foundation; either version 2 of the License, or (at your option) any |
18 | | later version. |
19 | | |
20 | | or both in parallel, as here. |
21 | | |
22 | | The GNU MP Library is distributed in the hope that it will be useful, but |
23 | | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
24 | | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
25 | | for more details. |
26 | | |
27 | | You should have received copies of the GNU General Public License and the |
28 | | GNU Lesser General Public License along with the GNU MP Library. If not, |
29 | | see https://www.gnu.org/licenses/. */ |
30 | | |
31 | | #include "gmp-impl.h" |
32 | | |
33 | | void |
34 | | mpz_clrbit (mpz_ptr d, mp_bitcnt_t bit_idx) |
35 | 0 | { |
36 | 0 | mp_size_t dsize = SIZ (d); |
37 | 0 | mp_ptr dp = PTR (d); |
38 | 0 | mp_size_t limb_idx; |
39 | 0 | mp_limb_t mask; |
40 | |
|
41 | 0 | limb_idx = bit_idx / GMP_NUMB_BITS; |
42 | 0 | mask = CNST_LIMB(1) << (bit_idx % GMP_NUMB_BITS); |
43 | 0 | if (dsize >= 0) |
44 | 0 | { |
45 | 0 | if (limb_idx < dsize) |
46 | 0 | { |
47 | 0 | mp_limb_t dlimb; |
48 | 0 | dlimb = dp[limb_idx] & ~mask; |
49 | 0 | dp[limb_idx] = dlimb; |
50 | |
|
51 | 0 | if (UNLIKELY ((dlimb == 0) + limb_idx == dsize)) /* dsize == limb_idx + 1 */ |
52 | 0 | { |
53 | | /* high limb became zero, must normalize */ |
54 | 0 | MPN_NORMALIZE (dp, limb_idx); |
55 | 0 | SIZ (d) = limb_idx; |
56 | 0 | } |
57 | 0 | } |
58 | 0 | else |
59 | 0 | ; |
60 | 0 | } |
61 | 0 | else |
62 | 0 | { |
63 | | /* Simulate two's complement arithmetic, i.e. simulate |
64 | | 1. Set OP = ~(OP - 1) [with infinitely many leading ones]. |
65 | | 2. clear the bit. |
66 | | 3. Set OP = ~OP + 1. */ |
67 | |
|
68 | 0 | dsize = -dsize; |
69 | |
|
70 | 0 | if (limb_idx < dsize) |
71 | 0 | { |
72 | 0 | mp_size_t zero_bound; |
73 | | |
74 | | /* No index upper bound on this loop, we're sure there's a non-zero limb |
75 | | sooner or later. */ |
76 | 0 | zero_bound = 0; |
77 | 0 | while (dp[zero_bound] == 0) |
78 | 0 | zero_bound++; |
79 | |
|
80 | 0 | if (limb_idx > zero_bound) |
81 | 0 | { |
82 | 0 | dp[limb_idx] |= mask; |
83 | 0 | } |
84 | 0 | else if (limb_idx == zero_bound) |
85 | 0 | { |
86 | 0 | mp_limb_t dlimb; |
87 | 0 | dlimb = (((dp[limb_idx] - 1) | mask) + 1) & GMP_NUMB_MASK; |
88 | 0 | dp[limb_idx] = dlimb; |
89 | |
|
90 | 0 | if (dlimb == 0) |
91 | 0 | { |
92 | | /* Increment at limb_idx + 1. Extend the number with a zero limb |
93 | | for simplicity. */ |
94 | 0 | dp = MPZ_REALLOC (d, dsize + 1); |
95 | 0 | dp[dsize] = 0; |
96 | 0 | MPN_INCR_U (dp + limb_idx + 1, dsize - limb_idx, 1); |
97 | 0 | dsize += dp[dsize]; |
98 | |
|
99 | 0 | SIZ (d) = -dsize; |
100 | 0 | } |
101 | 0 | } |
102 | 0 | else |
103 | 0 | ; |
104 | 0 | } |
105 | 0 | else |
106 | 0 | { |
107 | | /* Ugh. The bit should be cleared outside of the end of the |
108 | | number. We have to increase the size of the number. */ |
109 | 0 | dp = MPZ_REALLOC (d, limb_idx + 1); |
110 | 0 | SIZ (d) = -(limb_idx + 1); |
111 | 0 | MPN_ZERO (dp + dsize, limb_idx - dsize); |
112 | 0 | dp[limb_idx] = mask; |
113 | 0 | } |
114 | 0 | } |
115 | 0 | } |