xref: /openssl/doc/man3/BN_set_bit.pod (revision 7ed6de99)
1=pod
2
3=head1 NAME
4
5BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift,
6BN_lshift1, BN_rshift, BN_rshift1 - bit operations on BIGNUMs
7
8=head1 SYNOPSIS
9
10 #include <openssl/bn.h>
11
12 int BN_set_bit(BIGNUM *a, int n);
13 int BN_clear_bit(BIGNUM *a, int n);
14
15 int BN_is_bit_set(const BIGNUM *a, int n);
16
17 int BN_mask_bits(BIGNUM *a, int n);
18
19 int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
20 int BN_lshift1(BIGNUM *r, BIGNUM *a);
21
22 int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
23 int BN_rshift1(BIGNUM *r, BIGNUM *a);
24
25=head1 DESCRIPTION
26
27BN_set_bit() sets bit B<n> in B<a> to 1 (C<a|=(1E<lt>E<lt>n)>). The
28number is expanded if necessary.
29
30BN_clear_bit() sets bit B<n> in B<a> to 0 (C<a&=~(1E<lt>E<lt>n)>). An
31error occurs if B<a> is shorter than B<n> bits.
32
33BN_is_bit_set() tests if bit B<n> in B<a> is set.
34
35BN_mask_bits() truncates B<a> to an B<n> bit number
36(C<a&=~((~0)E<lt>E<lt>n)>). An error occurs if B<n> is negative. An error is
37also returned if the internal representation of B<a> is already shorter than
38B<n> bits. The internal representation depends on the platform's word size, and
39this error can be safely ignored. Use L<BN_num_bits(3)> to determine the exact
40number of bits if needed.
41
42BN_lshift() shifts B<a> left by B<n> bits and places the result in
43B<r> (C<r=a*2^n>). Note that B<n> must be nonnegative. BN_lshift1() shifts
44B<a> left by one and places the result in B<r> (C<r=2*a>).
45
46BN_rshift() shifts B<a> right by B<n> bits and places the result in
47B<r> (C<r=a/2^n>). Note that B<n> must be nonnegative. BN_rshift1() shifts
48B<a> right by one and places the result in B<r> (C<r=a/2>).
49
50For the shift functions, B<r> and B<a> may be the same variable.
51
52=head1 RETURN VALUES
53
54BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
55
56All other functions return 1 for success, 0 on error. The error codes
57can be obtained by L<ERR_get_error(3)>.
58
59=head1 SEE ALSO
60
61L<BN_num_bytes(3)>, L<BN_add(3)>
62
63=head1 COPYRIGHT
64
65Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved.
66
67Licensed under the Apache License 2.0 (the "License").  You may not use
68this file except in compliance with the License.  You can obtain a copy
69in the file LICENSE in the source distribution or at
70L<https://www.openssl.org/source/license.html>.
71
72=cut
73