BN_set_bit.pod revision 296465 
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<gt>E<gt>n)>).  An error occurs if B<a> already is
37shorter than B<n> bits.
38
39BN_lshift() shifts B<a> left by B<n> bits and places the result in
40B<r> (C<r=a*2^n>). Note that B<n> must be non-negative. BN_lshift1() shifts
41B<a> left by one and places the result in B<r> (C<r=2*a>).
42
43BN_rshift() shifts B<a> right by B<n> bits and places the result in
44B<r> (C<r=a/2^n>). Note that B<n> must be non-negative. BN_rshift1() shifts
45B<a> right by one and places the result in B<r> (C<r=a/2>).
46
47For the shift functions, B<r> and B<a> may be the same variable.
48
49=head1 RETURN VALUES
50
51BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
52
53All other functions return 1 for success, 0 on error. The error codes
54can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
55
56=head1 SEE ALSO
57
58L<bn(3)|bn(3)>, L<BN_num_bytes(3)|BN_num_bytes(3)>, L<BN_add(3)|BN_add(3)>
59
60=head1 HISTORY
61
62BN_set_bit(), BN_clear_bit(), BN_is_bit_set(), BN_mask_bits(),
63BN_lshift(), BN_lshift1(), BN_rshift(), and BN_rshift1() are available
64in all versions of SSLeay and OpenSSL.
65
66=cut
67