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
