| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift,
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| 6 | BN_lshift1, BN_rshift, BN_rshift1 - bit operations on BIGNUMs
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| 7 |
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| 8 | =head1 SYNOPSIS
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| 9 |
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| 10 | #include <openssl/bn.h>
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| 11 |
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| 12 | int BN_set_bit(BIGNUM *a, int n);
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| 13 | int BN_clear_bit(BIGNUM *a, int n);
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| 14 |
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| 15 | int BN_is_bit_set(const BIGNUM *a, int n);
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| 16 |
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| 17 | int BN_mask_bits(BIGNUM *a, int n);
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| 18 |
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| 19 | int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
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| 20 | int BN_lshift1(BIGNUM *r, BIGNUM *a);
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| 21 |
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| 22 | int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
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| 23 | int BN_rshift1(BIGNUM *r, BIGNUM *a);
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| 24 |
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| 25 | =head1 DESCRIPTION
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| 26 |
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| 27 | BN_set_bit() sets bit B<n> in B<a> to 1 (C<a|=(1E<lt>E<lt>n)>). The
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| 28 | number is expanded if necessary.
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| 29 |
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| 30 | BN_clear_bit() sets bit B<n> in B<a> to 0 (C<a&=~(1E<lt>E<lt>n)>). An
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| 31 | error occurs if B<a> is shorter than B<n> bits.
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| 32 |
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| 33 | BN_is_bit_set() tests if bit B<n> in B<a> is set.
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| 34 |
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| 35 | BN_mask_bits() truncates B<a> to an B<n> bit number
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| 36 | (C<a&=~((~0)E<gt>E<gt>n)>). An error occurs if B<a> already is
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| 37 | shorter than B<n> bits.
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| 38 |
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| 39 | BN_lshift() shifts B<a> left by B<n> bits and places the result in
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| 40 | B<r> (C<r=a*2^n>). Note that B<n> must be non-negative. BN_lshift1() shifts
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| 41 | B<a> left by one and places the result in B<r> (C<r=2*a>).
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| 42 |
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| 43 | BN_rshift() shifts B<a> right by B<n> bits and places the result in
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| 44 | B<r> (C<r=a/2^n>). Note that B<n> must be non-negative. BN_rshift1() shifts
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| 45 | B<a> right by one and places the result in B<r> (C<r=a/2>).
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| 46 |
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| 47 | For the shift functions, B<r> and B<a> may be the same variable.
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| 48 |
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| 49 | =head1 RETURN VALUES
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| 50 |
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| 51 | BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
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| 52 |
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| 53 | All other functions return 1 for success, 0 on error. The error codes
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| 54 | can be obtained by L<ERR_get_error(3)>.
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| 55 |
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| 56 | =head1 SEE ALSO
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| 57 |
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| 58 | L<BN_num_bytes(3)>, L<BN_add(3)>
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| 59 |
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| 60 | =head1 COPYRIGHT
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| 61 |
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| 62 | Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
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| 63 |
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| 64 | Licensed under the OpenSSL license (the "License"). You may not use
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| 65 | this file except in compliance with the License. You can obtain a copy
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| 66 | in the file LICENSE in the source distribution or at
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| 67 | L<https://www.openssl.org/source/license.html>.
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| 68 |
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| 69 | =cut
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