| 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_copy, BN_dup, BN_with_flags - copy BIGNUMs
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/bn.h>
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| 10 |
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| 11 | BIGNUM *BN_copy(BIGNUM *to, const BIGNUM *from);
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| 12 |
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| 13 | BIGNUM *BN_dup(const BIGNUM *from);
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| 14 |
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| 15 | void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags);
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| 16 |
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| 17 | =head1 DESCRIPTION
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| 18 |
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| 19 | BN_copy() copies B<from> to B<to>. BN_dup() creates a new B<BIGNUM>
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| 20 | containing the value B<from>.
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| 21 |
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| 22 | BN_with_flags creates a B<temporary> shallow copy of B<b> in B<dest>. It places
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| 23 | significant restrictions on the copied data. Applications that do no adhere to
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| 24 | these restrictions may encounter unexpected side effects or crashes. For that
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| 25 | reason use of this function is discouraged. Any flags provided in B<flags> will
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| 26 | be set in B<dest> in addition to any flags already set in B<b>. For example this
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| 27 | might commonly be used to create a temporary copy of a BIGNUM with the
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| 28 | B<BN_FLG_CONSTTIME> flag set for constant time operations. The temporary copy in
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| 29 | B<dest> will share some internal state with B<b>. For this reason the following
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| 30 | restrictions apply to the use of B<dest>:
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| 31 |
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| 32 | =over 2
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| 33 |
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| 34 | =item *
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| 35 |
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| 36 | B<dest> should be a newly allocated BIGNUM obtained via a call to BN_new(). It
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| 37 | should not have been used for other purposes or initialised in any way.
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| 38 |
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| 39 | =item *
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| 40 |
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| 41 | B<dest> must only be used in "read-only" operations, i.e. typically those
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| 42 | functions where the relevant parameter is declared "const".
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| 43 |
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| 44 | =item *
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| 45 |
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| 46 | B<dest> must be used and freed before any further subsequent use of B<b>
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| 47 |
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| 48 | =back
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| 49 |
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| 50 | =head1 RETURN VALUES
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| 51 |
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| 52 | BN_copy() returns B<to> on success, NULL on error. BN_dup() returns
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| 53 | the new B<BIGNUM>, and NULL on error. The error codes can be obtained
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| 54 | 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<ERR_get_error(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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