1=pod
2
3=head1 NAME
4
5BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
6
7=head1 SYNOPSIS
8
9 #include <openssl/bn.h>
10
11 void BN_CTX_start(BN_CTX *ctx);
12
13 BIGNUM *BN_CTX_get(BN_CTX *ctx);
14
15 void BN_CTX_end(BN_CTX *ctx);
16
17=head1 DESCRIPTION
18
19These functions are used to obtain temporary B<BIGNUM> variables from
20a B<BN_CTX> (which can been created by using L<BN_CTX_new(3)>)
21in order to save the overhead of repeatedly creating and
22freeing B<BIGNUM>s in functions that are called from inside a loop.
23
24A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
25called repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get()
26calls must be made before calling any other functions that use the
27B<ctx> as an argument.
28
29Finally, BN_CTX_end() must be called before returning from the function.
30When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from
31BN_CTX_get() become invalid.
32
33=head1 RETURN VALUES
34
35BN_CTX_start() and BN_CTX_end() return no values.
36
37BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error.
38Once BN_CTX_get() has failed, the subsequent calls will return B<NULL>
39as well, so it is sufficient to check the return value of the last
40BN_CTX_get() call. In case of an error, an error code is set, which
41can be obtained by L<ERR_get_error(3)>.
42
43
44=head1 SEE ALSO
45
46L<BN_CTX_new(3)>
47
48=head1 COPYRIGHT
49
50Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
51
52Licensed under the OpenSSL license (the "License").  You may not use
53this file except in compliance with the License.  You can obtain a copy
54in the file LICENSE in the source distribution or at
55L<https://www.openssl.org/source/license.html>.
56
57=cut
58