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