1*4724848cSchristos=pod 2*4724848cSchristos 3*4724848cSchristos=head1 NAME 4*4724848cSchristos 5*4724848cSchristosBN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables 6*4724848cSchristos 7*4724848cSchristos=head1 SYNOPSIS 8*4724848cSchristos 9*4724848cSchristos #include <openssl/bn.h> 10*4724848cSchristos 11*4724848cSchristos void BN_CTX_start(BN_CTX *ctx); 12*4724848cSchristos 13*4724848cSchristos BIGNUM *BN_CTX_get(BN_CTX *ctx); 14*4724848cSchristos 15*4724848cSchristos void BN_CTX_end(BN_CTX *ctx); 16*4724848cSchristos 17*4724848cSchristos=head1 DESCRIPTION 18*4724848cSchristos 19*4724848cSchristosThese functions are used to obtain temporary B<BIGNUM> variables from 20*4724848cSchristosa B<BN_CTX> (which can been created by using L<BN_CTX_new(3)>) 21*4724848cSchristosin order to save the overhead of repeatedly creating and 22*4724848cSchristosfreeing B<BIGNUM>s in functions that are called from inside a loop. 23*4724848cSchristos 24*4724848cSchristosA function must call BN_CTX_start() first. Then, BN_CTX_get() may be 25*4724848cSchristoscalled repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get() 26*4724848cSchristoscalls must be made before calling any other functions that use the 27*4724848cSchristosB<ctx> as an argument. 28*4724848cSchristos 29*4724848cSchristosFinally, BN_CTX_end() must be called before returning from the function. 30*4724848cSchristosIf B<ctx> is NULL, nothing is done. 31*4724848cSchristosWhen BN_CTX_end() is called, the B<BIGNUM> pointers obtained from 32*4724848cSchristosBN_CTX_get() become invalid. 33*4724848cSchristos 34*4724848cSchristos=head1 RETURN VALUES 35*4724848cSchristos 36*4724848cSchristosBN_CTX_start() and BN_CTX_end() return no values. 37*4724848cSchristos 38*4724848cSchristosBN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error. 39*4724848cSchristosOnce BN_CTX_get() has failed, the subsequent calls will return B<NULL> 40*4724848cSchristosas well, so it is sufficient to check the return value of the last 41*4724848cSchristosBN_CTX_get() call. In case of an error, an error code is set, which 42*4724848cSchristoscan be obtained by L<ERR_get_error(3)>. 43*4724848cSchristos 44*4724848cSchristos 45*4724848cSchristos=head1 SEE ALSO 46*4724848cSchristos 47*4724848cSchristosL<BN_CTX_new(3)> 48*4724848cSchristos 49*4724848cSchristos=head1 COPYRIGHT 50*4724848cSchristos 51*4724848cSchristosCopyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved. 52*4724848cSchristos 53*4724848cSchristosLicensed under the OpenSSL license (the "License"). You may not use 54*4724848cSchristosthis file except in compliance with the License. You can obtain a copy 55*4724848cSchristosin the file LICENSE in the source distribution or at 56*4724848cSchristosL<https://www.openssl.org/source/license.html>. 57*4724848cSchristos 58*4724848cSchristos=cut 59