1*2175Sjp161948=pod 2*2175Sjp161948 3*2175Sjp161948=head1 NAME 4*2175Sjp161948 5*2175Sjp161948BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables 6*2175Sjp161948 7*2175Sjp161948=head1 SYNOPSIS 8*2175Sjp161948 9*2175Sjp161948 #include <openssl/bn.h> 10*2175Sjp161948 11*2175Sjp161948 void BN_CTX_start(BN_CTX *ctx); 12*2175Sjp161948 13*2175Sjp161948 BIGNUM *BN_CTX_get(BN_CTX *ctx); 14*2175Sjp161948 15*2175Sjp161948 void BN_CTX_end(BN_CTX *ctx); 16*2175Sjp161948 17*2175Sjp161948=head1 DESCRIPTION 18*2175Sjp161948 19*2175Sjp161948These functions are used to obtain temporary B<BIGNUM> variables from 20*2175Sjp161948a B<BN_CTX> (which can been created by using L<BN_CTX_new(3)|BN_CTX_new(3)>) 21*2175Sjp161948in order to save the overhead of repeatedly creating and 22*2175Sjp161948freeing B<BIGNUM>s in functions that are called from inside a loop. 23*2175Sjp161948 24*2175Sjp161948A function must call BN_CTX_start() first. Then, BN_CTX_get() may be 25*2175Sjp161948called repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get() 26*2175Sjp161948calls must be made before calling any other functions that use the 27*2175Sjp161948B<ctx> as an argument. 28*2175Sjp161948 29*2175Sjp161948Finally, BN_CTX_end() must be called before returning from the function. 30*2175Sjp161948When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from 31*2175Sjp161948BN_CTX_get() become invalid. 32*2175Sjp161948 33*2175Sjp161948=head1 RETURN VALUES 34*2175Sjp161948 35*2175Sjp161948BN_CTX_start() and BN_CTX_end() return no values. 36*2175Sjp161948 37*2175Sjp161948BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error. 38*2175Sjp161948Once BN_CTX_get() has failed, the subsequent calls will return B<NULL> 39*2175Sjp161948as well, so it is sufficient to check the return value of the last 40*2175Sjp161948BN_CTX_get() call. In case of an error, an error code is set, which 41*2175Sjp161948can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 42*2175Sjp161948 43*2175Sjp161948 44*2175Sjp161948=head1 SEE ALSO 45*2175Sjp161948 46*2175Sjp161948L<BN_CTX_new(3)|BN_CTX_new(3)> 47*2175Sjp161948 48*2175Sjp161948=head1 HISTORY 49*2175Sjp161948 50*2175Sjp161948BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5. 51*2175Sjp161948 52*2175Sjp161948=cut 53