BN_CTX_start.pod revision 68651
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)|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)|ERR_get_error(3)>. 42 43 44=head1 SEE ALSO 45 46L<BN_CTX_new(3)|BN_CTX_new(3)> 47 48=head1 HISTORY 49 50BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5. 51 52=cut 53