BN_CTX_start, BN_CTX_get, BN_CTX_end - Use temporary
BN_CTX *ctx ); BIGNUM *BN_CTX_get(
BN_CTX *ctx ); void BN_CTX_end(
BN_CTX *ctx );
These functions are used to obtain temporary BIGNUM variables
from a BN_CTX (which can been created by using the
BN_CTX_new() function) in order to save the overhead of
repeatedly creating and freeing BIGNUMs in functions that
are called from inside a loop.
A function must call BN_CTX_start() first. Then,
BN_CTX_get() may be called repeatedly to obtain temporary
BIGNUMs. All BN_CTX_get() calls must be made before calling
any other functions that use the ctx as an argument.
Finally, BN_CTX_end() must be called before returning from
the function. When BN_CTX_end() is called, the BIGNUM
pointers obtained from BN_CTX_get() become invalid.
The BN_CTX_start() and BN_CTX_end() functions return no
The BN_CTX_get() function returns a pointer to the BIGNUM,
or NULL on error. Once BN_CTX_get() has failed, the subsequent
calls will return NULL as well, so it is sufficient
to check the return value of the last BN_CTX_get() call.
In case of an error, an error code is set, which can be
obtained by ERR_get_error().
The BN_CTX_start(), BN_CTX_get(), and BN_CTX_end() functions
were added in OpenSSL 0.9.5.
[ Back ]