NAME¶
BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
SYNOPSIS¶
#include <openssl/bn.h>
void BN_CTX_start(BN_CTX *ctx);
BIGNUM *BN_CTX_get(BN_CTX *ctx);
void BN_CTX_end(BN_CTX *ctx);
DESCRIPTION¶
These functions are used to obtain temporary
BIGNUM variables from a
BN_CTX (which can been created by using
BN_CTX_new(3)) 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.
RETURN VALUES¶
BN_CTX_start() and
BN_CTX_end() return no values.
BN_CTX_get() 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(3).
SEE ALSO¶
BN_CTX_new(3)
HISTORY¶
BN_CTX_start(),
BN_CTX_get() and
BN_CTX_end() were added in
OpenSSL 0.9.5.