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 be created 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. If
ctx is NULL, no action
occurs.
RETURN 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
HISTORY
BN_CTX_start(),
BN_CTX_get(), and
BN_CTX_end() first appeared in OpenSSL 0.9.5 and
have been available since OpenBSD 2.7.