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.
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
() were added in OpenSSL 0.9.5.