BN_CTX_start(3) OpenSSL BN_CTX_start(3)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 VALUESBN_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 ALSOBN_CTX_new(3)HISTORYBN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added
in OpenSSL 0.9.5.
11/Jul/2000 0.9.6j BN_CTX_start(3)
