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).
