BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
#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);
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.
If ctx is NULL, nothing is done.
When BN_CTX_end()
is called, the BIGNUM pointers obtained from
BN_CTX_get()
become invalid.
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).
BN_CTX_new(3)
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