NAME
BN_num_bits, BN_num_bytes, BN_num_bits_word — get BIGNUM size 
Synopsis
#include <openssl/bn.h> 
int
BN_num_bytes(const BIGNUM *a);
int BN_num_bits(const BIGNUM
*a); 
int BN_num_bits_word(BN_ULONG w);
DESCRIPTION
These functions return the size of a BIGNUM in
bytes or bits, and the size of an unsigned integer in bits. 
BN_num_bytes() is a macro. 
HISTORY
BN_num_bytes(), BN_num_bits() and BN_num_bits_word() are available
in all versions of SSLeay and OpenSSL.