BN_add_word, BN_sub_word, BN_mul_word, BN_div_word, BN_mod_word - arithmetic functions on BIGNUMs with integers
#include <openssl/bn.h>
int BN_add_word(BIGNUM *a, BN_ULONG w);
int BN_sub_word(BIGNUM *a, BN_ULONG w);
int BN_mul_word(BIGNUM *a, BN_ULONG w);
BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w);
BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w);
These functions perform arithmetic operations on BIGNUMs with unsigned integers. They are much more efficient than the normal BIGNUM arithmetic operations.
BN_add_word() adds w to a (a+=w).
BN_sub_word() subtracts w from a (a-=w).
BN_mul_word() multiplies a and w (a*=w).
BN_div_word() divides a by w (a/=w) and returns the remainder.
BN_mod_word() returns the remainder of a divided by w (a%w).
For BN_div_word() and BN_mod_word(), w must not be 0.
BN_add_word(), BN_sub_word() and BN_mul_word() return 1 for success, 0
on error. The error codes can be obtained by ERR_get_error.
BN_mod_word() and BN_div_word() return a%w on success and
(BN_ULONG)-1 if an error occurred.
BN_add_word() and BN_mod_word() are available in all versions of
SSLeay and OpenSSL. BN_div_word() was added in SSLeay 0.8, and
BN_sub_word() and BN_mul_word() in SSLeay 0.9.0.
Before 0.9.8a the return value for BN_div_word() and BN_mod_word()
in case of an error was 0.