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.
RETURN VALUES
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(3).
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.