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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(3).

BN_mod_word() and BN_div_word() return a%w on success and (BN_ULONG)-1 if an error occurred.


bn(3), ERR_get_error(3), BN_add(3)


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.