NAME

BN_zero_ex, BN_zero, BN_one, BN_value_one, BN_set_word, BN_get_word — BIGNUM assignment operations

SYNOPSIS

#include <openssl/bn.h> void
BN_zero_ex(BIGNUM *a); int
BN_zero(BIGNUM *a); int
BN_one(BIGNUM *a); const BIGNUM *
BN_value_one(void); int
BN_set_word(BIGNUM *a, BN_ULONG w); BN_ULONG
BN_get_word(const BIGNUM *a);

DESCRIPTION

BN_ULONG is a macro that expands to an unsigned integral type optimized for the most efficient implementation on the local platform. It is unsigned long (= uint64_t) on _LP64 platforms and unsigned int (= uint32_t) elsewhere. BN_zero_ex(), BN_one(), and BN_set_word() set a to the values 0, 1 and w respectively. BN_zero() is a deprecated version of BN_zero_ex() that may attempt to allocate memory; consequently, and in contrast to BN_zero_ex(), it may fail. BN_zero() and BN_one() are macros. BN_value_one() returns a BIGNUM constant of value 1. This constant is useful for comparisons and assignments.

RETURN VALUES

BN_get_word() returns the value a, or a number with all bits set if a cannot be represented as a BN_ULONG. BN_zero(), BN_one(), and BN_set_word() return 1 on success, 0 otherwise. BN_value_one() returns the constant.

SEE ALSO

BN_bn2bin(3), BN_new(3), BN_set_bit(3), BN_set_negative(3)

HISTORY

BN_zero(), BN_one(), BN_value_one(), and BN_set_word() first appeared in SSLeay 0.5.1. BN_get_word() first appeared in SSLeay 0.6.0. These functions have been available since OpenBSD 2.4. BN_zero_ex() first appeared in OpenSSL 0.9.8 and has been available since OpenBSD 4.5.

BUGS

Someone might change the constant. If the value of a BIGNUM is equal to a BN_ULONG with all bits set, the return value of BN_get_word() collides with return value used to indicate errors. BN_ULONG should probably be a typedef rather than a macro.