BN_zero, BN_one, BN_value_one, BN_set_word, BN_get_word - BIGNUM assignment operations
#include <openssl/bn.h> void BN_zero(BIGNUM *a); int BN_one(BIGNUM *a); const BIGNUM *BN_value_one(void); int BN_set_word(BIGNUM *a, BN_ULONG w); unsigned BN_ULONG BN_get_word(BIGNUM *a);
BN_ULONG is a macro that will be an unsigned integral type optimized for the most efficient implementation on the local platform.
BN_zero(), BN_one() and BN_set_word() set a to the values 0, 1 and w respectively. BN_zero() and BN_one() are macros.
BN_value_one() returns a BIGNUM constant of value 1. This constant is useful for use in comparisons and assignment.
BN_get_word() returns a, if it can be represented as a BN_ULONG.
BN_get_word() returns the value a, or all-bits-set if a cannot be represented as a single integer.
BN_one() and BN_set_word() return 1 on success, 0 otherwise. BN_value_one() returns the constant. BN_zero() never fails and returns no value.
If a BIGNUM is equal to the value of all-bits-set, it will collide with the error condition returned by BN_get_word() which uses that as an error value.
BN_ULONG should probably be a typedef.
In OpenSSL 0.9.8, BN_zero() was changed to not return a value; previous versions returned an int.
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