NAME¶
BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift, BN_lshift1,
BN_rshift, BN_rshift1 - bit operations on BIGNUMs
SYNOPSIS¶
#include <openssl/bn.h>
int BN_set_bit(BIGNUM *a, int n);
int BN_clear_bit(BIGNUM *a, int n);
int BN_is_bit_set(const BIGNUM *a, int n);
int BN_mask_bits(BIGNUM *a, int n);
int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
int BN_lshift1(BIGNUM *r, BIGNUM *a);
int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
int BN_rshift1(BIGNUM *r, BIGNUM *a);
DESCRIPTION¶
BN_set_bit() sets bit
n in
a to 1
("a|=(1<<n)"). The number is expanded if necessary.
BN_clear_bit() sets bit
n in
a to 0
("a&=~(1<<n)"). An error occurs if
a is shorter
than
n bits.
BN_is_bit_set() tests if bit
n in
a is set.
BN_mask_bits() truncates
a to an
n bit number
("a&=~((~0)>>n)"). An error occurs if
a already is
shorter than
n bits.
BN_lshift() shifts
a left by
n bits and places the result
in
r ("r=a*2^n"). Note that
n must be non-negative.
BN_lshift1() shifts
a left by one and places the result in
r ("r=2*a").
BN_rshift() shifts
a right by
n bits and places the result
in
r ("r=a/2^n"). Note that
n must be non-negative.
BN_rshift1() shifts
a right by one and places the result in
r ("r=a/2").
For the shift functions,
r and
a may be the same variable.
RETURN VALUES¶
BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
All other functions return 1 for success, 0 on error. The error codes can be
obtained by
ERR_get_error(3).
SEE ALSO¶
bn(3),
BN_num_bytes(3),
BN_add(3)
HISTORY¶
BN_set_bit(),
BN_clear_bit(),
BN_is_bit_set(),
BN_mask_bits(),
BN_lshift(),
BN_lshift1(),
BN_rshift(), and
BN_rshift1() are available in all versions of
SSLeay and OpenSSL.