Updated: 2021/Apr/14

```BN_set_bit(3)                       OpenSSL                      BN_set_bit(3)

NAME
BN_lshift1, BN_rshift, BN_rshift1 - bit operations on BIGNUMs

LIBRARY
libcrypto, -lcrypto

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_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 nonnegative. 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 nonnegative. 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).