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 BN_SET_BIT(3) Library Functions Manual BN_SET_BIT(3)

# NAME

BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift, BN_lshift1, BN_rshift, BN_rshift1bit 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
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).