BN_set_bit(3) — Subroutines

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

The BN_set_bit() function sets bit n in a to 1 (a|=(1<<n)). The number is expanded if necessary.

The BN_clear_bit() function sets bit n in a to 0 (a&=~(1<<n)). An error occurs if a is shorter than n bits.

The BN_is_bit_set() function tests if bit n in a is set.

The BN_mask_bits() function truncates a to an n bit number (a&=~((~0)>>n)). An error occurs if a already is shorter than n bits.

The BN_lshift() function shifts a left by n bits and places the result in r (r=a∗2^n). The BN_lshift1() function shifts a left by one and places the result in r (r=2∗a).

The BN_rshift() function shifts a right by n bits and places the result in r (r=a/2^n). The BN_rshift1() function 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

The BN_is_bit_set() function 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 using ERR_get_error().

HISTORY

The BN_set_bit(), BN_clear_bit(), BN_is_bit_set(), BN_mask_bits(), BN_lshift(), BN_lshift1(), BN_rshift(), and BN_rshift1() functions are available in all versions of SSLeay and OpenSSL.

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