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# 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_num_bytes(3), BN_add(3)

# COPYRIGHT

Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.