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✏️ Editing: BN_mask_bits.3

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.\" ========================================================================
.\"
.IX Title "BN_SET_BIT 3"
.TH BN_SET_BIT 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "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
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBBN_set_bit()\fR sets bit \fBn\fR in \fBa\fR to 1 (\f(CW\*(C`a|=(1<<n)\*(C'\fR). The
number is expanded if necessary.
.PP
\&\fBBN_clear_bit()\fR sets bit \fBn\fR in \fBa\fR to 0 (\f(CW\*(C`a&=~(1<<n)\*(C'\fR). An
error occurs if \fBa\fR is shorter than \fBn\fR bits.
.PP
\&\fBBN_is_bit_set()\fR tests if bit \fBn\fR in \fBa\fR is set.
.PP
\&\fBBN_mask_bits()\fR truncates \fBa\fR to an \fBn\fR bit number
(\f(CW\*(C`a&=~((~0)<<n)\*(C'\fR).  An error occurs if \fBa\fR already is
shorter than \fBn\fR bits.
.PP
\&\fBBN_lshift()\fR shifts \fBa\fR left by \fBn\fR bits and places the result in
\&\fBr\fR (\f(CW\*(C`r=a*2^n\*(C'\fR). Note that \fBn\fR must be nonnegative. \fBBN_lshift1()\fR shifts
\&\fBa\fR left by one and places the result in \fBr\fR (\f(CW\*(C`r=2*a\*(C'\fR).
.PP
\&\fBBN_rshift()\fR shifts \fBa\fR right by \fBn\fR bits and places the result in
\&\fBr\fR (\f(CW\*(C`r=a/2^n\*(C'\fR). Note that \fBn\fR must be nonnegative. \fBBN_rshift1()\fR shifts
\&\fBa\fR right by one and places the result in \fBr\fR (\f(CW\*(C`r=a/2\*(C'\fR).
.PP
For the shift functions, \fBr\fR and \fBa\fR may be the same variable.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBN_is_bit_set()\fR returns 1 if the bit is set, 0 otherwise.
.PP
All other functions return 1 for success, 0 on error. The error codes
can be obtained by \fBERR_get_error\fR\|(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBBN_num_bytes\fR\|(3), \fBBN_add\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.

MR SKB