216 lines
4.7 KiB
Groff
216 lines
4.7 KiB
Groff
.\" $OpenBSD: BN_set_bit.3,v 1.8 2021/11/30 18:34:35 tb Exp $
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.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.\"
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.\" This file was written by Ulf Moeller <ulf@openssl.org>.
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.\" Copyright (c) 2000, 2015 The OpenSSL Project. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: November 30 2021 $
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.Dt BN_SET_BIT 3
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.Os
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.Sh NAME
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.Nm BN_set_bit ,
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.Nm BN_clear_bit ,
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.Nm BN_is_bit_set ,
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.Nm BN_mask_bits ,
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.Nm BN_lshift ,
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.Nm BN_lshift1 ,
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.Nm BN_rshift ,
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.Nm BN_rshift1
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.Nd bit operations on BIGNUMs
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.Sh SYNOPSIS
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.In openssl/bn.h
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.Ft int
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.Fo BN_set_bit
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.Fa "BIGNUM *a"
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.Fa "int n"
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.Fc
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.Ft int
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.Fo BN_clear_bit
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.Fa "BIGNUM *a"
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.Fa "int n"
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.Fc
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.Ft int
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.Fo BN_is_bit_set
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.Fa "const BIGNUM *a"
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.Fa "int n"
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.Fc
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.Ft int
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.Fo BN_mask_bits
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.Fa "BIGNUM *a"
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.Fa "int n"
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.Fc
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.Ft int
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.Fo BN_lshift
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.Fa "BIGNUM *r"
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.Fa "const BIGNUM *a"
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.Fa "int n"
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.Fc
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.Ft int
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.Fo BN_lshift1
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.Fa "BIGNUM *r"
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.Fa "const BIGNUM *a"
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.Fc
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.Ft int
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.Fo BN_rshift
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.Fa "BIGNUM *r"
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.Fa "const BIGNUM *a"
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.Fa "int n"
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.Fc
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.Ft int
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.Fo BN_rshift1
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.Fa "BIGNUM *r"
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.Fa "const BIGNUM *a"
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.Fc
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.Sh DESCRIPTION
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.Fn BN_set_bit
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sets bit
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.Fa n
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in
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.Fa a
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to 1
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.Pq Li a|=(1<<n) .
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The number is expanded if necessary.
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.Pp
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.Fn BN_clear_bit
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sets bit
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.Fa n
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in
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.Fa a
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to 0
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.Pq Li a&=~(1<<n) .
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An error occurs if
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.Fa a
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is shorter than
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.Fa n
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bits.
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.Pp
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.Fn BN_is_bit_set
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tests if bit
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.Fa n
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in
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.Fa a
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is set.
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.Pp
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.Fn BN_mask_bits
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truncates
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.Fa a
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to an
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.Fa n
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bit number
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.Pq Li a&=~((~0)>>n) .
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An error occurs if
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.Fa a
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already is shorter than
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.Fa n
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bits.
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.Pp
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.Fn BN_lshift
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shifts
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.Fa a
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left by
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.Fa n
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bits and places the result in
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.Fa r
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.Pq Li r=a*2^n .
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Note that
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.Fa n
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must be non-negative.
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.Fn BN_lshift1
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shifts
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.Fa a
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left by one and places the result in
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.Fa r
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.Pq Li r=2*a .
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.Pp
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.Fn BN_rshift
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shifts
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.Fa a
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right by
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.Fa n
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bits and places the result in
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.Fa r
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.Pq Li r=a/2^n .
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Note that
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.Fa n
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must be non-negative.
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.Fn BN_rshift1
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shifts
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.Fa a
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right by one and places the result in
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.Fa r
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.Pq Li r=a/2 .
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.Pp
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For the shift functions,
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.Fa r
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and
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.Fa a
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may be the same variable.
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.Sh RETURN VALUES
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.Fn BN_is_bit_set
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returns 1 if the bit is set, 0 otherwise.
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.Pp
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All other functions return 1 for success, 0 on error.
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The error codes can be obtained by
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.Xr ERR_get_error 3 .
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.Sh SEE ALSO
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.Xr BN_add 3 ,
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.Xr BN_new 3 ,
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.Xr BN_num_bytes 3 ,
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.Xr BN_set_negative 3 ,
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.Xr BN_zero 3
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.Sh HISTORY
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.Fn BN_set_bit ,
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.Fn BN_clear_bit ,
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.Fn BN_is_bit_set ,
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.Fn BN_mask_bits ,
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.Fn BN_lshift ,
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.Fn BN_lshift1 ,
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.Fn BN_rshift ,
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and
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.Fn BN_rshift1
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first appeared in SSLeay 0.5.1 and have been available since
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.Ox 2.4 .
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