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.\" $OpenBSD: BN_zero.3,v 1.9 2018/03/27 17:35:50 schwarze Exp $
.\" full merge up to: OpenSSL a528d4f0 Oct 27 13:40:11 2015 -0400
.\" selective merge up to: OpenSSL b713c4ff Jan 22 14:41:09 2018 -0500
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000, 2001, 2002, 2018 The OpenSSL Project.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: March 27 2018 $
.Dt BN_ZERO 3
.Os
.Sh NAME
.Nm BN_zero ,
.Nm BN_one ,
.Nm BN_value_one ,
.Nm BN_set_word ,
.Nm BN_get_word
.Nd BIGNUM assignment operations
.Sh SYNOPSIS
.In openssl/bn.h
.Ft int
.Fo BN_zero
.Fa "BIGNUM *a"
.Fc
.Ft int
.Fo BN_one
.Fa "BIGNUM *a"
.Fc
.Ft const BIGNUM *
.Fo BN_value_one
.Fa void
.Fc
.Ft int
.Fo BN_set_word
.Fa "BIGNUM *a"
.Fa "BN_ULONG w"
.Fc
.Ft BN_ULONG
.Fo BN_get_word
.Fa "BIGNUM *a"
.Fc
.Sh DESCRIPTION
.Vt BN_ULONG
is a macro that expands to an unsigned integral type optimized
for the most efficient implementation on the local platform.
.Pp
.Fn BN_zero ,
.Fn BN_one ,
and
.Fn BN_set_word
set
.Fa a
to the values 0, 1 and
.Fa w
respectively.
.Fn BN_zero
and
.Fn BN_one
are macros.
.Pp
.Fn BN_value_one
returns a
.Vt BIGNUM
constant of value 1.
This constant is useful for comparisons and assignments.
.Sh RETURN VALUES
.Fn BN_get_word
returns the value
.Fa a ,
or a number with all bits set if
.Fa a
cannot be represented as a
.Vt BN_ULONG .
.Pp
.Fn BN_zero ,
.Fn BN_one ,
and
.Fn BN_set_word
return 1 on success, 0 otherwise.
.Fn BN_value_one
returns the constant.
.Sh SEE ALSO
.Xr BN_bn2bin 3 ,
.Xr BN_new 3 ,
.Xr BN_set_bit 3 ,
.Xr BN_set_negative 3
.Sh HISTORY
.Fn BN_zero ,
.Fn BN_one ,
.Fn BN_value_one ,
and
.Fn BN_set_word
first appeared in SSLeay 0.5.1.
.Fn BN_get_word
first appeared in SSLeay 0.6.0.
All these functions have been available since
.Ox 2.4 .
.Sh BUGS
Someone might change the constant.
.Pp
If the value of a
.Vt BIGNUM
is equal to a
.Vt BN_ULONG
with all bits set, the return value of
.Fn BN_get_word
collides with return value used to indicate errors.
.Pp
.Vt BN_ULONG
should probably be a typedef rather than a macro.
|
