1.\" $OpenBSD: BN_zero.3,v 1.10 2021/11/30 18:34:35 tb Exp $ 2.\" full merge up to: OpenSSL a528d4f0 Oct 27 13:40:11 2015 -0400 3.\" selective merge up to: OpenSSL b713c4ff Jan 22 14:41:09 2018 -0500 4.\" 5.\" This file was written by Ulf Moeller <ulf@openssl.org>. 6.\" Copyright (c) 2000, 2001, 2002, 2018 The OpenSSL Project. 7.\" All rights reserved. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in 18.\" the documentation and/or other materials provided with the 19.\" distribution. 20.\" 21.\" 3. All advertising materials mentioning features or use of this 22.\" software must display the following acknowledgment: 23.\" "This product includes software developed by the OpenSSL Project 24.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 25.\" 26.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 27.\" endorse or promote products derived from this software without 28.\" prior written permission. For written permission, please contact 29.\" openssl-core@openssl.org. 30.\" 31.\" 5. Products derived from this software may not be called "OpenSSL" 32.\" nor may "OpenSSL" appear in their names without prior written 33.\" permission of the OpenSSL Project. 34.\" 35.\" 6. Redistributions of any form whatsoever must retain the following 36.\" acknowledgment: 37.\" "This product includes software developed by the OpenSSL Project 38.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 39.\" 40.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 41.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 42.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 43.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 44.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 45.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 46.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 47.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 49.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 50.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 51.\" OF THE POSSIBILITY OF SUCH DAMAGE. 52.\" 53.Dd $Mdocdate: November 30 2021 $ 54.Dt BN_ZERO 3 55.Os 56.Sh NAME 57.Nm BN_zero , 58.Nm BN_one , 59.Nm BN_value_one , 60.Nm BN_set_word , 61.Nm BN_get_word 62.Nd BIGNUM assignment operations 63.Sh SYNOPSIS 64.In openssl/bn.h 65.Ft int 66.Fo BN_zero 67.Fa "BIGNUM *a" 68.Fc 69.Ft int 70.Fo BN_one 71.Fa "BIGNUM *a" 72.Fc 73.Ft const BIGNUM * 74.Fo BN_value_one 75.Fa void 76.Fc 77.Ft int 78.Fo BN_set_word 79.Fa "BIGNUM *a" 80.Fa "BN_ULONG w" 81.Fc 82.Ft BN_ULONG 83.Fo BN_get_word 84.Fa "const BIGNUM *a" 85.Fc 86.Sh DESCRIPTION 87.Vt BN_ULONG 88is a macro that expands to an unsigned integral type optimized 89for the most efficient implementation on the local platform. 90.Pp 91.Fn BN_zero , 92.Fn BN_one , 93and 94.Fn BN_set_word 95set 96.Fa a 97to the values 0, 1 and 98.Fa w 99respectively. 100.Fn BN_zero 101and 102.Fn BN_one 103are macros. 104.Pp 105.Fn BN_value_one 106returns a 107.Vt BIGNUM 108constant of value 1. 109This constant is useful for comparisons and assignments. 110.Sh RETURN VALUES 111.Fn BN_get_word 112returns the value 113.Fa a , 114or a number with all bits set if 115.Fa a 116cannot be represented as a 117.Vt BN_ULONG . 118.Pp 119.Fn BN_zero , 120.Fn BN_one , 121and 122.Fn BN_set_word 123return 1 on success, 0 otherwise. 124.Fn BN_value_one 125returns the constant. 126.Sh SEE ALSO 127.Xr BN_bn2bin 3 , 128.Xr BN_new 3 , 129.Xr BN_set_bit 3 , 130.Xr BN_set_negative 3 131.Sh HISTORY 132.Fn BN_zero , 133.Fn BN_one , 134.Fn BN_value_one , 135and 136.Fn BN_set_word 137first appeared in SSLeay 0.5.1. 138.Fn BN_get_word 139first appeared in SSLeay 0.6.0. 140All these functions have been available since 141.Ox 2.4 . 142.Sh BUGS 143Someone might change the constant. 144.Pp 145If the value of a 146.Vt BIGNUM 147is equal to a 148.Vt BN_ULONG 149with all bits set, the return value of 150.Fn BN_get_word 151collides with return value used to indicate errors. 152.Pp 153.Vt BN_ULONG 154should probably be a typedef rather than a macro. 155