=pod

=head1 NAME

BN_zero, BN_one, BN_value_one, BN_set_word, BN_get_word - BIGNUM assignment
operations

=head1 SYNOPSIS

 #include <openssl/bn.h>

 void BN_zero(BIGNUM *a);
 int BN_one(BIGNUM *a);

 const BIGNUM *BN_value_one(void);

 int BN_set_word(BIGNUM *a, BN_ULONG w);
 unsigned BN_ULONG BN_get_word(BIGNUM *a);

=head1 DESCRIPTION

B<BN_ULONG> is a macro that will be an unsigned integral type optimized
for the most efficient implementation on the local platform.

BN_zero(), BN_one() and BN_set_word() set B<a> to the values 0, 1 and
B<w> respectively.  BN_zero() and BN_one() are macros.

BN_value_one() returns a B<BIGNUM> constant of value 1. This constant
is useful for use in comparisons and assignment.

BN_get_word() returns B<a>, if it can be represented as a B<BN_ULONG>.

=head1 RETURN VALUES

BN_get_word() returns the value B<a>, or all-bits-set if B<a> cannot
be represented as a single integer.

BN_one() and BN_set_word() return 1 on success, 0 otherwise.
BN_value_one() returns the constant.
BN_zero() never fails and returns no value.

=head1 BUGS

If a B<BIGNUM> is equal to the value of all-bits-set, it will collide
with the error condition returned by BN_get_word() which uses that
as an error value.

B<BN_ULONG> should probably be a typedef.

=head1 SEE ALSO

L<BN_bn2bin(3)>

=head1 HISTORY

In OpenSSL 0.9.8, BN_zero() was changed to not return a value; previous
versions returned an int.

=head1 COPYRIGHT

Copyright 2000-2018 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
L<https://www.openssl.org/source/license.html>.

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