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.\" ========================================================================
.\"
.IX Title "BN_zero 3"
.TH BN_zero 3 "2019-12-20" "1.0.2u" "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_zero, BN_one, BN_value_one, BN_set_word, BN_get_word \- BIGNUM assignment
operations
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bn.h>
\&
\& int BN_zero(BIGNUM *a);
\& int BN_one(BIGNUM *a);
\&
\& const BIGNUM *BN_value_one(void);
\&
\& int BN_set_word(BIGNUM *a, BN_ULONG w);
\& BN_ULONG BN_get_word(BIGNUM *a);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fB\s-1BN_ULONG\s0\fR is a macro that will be an unsigned integral type optimied
for the most efficient implementation on the local platform.
.PP
\&\fBBN_zero()\fR, \fBBN_one()\fR and \fBBN_set_word()\fR set \fBa\fR to the values 0, 1 and
\&\fBw\fR respectively.  \fBBN_zero()\fR and \fBBN_one()\fR are macros.
.PP
\&\fBBN_value_one()\fR returns a \fB\s-1BIGNUM\s0\fR constant of value 1. This constant
is useful for use in comparisons and assignment.
.PP
\&\fBBN_get_word()\fR returns \fBa\fR, if it can be represented as a \fB\s-1BN_ULONG\s0\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBN_get_word()\fR returns the value \fBa\fR, or all-bits-set if \fBa\fR cannot
be represented as a \fB\s-1BN_ULONG\s0\fR.
.PP
\&\fBBN_zero()\fR, \fBBN_one()\fR and \fBBN_set_word()\fR return 1 on success, 0 otherwise.
\&\fBBN_value_one()\fR returns the constant.
.SH "BUGS"
.IX Header "BUGS"
If a \fB\s-1BIGNUM\s0\fR is equal to the value of all-bits-set, it will collide
with the error condition returned by \fBBN_get_word()\fR which uses that
as an error value.
.PP
\&\fB\s-1BN_ULONG\s0\fR should probably be a typedef.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBbn\fR\|(3), \fBBN_bn2bin\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBBN_zero()\fR, \fBBN_one()\fR and \fBBN_set_word()\fR are available in all versions of
SSLeay and OpenSSL. \fBBN_value_one()\fR and \fBBN_get_word()\fR were added in
SSLeay 0.8.
.PP
\&\fBBN_value_one()\fR was changed to return a true const \s-1BIGNUM\s0 * in OpenSSL
0.9.7.