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.\" ========================================================================
.\"
.IX Title "BN_CTX_new 3"
.TH BN_CTX_new 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.
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.nh
.SH "NAME"
BN_CTX_new, BN_CTX_init, BN_CTX_free \- allocate and free BN_CTX structures
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bn.h>
\&
\& BN_CTX *BN_CTX_new(void);
\&
\& void BN_CTX_free(BN_CTX *c);
.Ve
.PP
Deprecated:
.PP
.Vb 1
\& void BN_CTX_init(BN_CTX *c);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A \fB\s-1BN_CTX\s0\fR is a structure that holds \fB\s-1BIGNUM\s0\fR temporary variables used by
library functions. Since dynamic memory allocation to create \fB\s-1BIGNUM\s0\fRs
is rather expensive when used in conjunction with repeated subroutine
calls, the \fB\s-1BN_CTX\s0\fR structure is used.
.PP
\&\fBBN_CTX_new()\fR allocates and initializes a \fB\s-1BN_CTX\s0\fR
structure.
.PP
\&\fBBN_CTX_free()\fR frees the components of the \fB\s-1BN_CTX\s0\fR, and if it was
created by \fBBN_CTX_new()\fR, also the structure itself.
If \fBBN_CTX_start\fR\|(3) has been used on the \fB\s-1BN_CTX\s0\fR,
\&\fBBN_CTX_end\fR\|(3) must be called before the \fB\s-1BN_CTX\s0\fR
may be freed by \fBBN_CTX_free()\fR.
.PP
\&\fBBN_CTX_init()\fR (deprecated) initializes an existing uninitialized \fB\s-1BN_CTX\s0\fR.
This should not be used for new programs. Use \fBBN_CTX_new()\fR instead.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBN_CTX_new()\fR returns a pointer to the \fB\s-1BN_CTX\s0\fR. If the allocation fails,
it returns \fB\s-1NULL\s0\fR and sets an error code that can be obtained by
\&\fBERR_get_error\fR\|(3).
.PP
\&\fBBN_CTX_init()\fR and \fBBN_CTX_free()\fR have no return values.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBbn\fR\|(3), \fBERR_get_error\fR\|(3), \fBBN_add\fR\|(3),
\&\fBBN_CTX_start\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBBN_CTX_new()\fR and \fBBN_CTX_free()\fR are available in all versions on SSLeay
and OpenSSL. \fBBN_CTX_init()\fR was added in SSLeay 0.9.1b.