.\" $OpenBSD: ENGINE_add.3,v 1.1 2018/04/15 01:43:45 schwarze Exp $
.\" content checked up to: OpenSSL 1f13ad31 Dec 25 17:50:39 2017 +0800
.\"
.\" Copyright (c) 2018 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: April 15 2018 $
.Dt ENGINE_ADD 3
.Os
.Sh NAME
.Nm ENGINE_add ,
.Nm ENGINE_remove ,
.Nm ENGINE_get_first ,
.Nm ENGINE_get_last ,
.Nm ENGINE_get_next ,
.Nm ENGINE_get_prev ,
.Nm ENGINE_by_id
.Nd maintain a global list of ENGINE objects
.Sh SYNOPSIS
.In openssl/engine.h
.Ft int
.Fo ENGINE_add
.Fa "ENGINE *e"
.Fc
.Ft int
.Fo ENGINE_remove
.Fa "ENGINE *e"
.Fc
.Ft ENGINE *
.Fn ENGINE_get_first void
.Ft ENGINE *
.Fn ENGINE_get_last void
.Ft ENGINE *
.Fo ENGINE_get_next
.Fa "ENGINE *e"
.Fc
.Ft ENGINE *
.Fo ENGINE_get_prev
.Fa "ENGINE *e"
.Fc
.Ft ENGINE *
.Fo ENGINE_by_id
.Fa "const char *id"
.Fc
.Sh DESCRIPTION
The crypto library maintains a global list of
.Vt ENGINE
objects.
.Pp
.Fn ENGINE_add
appends
.Fa e
to the end of the list
and increments its structural reference count by 1.
The name and identifier of
.Fa e
have to be set with
.Xr ENGINE_set_name 3
and
.Xr ENGINE_set_id 3
before calling this function.
.Fn ENGINE_add
fails if the list already contains an
.Vt ENGINE
with the same identifier.
.Pp
.Fn ENGINE_remove
removes
.Fa e
from the list.
If successful, it calls
.Xr ENGINE_free 3
on
.Fa e .
.Pp
.Fn ENGINE_get_first
and
.Fn ENGINE_get_last
provide access to the first and last
.Vt ENGINE
object on the list, respectively.
Unless the list is empty, they increment the structural reference
count of the retrieved object by 1.
.Pp
.Fn ENGINE_get_next
and
.Fn ENGINE_get_prev
support iteration of the list.
They always call
.Xr ENGINE_free 3
on
.Fa e .
Unless the end of the list is reached, they increment the structural
reference count of the retrieved object by 1.
.Pp
.Fn ENGINE_by_id
searches the list for an
.Vt ENGINE
object with a matching
.Fa id .
If found, it increments  the structural reference count of the
retrieved object by 1.
.Sh RETURN VALUES
.Fn ENGINE_add
and
.Fn ENGINE_remove
return 1 on success or 0 on error.
.Pp
.Fn ENGINE_get_first
and
.Fn ENGINE_get_last
return an
.Vt ENGINE
object or
.Dv NULL
if the list is empty.
.Pp
.Fn ENGINE_get_next
and
.Fn ENGINE_get_prev
return an
.Vt ENGINE
object or
.Dv NULL
when the end of the list is reached.
.Pp
.Fn ENGINE_by_id
returns an
.Vt ENGINE
object or
.Dv NULL
if no matching object is found.