--- /dev/null
+.\" $OpenBSD: BIO_get_data.3,v 1.1 2018/02/19 14:08:52 schwarze Exp $
+.\" selective merge up to: OpenSSL e90fc053 Jul 15 09:39:45 2017 -0400
+.\"
+.\" This file was written by Matt Caswell <matt@openssl.org>
+.\" Copyright (c) 2016 The OpenSSL Project. All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
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+.\" software must display the following acknowledgment:
+.\" "This product includes software developed by the OpenSSL Project
+.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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+.Dd $Mdocdate: February 19 2018 $
+.Dt BIO_GET_DATA 3
+.Os
+.Sh NAME
+.Nm BIO_set_data ,
+.Nm BIO_get_data ,
+.Nm BIO_set_init
+.Nd manage BIO state information
+.Sh SYNOPSIS
+.In openssl/bio.h
+.Ft void
+.Fo BIO_set_data
+.Fa "BIO *a"
+.Fa "void *ptr"
+.Fc
+.Ft void *
+.Fo BIO_get_data
+.Fa "BIO *a"
+.Fc
+.Ft void
+.Fo BIO_set_init
+.Fa "BIO *a"
+.Fa "int init"
+.Fc
+.Sh DESCRIPTION
+These functions are mainly useful when implementing a custom BIO.
+.Pp
+The
+.Fn BIO_set_data
+function associates the custom data pointed to by
+.Fa ptr
+with the
+.Fa "BIO a" .
+This data can subsequently be retrieved via a call to
+.Fn BIO_get_data .
+This can be used by custom BIOs for storing implementation specific
+information.
+.Pp
+The
+.Fn BIO_set_init
+function sets the
+.Fa init
+flag in
+.Fa a
+to the specified value.
+A non-zero value indicates that initialisation is complete,
+whilst zero indicates that it is not.
+Often initialisation will complete
+during initial construction of the BIO.
+For some BIOs however, initialisation may not be complete until
+additional steps have been taken, for example through calling custom
+ctrls.
+.Sh RETURN VALUES
+.Fn BIO_get_data
+returns a pointer to the implementation specific custom data associated
+with
+.Fa a ,
+or
+.Dv NULL
+if none is set.
+.Sh SEE ALSO
+.Xr BIO_meth_new 3 ,
+.Xr BIO_new 3
+.Sh HISTORY
+These functions first appeared in OpenSSL 1.1.0.