.\"	$OpenBSD: BIO_new.3,v 1.4 2016/11/07 15:52:47 jmc Exp $
.\"
.Dd $Mdocdate: November 7 2016 $
.Dt BIO_NEW 3
.Os
.Sh NAME
.Nm BIO_new ,
.Nm BIO_set ,
.Nm BIO_free ,
.Nm BIO_vfree ,
.Nm BIO_free_all
.Nd BIO allocation and freeing functions
.Sh SYNOPSIS
.In openssl/bio.h
.Ft BIO *
.Fo BIO_new
.Fa "BIO_METHOD *type"
.Fc
.Ft int
.Fo BIO_set
.Fa "BIO *a"
.Fa "BIO_METHOD *type"
.Fc
.Ft int
.Fo BIO_free
.Fa "BIO *a"
.Fc
.Ft void
.Fo BIO_vfree
.Fa "BIO *a"
.Fc
.Ft void
.Fo BIO_free_all
.Fa "BIO *a"
.Fc
.Sh DESCRIPTION
The
.Fn BIO_new
function returns a new BIO using method
.Fa type .
.Pp
.Fn BIO_set
sets the method of an already existing BIO.
.Pp
.Fn BIO_free
frees up a single BIO;
.Fn BIO_vfree
also frees up a single BIO, but it does not return a value.
Calling
.Fn BIO_free
may also have some effect on the underlying I/O structure,
for example it may close the file being
referred to under certain circumstances.
For more details see the individual
.Vt BIO_METHOD
descriptions.
.Pp
.Fn BIO_free_all
frees up an entire BIO chain.
It does not halt if an error occurs
freeing up an individual BIO in the chain.
.Pp
Some BIOs (such as memory BIOs) can be used immediately after calling
.Fn BIO_new .
Others (such as file BIOs) need some additional initialization, and
frequently a utility function exists to create and initialize such BIOs.
.Pp
If
.Fn BIO_free
is called on a BIO chain, it will only free one BIO,
resulting in a memory leak.
.Pp
Calling
.Fn BIO_free_all
on a single BIO has the same effect as calling
.Fn BIO_free
on it other than the discarded return value.
.Pp
Normally the
.Fa type
argument is supplied by a function which returns a pointer to a
.Vt BIO_METHOD .
There is a naming convention for such functions:
a source/sink BIO is normally called
.Fn BIO_s_*
and a filter BIO
.Fn BIO_f_* .
.Sh RETURN VALUES
.Fn BIO_new
returns a newly created BIO or
.Dv NULL
if the call fails.
.Pp
.Fn BIO_set
and
.Fn BIO_free
return 1 for success and 0 for failure.
.Pp
.Fn BIO_free_all
and
.Fn BIO_vfree
do not return values.
.Sh EXAMPLES
Create a memory BIO:
.Pp
.Dl BIO *mem = BIO_new(BIO_s_mem());