.\" $OpenBSD: BIO_new.3,v 1.8 2017/03/25 17:15:59 schwarze Exp $ .\" OpenSSL doc/man3/BIO_new.pod ca3a82c3 Mar 25 11:31:18 2015 -0400 .\" OpenSSL doc/man7/bio.pod a9c85cea Nov 11 09:33:55 2016 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2000, 2015, 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 .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: March 25 2017 $ .Dt BIO_NEW 3 .Os .Sh NAME .Nm BIO_new , .Nm BIO_set , .Nm BIO_free , .Nm BIO_vfree , .Nm BIO_free_all .Nd construct and destruct I/O abstraction objects .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 A .Vt BIO is an I/O abstraction object, hiding many of the underlying I/O details from an application. If an application uses BIOs for its I/O, it can transparently handle SSL connections, unencrypted network connections, and file I/O. .Pp The .Fn BIO_new function constructs a new .Vt BIO using the method .Fa type . There are two groups of BIO types, source/sink BIOs and filter BIOs. .Pp Source/sink BIOs provide input or consume output. Examples include socket BIOs and file BIOs. .Pp Filter BIOs take data from one BIO and pass it through to another, or to the application, forming a chain of BIOs. The data may be left unmodified (for example by a message digest BIO) or translated (for example by an encryption BIO). The effect of a filter BIO may change according to the I/O operation it is performing: for example an encryption BIO will encrypt data if it is written to and decrypt data if it is read from. .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 utility functions exists to construct and initialize such BIOs. .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: the methods for source/sink BIOs are called .Fn BIO_s_* and those for filter BIOs .Fn BIO_f_* . .Pp .Fn BIO_set sets the method of an already existing BIO. .Pp .Fn BIO_free and .Fn BIO_vfree destruct a single BIO, which may also have some effect on the underlying I/O structure, for example it may close the file being referred to under certain circumstances. If .Fa a is a .Dv NULL pointer, no action occurs. If .Fn BIO_free is called on a BIO chain, it will only destruct one BIO, resulting in a memory leak. .Pp .Fn BIO_free_all destructs an entire BIO chain. It does not halt if an error occurs destructing an individual BIO in the chain. If .Fa a is a .Dv NULL pointer, no action occurs. Calling .Fn BIO_free_all on a single BIO has the same effect as .Fn BIO_vfree . .Pp Common I/O functions are documented in .Xr BIO_read 3 . Forming chains is explained in .Xr BIO_push 3 ; inspecting them is explained in .Xr BIO_find_type 3 . For more details about the different kinds of BIOs, see the individual .Vt BIO_METHOD manual pages. .Sh RETURN VALUES .Fn BIO_new returns a newly constructed .Vt BIO object or .Dv NULL on failure. .Pp .Fn BIO_set and .Fn BIO_free return 1 for success or 0 for failure. .Sh EXAMPLES Create a memory BIO: .Pp .Dl BIO *mem = BIO_new(BIO_s_mem()); .Sh SEE ALSO .Xr BIO_ctrl 3 , .Xr BIO_f_base64 3 , .Xr BIO_f_buffer 3 , .Xr BIO_f_cipher 3 , .Xr BIO_f_md 3 , .Xr BIO_f_null 3 , .Xr BIO_f_ssl 3 , .Xr BIO_find_type 3 , .Xr BIO_get_ex_new_index 3 , .Xr BIO_printf 3 , .Xr BIO_push 3 , .Xr BIO_read 3 , .Xr BIO_s_accept 3 , .Xr BIO_s_bio 3 , .Xr BIO_s_connect 3 , .Xr BIO_s_fd 3 , .Xr BIO_s_file 3 , .Xr BIO_s_mem 3 , .Xr BIO_s_null 3 , .Xr BIO_s_socket 3 , .Xr BIO_set_callback 3 , .Xr BIO_should_retry 3