DragonFly On-Line Manual Pages
BIO(3) DragonFly Library Functions Manual BIO(3)
BIO -- I/O abstraction
A BIO is an I/O abstraction, it hides many of the underlying I/O details
from an application. If an application uses a BIO for its I/O, it can
transparently handle SSL connections, unencrypted network connections and
There are two types of BIO, a source/sink BIO and a filter BIO.
As its name implies, a source/sink BIO is a source and/or sink of data,
examples include a socket BIO and a file BIO.
A filter BIO takes data from one BIO and passes it through to another, or
to the application. The data may be left unmodified (for example a mes-
sage digest BIO) or translated (for example 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
being written to and decrypt data if it is being read from.
BIOs can be joined together to form a chain (a single BIO is a chain with
one component). A chain normally consist of one source/sink BIO and one
or more filter BIOs. Data read from or written to the first BIO then
traverses the chain to the end (normally a source/sink BIO).
BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3),
BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3), BIO_find_type(3), BIO_new(3),
BIO_new_bio_pair(3), BIO_push(3), BIO_read(3), BIO_s_accept(3),
BIO_s_bio(3), BIO_s_connect(3), BIO_s_fd(3), BIO_s_file(3), BIO_s_mem(3),
BIO_s_null(3), BIO_s_socket(3), BIO_set_callback(3), BIO_should_retry(3)
DragonFly 4.7 July 17, 2014 DragonFly 4.7
BIO_GET_DATA(3) OpenSSL BIO_GET_DATA(3)
BIO_set_data, BIO_get_data, BIO_set_init, BIO_get_init,
BIO_set_shutdown, BIO_get_shutdown - functions for managing BIO state
void BIO_set_data(BIO *a, void *ptr);
void *BIO_get_data(BIO *a);
void BIO_set_init(BIO *a, int init);
int BIO_get_init(BIO *a);
void BIO_set_shutdown(BIO *a, int shut);
int BIO_get_shutdown(BIO *a);
These functions are mainly useful when implementing a custom BIO.
The BIO_set_data() function associates the custom data pointed to by
ptr with the BIO. This data can subsequently be retrieved via a call to
BIO_get_data(). This can be used by custom BIOs for storing
implementation specific information.
The BIO_set_init() function sets the value of the BIO's "init" flag to
indicate whether initialisation has been completed for this BIO or not.
A nonzero 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 complete until after additional steps have occurred (for
example through calling custom ctrls). The BIO_get_init() function
returns the value of the "init" flag.
The BIO_set_shutdown() and BIO_get_shutdown() functions set and get the
state of this BIO's shutdown (i.e. BIO_CLOSE) flag. If set then the
underlying resource is also closed when the BIO is freed.
BIO_get_data() returns a pointer to the implementation specific custom
data associated with this BIO, or NULL if none has been set.
BIO_get_init() returns the state of the BIO's init flag.
BIO_get_shutdown() returns the stat of the BIO's shutdown (i.e.
The functions described here were added in OpenSSL 1.1.0.
Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
1.1.1t 2023-02-07 BIO_GET_DATA(3)