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_PRINTF(3) OpenSSL BIO_PRINTF(3)
BIO_printf, BIO_vprintf, BIO_snprintf, BIO_vsnprintf - formatted output
to a BIO
int BIO_printf(BIO *bio, const char *format, ...)
int BIO_vprintf(BIO *bio, const char *format, va_list args)
int BIO_snprintf(char *buf, size_t n, const char *format, ...)
int BIO_vsnprintf(char *buf, size_t n, const char *format, va_list args)
BIO_printf() is similar to the standard C printf() function, except
that the output is sent to the specified BIO, bio, rather than standard
output. All common format specifiers are supported.
BIO_vprintf() is similar to the vprintf() function found on many
platforms, the output is sent to the specified BIO, bio, rather than
standard output. All common format specifiers are supported. The
argument list args is a stdarg argument list.
BIO_snprintf() is for platforms that do not have the common snprintf()
function. It is like sprintf() except that the size parameter, n,
specifies the size of the output buffer.
BIO_vsnprintf() is to BIO_snprintf() as BIO_vprintf() is to
All functions return the number of bytes written, or -1 on error. For
BIO_snprintf() and BIO_vsnprintf() this includes when the output buffer
is too small.
Copyright 2017 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
1.1.1q 2022-07-05 BIO_PRINTF(3)