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- =pod
- =head1 NAME
- bio - Basic I/O abstraction
- =head1 SYNOPSIS
- =for openssl generic
- #include <openssl/bio.h>
- =head1 DESCRIPTION
- 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 file I/O.
- There are two type 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 the application. The data may be left unmodified (for
- example a message 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).
- Some BIOs (such as memory BIOs) can be used immediately after calling
- BIO_new(). Others (such as file BIOs) need some additional initialization,
- and frequently a utility function exists to create and initialize such BIOs.
- If BIO_free() is called on a BIO chain it will only free one BIO resulting
- in a memory leak.
- Calling BIO_free_all() on a single BIO has the same effect as calling
- BIO_free() on it other than the discarded return value.
- Normally the I<type> argument is supplied by a function which returns a
- pointer to a BIO_METHOD. There is a naming convention for such functions:
- a source/sink BIO typically starts with I<BIO_s_> and
- a filter BIO with I<BIO_f_>.
- =head1 EXAMPLES
- Create a memory BIO:
- BIO *mem = BIO_new(BIO_s_mem());
- =head1 SEE ALSO
- L<BIO_ctrl(3)>,
- L<BIO_f_base64(3)>, L<BIO_f_buffer(3)>,
- L<BIO_f_cipher(3)>, L<BIO_f_md(3)>,
- L<BIO_f_null(3)>, L<BIO_f_ssl(3)>,
- L<BIO_find_type(3)>, L<BIO_new(3)>,
- L<BIO_new_bio_pair(3)>,
- L<BIO_push(3)>, L<BIO_read_ex(3)>,
- L<BIO_s_accept(3)>, L<BIO_s_bio(3)>,
- L<BIO_s_connect(3)>, L<BIO_s_fd(3)>,
- L<BIO_s_file(3)>, L<BIO_s_mem(3)>,
- L<BIO_s_null(3)>, L<BIO_s_socket(3)>,
- L<BIO_set_callback(3)>,
- L<BIO_should_retry(3)>
- =head1 COPYRIGHT
- Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
- Licensed under the Apache License 2.0 (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
- L<https://www.openssl.org/source/license.html>.
- =cut
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