1BIO(7)                              OpenSSL                             BIO(7)
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NAME

6       bio - Basic I/O abstraction
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SYNOPSIS

9        #include <openssl/bio.h>
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DESCRIPTION

12       A BIO is an I/O abstraction, it hides many of the underlying I/O
13       details from an application. If an application uses a BIO for its I/O
14       it can transparently handle SSL connections, unencrypted network
15       connections and file I/O.
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17       There are two type of BIO, a source/sink BIO and a filter BIO.
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19       As its name implies a source/sink BIO is a source and/or sink of data,
20       examples include a socket BIO and a file BIO.
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22       A filter BIO takes data from one BIO and passes it through to another,
23       or the application. The data may be left unmodified (for example a
24       message digest BIO) or translated (for example an encryption BIO). The
25       effect of a filter BIO may change according to the I/O operation it is
26       performing: for example an encryption BIO will encrypt data if it is
27       being written to and decrypt data if it is being read from.
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29       BIOs can be joined together to form a chain (a single BIO is a chain
30       with one component). A chain normally consist of one source/sink BIO
31       and one or more filter BIOs. Data read from or written to the first BIO
32       then traverses the chain to the end (normally a source/sink BIO).
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34       Some BIOs (such as memory BIOs) can be used immediately after calling
35       BIO_new(). Others (such as file BIOs) need some additional
36       initialization, and frequently a utility function exists to create and
37       initialize such BIOs.
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39       If BIO_free() is called on a BIO chain it will only free one BIO
40       resulting in a memory leak.
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42       Calling BIO_free_all() on a single BIO has the same effect as calling
43       BIO_free() on it other than the discarded return value.
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45       Normally the type argument is supplied by a function which returns a
46       pointer to a BIO_METHOD. There is a naming convention for such
47       functions: a source/sink BIO is normally called BIO_s_*() and a filter
48       BIO BIO_f_*();
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EXAMPLES

51       Create a memory BIO:
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53        BIO *mem = BIO_new(BIO_s_mem());
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SEE ALSO

56       BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3),
57       BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3), BIO_find_type(3), BIO_new(3),
58       BIO_new_bio_pair(3), BIO_push(3), BIO_read_ex(3), BIO_s_accept(3),
59       BIO_s_bio(3), BIO_s_connect(3), BIO_s_fd(3), BIO_s_file(3),
60       BIO_s_mem(3), BIO_s_null(3), BIO_s_socket(3), BIO_set_callback(3),
61       BIO_should_retry(3)
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64       Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
65
66       Licensed under the OpenSSL license (the "License").  You may not use
67       this file except in compliance with the License.  You can obtain a copy
68       in the file LICENSE in the source distribution or at
69       <https://www.openssl.org/source/license.html>.
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731.1.1l                            2021-09-15                            BIO(7)
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