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Title "BIO 7" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
bio - Basic I/O abstraction Header "SYNOPSIS" .Vb 1 #include <openssl/bio.h> .Ve Header "DESCRIPTION" A \s-1BIO\s0 is an I/O abstraction, it hides many of the underlying I/O details from an application. If an application uses a \s-1BIO\s0 for its I/O it can transparently handle \s-1SSL\s0 connections, unencrypted network connections and file I/O.

There are two types of \s-1BIO,\s0 a source/sink \s-1BIO\s0 and a filter \s-1BIO.\s0

As its name implies a source/sink \s-1BIO\s0 is a source and/or sink of data, examples include a socket \s-1BIO\s0 and a file \s-1BIO.\s0

A filter \s-1BIO\s0 takes data from one \s-1BIO\s0 and passes it through to another, or the application. The data may be left unmodified (for example a message digest \s-1BIO\s0) or translated (for example an encryption \s-1BIO\s0). The effect of a filter \s-1BIO\s0 may change according to the I/O operation it is performing: for example an encryption \s-1BIO\s0 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 \s-1BIO\s0 is a chain with one component). A chain normally consists of one source/sink \s-1BIO\s0 and one or more filter BIOs. Data read from or written to the first \s-1BIO\s0 then traverses the chain to the end (normally a source/sink \s-1BIO\s0).

Some BIOs (such as memory BIOs) can be used immediately after calling \fBBIO_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 \s-1BIO\s0 chain it will only free one \s-1BIO\s0 resulting in a memory leak.

Calling BIO_free_all() on a single \s-1BIO\s0 has the same effect as calling \fBBIO_free() on it other than the discarded return value.

Normally the type argument is supplied by a function which returns a pointer to a \s-1BIO_METHOD.\s0 There is a naming convention for such functions: a source/sink \s-1BIO\s0 typically starts with BIO_s_ and a filter \s-1BIO\s0 with BIO_f_.

Header "EXAMPLES" Create a memory \s-1BIO:\s0

.Vb 1 BIO *mem = BIO_new(BIO_s_mem()); .Ve

Header "SEE ALSO" \fBBIO_ctrl\|(3), \fBBIO_f_base64\|(3), BIO_f_buffer\|(3), \fBBIO_f_cipher\|(3), BIO_f_md\|(3), \fBBIO_f_null\|(3), BIO_f_ssl\|(3), \fBBIO_f_readbuffer\|(3), \fBBIO_find_type\|(3), BIO_new\|(3), \fBBIO_new_bio_pair\|(3), \fBBIO_push\|(3), BIO_read_ex\|(3), \fBBIO_s_accept\|(3), BIO_s_bio\|(3), \fBBIO_s_connect\|(3), BIO_s_fd\|(3), \fBBIO_s_file\|(3), BIO_s_mem\|(3), \fBBIO_s_null\|(3), BIO_s_socket\|(3), \fBBIO_set_callback\|(3), \fBBIO_should_retry\|(3) Header "COPYRIGHT" Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.