Edit File: bio.7
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" bio \- Basic I/O abstraction .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/bio.h> .Ve .SH "DESCRIPTION" .IX 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. .PP There are two type of \s-1BIO,\s0 a source/sink \s-1BIO\s0 and a filter \s-1BIO.\s0 .PP 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 .PP 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. .PP BIOs can be joined together to form a chain (a single \s-1BIO\s0 is a chain with one component). A chain normally consist 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). .PP Some BIOs (such as memory BIOs) can be used immediately after calling \&\fBBIO_new()\fR. Others (such as file BIOs) need some additional initialization, and frequently a utility function exists to create and initialize such BIOs. .PP If \fBBIO_free()\fR is called on a \s-1BIO\s0 chain it will only free one \s-1BIO\s0 resulting in a memory leak. .PP Calling \fBBIO_free_all()\fR on a single \s-1BIO\s0 has the same effect as calling \&\fBBIO_free()\fR on it other than the discarded return value. .PP Normally the \fBtype\fR 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 is normally called BIO_s_*() and a filter \s-1BIO\s0 BIO_f_*(); .SH "EXAMPLES" .IX Header "EXAMPLES" Create a memory \s-1BIO:\s0 .PP .Vb 1 \& BIO *mem = BIO_new(BIO_s_mem()); .Ve .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBBIO_ctrl\fR\|(3), \&\fBBIO_f_base64\fR\|(3), \fBBIO_f_buffer\fR\|(3), \&\fBBIO_f_cipher\fR\|(3), \fBBIO_f_md\fR\|(3), \&\fBBIO_f_null\fR\|(3), \fBBIO_f_ssl\fR\|(3), \&\fBBIO_find_type\fR\|(3), \fBBIO_new\fR\|(3), \&\fBBIO_new_bio_pair\fR\|(3), \&\fBBIO_push\fR\|(3), \fBBIO_read_ex\fR\|(3), \&\fBBIO_s_accept\fR\|(3), \fBBIO_s_bio\fR\|(3), \&\fBBIO_s_connect\fR\|(3), \fBBIO_s_fd\fR\|(3), \&\fBBIO_s_file\fR\|(3), \fBBIO_s_mem\fR\|(3), \&\fBBIO_s_null\fR\|(3), \fBBIO_s_socket\fR\|(3), \&\fBBIO_set_callback\fR\|(3), \&\fBBIO_should_retry\fR\|(3) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2000\-2019 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (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>.