112 lines
5.5 KiB
HTML
112 lines
5.5 KiB
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<?xml version="1.0" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>BIO_get_rpoll_descriptor</title>
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<meta http-equiv="content-type" content="text/html; charset=utf-8" />
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<link rev="made" href="mailto:" />
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</head>
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<body>
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<ul id="index">
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<li><a href="#NAME">NAME</a></li>
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<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
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<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
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<li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
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<li><a href="#SEE-ALSO">SEE ALSO</a></li>
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<li><a href="#HISTORY">HISTORY</a></li>
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<li><a href="#COPYRIGHT">COPYRIGHT</a></li>
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</ul>
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<h1 id="NAME">NAME</h1>
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<p>BIO_get_rpoll_descriptor, BIO_get_wpoll_descriptor - obtain a structure which can be used to determine when a BIO object can next be read or written</p>
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<h1 id="SYNOPSIS">SYNOPSIS</h1>
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<pre><code> #include <openssl/bio.h>
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typedef struct bio_poll_descriptor_st {
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uint32_t type;
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union {
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int fd;
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void *custom;
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uintptr_t custom_ui;
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} value;
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} BIO_POLL_DESCRIPTOR;
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int BIO_get_rpoll_descriptor(BIO *b, BIO_POLL_DESCRIPTOR *desc);
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int BIO_get_wpoll_descriptor(BIO *b, BIO_POLL_DESCRIPTOR *desc);</code></pre>
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<h1 id="DESCRIPTION">DESCRIPTION</h1>
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<p>BIO_get_rpoll_descriptor() and BIO_get_wpoll_descriptor(), on success, fill <i>*desc</i> with a poll descriptor. A poll descriptor is a tagged union structure which represents some kind of OS or non-OS resource which can be used to synchronise on I/O availability events.</p>
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<p>BIO_get_rpoll_descriptor() outputs a descriptor which can be used to determine when the BIO can (potentially) next be read, and BIO_get_wpoll_descriptor() outputs a descriptor which can be used to determine when the BIO can (potentially) next be written.</p>
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<p>It is permissible for BIO_get_rpoll_descriptor() and BIO_get_wpoll_descriptor() to output the same descriptor.</p>
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<p>Poll descriptors can represent different kinds of information. A typical kind of resource which might be represented by a poll descriptor is an OS file descriptor which can be used with APIs such as select().</p>
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<p>The kinds of poll descriptor defined by OpenSSL are:</p>
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<dl>
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<dt id="BIO_POLL_DESCRIPTOR_TYPE_NONE">BIO_POLL_DESCRIPTOR_TYPE_NONE</dt>
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<dd>
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<p>Represents the absence of a valid poll descriptor. It may be used by BIO_get_rpoll_descriptor() or BIO_get_wpoll_descriptor() to indicate that the BIO is not pollable for readability or writeability respectively.</p>
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<p>For this type, no field within the <i>value</i> field of the <b>BIO_POLL_DESCRIPTOR</b> is valid.</p>
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</dd>
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<dt id="BIO_POLL_DESCRIPTOR_TYPE_SOCK_FD">BIO_POLL_DESCRIPTOR_TYPE_SOCK_FD</dt>
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<dd>
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<p>The poll descriptor represents an OS socket resource. The field <i>value.fd</i> in the <b>BIO_POLL_DESCRIPTOR</b> is valid if it is not set to -1.</p>
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<p>The resource is whatever kind of handle is used by a given OS to represent sockets, which may vary by OS. For example, on Windows, the value is a <b>SOCKET</b> for use with the Winsock API. On POSIX-like platforms, it is a file descriptor.</p>
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<p>Where a poll descriptor of this type is output by BIO_get_rpoll_descriptor(), it should be polled for readability to determine when the BIO might next be able to successfully complete a BIO_read() operation; likewise, where a poll descriptor of this type is output by BIO_get_wpoll_descriptor(), it should be polled for writeability to determine when the BIO might next be able to successfully complete a BIO_write() operation.</p>
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</dd>
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<dt id="BIO_POLL_DESCRIPTOR_CUSTOM_START">BIO_POLL_DESCRIPTOR_CUSTOM_START</dt>
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<dd>
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<p>Type values beginning with this value (inclusive) are reserved for application allocation for custom poll descriptor types. Any of the definitions in the union field <i>value</i> can be used by the application arbitrarily as opaque values.</p>
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</dd>
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</dl>
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<p>Because poll descriptors are a tagged union structure, they can represent different kinds of information. New types of poll descriptor may be defined, including by applications, according to their needs.</p>
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<h1 id="RETURN-VALUES">RETURN VALUES</h1>
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<p>The functions BIO_get_rpoll_descriptor() and BIO_get_wpoll_descriptor() return 1 on success and 0 on failure.</p>
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<p>These functions are permitted to succeed and initialise <i>*desc</i> with a poll descriptor of type <b>BIO_POLL_DESCRIPTOR_TYPE_NONE</b> to indicate that the BIO is not pollable for readability or writeability respectively.</p>
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<h1 id="SEE-ALSO">SEE ALSO</h1>
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<p><a href="../man3/SSL_handle_events.html">SSL_handle_events(3)</a>, <a href="../man3/SSL_get_event_timeout.html">SSL_get_event_timeout(3)</a>, <a href="../man3/SSL_get_rpoll_descriptor.html">SSL_get_rpoll_descriptor(3)</a>, <a href="../man3/SSL_get_wpoll_descriptor.html">SSL_get_wpoll_descriptor(3)</a>, <a href="../man7/bio.html">bio(7)</a></p>
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<h1 id="HISTORY">HISTORY</h1>
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<p>The SSL_get_rpoll_descriptor() and SSL_get_wpoll_descriptor() functions were added in OpenSSL 3.2.</p>
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<h1 id="COPYRIGHT">COPYRIGHT</h1>
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<p>Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.</p>
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<p>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 <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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</body>
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</html>
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