396 lines
18 KiB
HTML
396 lines
18 KiB
HTML
<?xml version="1.0" encoding="utf-8" ?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="generator" content="Docutils 0.10: http://docutils.sourceforge.net/" />
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<title></title>
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<meta name="author" content="Arvid Norberg, arvid@rasterbar.com" />
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<link rel="stylesheet" type="text/css" href="../../css/base.css" />
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<link rel="stylesheet" href="style.css" type="text/css" />
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<style type="text/css">
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/* Hides from IE-mac \*/
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* html pre { height: 1%; }
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/* End hide from IE-mac */
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</style>
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</head>
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<body>
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<div class="document">
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<div id="container">
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<div id="headerNav">
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<ul>
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<li class="first"><a href="/">Home</a></li>
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<li><a href="../../products.html">Products</a></li>
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<li><a href="../../contact.html">Contact</a></li>
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</ul>
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</div>
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<div id="header">
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<div id="orange"></div>
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<div id="logo"></div>
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</div>
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<div id="main">
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<table class="docinfo" frame="void" rules="none">
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<col class="docinfo-name" />
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<col class="docinfo-content" />
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<tbody valign="top">
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<tr><th class="docinfo-name">Author:</th>
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<td>Arvid Norberg, <a class="last reference external" href="mailto:arvid@rasterbar.com">arvid@rasterbar.com</a></td></tr>
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</tbody>
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</table>
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<div class="section" id="libtorrent-plugins">
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<h1>libtorrent plugins</h1>
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<div class="contents topic" id="contents">
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<p class="topic-title first">Contents</p>
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<ul class="simple">
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<li><a class="reference internal" href="#libtorrent-plugins" id="id1">libtorrent plugins</a><ul>
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<li><a class="reference internal" href="#a-word-of-caution" id="id2">a word of caution</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#plugin-interface" id="id3">plugin interface</a></li>
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<li><a class="reference internal" href="#plugin" id="id4">plugin</a></li>
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<li><a class="reference internal" href="#torrent-plugin" id="id5">torrent_plugin</a><ul>
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<li><a class="reference internal" href="#new-connection" id="id6">new_connection()</a></li>
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<li><a class="reference internal" href="#on-piece-pass-on-piece-fail" id="id7">on_piece_pass() on_piece_fail()</a></li>
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<li><a class="reference internal" href="#tick" id="id8">tick()</a></li>
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<li><a class="reference internal" href="#on-pause-on-resume" id="id9">on_pause() on_resume()</a></li>
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<li><a class="reference internal" href="#on-files-checked" id="id10">on_files_checked()</a></li>
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<li><a class="reference internal" href="#on-add-peer" id="id11">on_add_peer()</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#peer-plugin" id="id12">peer_plugin</a></li>
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<li><a class="reference internal" href="#disk-buffer-holder" id="id13">disk_buffer_holder</a></li>
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<li><a class="reference internal" href="#custom-alerts" id="id14">custom alerts</a></li>
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</ul>
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</div>
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<p>libtorrent has a plugin interface for implementing extensions to the protocol.
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These can be general extensions for transferring metadata or peer exchange
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extensions, or it could be used to provide a way to customize the protocol
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to fit a particular (closed) network.</p>
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<p>In short, the plugin interface makes it possible to:</p>
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<ul class="simple">
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<li>register extension messages (sent in the extension handshake), see
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<a class="reference external" href="extension_protocol.html">extensions</a>.</li>
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<li>add data and parse data from the extension handshake.</li>
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<li>send extension messages and standard bittorrent messages.</li>
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<li>override or block the handling of standard bittorrent messages.</li>
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<li>save and restore state via the session state</li>
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<li>see all alerts that are posted</li>
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</ul>
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<div class="section" id="a-word-of-caution">
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<h2>a word of caution</h2>
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<p>Writing your own plugin is a very easy way to introduce serious bugs such as
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dead locks and race conditions. Since a plugin has access to internal
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structures it is also quite easy to sabotage libtorrent's operation.</p>
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<p>All the callbacks in this interface are called with the main libtorrent thread
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mutex locked. And they are always called from the libtorrent network thread. In
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case portions of your plugin are called from other threads, typically the main
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thread, you cannot use any of the member functions on the internal structures
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in libtorrent, since those require the mutex to be locked. Futhermore, you would
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also need to have a mutex on your own shared data within the plugin, to make
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sure it is not accessed at the same time from the libtorrent thread (through a
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callback). See <a class="reference external" href="http://www.boost.org/doc/html/mutex.html">boost thread's mutex</a>. If you need to send out a message from
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another thread, it is advised to use an internal queue, and do the actual
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sending in <tt class="docutils literal">tick()</tt>.</p>
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<p>Since the plugin interface gives you easy access to internal structures, it
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is not supported as a stable API. Plugins should be considered spcific to a
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specific version of libtorrent. Although, in practice the internals mostly
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don't change that dramatically.</p>
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</div>
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</div>
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<div class="section" id="plugin-interface">
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<h1>plugin interface</h1>
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<p>The plugin interface consists of three base classes that the plugin may
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implement. These are called <tt class="docutils literal">plugin</tt>, <tt class="docutils literal">torrent_plugin</tt> and <tt class="docutils literal">peer_plugin</tt>.
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They are found in the <tt class="docutils literal"><libtorrent/extensions.hpp></tt> header.</p>
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<p>These plugins are instantiated for each session, torrent and possibly each peer,
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respectively.</p>
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<p>For plugins that only need per torrent state, it is enough to only implement
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<tt class="docutils literal">torrent_plugin</tt> and pass a constructor function or function object to
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<tt class="docutils literal"><span class="pre">session::add_extension()</span></tt> or <tt class="docutils literal"><span class="pre">torrent_handle::add_extension()</span></tt> (if the
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torrent has already been started and you want to hook in the extension at
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run-time).</p>
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<p>The signature of the function is:</p>
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<pre class="literal-block">
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boost::shared_ptr<torrent_plugin> (*)(torrent*, void*);
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</pre>
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<p>The first argument is the internal torrent object, the second argument
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is the userdata passed to <tt class="docutils literal"><span class="pre">session::add_torrent()</span></tt> or
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<tt class="docutils literal"><span class="pre">torrent_handle::add_extension()</span></tt>.</p>
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<p>The function should return a <tt class="docutils literal"><span class="pre">boost::shared_ptr<torrent_plugin></span></tt> which
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may or may not be 0. If it is a null pointer, the extension is simply ignored
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for this torrent. If it is a valid pointer (to a class inheriting
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<tt class="docutils literal">torrent_plugin</tt>), it will be associated with this torrent and callbacks
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will be made on torrent events.</p>
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<p>For more elaborate plugins which require session wide state, you would
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implement <tt class="docutils literal">plugin</tt>, construct an object (in a <tt class="docutils literal"><span class="pre">boost::shared_ptr</span></tt>) and pass
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it in to <tt class="docutils literal"><span class="pre">session::add_extension()</span></tt>.</p>
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</div>
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<div class="section" id="plugin">
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<h1>plugin</h1>
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<pre class="literal-block">
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struct plugin
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{
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virtual ~plugin();
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virtual boost::shared_ptr<torrent_plugin> new_torrent(torrent* t, void* user);
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virtual void added(boost::weak_ptr<aux::session_impl> s);
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virtual void on_alert(alert const* a);
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virtual void on_tick();
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virtual void save_state(entry& ent) const;
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virtual void load_state(lazy_entry const& ent);
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};
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</pre>
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</div>
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<div class="section" id="torrent-plugin">
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<h1>torrent_plugin</h1>
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<p>The synopsis for <tt class="docutils literal">torrent_plugin</tt> follows:</p>
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<pre class="literal-block">
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struct torrent_plugin
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{
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virtual ~torrent_plugin();
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virtual boost::shared_ptr<peer_plugin> new_connection(peer_connection*);
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virtual void on_piece_pass(int index);
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virtual void on_piece_failed(int index);
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virtual void tick();
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virtual bool on_pause();
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virtual bool on_resume();
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virtual void on_files_checked();
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virtual void on_state(int s);
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enum flags_t {
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first_time = 1,
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filtered = 2
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};
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virtual void on_add_peer(tcp::endpoint const& ip
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, int src, int flags);
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};
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</pre>
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<p>This is the base class for a torrent_plugin. Your derived class is (if added
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as an extension) instantiated for each torrent in the session. The callback
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hook functions are defined as follows.</p>
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<div class="section" id="new-connection">
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<h2>new_connection()</h2>
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<pre class="literal-block">
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boost::shared_ptr<peer_plugin> new_connection(peer_connection*);
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</pre>
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<p>This function is called each time a new peer is connected to the torrent. You
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may choose to ignore this by just returning a default constructed
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<tt class="docutils literal">shared_ptr</tt> (in which case you don't need to override this member
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function).</p>
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<p>If you need an extension to the peer connection (which most plugins do) you
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are supposed to return an instance of your <tt class="docutils literal">peer_plugin</tt> class. Which in
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turn will have its hook functions called on event specific to that peer.</p>
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<p>The <tt class="docutils literal">peer_connection</tt> will be valid as long as the <tt class="docutils literal">shared_ptr</tt> is being
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held by the torrent object. So, it is generally a good idea to not keep a
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<tt class="docutils literal">shared_ptr</tt> to your own peer_plugin. If you want to keep references to it,
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use <tt class="docutils literal">weak_ptr</tt>.</p>
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<p>If this function throws an exception, the connection will be closed.</p>
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</div>
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<div class="section" id="on-piece-pass-on-piece-fail">
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<h2>on_piece_pass() on_piece_fail()</h2>
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<pre class="literal-block">
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void on_piece_pass(int index);
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void on_piece_failed(int index);
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</pre>
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<p>These hooks are called when a piece passes the hash check or fails the hash
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check, respectively. The <tt class="docutils literal">index</tt> is the piece index that was downloaded.
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It is possible to access the list of peers that participated in sending the
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piece through the <tt class="docutils literal">torrent</tt> and the <tt class="docutils literal">piece_picker</tt>.</p>
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</div>
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<div class="section" id="tick">
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<h2>tick()</h2>
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<pre class="literal-block">
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void tick();
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</pre>
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<p>This hook is called approximately once per second. It is a way of making it
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easy for plugins to do timed events, for sending messages or whatever.</p>
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</div>
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<div class="section" id="on-pause-on-resume">
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<h2>on_pause() on_resume()</h2>
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<pre class="literal-block">
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bool on_pause();
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bool on_resume();
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</pre>
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<p>These hooks are called when the torrent is paused and unpaused respectively.
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The return value indicates if the event was handled. A return value of
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<tt class="docutils literal">true</tt> indicates that it was handled, and no other plugin after this one
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will have this hook function called, and the standard handler will also not be
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invoked. So, returning true effectively overrides the standard behavior of
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pause or unpause.</p>
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<p>Note that if you call <tt class="docutils literal">pause()</tt> or <tt class="docutils literal">resume()</tt> on the torrent from your
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handler it will recurse back into your handler, so in order to invoke the
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standard handler, you have to keep your own state on whether you want standard
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behavior or overridden behavior.</p>
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</div>
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<div class="section" id="on-files-checked">
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<h2>on_files_checked()</h2>
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<pre class="literal-block">
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void on_files_checked();
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</pre>
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<p>This function is called when the initial files of the torrent have been
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checked. If there are no files to check, this function is called immediately.</p>
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<p>i.e. This function is always called when the torrent is in a state where it
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can start downloading.</p>
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</div>
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<div class="section" id="on-add-peer">
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<h2>on_add_peer()</h2>
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<pre class="literal-block">
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enum flags_t {
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first_time = 1,
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filtered = 2
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};
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virtual void on_add_peer(tcp::endpoint const& ip
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, int src, int flags);
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</pre>
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<p>This function is called whenever we hear about a peer from any peer source,
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such as the tracker, PEX, DHT or Local peer discovery.</p>
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<p><tt class="docutils literal">src</tt> is a bitmask of <tt class="docutils literal"><span class="pre">peer_info::peer_source_flags</span></tt>:</p>
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<pre class="literal-block">
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enum peer_source_flags
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{
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tracker = 0x1,
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dht = 0x2,
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pex = 0x4,
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lsd = 0x8,
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resume_data = 0x10,
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incoming = 0x20
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};
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</pre>
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<p><tt class="docutils literal">flags</tt> is a bitmask of:</p>
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<pre class="literal-block">
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enum flags_t {
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first_time = 1,
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filtered = 2
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};
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</pre>
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<p>If the <tt class="docutils literal">filtered</tt> flag is set, it means the peer wasn't added to the
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peer list because of and IP filter, port filter, reserved ports filter.</p>
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</div>
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</div>
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<div class="section" id="peer-plugin">
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<h1>peer_plugin</h1>
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<pre class="literal-block">
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struct peer_plugin
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{
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virtual ~peer_plugin();
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virtual void add_handshake(entry&);
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virtual bool on_handshake(char const* reserved_bits);
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virtual bool on_extension_handshake(lazy_entry const& h);
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virtual bool on_choke();
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virtual bool on_unchoke();
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virtual bool on_interested();
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virtual bool on_not_interested();
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virtual bool on_have(int index);
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virtual bool on_bitfield(bitfield const& bits);
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virtual bool on_have_all();
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virtual bool on_have_none();
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virtual bool on_allowed_fast(int index);
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virtual bool on_request(peer_request const& req);
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virtual bool on_piece(peer_request const& piece, disk_buffer_holder& buffer);
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virtual bool on_cancel(peer_request const& req);
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virtual bool on_reject(peer_request const& req);
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virtual bool on_suggest(int index);
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virtual bool on_extended(int length
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, int msg, buffer::const_interval body);
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virtual bool on_unknown_message(int length, int msg
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, buffer::const_interval body);
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virtual void on_piece_pass(int index);
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virtual void on_piece_failed(int index);
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virtual void tick();
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virtual bool write_request(peer_request const& r);
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};
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</pre>
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</div>
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<div class="section" id="disk-buffer-holder">
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<h1>disk_buffer_holder</h1>
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<pre class="literal-block">
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struct disk_buffer_holder
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{
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disk_buffer_holder(aux::session_impl& s, char* b);
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~disk_buffer_holder();
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char* release();
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char* buffer();
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};
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</pre>
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<p>The disk buffer holder acts like a <tt class="docutils literal">scoped_ptr</tt> that frees a disk buffer
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when it's destructed, unless it's released. <tt class="docutils literal">release</tt> returns the disk
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buffer and transferres ownership and responsibility to free it to the caller.</p>
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<p>A disk buffer is freed by passing it to <tt class="docutils literal"><span class="pre">session_impl::free_disk_buffer()</span></tt>.</p>
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<p><tt class="docutils literal">buffer()</tt> returns the pointer without transferring responsibility. If
|
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this buffer has been released, <tt class="docutils literal">buffer()</tt> will return 0.</p>
|
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</div>
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<div class="section" id="custom-alerts">
|
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<h1>custom alerts</h1>
|
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<p>Since plugins are running within internal libtorrent threads, one convenient
|
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way to communicate with the client is to post custom alerts.</p>
|
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<p>The expected interface of any alert, apart from deriving from the <tt class="docutils literal">alert</tt>
|
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base class, looks like this:</p>
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<pre class="literal-block">
|
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const static int alert_type = <em><unique alert ID></em>;
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virtual int type() const { return alert_type; }
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virtual std::string message() const;
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virtual std::auto_ptr<alert> clone() const
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{ return std::auto_ptr<alert>(new name(*this)); }
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const static int static_category = <em><bitmask of alert::category_t flags></em>;
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virtual int category() const { return static_category; }
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virtual char const* what() const { return <em><string literal of the name of this alert></em>; }
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</pre>
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<p>The <tt class="docutils literal">alert_type</tt> is used for the type-checking in <tt class="docutils literal">alert_cast</tt>. It must not collide with
|
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any other alert. The built-in alerts in libtorrent will not use alert type IDs greater than
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<tt class="docutils literal">user_alert_id</tt>. When defining your own alert, make sure it's greater than this constant.</p>
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<p><tt class="docutils literal">type()</tt> is the run-time equivalence of the <tt class="docutils literal">alert_type</tt>.</p>
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<p>The <tt class="docutils literal">message()</tt> virtual function is expected to construct a useful string representation
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of the alert and the event or data it represents. Something convenient to put in a log file
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for instance.</p>
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<p><tt class="docutils literal">clone()</tt> is used internally to copy alerts. The suggested implementation of simply
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allocating a new instance as a copy of <tt class="docutils literal">*this</tt> is all that's expected.</p>
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<p>The static category is required for checking wether or not the category for a specific alert
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is enabled or not, without instantiating the alert. The <tt class="docutils literal">category</tt> virtual function is
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the run-time equivalence.</p>
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<p>The <tt class="docutils literal">what()</tt> virtual function may simply be a string literal of the class name of
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your alert.</p>
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<p>For more information, see the <a class="reference external" href="reference-Alerts.html">alert section</a>.</p>
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</div>
|
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</div>
|
|
<div id="footer">
|
|
<span>Copyright © 2005-2013 Rasterbar Software.</span>
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</div>
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</div>
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<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
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</script>
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<script type="text/javascript">
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_uacct = "UA-1599045-1";
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