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<title>LWP::Protocol - Base class for LWP protocols</title>
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<h1><a>LWP::Protocol - Base class for LWP protocols</a></h1>
<p><a name="__index__"></a></p>
<!-- INDEX BEGIN -->
<ul>
<li><a href="#name">NAME</a></li>
<li><a href="#synopsis">SYNOPSIS</a></li>
<li><a href="#description">DESCRIPTION</a></li>
<li><a href="#see_also">SEE ALSO</a></li>
<li><a href="#copyright">COPYRIGHT</a></li>
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<p>
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<h1><a name="name">NAME</a></h1>
<p>LWP::Protocol - Base class for LWP protocols</p>
<p>
</p>
<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
<span class="keyword">package</span> <span class="variable">LWP::Protocol::foo</span><span class="operator">;</span>
<span class="keyword">require</span> <span class="variable">LWP::Protocol</span><span class="operator">;</span>
<span class="variable">@ISA</span><span class="operator">=</span><span class="string">qw(LWP::Protocol)</span><span class="operator">;</span>
</pre>
<p>
</p>
<hr />
<h1><a name="description">DESCRIPTION</a></h1>
<p>This class is used a the base class for all protocol implementations
supported by the LWP library.</p>
<p>When creating an instance of this class using
<a href="#item_create"><code>LWP::Protocol::create($url)</code></a>, and you get an initialised subclass
appropriate for that access method. In other words, the
LWP::Protocol::create() function calls the constructor for one of its
subclasses.</p>
<p>All derived LWP::Protocol classes need to override the <a href="#item_request"><code>request()</code></a>
method which is used to service a request. The overridden method can
make use of the <a href="#item_collect"><code>collect()</code></a> function to collect together chunks of data
as it is received.</p>
<p>The following methods and functions are provided:</p>
<dl>
<dt><strong><a name="item_new">$prot = LWP::Protocol-><code>new()</code></a></strong>
<dd>
<p>The LWP::Protocol constructor is inherited by subclasses. As this is a
virtual base class this method should <strong>not</strong> be called directly.</p>
</dd>
</li>
<dt><strong><a name="item_create">$prot = LWP::Protocol::create($scheme)</a></strong>
<dd>
<p>Create an object of the class implementing the protocol to handle the
given scheme. This is a function, not a method. It is more an object
factory than a constructor. This is the function user agents should
use to access protocols.</p>
</dd>
</li>
<dt><strong><a name="item_implementor">$class = LWP::Protocol::implementor($scheme, [$class])</a></strong>
<dd>
<p>Get and/or set implementor class for a scheme. Returns '' if the
specified scheme is not supported.</p>
</dd>
</li>
<dt><strong><a name="item_request">$prot-><code>request(...)</code></a></strong>
<dd>
<pre>
<span class="variable">$response</span> <span class="operator">=</span> <span class="variable">$protocol</span><span class="operator">-></span><span class="variable">request</span><span class="operator">(</span><span class="variable">$request</span><span class="operator">,</span> <span class="variable">$proxy</span><span class="operator">,</span> <span class="keyword">undef</span><span class="operator">);</span>
<span class="variable">$response</span> <span class="operator">=</span> <span class="variable">$protocol</span><span class="operator">-></span><span class="variable">request</span><span class="operator">(</span><span class="variable">$request</span><span class="operator">,</span> <span class="variable">$proxy</span><span class="operator">,</span> <span class="string">'/tmp/sss'</span><span class="operator">);</span>
<span class="variable">$response</span> <span class="operator">=</span> <span class="variable">$protocol</span><span class="operator">-></span><span class="variable">request</span><span class="operator">(</span><span class="variable">$request</span><span class="operator">,</span> <span class="variable">$proxy</span><span class="operator">,</span> <span class="operator">\&</span><span class="variable">callback</span><span class="operator">,</span> <span class="number">1024</span><span class="operator">);</span>
</pre>
</dd>
<dd>
<p>Dispatches a request over the protocol, and returns a response
object. This method needs to be overridden in subclasses. Refer to
<a href="../../lib/LWP/UserAgent.html">the LWP::UserAgent manpage</a> for description of the arguments.</p>
</dd>
<dt><strong><a name="item_collect">$prot->collect($arg, $response, $collector)</a></strong>
<dd>
<p>Called to collect the content of a request, and process it
appropriately into a scalar, file, or by calling a callback. If $arg
is undefined, then the content is stored within the $response. If
$arg is a simple scalar, then $arg is interpreted as a file name and
the content is written to this file. If $arg is a reference to a
routine, then content is passed to this routine.</p>
</dd>
<dd>
<p>The $collector is a routine that will be called and which is
responsible for returning pieces (as ref to scalar) of the content to
process. The $collector signals EOF by returning a reference to an
empty sting.</p>
</dd>
<dd>
<p>The return value from <a href="#item_collect"><code>collect()</code></a> is the $response object reference.</p>
</dd>
<dd>
<p><strong>Note:</strong> We will only use the callback or file argument if
$response->is_success(). This avoids sending content data for
redirects and authentication responses to the callback which would be
confusing.</p>
</dd>
</li>
<dt><strong><a name="item_collect_once">$prot->collect_once($arg, $response, $content)</a></strong>
<dd>
<p>Can be called when the whole response content is available as
$content. This will invoke <a href="#item_collect"><code>collect()</code></a> with a collector callback that
returns a reference to $content the first time and an empty string the
next.</p>
</dd>
</li>
</dl>
<p>
</p>
<hr />
<h1><a name="see_also">SEE ALSO</a></h1>
<p>Inspect the <em>LWP/Protocol/file.pm</em> and <em>LWP/Protocol/http.pm</em> files
for examples of usage.</p>
<p>
</p>
<hr />
<h1><a name="copyright">COPYRIGHT</a></h1>
<p>Copyright 1995-2001 Gisle Aas.</p>
<p>This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.</p>
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