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ISBN : 978-2-7460-9712-4
EAN : 9782746097124
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CentOS 2.1AS







LWP: :Protocol − Base class for LWP protocols


 package LWP::Protocol::foo;
 require LWP::Protocol;


This class is used a the base class for all protocol implementations supported by the LWP library.

When creating an instance of this class using "LWP::Protocol::create($url)", and you get an initialised subclass appropriate for that access method. In other words, the LWP:\fIs0:Protocol::create() function calls the constructor for one of its subclasses.

All derived LWP: :Protocol classes need to override the request() method which is used to service a request. The overridden method can make use of the collect() function to collect together chunks of data as it is received.

The following methods and functions are provided:
$prot =
LWP: :Protocol->new()

The LWP: :Protocol constructor is inherited by subclasses. As this is a virtual base class this method should not be called directly.

$prot = LWP: :Protocol::create($url)

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.

$class = LWP: :Protocol::implementor($scheme, [$class])

Get and/or set implementor class for a scheme. Returns ’’ if the specified scheme is not supported.


 $response = $protocol->request($request, $proxy, undef);
 $response = $protocol->request($request, $proxy, ’/tmp/sss’);
 $response = $protocol->request($request, $proxy, \&callback, 1024);

Dispactches a request over the protocol, and returns a response object. This method needs to be overridden in subclasses. Referer to the LWP::UserAgent manpage for description of the arguments.


Get and set the timeout value in seconds


Should we initialize response headers from the <head> section of HTML documents.

$prot->collect($arg, $response, $collector)

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.

The $collector is a routine that will be called and which is reponsible for returning pieces (as ref to scalar) of the content to process. The $collector signals EOF by returning a reference to an empty sting.

The return value from collect() is the $response object reference.

Note: We will only use the callback or file argument if $response->is_success(). This avoids sendig content data for redirects and authentization responses to the callback which would be confusing.

$prot->collect_once($arg, $response, $content)

Can be called when the whole response content is available as $content. This will invoke collect() with a collector callback that returns a reference to $content the first time and an empty string the next.


Inspect the LWP/Protocol/file.pm and LWP/Protocol/http.pm files for examples of usage.


Copyright 1995−2000 Gisle Aas.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.