LWP::Protocol - Base class for LWP protocols
package LWP::Protocol::foo; require LWP::Protocol; @ISA=qw(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::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.
- $prot = LWP::Protocol::create($scheme)
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);
Dispatches a request over the protocol, and returns a response object. This method needs to be overridden in subclasses. Refer to LWP::UserAgent for description of the arguments.
- $prot->collect($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 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.
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 sending content data for redirects and authentication 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 1995-2001 Gisle Aas.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.