LWP::Protocol - Base class for LWP protocols
SYNOPSIS
package LWP::Protocol::foo;
require LWP::Protocol;
@ISA=qw(LWP::Protocol);
DESCRIPTION
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 = new HTTP::Protocol;
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.
$prot->request(...)
$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
$prot->use_alarm($yesno)
Indicates if the library is allowed to use the core
alarm() function to implement timeouts.
$prot->parse_head($yesno)
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.
SEE ALSO
Inspect the LWP/Protocol/file.pm and LWP/Protocol/http.pm
files for examples of usage.
COPYRIGHT
Copyright 1995-1997 Gisle Aas.
This library is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.