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.
Dispactches a request over the protocol, and returns a response
object. This method needs to be overridden in subclasses. Referer 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
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 1995-2001 Gisle Aas.
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.