NAME

       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 = 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.

       $prot->request(...)
            $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.

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.