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.\" ========================================================================
.\"
.IX Title "LWP::Protocol 3"
.TH LWP::Protocol 3 "2018-07-16" "perl v5.16.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
LWP::Protocol \- Base class for LWP protocols
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& package LWP::Protocol::foo;
\& use base qw(LWP::Protocol);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This class is used as the base class for all protocol implementations
supported by the \s-1LWP\s0 library.
.PP
When creating an instance of this class using
\&\f(CW\*(C`LWP::Protocol::create($url)\*(C'\fR, and you get an initialized subclass
appropriate for that access method. In other words, the
\&\*(L"create\*(R" in LWP::Protocol function calls the constructor for one of its
subclasses.
.PP
All derived \f(CW\*(C`LWP::Protocol\*(C'\fR classes need to override the \fIrequest()\fR
method which is used to service a request. The overridden method can
make use of the \fIcollect()\fR function to collect together chunks of data
as it is received.
.SH "METHODS"
.IX Header "METHODS"
The following methods and functions are provided:
.SS "new"
.IX Subsection "new"
.Vb 1
\&    my $prot = LWP::Protocol\->new();
.Ve
.PP
The LWP::Protocol constructor is inherited by subclasses. As this is a
virtual base class this method should \fBnot\fR be called directly.
.SS "create"
.IX Subsection "create"
.Vb 1
\&    my $prot = LWP::Protocol::create($scheme)
.Ve
.PP
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.
.SS "implementor"
.IX Subsection "implementor"
.Vb 1
\&    my $class = LWP::Protocol::implementor($scheme, [$class])
.Ve
.PP
Get and/or set implementor class for a scheme.  Returns \f(CW\*(Aq\*(Aq\fR if the
specified scheme is not supported.
.SS "request"
.IX Subsection "request"
.Vb 3
\&    $response = $protocol\->request($request, $proxy, undef);
\&    $response = $protocol\->request($request, $proxy, \*(Aq/tmp/sss\*(Aq);
\&    $response = $protocol\->request($request, $proxy, \e&callback, 1024);
.Ve
.PP
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.
.SS "collect"
.IX Subsection "collect"
.Vb 3
\&    my $res = $prot\->collect(undef, $response, $collector); # stored in $response
\&    my $res = $prot\->collect($filename, $response, $collector);
\&    my $res = $prot\->collect(sub { ... }, $response, $collector);
.Ve
.PP
Collect the content of a request, and process it appropriately into a scalar,
file, or by calling a callback. If the first parameter is undefined, then the
content is stored within the \f(CW$response\fR. If it's a simple scalar, then it's
interpreted as a file name and the content is written to this file.  If it's a
code reference, then content is passed to this routine.
.PP
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 \f(CW$collector\fR signals \f(CW\*(C`EOF\*(C'\fR by returning a reference to an
empty string.
.PP
The return value is the HTTP::Response object reference.
.PP
\&\fBNote:\fR We will only use the callback or file argument if
\&\f(CW\*(C`$response\->is_success()\*(C'\fR.  This avoids sending content data for
redirects and authentication responses to the callback which would be
confusing.
.SS "collect_once"
.IX Subsection "collect_once"
.Vb 1
\&    $prot\->collect_once($arg, $response, $content)
.Ve
.PP
Can be called when the whole response content is available as content. This
will invoke \*(L"collect\*(R" in LWP::Protocol with a collector callback that
returns a reference to \f(CW$content\fR the first time and an empty string the
next.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Inspect the \fILWP/Protocol/file.pm\fR and \fILWP/Protocol/http.pm\fR files
for examples of usage.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 1995\-2001 Gisle Aas.
.PP
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.