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.\" ========================================================================
.\"
.IX Title "LWP::Protocol 3pm"
.TH LWP::Protocol 3pm "2023-03-01" "perl v5.36.0" "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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.nh
.SH "NAME"
LWP::Protocol \- Base class for LWP protocols
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& package LWP::Protocol::foo;
\& use parent 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 \f(CW\*(C`request()\*(C'\fR
method which is used to service a request. The overridden method can
make use of the \f(CW\*(C`collect()\*(C'\fR method 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 4
\&    $response = $protocol\->request($request, $proxy, undef);
\&    $response = $protocol\->request($request, $proxy, \*(Aq/tmp/sss\*(Aq);
\&    $response = $protocol\->request($request, $proxy, \e&callback, 1024);
\&    $response = $protocol\->request($request, $proxy, $fh);
.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.
If it is a filehandle, or similar, such as a File::Temp object,
content will be written to it.
.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.