?? protocol.pm
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# $Id: Protocol.pm,v 1.1 1999/07/21 19:12:33 kraven Exp $package LWP::Protocol;=head1 NAMELWP::Protocol - Base class for LWP protocols=head1 SYNOPSIS package LWP::Protocol::foo; require LWP::Protocol; @ISA=qw(LWP::Protocol);=head1 DESCRIPTIONThis class is used a the base class for all protocol implementationssupported by the LWP library.When creating an instance of this class usingC<LWP::Protocol::create($url)>, and you get an initialised subclassappropriate for that access method. In other words, theLWP::Protocol::create() function calls the constructor for one of itssubclasses.All derived LWP::Protocol classes need to override the request()method which is used to service a request. The overridden method canmake use of the collect() function to collect together chunks of dataas it is received.The following methods and functions are provided:=over 4=cut#####################################################################require LWP::MemberMixin;@ISA = qw(LWP::MemberMixin);$VERSION = sprintf("%d.%02d", q$Revision: 1.1 $ =~ /(\d+)\.(\d+)/);use strict;use Carp ();use HTTP::Status 'RC_INTERNAL_SERVER_ERROR';require HTML::HeadParser;my %ImplementedBy = (); # scheme => classname=item $prot = new HTTP::Protocol;The LWP::Protocol constructor is inherited by subclasses. As this is avirtual base class this method should B<not> be called directly.=cutsub new{ my($class) = @_; my $self = bless { 'timeout' => 0, 'parse_head' => 1, }, $class; $self;}=item $prot = LWP::Protocol::create($url)Create an object of the class implementing the protocol to handle thegiven scheme. This is a function, not a method. It is more an objectfactory than a constructor. This is the function user agents shoulduse to access protocols.=cutsub create{ my $scheme = shift; my $impclass = LWP::Protocol::implementor($scheme) or Carp::croak("Protocol scheme '$scheme' is not supported"); # hand-off to scheme specific implementation sub-class return $impclass->new($scheme);}=item $class = LWP::Protocol::implementor($scheme, [$class])Get and/or set implementor class for a scheme. Returns '' if thespecified scheme is not supported.=cutsub implementor{ my($scheme, $impclass) = @_; if ($impclass) { $ImplementedBy{$scheme} = $impclass; } my $ic = $ImplementedBy{$scheme}; return $ic if $ic; return '' unless $scheme =~ /^([.+\-\w]+)$/; # check valid URL schemes $scheme = $1; # untaint $scheme =~ s/[.+\-]/_/g; # make it a legal module name # scheme not yet known, look for a 'use'd implementation $ic = "LWP::Protocol::$scheme"; # default location $ic = "LWP::Protocol::nntp" if $scheme eq 'news'; #XXX ugly hack no strict 'refs'; # check we actually have one for the scheme: unless (defined @{"${ic}::ISA"}) { # try to autoload it eval "require $ic"; if ($@) { if ($@ =~ /^Can't locate/) { #' #emacs get confused by ' $ic = ''; } else { die "$@\n"; } } } $ImplementedBy{$scheme} = $ic if $ic; $ic;}=item $prot->request(...) $response = $protocol->request($request, $proxy, undef); $response = $protocol->request($request, $proxy, '/tmp/sss'); $response = $protocol->request($request, $proxy, \&callback, 1024);Dispactches a request over the protocol, and returns a responseobject. This method needs to be overridden in subclasses. Referer toL<LWP::UserAgent> for description of the arguments.=cutsub request{ my($self, $request, $proxy, $arg, $size, $timeout) = @_; Carp::croak('LWP::Protocol::request() needs to be overridden in subclasses');}=item $prot->timeout($seconds)Get and set the timeout value in seconds=item $prot->parse_head($yesno)Should we initialize response headers from the <head> section of HTMLdocuments.=cutsub timeout { shift->_elem('timeout', @_); }sub parse_head { shift->_elem('parse_head', @_); }sub max_size { shift->_elem('max_size', @_); }=item $prot->collect($arg, $response, $collector)Called to collect the content of a request, and process itappropriately into a scalar, file, or by calling a callback. If $argis undefined, then the content is stored within the $response. If$arg is a simple scalar, then $arg is interpreted as a file name andthe content is written to this file. If $arg is a reference to aroutine, then content is passed to this routine.The $collector is a routine that will be called and which isreponsible for returning pieces (as ref to scalar) of the content toprocess. The $collector signals EOF by returning a reference to anempty sting.The return value from collect() is the $response object reference.B<Note:> We will only use the callback or file argument if$response->is_success(). This avoids sendig content data forredirects and authentization responses to the callback which would beconfusing.=cutsub collect{ my ($self, $arg, $response, $collector) = @_; my $content; my($parse_head, $timeout, $max_size) = @{$self}{qw(parse_head timeout max_size)}; my $parser; if ($parse_head && $response->content_type eq 'text/html') { $parser = HTML::HeadParser->new($response->{'_headers'}); } my $content_size = 0; if (!defined($arg) || !$response->is_success) { # scalar while ($content = &$collector, length $$content) { if ($parser) { $parser->parse($$content) or undef($parser); } LWP::Debug::debug("read " . length($$content) . " bytes"); $response->add_content($$content); $content_size += length($$content); if ($max_size && $content_size > $max_size) { LWP::Debug::debug("Aborting because size limit exceeded"); my $tot = $response->header("Content-Length") || 0; $response->header("X-Content-Range", "bytes 0-$content_size/$tot"); last; } } } elsif (!ref($arg)) { # filename open(OUT, ">$arg") or return new HTTP::Response RC_INTERNAL_SERVER_ERROR, "Cannot write to '$arg': $!"; binmode(OUT); local($\) = ""; # ensure standard $OUTPUT_RECORD_SEPARATOR while ($content = &$collector, length $$content) { if ($parser) { $parser->parse($$content) or undef($parser); } LWP::Debug::debug("read " . length($$content) . " bytes"); print OUT $$content; $content_size += length($$content); if ($max_size && $content_size > $max_size) { LWP::Debug::debug("Aborting because size limit exceeded"); my $tot = $response->header("Content-Length") || 0; $response->header("X-Content-Range", "bytes 0-$content_size/$tot"); last; } } close(OUT); } elsif (ref($arg) eq 'CODE') { # read into callback while ($content = &$collector, length $$content) { if ($parser) { $parser->parse($$content) or undef($parser); } LWP::Debug::debug("read " . length($$content) . " bytes"); eval { &$arg($$content, $response, $self); }; if ($@) { chomp($@); $response->header('X-Died' => $@); last; } } } else { return new HTTP::Response RC_INTERNAL_SERVER_ERROR, "Unexpected collect argument '$arg'"; } $response;}=item $prot->collect_once($arg, $response, $content)Can be called when the whole response content is available as$content. This will invoke collect() with a collector callback thatreturns a reference to $content the first time and an empty string thenext.=cutsub collect_once{ my($self, $arg, $response) = @_; my $content = \ $_[3]; my $first = 1; $self->collect($arg, $response, sub { return $content if $first--; return \ ""; });}1;=head1 SEE ALSOInspect the F<LWP/Protocol/file.pm> and F<LWP/Protocol/http.pm> filesfor examples of usage.=head1 COPYRIGHTCopyright 1995-1997 Gisle Aas.This library is free software; you can redistribute it and/ormodify it under the same terms as Perl itself.=cut?? 快捷鍵說明
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