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325 lines
11 KiB
325 lines
11 KiB
package CGI::Push;
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# See the bottom of this file for the POD documentation. Search for the
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# string '=head'.
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# You can run this file through either pod2man or pod2html to produce pretty
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# documentation in manual or html file format (these utilities are part of the
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# Perl 5 distribution).
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# Copyright 1995-2000, Lincoln D. Stein. All rights reserved.
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# It may be used and modified freely, but I do request that this copyright
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# notice remain attached to the file. You may modify this module as you
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# wish, but if you redistribute a modified version, please attach a note
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# listing the modifications you have made.
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# The most recent version and complete docs are available at:
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# http://stein.cshl.org/WWW/software/CGI/
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$CGI::Push::VERSION='1.04';
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use CGI;
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use CGI::Util 'rearrange';
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@ISA = ('CGI');
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$CGI::DefaultClass = 'CGI::Push';
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$CGI::Push::AutoloadClass = 'CGI';
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# add do_push() and push_delay() to exported tags
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push(@{$CGI::EXPORT_TAGS{':standard'}},'do_push','push_delay');
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sub do_push {
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my ($self,@p) = CGI::self_or_default(@_);
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# unbuffer output
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$| = 1;
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srand;
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my ($random) = sprintf("%08.0f",rand()*1E8);
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my ($boundary) = "----=_NeXtPaRt$random";
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my (@header);
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my ($type,$callback,$delay,$last_page,$cookie,$target,$expires,$nph,@other) = rearrange([TYPE,NEXT_PAGE,DELAY,LAST_PAGE,[COOKIE,COOKIES],TARGET,EXPIRES,NPH],@p);
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$type = 'text/html' unless $type;
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$callback = \&simple_counter unless $callback && ref($callback) eq 'CODE';
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$delay = 1 unless defined($delay);
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$self->push_delay($delay);
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$nph = 1 unless defined($nph);
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my(@o);
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foreach (@other) { push(@o,split("=")); }
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push(@o,'-Target'=>$target) if defined($target);
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push(@o,'-Cookie'=>$cookie) if defined($cookie);
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push(@o,'-Type'=>"multipart/x-mixed-replace;boundary=\"$boundary\"");
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push(@o,'-Server'=>"CGI.pm Push Module") if $nph;
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push(@o,'-Status'=>'200 OK');
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push(@o,'-nph'=>1) if $nph;
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print $self->header(@o);
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$boundary = "$CGI::CRLF--$boundary";
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print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.${boundary}$CGI::CRLF";
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my (@contents) = &$callback($self,++$COUNTER);
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# now we enter a little loop
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while (1) {
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print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
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print @contents;
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@contents = &$callback($self,++$COUNTER);
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if ((@contents) && defined($contents[0])) {
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print "${boundary}$CGI::CRLF";
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do_sleep($self->push_delay()) if $self->push_delay();
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} else {
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if ($last_page && ref($last_page) eq 'CODE') {
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print "${boundary}$CGI::CRLF";
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do_sleep($self->push_delay()) if $self->push_delay();
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print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
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print &$last_page($self,$COUNTER);
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}
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print "${boundary}--$CGI::CRLF";
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last;
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}
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}
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print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.$CGI::CRLF";
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}
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sub simple_counter {
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my ($self,$count) = @_;
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return $self->start_html("CGI::Push Default Counter"),
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$self->h1("CGI::Push Default Counter"),
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"This page has been updated ",$self->strong($count)," times.",
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$self->hr(),
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$self->a({'-href'=>'http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html'},'CGI.pm home page'),
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$self->end_html;
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}
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sub do_sleep {
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my $delay = shift;
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if ( ($delay >= 1) && ($delay!~/\./) ){
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sleep($delay);
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} else {
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select(undef,undef,undef,$delay);
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}
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}
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sub push_delay {
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my ($self,$delay) = CGI::self_or_default(@_);
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return defined($delay) ? $self->{'.delay'} =
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$delay : $self->{'.delay'};
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}
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1;
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=head1 NAME
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CGI::Push - Simple Interface to Server Push
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=head1 SYNOPSIS
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use CGI::Push qw(:standard);
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do_push(-next_page=>\&next_page,
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-last_page=>\&last_page,
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-delay=>0.5);
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sub next_page {
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my($q,$counter) = @_;
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return undef if $counter >= 10;
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return start_html('Test'),
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h1('Visible'),"\n",
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"This page has been called ", strong($counter)," times",
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end_html();
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}
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sub last_page {
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my($q,$counter) = @_;
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return start_html('Done'),
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h1('Finished'),
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strong($counter - 1),' iterations.',
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end_html;
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}
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=head1 DESCRIPTION
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CGI::Push is a subclass of the CGI object created by CGI.pm. It is
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specialized for server push operations, which allow you to create
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animated pages whose content changes at regular intervals.
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You provide CGI::Push with a pointer to a subroutine that will draw
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one page. Every time your subroutine is called, it generates a new
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page. The contents of the page will be transmitted to the browser
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in such a way that it will replace what was there beforehand. The
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technique will work with HTML pages as well as with graphics files,
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allowing you to create animated GIFs.
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Only Netscape Navigator supports server push. Internet Explorer
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browsers do not.
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=head1 USING CGI::Push
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CGI::Push adds one new method to the standard CGI suite, do_push().
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When you call this method, you pass it a reference to a subroutine
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that is responsible for drawing each new page, an interval delay, and
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an optional subroutine for drawing the last page. Other optional
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parameters include most of those recognized by the CGI header()
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method.
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You may call do_push() in the object oriented manner or not, as you
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prefer:
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use CGI::Push;
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$q = new CGI::Push;
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$q->do_push(-next_page=>\&draw_a_page);
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-or-
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use CGI::Push qw(:standard);
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do_push(-next_page=>\&draw_a_page);
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Parameters are as follows:
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=over 4
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=item -next_page
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do_push(-next_page=>\&my_draw_routine);
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This required parameter points to a reference to a subroutine responsible for
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drawing each new page. The subroutine should expect two parameters
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consisting of the CGI object and a counter indicating the number
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of times the subroutine has been called. It should return the
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contents of the page as an B<array> of one or more items to print.
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It can return a false value (or an empty array) in order to abort the
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redrawing loop and print out the final page (if any)
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sub my_draw_routine {
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my($q,$counter) = @_;
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return undef if $counter > 100;
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return start_html('testing'),
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h1('testing'),
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"This page called $counter times";
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}
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You are of course free to refer to create and use global variables
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within your draw routine in order to achieve special effects.
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=item -last_page
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This optional parameter points to a reference to the subroutine
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responsible for drawing the last page of the series. It is called
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after the -next_page routine returns a false value. The subroutine
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itself should have exactly the same calling conventions as the
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-next_page routine.
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=item -type
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This optional parameter indicates the content type of each page. It
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defaults to "text/html". Normally the module assumes that each page
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is of a homogenous MIME type. However if you provide either of the
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magic values "heterogeneous" or "dynamic" (the latter provided for the
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convenience of those who hate long parameter names), you can specify
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the MIME type -- and other header fields -- on a per-page basis. See
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"heterogeneous pages" for more details.
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=item -delay
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This indicates the delay, in seconds, between frames. Smaller delays
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refresh the page faster. Fractional values are allowed.
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B<If not specified, -delay will default to 1 second>
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=item -cookie, -target, -expires, -nph
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These have the same meaning as the like-named parameters in
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CGI::header().
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If not specified, -nph will default to 1 (as needed for many servers, see below).
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=back
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=head2 Heterogeneous Pages
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Ordinarily all pages displayed by CGI::Push share a common MIME type.
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However by providing a value of "heterogeneous" or "dynamic" in the
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do_push() -type parameter, you can specify the MIME type of each page
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on a case-by-case basis.
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If you use this option, you will be responsible for producing the
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HTTP header for each page. Simply modify your draw routine to
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look like this:
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sub my_draw_routine {
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my($q,$counter) = @_;
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return header('text/html'), # note we're producing the header here
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start_html('testing'),
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h1('testing'),
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"This page called $counter times";
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}
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You can add any header fields that you like, but some (cookies and
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status fields included) may not be interpreted by the browser. One
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interesting effect is to display a series of pages, then, after the
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last page, to redirect the browser to a new URL. Because redirect()
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does b<not> work, the easiest way is with a -refresh header field,
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as shown below:
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sub my_draw_routine {
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my($q,$counter) = @_;
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return undef if $counter > 10;
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return header('text/html'), # note we're producing the header here
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start_html('testing'),
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h1('testing'),
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"This page called $counter times";
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}
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sub my_last_page {
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return header(-refresh=>'5; URL=http://somewhere.else/finished.html',
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-type=>'text/html'),
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start_html('Moved'),
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h1('This is the last page'),
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'Goodbye!'
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hr,
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end_html;
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}
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=head2 Changing the Page Delay on the Fly
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If you would like to control the delay between pages on a page-by-page
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basis, call push_delay() from within your draw routine. push_delay()
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takes a single numeric argument representing the number of seconds you
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wish to delay after the current page is displayed and before
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displaying the next one. The delay may be fractional. Without
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parameters, push_delay() just returns the current delay.
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=head1 INSTALLING CGI::Push SCRIPTS
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Server push scripts must be installed as no-parsed-header (NPH)
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scripts in order to work correctly on many servers. On Unix systems,
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this is most often accomplished by prefixing the script's name with "nph-".
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Recognition of NPH scripts happens automatically with WebSTAR and
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Microsoft IIS. Users of other servers should see their documentation
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for help.
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Apache web server from version 1.3b2 on does not need server
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push scripts installed as NPH scripts: the -nph parameter to do_push()
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may be set to a false value to disable the extra headers needed by an
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NPH script.
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=head1 AUTHOR INFORMATION
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Copyright 1995-1998, Lincoln D. Stein. All rights reserved.
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This library is free software; you can redistribute it and/or modify
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it under the same terms as Perl itself.
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Address bug reports and comments to: [email protected]
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=head1 BUGS
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This section intentionally left blank.
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=head1 SEE ALSO
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L<CGI::Carp>, L<CGI>
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=cut
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