3 # See the bottom of this file for the POD documentation. Search for the
6 # You can run this file through either pod2man or pod2html to produce pretty
7 # documentation in manual or html file format (these utilities are part of the
8 # Perl 5 distribution).
10 # Copyright 1995,1996, Lincoln D. Stein. All rights reserved.
11 # It may be used and modified freely, but I do request that this copyright
12 # notice remain attached to the file. You may modify this module as you
13 # wish, but if you redistribute a modified version, please attach a note
14 # listing the modifications you have made.
16 # The most recent version and complete docs are available at:
17 # http://stein.cshl.org/WWW/software/CGI/
19 $CGI::Push::VERSION='1.02';
21 use CGI::Util 'rearrange';
24 $CGI::DefaultClass = 'CGI::Push';
25 $CGI::Push::AutoloadClass = 'CGI';
27 # add do_push() and push_delay() to exported tags
28 push(@{$CGI::EXPORT_TAGS{':standard'}},'do_push','push_delay');
31 my ($self,@p) = CGI::self_or_default(@_);
36 my ($random) = sprintf("%16.0f",rand()*1E16);
37 my ($boundary) = "----------------------------------$random";
40 my ($type,$callback,$delay,$last_page,$cookie,$target,$expires,@other) =
41 rearrange([TYPE,NEXT_PAGE,DELAY,LAST_PAGE,[COOKIE,COOKIES],TARGET,EXPIRES],@p);
42 $type = 'text/html' unless $type;
43 $callback = \&simple_counter unless $callback && ref($callback) eq 'CODE';
44 $delay = 1 unless defined($delay);
45 $self->push_delay($delay);
48 foreach (@other) { push(@o,split("=")); }
49 push(@o,'-Target'=>$target) if defined($target);
50 push(@o,'-Cookie'=>$cookie) if defined($cookie);
51 push(@o,'-Type'=>"multipart/x-mixed-replace; boundary=$boundary");
52 push(@o,'-Server'=>"CGI.pm Push Module");
53 push(@o,'-Status'=>'200 OK');
55 print $self->header(@o);
56 print "${boundary}$CGI::CRLF";
58 # now we enter a little loop
61 last unless (@contents = &$callback($self,++$COUNTER)) && defined($contents[0]);
62 print "Content-type: ${type}$CGI::CRLF$CGI::CRLF"
63 unless $type eq 'dynamic';
64 print @contents,"$CGI::CRLF";
65 print "${boundary}$CGI::CRLF";
66 do_sleep($self->push_delay()) if $self->push_delay();
70 if ($last_page && ref($last_page) eq 'CODE') {
71 print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
72 print &$last_page($self,$COUNTER),"$CGI::CRLF${boundary}$CGI::CRLF";
77 my ($self,$count) = @_;
79 CGI->start_html("CGI::Push Default Counter"),
80 CGI->h1("CGI::Push Default Counter"),
81 "This page has been updated ",CGI->strong($count)," times.",
83 CGI->a({'-href'=>'http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html'},'CGI.pm home page'),
90 if ( ($delay >= 1) && ($delay!~/\./) ){
93 select(undef,undef,undef,$delay);
98 my ($self,$delay) = CGI::self_or_default(@_);
99 return defined($delay) ? $self->{'.delay'} =
100 $delay : $self->{'.delay'};
107 CGI::Push - Simple Interface to Server Push
111 use CGI::Push qw(:standard);
113 do_push(-next_page=>\&next_page,
114 -last_page=>\&last_page,
118 my($q,$counter) = @_;
119 return undef if $counter >= 10;
120 return start_html('Test'),
122 "This page has been called ", strong($counter)," times",
127 my($q,$counter) = @_;
128 return start_html('Done'),
130 strong($counter),' iterations.',
136 CGI::Push is a subclass of the CGI object created by CGI.pm. It is
137 specialized for server push operations, which allow you to create
138 animated pages whose content changes at regular intervals.
140 You provide CGI::Push with a pointer to a subroutine that will draw
141 one page. Every time your subroutine is called, it generates a new
142 page. The contents of the page will be transmitted to the browser
143 in such a way that it will replace what was there beforehand. The
144 technique will work with HTML pages as well as with graphics files,
145 allowing you to create animated GIFs.
147 Only Netscape Navigator supports server push. Internet Explorer
150 =head1 USING CGI::Push
152 CGI::Push adds one new method to the standard CGI suite, do_push().
153 When you call this method, you pass it a reference to a subroutine
154 that is responsible for drawing each new page, an interval delay, and
155 an optional subroutine for drawing the last page. Other optional
156 parameters include most of those recognized by the CGI header()
159 You may call do_push() in the object oriented manner or not, as you
164 $q->do_push(-next_page=>\&draw_a_page);
168 use CGI::Push qw(:standard);
169 do_push(-next_page=>\&draw_a_page);
171 Parameters are as follows:
177 do_push(-next_page=>\&my_draw_routine);
179 This required parameter points to a reference to a subroutine responsible for
180 drawing each new page. The subroutine should expect two parameters
181 consisting of the CGI object and a counter indicating the number
182 of times the subroutine has been called. It should return the
183 contents of the page as an B<array> of one or more items to print.
184 It can return a false value (or an empty array) in order to abort the
185 redrawing loop and print out the final page (if any)
187 sub my_draw_routine {
188 my($q,$counter) = @_;
189 return undef if $counter > 100;
190 return start_html('testing'),
192 "This page called $counter times";
195 You are of course free to refer to create and use global variables
196 within your draw routine in order to achieve special effects.
200 This optional parameter points to a reference to the subroutine
201 responsible for drawing the last page of the series. It is called
202 after the -next_page routine returns a false value. The subroutine
203 itself should have exactly the same calling conventions as the
208 This optional parameter indicates the content type of each page. It
209 defaults to "text/html". Normally the module assumes that each page
210 is of a homogenous MIME type. However if you provide either of the
211 magic values "heterogeneous" or "dynamic" (the latter provided for the
212 convenience of those who hate long parameter names), you can specify
213 the MIME type -- and other header fields -- on a per-page basis. See
214 "heterogeneous pages" for more details.
218 This indicates the delay, in seconds, between frames. Smaller delays
219 refresh the page faster. Fractional values are allowed.
221 B<If not specified, -delay will default to 1 second>
223 =item -cookie, -target, -expires
225 These have the same meaning as the like-named parameters in
230 =head2 Heterogeneous Pages
232 Ordinarily all pages displayed by CGI::Push share a common MIME type.
233 However by providing a value of "heterogeneous" or "dynamic" in the
234 do_push() -type parameter, you can specify the MIME type of each page
235 on a case-by-case basis.
237 If you use this option, you will be responsible for producing the
238 HTTP header for each page. Simply modify your draw routine to
241 sub my_draw_routine {
242 my($q,$counter) = @_;
243 return header('text/html'), # note we're producing the header here
244 start_html('testing'),
246 "This page called $counter times";
249 You can add any header fields that you like, but some (cookies and
250 status fields included) may not be interpreted by the browser. One
251 interesting effect is to display a series of pages, then, after the
252 last page, to redirect the browser to a new URL. Because redirect()
253 does b<not> work, the easiest way is with a -refresh header field,
256 sub my_draw_routine {
257 my($q,$counter) = @_;
258 return undef if $counter > 10;
259 return header('text/html'), # note we're producing the header here
260 start_html('testing'),
262 "This page called $counter times";
266 header(-refresh=>'5; URL=http://somewhere.else/finished.html',
269 h1('This is the last page'),
275 =head2 Changing the Page Delay on the Fly
277 If you would like to control the delay between pages on a page-by-page
278 basis, call push_delay() from within your draw routine. push_delay()
279 takes a single numeric argument representing the number of seconds you
280 wish to delay after the current page is displayed and before
281 displaying the next one. The delay may be fractional. Without
282 parameters, push_delay() just returns the current delay.
284 =head1 INSTALLING CGI::Push SCRIPTS
286 Server push scripts B<must> be installed as no-parsed-header (NPH)
287 scripts in order to work correctly. On Unix systems, this is most
288 often accomplished by prefixing the script's name with "nph-".
289 Recognition of NPH scripts happens automatically with WebSTAR and
290 Microsoft IIS. Users of other servers should see their documentation
293 =head1 AUTHOR INFORMATION
295 Copyright 1995-1998, Lincoln D. Stein. All rights reserved.
297 This library is free software; you can redistribute it and/or modify
298 it under the same terms as Perl itself.
300 Address bug reports and comments to: lstein@cshl.org
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