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://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html
18 # ftp://ftp-genome.wi.mit.edu/pub/software/WWW/
20 $CGI::Push::VERSION='1.01';
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 $self->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 =head1 USING CGI::Push
149 CGI::Push adds one new method to the standard CGI suite, do_push().
150 When you call this method, you pass it a reference to a subroutine
151 that is responsible for drawing each new page, an interval delay, and
152 an optional subroutine for drawing the last page. Other optional
153 parameters include most of those recognized by the CGI header()
156 You may call do_push() in the object oriented manner or not, as you
161 $q->do_push(-next_page=>\&draw_a_page);
165 use CGI::Push qw(:standard);
166 do_push(-next_page=>\&draw_a_page);
168 Parameters are as follows:
174 do_push(-next_page=>\&my_draw_routine);
176 This required parameter points to a reference to a subroutine responsible for
177 drawing each new page. The subroutine should expect two parameters
178 consisting of the CGI object and a counter indicating the number
179 of times the subroutine has been called. It should return the
180 contents of the page as an B<array> of one or more items to print.
181 It can return a false value (or an empty array) in order to abort the
182 redrawing loop and print out the final page (if any)
184 sub my_draw_routine {
185 my($q,$counter) = @_;
186 return undef if $counter > 100;
187 return start_html('testing'),
189 "This page called $counter times";
192 You are of course free to refer to create and use global variables
193 within your draw routine in order to achieve special effects.
197 This optional parameter points to a reference to the subroutine
198 responsible for drawing the last page of the series. It is called
199 after the -next_page routine returns a false value. The subroutine
200 itself should have exactly the same calling conventions as the
205 This optional parameter indicates the content type of each page. It
206 defaults to "text/html". Normally the module assumes that each page
207 is of a homogenous MIME type. However if you provide either of the
208 magic values "heterogeneous" or "dynamic" (the latter provided for the
209 convenience of those who hate long parameter names), you can specify
210 the MIME type -- and other header fields -- on a per-page basis. See
211 "heterogeneous pages" for more details.
215 This indicates the delay, in seconds, between frames. Smaller delays
216 refresh the page faster. Fractional values are allowed.
218 B<If not specified, -delay will default to 1 second>
220 =item -cookie, -target, -expires
222 These have the same meaning as the like-named parameters in
227 =head2 Heterogeneous Pages
229 Ordinarily all pages displayed by CGI::Push share a common MIME type.
230 However by providing a value of "heterogeneous" or "dynamic" in the
231 do_push() -type parameter, you can specify the MIME type of each page
232 on a case-by-case basis.
234 If you use this option, you will be responsible for producing the
235 HTTP header for each page. Simply modify your draw routine to
238 sub my_draw_routine {
239 my($q,$counter) = @_;
240 return header('text/html'), # note we're producing the header here
241 start_html('testing'),
243 "This page called $counter times";
246 You can add any header fields that you like, but some (cookies and
247 status fields included) may not be interpreted by the browser. One
248 interesting effect is to display a series of pages, then, after the
249 last page, to redirect the browser to a new URL. Because redirect()
250 does b<not> work, the easiest way is with a -refresh header field,
253 sub my_draw_routine {
254 my($q,$counter) = @_;
255 return undef if $counter > 10;
256 return header('text/html'), # note we're producing the header here
257 start_html('testing'),
259 "This page called $counter times";
263 header(-refresh=>'5; URL=http://somewhere.else/finished.html',
266 h1('This is the last page'),
272 =head2 Changing the Page Delay on the Fly
274 If you would like to control the delay between pages on a page-by-page
275 basis, call push_delay() from within your draw routine. push_delay()
276 takes a single numeric argument representing the number of seconds you
277 wish to delay after the current page is displayed and before
278 displaying the next one. The delay may be fractional. Without
279 parameters, push_delay() just returns the current delay.
281 =head1 INSTALLING CGI::Push SCRIPTS
283 Server push scripts B<must> be installed as no-parsed-header (NPH)
284 scripts in order to work correctly. On Unix systems, this is most
285 often accomplished by prefixing the script's name with "nph-".
286 Recognition of NPH scripts happens automatically with WebSTAR and
287 Microsoft IIS. Users of other servers should see their documentation
292 This is a new module. It hasn't been extensively tested.
294 =head1 AUTHOR INFORMATION
296 be used and modified freely, but I do request that this copyright
297 notice remain attached to the file. You may modify this module as you
298 wish, but if you redistribute a modified version, please attach a note
299 listing the modifications you have made.
301 Address bug reports and comments to:
302 lstein@genome.wi.mit.edu
306 This section intentionally left blank.