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[p5sagit/p5-mst-13.2.git] / lib / CGI / Push.pm
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54310121 1package CGI::Push;
2
3# See the bottom of this file for the POD documentation. Search for the
4# string '=head'.
5
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).
9
ba056755 10# Copyright 1995-2000, Lincoln D. Stein. All rights reserved.
54310121 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.
15
16# The most recent version and complete docs are available at:
71f3e297 17# http://stein.cshl.org/WWW/software/CGI/
54310121 18
ba056755 19$CGI::Push::VERSION='1.04';
54310121 20use CGI;
3d1a2ec4 21use CGI::Util 'rearrange';
54310121 22@ISA = ('CGI');
23
424ec8fa 24$CGI::DefaultClass = 'CGI::Push';
25$CGI::Push::AutoloadClass = 'CGI';
26
27# add do_push() and push_delay() to exported tags
28push(@{$CGI::EXPORT_TAGS{':standard'}},'do_push','push_delay');
54310121 29
30sub do_push {
424ec8fa 31 my ($self,@p) = CGI::self_or_default(@_);
54310121 32
33 # unbuffer output
34 $| = 1;
35 srand;
ba056755 36 my ($random) = sprintf("%08.0f",rand()*1E8);
37 my ($boundary) = "----=_NeXtPaRt$random";
54310121 38
39 my (@header);
ba056755 40 my ($type,$callback,$delay,$last_page,$cookie,$target,$expires,$nph,@other) = rearrange([TYPE,NEXT_PAGE,DELAY,LAST_PAGE,[COOKIE,COOKIES],TARGET,EXPIRES,NPH],@p);
54310121 41 $type = 'text/html' unless $type;
42 $callback = \&simple_counter unless $callback && ref($callback) eq 'CODE';
43 $delay = 1 unless defined($delay);
424ec8fa 44 $self->push_delay($delay);
ba056755 45 $nph = 1 unless defined($nph);
54310121 46
47 my(@o);
48 foreach (@other) { push(@o,split("=")); }
49 push(@o,'-Target'=>$target) if defined($target);
50 push(@o,'-Cookie'=>$cookie) if defined($cookie);
ba056755 51 push(@o,'-Type'=>"multipart/x-mixed-replace;boundary=\"$boundary\"");
52 push(@o,'-Server'=>"CGI.pm Push Module") if $nph;
54310121 53 push(@o,'-Status'=>'200 OK');
ba056755 54 push(@o,'-nph'=>1) if $nph;
54310121 55 print $self->header(@o);
ba056755 56
57 $boundary = "$CGI::CRLF--$boundary";
58
59 print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.${boundary}$CGI::CRLF";
60
61 my (@contents) = &$callback($self,++$COUNTER);
3d1a2ec4 62
54310121 63 # now we enter a little loop
54310121 64 while (1) {
ba056755 65 print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
66 print @contents;
67 @contents = &$callback($self,++$COUNTER);
68 if ((@contents) && defined($contents[0])) {
69 print "${boundary}$CGI::CRLF";
70 do_sleep($self->push_delay()) if $self->push_delay();
71 } else {
72 if ($last_page && ref($last_page) eq 'CODE') {
73 print "${boundary}$CGI::CRLF";
74 do_sleep($self->push_delay()) if $self->push_delay();
75 print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
76 print &$last_page($self,$COUNTER);
77 }
78 print "${boundary}--$CGI::CRLF";
79 last;
80 }
54310121 81 }
ba056755 82 print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.$CGI::CRLF";
54310121 83}
84
85sub simple_counter {
86 my ($self,$count) = @_;
ba056755 87 return $self->start_html("CGI::Push Default Counter"),
88 $self->h1("CGI::Push Default Counter"),
89 "This page has been updated ",$self->strong($count)," times.",
90 $self->hr(),
91 $self->a({'-href'=>'http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html'},'CGI.pm home page'),
92 $self->end_html;
54310121 93}
94
95sub do_sleep {
96 my $delay = shift;
97 if ( ($delay >= 1) && ($delay!~/\./) ){
ba056755 98 sleep($delay);
54310121 99 } else {
ba056755 100 select(undef,undef,undef,$delay);
54310121 101 }
102}
103
424ec8fa 104sub push_delay {
ba056755 105 my ($self,$delay) = CGI::self_or_default(@_);
106 return defined($delay) ? $self->{'.delay'} =
107 $delay : $self->{'.delay'};
424ec8fa 108}
109
54310121 1101;
111
112=head1 NAME
113
114CGI::Push - Simple Interface to Server Push
115
116=head1 SYNOPSIS
117
118 use CGI::Push qw(:standard);
119
120 do_push(-next_page=>\&next_page,
121 -last_page=>\&last_page,
122 -delay=>0.5);
123
124 sub next_page {
125 my($q,$counter) = @_;
126 return undef if $counter >= 10;
127 return start_html('Test'),
ba056755 128 h1('Visible'),"\n",
54310121 129 "This page has been called ", strong($counter)," times",
130 end_html();
ba056755 131 }
54310121 132
ba056755 133 sub last_page {
134 my($q,$counter) = @_;
135 return start_html('Done'),
136 h1('Finished'),
137 strong($counter - 1),' iterations.',
138 end_html;
139 }
54310121 140
141=head1 DESCRIPTION
142
143CGI::Push is a subclass of the CGI object created by CGI.pm. It is
144specialized for server push operations, which allow you to create
145animated pages whose content changes at regular intervals.
146
147You provide CGI::Push with a pointer to a subroutine that will draw
148one page. Every time your subroutine is called, it generates a new
149page. The contents of the page will be transmitted to the browser
150in such a way that it will replace what was there beforehand. The
151technique will work with HTML pages as well as with graphics files,
152allowing you to create animated GIFs.
153
3d1a2ec4 154Only Netscape Navigator supports server push. Internet Explorer
155browsers do not.
156
54310121 157=head1 USING CGI::Push
158
159CGI::Push adds one new method to the standard CGI suite, do_push().
160When you call this method, you pass it a reference to a subroutine
161that is responsible for drawing each new page, an interval delay, and
162an optional subroutine for drawing the last page. Other optional
163parameters include most of those recognized by the CGI header()
164method.
165
166You may call do_push() in the object oriented manner or not, as you
167prefer:
168
169 use CGI::Push;
170 $q = new CGI::Push;
171 $q->do_push(-next_page=>\&draw_a_page);
172
173 -or-
3e3baf6d 174
54310121 175 use CGI::Push qw(:standard);
176 do_push(-next_page=>\&draw_a_page);
177
178Parameters are as follows:
179
180=over 4
3e3baf6d 181
54310121 182=item -next_page
183
184 do_push(-next_page=>\&my_draw_routine);
185
186This required parameter points to a reference to a subroutine responsible for
187drawing each new page. The subroutine should expect two parameters
188consisting of the CGI object and a counter indicating the number
189of times the subroutine has been called. It should return the
190contents of the page as an B<array> of one or more items to print.
191It can return a false value (or an empty array) in order to abort the
192redrawing loop and print out the final page (if any)
193
194 sub my_draw_routine {
195 my($q,$counter) = @_;
196 return undef if $counter > 100;
197 return start_html('testing'),
198 h1('testing'),
ba056755 199 "This page called $counter times";
54310121 200 }
201
424ec8fa 202You are of course free to refer to create and use global variables
203within your draw routine in order to achieve special effects.
204
54310121 205=item -last_page
206
207This optional parameter points to a reference to the subroutine
208responsible for drawing the last page of the series. It is called
209after the -next_page routine returns a false value. The subroutine
210itself should have exactly the same calling conventions as the
211-next_page routine.
212
213=item -type
214
215This optional parameter indicates the content type of each page. It
424ec8fa 216defaults to "text/html". Normally the module assumes that each page
71f3e297 217is of a homogenous MIME type. However if you provide either of the
424ec8fa 218magic values "heterogeneous" or "dynamic" (the latter provided for the
219convenience of those who hate long parameter names), you can specify
220the MIME type -- and other header fields -- on a per-page basis. See
221"heterogeneous pages" for more details.
54310121 222
223=item -delay
224
225This indicates the delay, in seconds, between frames. Smaller delays
226refresh the page faster. Fractional values are allowed.
227
228B<If not specified, -delay will default to 1 second>
229
ba056755 230=item -cookie, -target, -expires, -nph
54310121 231
232These have the same meaning as the like-named parameters in
233CGI::header().
234
ba056755 235If not specified, -nph will default to 1 (as needed for many servers, see below).
236
54310121 237=back
238
424ec8fa 239=head2 Heterogeneous Pages
240
241Ordinarily all pages displayed by CGI::Push share a common MIME type.
242However by providing a value of "heterogeneous" or "dynamic" in the
243do_push() -type parameter, you can specify the MIME type of each page
244on a case-by-case basis.
245
246If you use this option, you will be responsible for producing the
247HTTP header for each page. Simply modify your draw routine to
248look like this:
249
250 sub my_draw_routine {
251 my($q,$counter) = @_;
252 return header('text/html'), # note we're producing the header here
ba056755 253 start_html('testing'),
424ec8fa 254 h1('testing'),
ba056755 255 "This page called $counter times";
424ec8fa 256 }
257
258You can add any header fields that you like, but some (cookies and
259status fields included) may not be interpreted by the browser. One
260interesting effect is to display a series of pages, then, after the
261last page, to redirect the browser to a new URL. Because redirect()
262does b<not> work, the easiest way is with a -refresh header field,
263as shown below:
264
265 sub my_draw_routine {
266 my($q,$counter) = @_;
ba056755 267 return undef if $counter > 10;
424ec8fa 268 return header('text/html'), # note we're producing the header here
ba056755 269 start_html('testing'),
424ec8fa 270 h1('testing'),
ba056755 271 "This page called $counter times";
424ec8fa 272 }
3cb6de81 273
424ec8fa 274 sub my_last_page {
ba056755 275 return header(-refresh=>'5; URL=http://somewhere.else/finished.html',
276 -type=>'text/html'),
277 start_html('Moved'),
278 h1('This is the last page'),
279 'Goodbye!'
280 hr,
281 end_html;
424ec8fa 282 }
283
284=head2 Changing the Page Delay on the Fly
285
286If you would like to control the delay between pages on a page-by-page
287basis, call push_delay() from within your draw routine. push_delay()
288takes a single numeric argument representing the number of seconds you
289wish to delay after the current page is displayed and before
290displaying the next one. The delay may be fractional. Without
291parameters, push_delay() just returns the current delay.
292
54310121 293=head1 INSTALLING CGI::Push SCRIPTS
294
ba056755 295Server push scripts must be installed as no-parsed-header (NPH)
296scripts in order to work correctly on many servers. On Unix systems,
297this is most often accomplished by prefixing the script's name with "nph-".
54310121 298Recognition of NPH scripts happens automatically with WebSTAR and
299Microsoft IIS. Users of other servers should see their documentation
300for help.
301
ba056755 302Apache web server from version 1.3b2 on does not need server
303push scripts installed as NPH scripts: the -nph parameter to do_push()
304may be set to a false value to disable the extra headers needed by an
305NPH script.
306
54310121 307=head1 AUTHOR INFORMATION
308
71f3e297 309Copyright 1995-1998, Lincoln D. Stein. All rights reserved.
310
311This library is free software; you can redistribute it and/or modify
312it under the same terms as Perl itself.
54310121 313
71f3e297 314Address bug reports and comments to: lstein@cshl.org
54310121 315
316=head1 BUGS
317
318This section intentionally left blank.
319
320=head1 SEE ALSO
321
322L<CGI::Carp>, L<CGI>
3e3baf6d 323
54310121 324=cut
325