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1 package 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 10 # Copyright 1995-2000, 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. 15 16 # The most recent version and complete docs are available at: 17 # http://stein.cshl.org/WWW/software/CGI/ 18 19 $CGI::Push::VERSION='1.04'; 20 use CGI; 21 use CGI::Util 'rearrange'; 22 @ISA = ('CGI'); 23 24 $CGI::DefaultClass = 'CGI::Push'; 25 $CGI::Push::AutoloadClass = 'CGI'; 26 27 # add do_push() and push_delay() to exported tags 28 push(@{$CGI::EXPORT_TAGS{':standard'}},'do_push','push_delay'); 29 30 sub do_push { 31 my ($self,@p) = CGI::self_or_default(@_); 32 33 # unbuffer output 34 $| = 1; 35 srand; 36 my ($random) = sprintf("%08.0f",rand()*1E8); 37 my ($boundary) = "----=_NeXtPaRt$random"; 38 39 my (@header); 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); 41 $type = 'text/html' unless $type; 42 $callback = \&simple_counter unless $callback && ref($callback) eq 'CODE'; 43 $delay = 1 unless defined($delay); 44 $self->push_delay($delay); 45 $nph = 1 unless defined($nph); 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); 51 push(@o,'-Type'=>"multipart/x-mixed-replace;boundary=\"$boundary\""); 52 push(@o,'-Server'=>"CGI.pm Push Module") if $nph; 53 push(@o,'-Status'=>'200 OK'); 54 push(@o,'-nph'=>1) if $nph; 55 print $self->header(@o); 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); 62 63 # now we enter a little loop 64 while (1) { 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}--$CGI::CRLF"; 79 last; 80 } 81 } 82 print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.$CGI::CRLF"; 83 } 84 85 sub simple_counter { 86 my ($self,$count) = @_; 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; 93 } 94 95 sub do_sleep { 96 my $delay = shift; 97 if ( ($delay >= 1) && ($delay!~/\./) ){ 98 sleep($delay); 99 } else { 100 select(undef,undef,undef,$delay); 101 } 102 } 103 104 sub push_delay { 105 my ($self,$delay) = CGI::self_or_default(@_); 106 return defined($delay) ? $self->{'.delay'} = 107 $delay : $self->{'.delay'}; 108 } 109 110 1; 111 112 =head1 NAME 113 114 CGI::Push - Simple Interface to Server Push 115 116 =head1 SYNOPSIS 117 118 use CGI::Push qw(:standard); 119 120 do_push(-next_page=>\&next_page, 121 -last_page=>\&last_page, 122 -delay=>0.5); 123 124 sub next_page { 125 my($q,$counter) = @_; 126 return undef if $counter >= 10; 127 return start_html('Test'), 128 h1('Visible'),"\n", 129 "This page has been called ", strong($counter)," times", 130 end_html(); 131 } 132 133 sub last_page { 134 my($q,$counter) = @_; 135 return start_html('Done'), 136 h1('Finished'), 137 strong($counter - 1),' iterations.', 138 end_html; 139 } 140 141 =head1 DESCRIPTION 142 143 CGI::Push is a subclass of the CGI object created by CGI.pm. It is 144 specialized for server push operations, which allow you to create 145 animated pages whose content changes at regular intervals. 146 147 You provide CGI::Push with a pointer to a subroutine that will draw 148 one page. Every time your subroutine is called, it generates a new 149 page. The contents of the page will be transmitted to the browser 150 in such a way that it will replace what was there beforehand. The 151 technique will work with HTML pages as well as with graphics files, 152 allowing you to create animated GIFs. 153 154 Only Netscape Navigator supports server push. Internet Explorer 155 browsers do not. 156 157 =head1 USING CGI::Push 158 159 CGI::Push adds one new method to the standard CGI suite, do_push(). 160 When you call this method, you pass it a reference to a subroutine 161 that is responsible for drawing each new page, an interval delay, and 162 an optional subroutine for drawing the last page. Other optional 163 parameters include most of those recognized by the CGI header() 164 method. 165 166 You may call do_push() in the object oriented manner or not, as you 167 prefer: 168 169 use CGI::Push; 170 $q = new CGI::Push; 171 $q->do_push(-next_page=>\&draw_a_page); 172 173 -or- 174 175 use CGI::Push qw(:standard); 176 do_push(-next_page=>\&draw_a_page); 177 178 Parameters are as follows: 179 180 =over 4 181 182 =item -next_page 183 184 do_push(-next_page=>\&my_draw_routine); 185 186 This required parameter points to a reference to a subroutine responsible for 187 drawing each new page. The subroutine should expect two parameters 188 consisting of the CGI object and a counter indicating the number 189 of times the subroutine has been called. It should return the 190 contents of the page as an B<array> of one or more items to print. 191 It can return a false value (or an empty array) in order to abort the 192 redrawing loop and print out the final page (if any) 193 194 sub my_draw_routine { 195 my($q,$counter) = @_; 196 return undef if $counter > 100; 197 return start_html('testing'), 198 h1('testing'), 199 "This page called $counter times"; 200 } 201 202 You are of course free to refer to create and use global variables 203 within your draw routine in order to achieve special effects. 204 205 =item -last_page 206 207 This optional parameter points to a reference to the subroutine 208 responsible for drawing the last page of the series. It is called 209 after the -next_page routine returns a false value. The subroutine 210 itself should have exactly the same calling conventions as the 211 -next_page routine. 212 213 =item -type 214 215 This optional parameter indicates the content type of each page. It 216 defaults to "text/html". Normally the module assumes that each page 217 is of a homogenous MIME type. However if you provide either of the 218 magic values "heterogeneous" or "dynamic" (the latter provided for the 219 convenience of those who hate long parameter names), you can specify 220 the MIME type -- and other header fields -- on a per-page basis. See 221 "heterogeneous pages" for more details. 222 223 =item -delay 224 225 This indicates the delay, in seconds, between frames. Smaller delays 226 refresh the page faster. Fractional values are allowed. 227 228 B<If not specified, -delay will default to 1 second> 229 230 =item -cookie, -target, -expires, -nph 231 232 These have the same meaning as the like-named parameters in 233 CGI::header(). 234 235 If not specified, -nph will default to 1 (as needed for many servers, see below). 236 237 =back 238 239 =head2 Heterogeneous Pages 240 241 Ordinarily all pages displayed by CGI::Push share a common MIME type. 242 However by providing a value of "heterogeneous" or "dynamic" in the 243 do_push() -type parameter, you can specify the MIME type of each page 244 on a case-by-case basis. 245 246 If you use this option, you will be responsible for producing the 247 HTTP header for each page. Simply modify your draw routine to 248 look like this: 249 250 sub my_draw_routine { 251 my($q,$counter) = @_; 252 return header('text/html'), # note we're producing the header here 253 start_html('testing'), 254 h1('testing'), 255 "This page called $counter times"; 256 } 257 258 You can add any header fields that you like, but some (cookies and 259 status fields included) may not be interpreted by the browser. One 260 interesting effect is to display a series of pages, then, after the 261 last page, to redirect the browser to a new URL. Because redirect() 262 does b<not> work, the easiest way is with a -refresh header field, 263 as shown below: 264 265 sub my_draw_routine { 266 my($q,$counter) = @_; 267 return undef if $counter > 10; 268 return header('text/html'), # note we're producing the header here 269 start_html('testing'), 270 h1('testing'), 271 "This page called $counter times"; 272 } 273 274 sub my_last_page { 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; 282 } 283 284 =head2 Changing the Page Delay on the Fly 285 286 If you would like to control the delay between pages on a page-by-page 287 basis, call push_delay() from within your draw routine. push_delay() 288 takes a single numeric argument representing the number of seconds you 289 wish to delay after the current page is displayed and before 290 displaying the next one. The delay may be fractional. Without 291 parameters, push_delay() just returns the current delay. 292 293 =head1 INSTALLING CGI::Push SCRIPTS 294 295 Server push scripts must be installed as no-parsed-header (NPH) 296 scripts in order to work correctly on many servers. On Unix systems, 297 this is most often accomplished by prefixing the script's name with "nph-". 298 Recognition of NPH scripts happens automatically with WebSTAR and 299 Microsoft IIS. Users of other servers should see their documentation 300 for help. 301 302 Apache web server from version 1.3b2 on does not need server 303 push scripts installed as NPH scripts: the -nph parameter to do_push() 304 may be set to a false value to disable the extra headers needed by an 305 NPH script. 306 307 =head1 AUTHOR INFORMATION 308 309 Copyright 1995-1998, Lincoln D. Stein. All rights reserved. 310 311 This library is free software; you can redistribute it and/or modify 312 it under the same terms as Perl itself. 313 314 Address bug reports and comments to: lstein@cshl.org 315 316 =head1 BUGS 317 318 This section intentionally left blank. 319 320 =head1 SEE ALSO 321 322 L<CGI::Carp>, L<CGI> 323 324 =cut 325
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