lib/CGI/Push.pm

package CGI::Push;

# See the bottom of this file for the POD documentation.  Search for the
# string '=head'.

# You can run this file through either pod2man or pod2html to produce pretty
# documentation in manual or html file format (these utilities are part of the
# Perl 5 distribution).

# Copyright 1995-2000, Lincoln D. Stein.  All rights reserved.
# It may be used and modified freely, but I do request that this copyright
# notice remain attached to the file.  You may modify this module as you 
# wish, but if you redistribute a modified version, please attach a note
# listing the modifications you have made.

# The most recent version and complete docs are available at:
#   http://stein.cshl.org/WWW/software/CGI/

$CGI::Push::VERSION='1.04';
use CGI;
use CGI::Util 'rearrange';
@ISA = ('CGI');

$CGI::DefaultClass = 'CGI::Push';
$CGI::Push::AutoloadClass = 'CGI';

# add do_push() and push_delay() to exported tags
push(@{$CGI::EXPORT_TAGS{':standard'}},'do_push','push_delay');

sub do_push {
    my ($self,@p) = CGI::self_or_default(@_);

    # unbuffer output
    $| = 1;
    srand;
    my ($random) = sprintf("%08.0f",rand()*1E8);
    my ($boundary) = "----=_NeXtPaRt$random";

    my (@header);
    my ($type,$callback,$delay,$last_page,$cookie,$target,$expires,$nph,@other) = rearrange([TYPE,NEXT_PAGE,DELAY,LAST_PAGE,[COOKIE,COOKIES],TARGET,EXPIRES,NPH],@p);
    $type = 'text/html' unless $type;
    $callback = \&simple_counter unless $callback && ref($callback) eq 'CODE';
    $delay = 1 unless defined($delay);
    $self->push_delay($delay);
    $nph = 1 unless defined($nph);

    my(@o);
    foreach (@other) { push(@o,split("=")); }
    push(@o,'-Target'=>$target) if defined($target);
    push(@o,'-Cookie'=>$cookie) if defined($cookie);
    push(@o,'-Type'=>"multipart/x-mixed-replace;boundary=\"$boundary\"");
    push(@o,'-Server'=>"CGI.pm Push Module") if $nph;
    push(@o,'-Status'=>'200 OK');
    push(@o,'-nph'=>1) if $nph;
    print $self->header(@o);

    $boundary = "$CGI::CRLF--$boundary";

    print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.${boundary}$CGI::CRLF";

    my (@contents) = &$callback($self,++$COUNTER);

    # now we enter a little loop
    while (1) {
        print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
        print @contents;
        @contents = &$callback($self,++$COUNTER);
        if ((@contents) && defined($contents[0])) {
            print "${boundary}$CGI::CRLF";
            do_sleep($self->push_delay()) if $self->push_delay();
        } else {
            if ($last_page && ref($last_page) eq 'CODE') {
                print "${boundary}$CGI::CRLF";
                do_sleep($self->push_delay()) if $self->push_delay();
                print "Content-type: ${type}$CGI::CRLF$CGI::CRLF" unless $type =~ /^dynamic|heterogeneous$/i;
                print  &$last_page($self,$COUNTER);
            }
            print "${boundary}--$CGI::CRLF";
            last;
        }
    }
    print "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY.$CGI::CRLF";
}

sub simple_counter {
    my ($self,$count) = @_;
    return $self->start_html("CGI::Push Default Counter"),
           $self->h1("CGI::Push Default Counter"),
           "This page has been updated ",$self->strong($count)," times.",
           $self->hr(),
           $self->a({'-href'=>'http://www.genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html'},'CGI.pm home page'),
           $self->end_html;
}

sub do_sleep {
    my $delay = shift;
    if ( ($delay >= 1) && ($delay!~/\./) ){
        sleep($delay);
    } else {
        select(undef,undef,undef,$delay);
    }
}

sub push_delay {
    my ($self,$delay) = CGI::self_or_default(@_);
    return defined($delay) ? $self->{'.delay'} = 
        $delay : $self->{'.delay'};
}

1;

=head1 NAME

CGI::Push - Simple Interface to Server Push

=head1 SYNOPSIS

    use CGI::Push qw(:standard);

    do_push(-next_page=>\&next_page,
            -last_page=>\&last_page,
            -delay=>0.5);

    sub next_page {
        my($q,$counter) = @_;
        return undef if $counter >= 10;
        return start_html('Test'),
               h1('Visible'),"\n",
               "This page has been called ", strong($counter)," times",
               end_html();
    }

    sub last_page {
        my($q,$counter) = @_;
        return start_html('Done'),
               h1('Finished'),
               strong($counter - 1),' iterations.',
               end_html;
    }

=head1 DESCRIPTION

CGI::Push is a subclass of the CGI object created by CGI.pm.  It is
specialized for server push operations, which allow you to create
animated pages whose content changes at regular intervals.

You provide CGI::Push with a pointer to a subroutine that will draw
one page.  Every time your subroutine is called, it generates a new
page.  The contents of the page will be transmitted to the browser
in such a way that it will replace what was there beforehand.  The
technique will work with HTML pages as well as with graphics files, 
allowing you to create animated GIFs.

Only Netscape Navigator supports server push.  Internet Explorer
browsers do not.

=head1 USING CGI::Push

CGI::Push adds one new method to the standard CGI suite, do_push().
When you call this method, you pass it a reference to a subroutine
that is responsible for drawing each new page, an interval delay, and
an optional subroutine for drawing the last page.  Other optional
parameters include most of those recognized by the CGI header()
method.

You may call do_push() in the object oriented manner or not, as you
prefer:

    use CGI::Push;
    $q = new CGI::Push;
    $q->do_push(-next_page=>\&draw_a_page);

        -or-

    use CGI::Push qw(:standard);
    do_push(-next_page=>\&draw_a_page);

Parameters are as follows:

=over 4

=item -next_page

    do_push(-next_page=>\&my_draw_routine);

This required parameter points to a reference to a subroutine responsible for
drawing each new page.  The subroutine should expect two parameters
consisting of the CGI object and a counter indicating the number
of times the subroutine has been called.  It should return the
contents of the page as an B<array> of one or more items to print.  
It can return a false value (or an empty array) in order to abort the
redrawing loop and print out the final page (if any)

    sub my_draw_routine {
        my($q,$counter) = @_;
        return undef if $counter > 100;
        return start_html('testing'),
               h1('testing'),
               "This page called $counter times";
    }

You are of course free to refer to create and use global variables
within your draw routine in order to achieve special effects.

=item -last_page

This optional parameter points to a reference to the subroutine
responsible for drawing the last page of the series.  It is called
after the -next_page routine returns a false value.  The subroutine
itself should have exactly the same calling conventions as the
-next_page routine.

=item -type

This optional parameter indicates the content type of each page.  It
defaults to "text/html".  Normally the module assumes that each page
is of a homogenous MIME type.  However if you provide either of the
magic values "heterogeneous" or "dynamic" (the latter provided for the
convenience of those who hate long parameter names), you can specify
the MIME type -- and other header fields -- on a per-page basis.  See 
"heterogeneous pages" for more details.

=item -delay

This indicates the delay, in seconds, between frames.  Smaller delays
refresh the page faster.  Fractional values are allowed.

B<If not specified, -delay will default to 1 second>

=item -cookie, -target, -expires, -nph

These have the same meaning as the like-named parameters in
CGI::header().

If not specified, -nph will default to 1 (as needed for many servers, see below).

=back

=head2 Heterogeneous Pages

Ordinarily all pages displayed by CGI::Push share a common MIME type.
However by providing a value of "heterogeneous" or "dynamic" in the
do_push() -type parameter, you can specify the MIME type of each page
on a case-by-case basis.  

If you use this option, you will be responsible for producing the
HTTP header for each page.  Simply modify your draw routine to
look like this:

    sub my_draw_routine {
        my($q,$counter) = @_;
        return header('text/html'),   # note we're producing the header here
               start_html('testing'),
               h1('testing'),
               "This page called $counter times";
    }

You can add any header fields that you like, but some (cookies and
status fields included) may not be interpreted by the browser.  One
interesting effect is to display a series of pages, then, after the
last page, to redirect the browser to a new URL.  Because redirect() 
does b<not> work, the easiest way is with a -refresh header field,
as shown below:

    sub my_draw_routine {
        my($q,$counter) = @_;
        return undef if $counter > 10;
        return header('text/html'),   # note we're producing the header here
               start_html('testing'),
               h1('testing'),
               "This page called $counter times";
    }

    sub my_last_page {
        return header(-refresh=>'5; URL=http://somewhere.else/finished.html',
                      -type=>'text/html'),
               start_html('Moved'),
               h1('This is the last page'),
               'Goodbye!'
               hr,
               end_html; 
    }

=head2 Changing the Page Delay on the Fly

If you would like to control the delay between pages on a page-by-page
basis, call push_delay() from within your draw routine.  push_delay()
takes a single numeric argument representing the number of seconds you
wish to delay after the current page is displayed and before
displaying the next one.  The delay may be fractional.  Without
parameters, push_delay() just returns the current delay.

=head1 INSTALLING CGI::Push SCRIPTS

Server push scripts must be installed as no-parsed-header (NPH)
scripts in order to work correctly on many servers.  On Unix systems,
this is most often accomplished by prefixing the script's name with "nph-".  
Recognition of NPH scripts happens automatically with WebSTAR and 
Microsoft IIS.  Users of other servers should see their documentation
for help.

Apache web server from version 1.3b2 on does not need server
push scripts installed as NPH scripts: the -nph parameter to do_push()
may be set to a false value to disable the extra headers needed by an
NPH script.

=head1 AUTHOR INFORMATION

Copyright 1995-1998, Lincoln D. Stein.  All rights reserved.  

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

Address bug reports and comments to: lstein@cshl.org

=head1 BUGS

This section intentionally left blank.

=head1 SEE ALSO

L<CGI::Carp>, L<CGI>

=cut

Revision:	1.1
Committed:	Thu Jun 30 14:27:09 2005 UTC (21 years, 4 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	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