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Push (3)
  • >> Push (3) ( Solaris man: Библиотечные вызовы )
  • 
    
    

    NAME

         CGI::Push - Simple Interface to Server Push
    
    
    

    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),' iterations.',
                         end_html;
              }
    
    
    
    

    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.
    
    
    

    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:
    
         -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 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.
    
         -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.
    
         -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.
    
         -delay
             This indicates the delay, in seconds, between frames.
             Smaller delays refresh the page faster.  Fractional
             values are allowed.
    
             If not specified, -delay will default to 1 second
    
         -cookie, -target, -expires
             These have the same meaning as the like-named parameters
             in CGI::header().
    
         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 {
                 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;
             }
    
    
         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.
    
    
    

    INSTALLING CGI::Push SCRIPTS

         Server push scripts must be installed as no-parsed-header
         (NPH) scripts in order to work correctly.  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.
    
    
    

    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
    
    
    

    BUGS

         This section intentionally left blank.
    
    
    

    SEE ALSO

         the CGI::Carp manpage, the CGI manpage
    
    
    
    


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