Passing data structures between Stacked Handlers

[Thomas Klausner <do...@zsi.at>]

Hi!

Is there a module that can do "Stacked Handler Pipelining", but 
doesn't pass around tied filehandles but data structures ?

If there isn't, could it be implemented by dumping the data 
structure to $r->notes (with Data::Dumper) and have it eval'ed back 
by the next handler?


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O_xyderkes
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Re: Passing data structures between Stacked Handlers

[sp...@vancouver.yi.org]

On Sun, 12 Nov 2000, Dave Kaufman wrote:

> > Is there a module that can do "Stacked Handler Pipelining", but 
> > doesn't pass around tied filehandles but data structures ?

Can't you allocate some generic namespace, or better yet, create your own
package called config and in that export functions get_config set_config
They will get/set a package wide variable. Then you make new,DESTROY, and
what other functions you need. Then you create/set object in the Init
module and the way you go, call get_config in each of the stacked modules
and insert data into it, so it will be passed along. Simple alternative,
you can store a hash in package wide namespace of the first package, and
access that via hashref, which is more convinient or Package::hashname
notation.
Thats how I did it.

> > If there isn't, could it be implemented by dumping the data 
> > structure to $r->notes (with Data::Dumper) and have it eval'ed back 
> > by the next handler?

God NO! Have you read of overhead incurring on eval? Might as well go back
to the days of PerlCGI,<choke, choke>

Hope that helped.
Pavel

Re: Passing data structures between Stacked Handlers

[Dave Kaufman <dk...@nac.net>]

"Thomas Klausner" <do...@zsi.at> wrote:
> Is there a module that can do "Stacked Handler Pipelining", but 
> doesn't pass around tied filehandles but data structures ?
 
Andreas König's Apache::HeavyCGI is a nice alternative approach to the use of stacked handlers.  

> If there isn't, could it be implemented by dumping the data 
> structure to $r->notes (with Data::Dumper) and have it eval'ed back 
> by the next handler?

I just started playing around with HeavyCGI, but it uses the "Singleton" approach: one master handler "dispatches" each request to to all the modules that are needed, first allowing each a shot at processing headers (last-mod times, conditional tests, early errors, etc), then for content, and finally for cleanup, fixup, etc.  this lets them all play together without the strict stacking and inefficient error-handling of stacked hadlers.

http://search.cpan.org/search?dist=Apache-HeavyCGI

-dave

Re: Passing data structures between Stacked Handlers

[Thomas Klausner <do...@zsi.at>]

Hi!

> If you use $r->pnotes, you can just put a reference to an arbitrary data
> structure into it and it will still be there in the next handler.  No
> need to serialize it with Data::Dumper.  Better than using a normal
> global because it gets automatically cleaned up after the request.
Thanks for the info.

Ken Williams <ke...@forum.swarthmore.edu> also told me that 
$r->pnotes wasn't included in the Eagle Book because it (pnotes, 
not the book) wasn't implemented then. The old problem with 
books.


-- 
D_OMM              http://domm.zsi.at
O_xyderkes
M_echanen    NEU (naja): Wohnungs-Historie
M_asteuei     http://domm.zsi.at/curvit/wohnen.html

Re: Passing data structures between Stacked Handlers

[Perrin Harkins <pe...@primenet.com>]

Thomas Klausner wrote:
> If there isn't, could it be implemented by dumping the data
> structure to $r->notes (with Data::Dumper) and have it eval'ed back
> by the next handler?

If you use $r->pnotes, you can just put a reference to an arbitrary data
structure into it and it will still be there in the next handler.  No
need to serialize it with Data::Dumper.  Better than using a normal
global because it gets automatically cleaned up after the request.
- Perrin