/*

  
  					W3C Sample Code Library libwww BEFORE and AFTER Filters


!
  Standard BEFORE and AFTER Filters
!
*/

/*
**	(c) COPYRIGHT MIT 1995.
**	Please first read the full copyright statement in the file COPYRIGH.
*/

/*

This module provides a set of default BEFORE and AFTER filters
that can be registered by the Net manager to be
called before and after a request. All filters can be registered either to
be called globally (all requests) or locally (pr request basis).

This module is implemented by HTFilter.c, and it
is a part of the  W3C Sample Code
Library.
*/

#ifndef HTFILTER_H
#define HTFILTER_H
#include "WWWLib.h"

/*
.
  BEFORE Filters
.

This is a standard set of BEFORE filters which the application may
initialize. This can be done in an easy way using the function
HTBeforeInit() in the Initialization
interface.
(
  Proxy and Gateway BEFORE filter
)

Checks for registerd proxy servers or gateways and sees whether this request
should be redirected to a proxy or a gateway. Proxies have higher priority
than gateways so we look for them first! For HTTP/1.0 and HTTP/1.1 we may
only send a full URL (including the host portion) to proxy servers. Therefore,
we tell the Library whether to use the full URL or the traditional HTTP one
without the host part.
*/

extern HTNetBefore HTProxyFilter;

/*
(
  Rule Translation BEFORE Filter
)

If we have a set of rules loaded (see the Rule manager) then check before
each request whether how that should be translated. The trick is that a parent
anchor has a "address" which is the part from the URL we used when we created
the anchor. However, it also have a "physical address" which is the place
we are actually going to look for the resource. Hence this filter translates
from the address to the physical address (if any translations are found)
*/

extern HTNetBefore HTRuleFilter;

/*
(
  Memory Cache (History List) Validation BEFORE Filter
)

Check if document is already loaded. The user can define whether the history
list should follow normal expiration or work as a traditional history list
where expired documents are not updated. We don't check for anything but
existence proof of a document associated with the anchor as the definition
is left to the application.
*/

extern HTNetBefore HTMemoryCacheFilter;

/*
(
  Persistent Cache Validation BEFORE Filter
)

Check the cache mode to see if we can use an already loaded version of this
document. If so and our copy is valid then we don't have to go out and get
it unless we are forced to
*/

extern HTNetBefore HTCacheFilter;

/*
(
  Client side authentication BEFORE filter
)

The filter generates the credentials required to access a document Getting
the credentials may involve asking the user in which case we use the methods
registered by the HTAlert module
*/
    
extern HTNetBefore HTCredentialsFilter;

/*
.
  AFTER Filters
.

Like BEFORE filters we provide a default set of typical AFTER
filters that may be initialized by the application. Again, an easy way of
doing this is to call the HTAfterInit() function in the
Initialization interface.
(
  Persistent Cache Update AFTER filter
)

On our way out we catch the metainformation and stores it in our persistent
store. If we have a cache validation (a 304 response then we use the new
metainformation and merges it with the existing information already captured
in the cache.
*/

extern HTNetAfter HTCacheUpdateFilter;

/*
(
  Error and Information filter
)

It checks the status code from a request and generates an error/information
message if required.
*/

extern HTNetAfter HTInfoFilter;

/*
(
  Redirection filter
)

The redirection handler only handles automatic redirections on the GET
or HEAD method (or any other safe method). The users is asked for
all other methods.
*/

extern HTNetAfter HTRedirectFilter;

/*
(
  Proxy Redirection filter
)

This filter handles a "305 Use Proxy" response and retries the
request through the proxy
*/

extern HTNetAfter HTUseProxyFilter;

/*
(
  Client side authentication filter
)

The client side authentication filter uses the user dialog messages registered
in the HTAlert module. By default these are the
ones used by the line mode browser but you can just register something else.
*/

extern HTNetAfter HTAuthFilter;

/*
(
  Request Common Log File Filter
)

Default Logging filter using the log manager provided by the
Log Manager.
*/

extern HTNetAfter HTLogFilter;

/*

(
  Request Referer Log File Filter
)

Default Referer Log filter using the log manager provided by the
Log Manager.
*/

extern HTNetAfter HTRefererFilter;

/*

*/

#endif /* HTFILTER_H */

/*

  

  @(#) $Id: HTFilter.html,v 2.11 1998/05/14 02:10:29 frystyk Exp $

*/
