# Application Interface

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

In addition top the basic W3C Reference Library WWWLib interface you may include the other interfaces depending on the needs of your application. However, it is not required and none of the files included below are ever used in the core part of the Library itself. Only if this file is included, the extra modules will get included in the linked object code. It is also possible to include only a subset of the files below if the functionality you are after is covered by them. This interface contains many application specific features including a set of default BEFORE and AFTER filters.

    #ifndef WWWAPP_H
    #define WWWAPP_H

    #ifdef __cplusplus
    extern "C" {
    #endif

### System dependencies

The sysdep.h file includes system-specific include files and flags for I/O to network and disk. The only reason for this file is that the Internet world is more complicated than Posix and ANSI.

    #include "sysdep.h"

### Event Manager

The core part of libwww only provides the hooks for the event manager. There is no event loop internal to the core part. Instead the application must provide the event loop in order to use either pseudo threads or real threads. If the application only uses blocking sockets without threads then it is not required to register any event loop at all. We provide a default implementation of an event loop which you can either take or get some ideas from.

    #include "HTEvntrg.h"

### Managing the Home Page

This module provides some "make life easier" functions in order to get the application going. They help you generate the first anchor, also called the home anchor. It also contains a nice set of default WWW addresses.

    #include "HTHome.h"

### User Dialogs and Messages

You can register a set of callback functions to handle user prompting, error messages, confimations etc. Here we give a set of functions that can be used on almost anu thinkable platform. If you want to provide your own platform dependent implementation then fine :-)

    #include "HTDialog.h"

### Load, Upload, and Search URLs

Even though you may use the API for the HTRequest object directly in order to issue a request, you will probably find that in real life it is easier to use a higher level abstraction API. This API is provided by the HTAccess module where you will find all kind of functions for down loading a URL etc.

    #include "HTAccess.h"

### Rule File Management

Another way to initialize applications is to use a rule file, also known as a configuration file. This is for example the case with the W3C httpd and the W3C Line Mode Browser. This module provides basic support for configuration file management and the application can use this is desired. The module is not referred to by the Library. Reading a rule file is implemented as a stream converter so that a rule file can come from anywhere, even across the network!

    #include "HTRules.h"

### Proxies and Gateways

Applications do not have to provide native support for all protocols, they can in many situations rely on the support of proxies and gateways to help doing the job. Proxy servers are often used to carry client requests through a firewall where they can provide services like corporate caching and other network optimizations. Both Proxy servers and gateways can serve as "protocol translators" which can convert a request in the main Web protocol, HTTP, to an equivalent request in another protocol, for example NNTP, FTP, or Gopher. In case a proxy server or a gateway is available to the application, it can therefore by use of HTTP forward all requests to for example a proxy server which then handle the communications with the remote server, for example using FTP about the document and return it to the application (proxy client) using HTTP.

    #include "HTProxy.h"

### BEFORE and AFTER Filters

Before a request has been issued and after it has terminated the application often has to do some action as a result of the request (and of the result of the request). The Client Profile Interface Library provides a set of standard BEFORE and AFTER filters to handle caching, redirection, authentication, logging etc.

    #include "HTFilter.h"

### Logging

Often it is required to log the requests issued to the Library. This can either be the case if the application is a server or it can also be useful in a client application. This module provides a simple logging mechanism which can be enabled if needed.

    #include "HTLog.h"

### History Management

Another type of logging is keeping track of which documents a user has visited when browsing along on the Web. The Library history manager provides a basic set of functionality to keep track of a linear history list.

    #include "HTHist.h"

End of application specific modules

    #ifdef __cplusplus
    } /* end extern C definitions */
    #endif

    #endif