# Proxy and gateway Manager

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

This module keeps a list of proxies and gateways to be contacted on a request in stead of requesting it directly from the origin server. The module replaces the old system of environment variables for gateways and proxies. However for backward compatibility there is a function that reads the environment variables at start up. Note that there is a difference between a proxy and a gateway - the difference is the way the URL is set up in the RequestLine of the HTTP request. If the original, full URL looks like `"http://www.w3.org/test.html"` then the result will for a proxy is `"http://www.w3.org/test.html"` and a gateway `"/www.w3.org/test.html"`

The module is implemented by HTProxy.c, and it is a part of the W3C Sample Code Library.

    #ifndef HTPROXY_H
    #define HTPROXY_H

    #include "HTList.h"

## Registering a proxy server

A proxy server is registered with a corresponding access method, for example http, ftp etc. The `proxy' parameter should be a fully valid name, like `http://proxy.w3.org:8001` but domain name is not required. If an entry exists for this access then delete it and use the new one.

    extern BOOL HTProxy_add		(const char * access, const char * proxy);
    extern BOOL HTProxy_deleteAll	(void);

The remove function removes all registered proxies. This is automatically done in HTLibTerminate()

## Registering a host or domain with no proxy

The noproxy list is a list of host names and domain names where we don't contact a proxy even though a proxy is in fact registered for this particular access method . When registering a noproxy item, you can specify a specific port for this access method in which case it isvalid only for requests to this port. If `port' is '0' then it applies to all ports and if `access' is NULL then it applies to to all access methods. Examples of host names are `w3.org` and `www.close.com`

    extern BOOL HTNoProxy_add	(const char * host, const char * access,
    				 unsigned port);
    extern BOOL HTNoProxy_deleteAll	(void);

The remove function removes all entries in the list. This is automatically done in HTLibTerminate()

## Look for a Proxy server

This function evaluates the lists of registered proxies and if one is found for the actual access method and it is not registered in the `noproxy' list, then a URL containing the host to be contacted is returned to the caller. This string must be freed be the caller.

    extern char * HTProxy_find	(const char * url);

## Registering a gateway

A gateway is registered with a corresponding access method, for example http, ftp etc. The `gate' parameter should be a fully valid name, like `http://gateway.w3.org:8001` but domain name is not required. If an entry exists for this access then delete it and use the new one.

    extern BOOL HTGateway_add	(const char * access, const char * gate);
    extern BOOL HTGateway_deleteAll	(void);

The remove function removes all registered proxies. This is automatically done in HTLibTerminate()

## Look for a Gateway

This function evaluates the lists of registered gateways and if one is found for the actual access method then it is returned and must be freed by the caller.

    extern char * HTGateway_find	(const char * url);

## Backwards Compability with Environment Variables

This function maintains backwards compatibility with the old environment variables and searches for the most common values: http, ftp, news, wais, and gopher

    extern void HTProxy_getEnvVar	(void);

    #endif /* HTPROXY_H */