Copyright (C) 1995, Digital Equipment Corporation. 
 All rights reserved. 
 Last modified on Tue Mar 18 15:47:53 PST 1997 by steveg 


This interface provides a general structure for HTTP applications. The client writes the handlers for arguments, logging, request, and replies while the library handles the basic HTTP processing.

  App, HTTP, IP, Rd, Wr;

  RequestPriority = {High, Normal, Low};

  RequestHandler <: RequestHandlerPublic;
  RequestHandlerPublic = OBJECT
    priority: RequestPriority := RequestPriority.Normal;
    accept(request: HTTP.Request; serverData: REFANY;
           VAR (* OUT *) acceptState: REFANY;
           log: App.Log): BOOLEAN RAISES {App.Error};
    (* returns TRUE if the handler is prepared to accept the

       "serverData" is data given to the "Serve" procedure by the application.
       "acceptState" is passed on to "request" if if the request is accepted.

    request(request: HTTP.Request;
            serverData, acceptState: REFANY;
            rd: Rd.T; wr: Wr.T; log: App.Log)
            RAISES {App.Error};
    (* "request" is invoked in its own thread for a request received
       by the server.

       "serverData" is data passed to the "Serve" procedure
       "acceptState" is data created in the "accept" method
       "request" is a parsed HTTP header,
       "rd" is a reader on the the remainder of the request.
       "wr" is a writer for the reply.
       "log" is for reporting conditions to the server's log.
          "status" and "error" messages to "log" are also written to

  ReplyHandler <: ReplyHandlerPublic;
  ReplyHandlerPublic = OBJECT
    reply(reply: HTTP.Reply; rd: Rd.T; wr: Wr.T; log: App.Log)
          RAISES {App.Error};
    (* reply is normally invoked to handle the reply of
       a client request or proxied request.

       "reply" is the parsed headers of the reply.  "rd" is a reader
       on the remainder of the reply.

       "wr" is the writer given to the "Client" call.

       "log" is for reporting conditions to the server's log.

       The reply handler filters the contents of "rd" and writes
       them to "wr".

  Server <: ServerPublic;
  ServerPublic = OBJECT
    server: TEXT;
    port: INTEGER;
    endpoint: IP.Endpoint;
    init(server: TEXT; port: INTEGER; log: App.Log): Server
      RAISES {App.Error};
    (* initializes server, port and sets the endpoint.  If
       "server" = "DIRECT" then the server will not
       proxy but will go directly to the true destination *)
    initParse(serverAndPort: TEXT; log: App.Log): Server
      RAISES {App.Error};
    (* "serverAndPort" is in <server>[:<port>] or
       http://<server>[:port]/" format (the latter is for compatibility
       with Mosaic environment variables).  If the port is
       not given, then "defaultPort" is used.
       If serverAndPort = "DIRECT" then the server will not
       proxy but will go directly to the true destination

  ServerList = REF RECORD
                     head: Server;
                     tail: ServerList := NIL;

  ProxyRules = REF RECORD
                    hostPattern: TEXT;
                    proxy     : ServerList;
                    tail      : ProxyRules;

  Proxy <: ProxyPublic;
  (* a "proxy" is a list of proxy rules: host patterns and proxies.
     When proxying, a host is matched against each pattern in order and
     the first matching pattern wins.  Each proxy in the proxy server
     list is tried in turn.  If the proxy server is "DIRECT" then a
     direct connection to the URL's server is tried.  If any
     connection fails, the next proxy server is tried.

     There is a "*:DIRECT" proxy rule as the last rule (set by "init").
  ProxyPublic =
      rules, tail: ProxyRules;
      init (): Proxy;
      add (rule: TEXT; log: App.Log) RAISES {App.Error};
      (* "add" adds a new proxy rule to the end of the proxy rules

         "rule" is a text formatted:
         <hostPattern> <server>[,<server>]*

         "hostPattern" is a simple pattern including '?' to match
         any one character and '*' to match any sequence of 0 or more

         if any "server" is "DIRECT" then it corresponds to
         a non-proxy direct connection

PROCEDURE Serve (port, serviceValue: INTEGER;
                 log               : App.Log   := NIL;
                 serverData        : REFANY    := NIL  )
  RAISES {App.Error};
Listen sits in a loop waiting for HTTP requests on port. Messages written to log should be presented to the user of the application (as desired).

serverData is passed to the accept and request methods of the RequestHandlers when requests are made. Any request handler that matches the port or the serviceValue may be called.

If log = NIL then the log handler will write to stdout and to the wr of the request

PROCEDURE ServerPort(port, service: INTEGER): BOOLEAN;
Return TRUE if there has been a call on Serve for port and service

PROCEDURE Client(request: HTTP.Request;
                 proxy: Proxy;
                 style: HTTP.Style;
                 rd: Rd.T;
                 wr: Wr.T;
                 handler: ReplyHandler;
                 service: INTEGER;
                 log: App.Log := NIL) RAISES {App.Error};
Make a client request or proxy a client request. The request is made directly if there is no proxy given or the proxy rule matching the URL specifies DIRECT.

If style is NIL, then DefaultStyle() is used.

Program information (user-agent, or via) header is added automatically to the request.

Host: header is added automatically to the request

If rd is not NIL, read from rd and send it with the request.

After request is sent to the server, the header of the reply is parsed and handler.reply is called with wr for its output.

service is the number of the service associated with a Serve call. It is used to determine if the request is to a port associated with the current service or another. If you didn't make a Serve call then use AnyService.

If log = NIL then log := App.defaultLog

  AnyPort = 0;
  AnyService = 0;

PROCEDURE RegisterRequestHandler(port: INTEGER; handler: RequestHandler);
Adds handler to the handlers known to the server. When the server gets a request, it invokes the handlers until one services the request. The handler will only get called if port matches the server's port or port = AnyPort or if port < 0 then port represents a service type, and the request handler is invoked if port matches the server's service type. (Make sure the services have different values, :-)

NOTE: a given request handler can only listen on a single port

  ServerPushBoundaryString = "ServerPushBoundary\n";
  ServerPushBoundaryStringStart = "--ServerPushBoundary\n";
  ServerPushBoundaryStringEnd = "--ServerPushBoundary--\n";

PROCEDURE ServerPushSupported(request: HTTP.Request): BOOLEAN;

PROCEDURE ServerPushFrame(wr: Wr.T; contentType: TEXT := "text/html";
                          msg: TEXT; log: App.Log) RAISES {App.Error};

PROCEDURE DefaultProxy(log: App.Log := NIL): Proxy RAISES {App.Error};
returns the proxy defined by the user arguments given (must be called AFTER App.InitializeArguments):

switch env config default -pac HTTP_PAC pac: *: DIRECT

If log = NIL then DefaultLog will be used.