The Web interface retrieves documents from the World Wide Web using an http proxy server. Details about the HTTP protocol are in

           http://info.cern.ch/hypertext/WWW/Protocols/HTTP/HTTP2.html

INTERFACE Web;

IMPORT Date, IP, Rd, Thread;

EXCEPTION Error(TEXT);

TYPE T <: ROOT;

A Web.T identifies an http proxy server. The routines in this interface that take a Web.T as a parameter accept the value NIL, which represents the default proxy server obtained by calling Setup(NIL).

CONST
  DefaultProxyHost   = NIL;
       (* At SRC, set it to "http://www-proxy.pa.dec.com:8080/" instead *)
  DefaultNoProxyList = "";
       (*  At SRC, set it to "src-www,.dec.com" instead *)

PROCEDURE Setup (proxyURL, noProxyList: TEXT := NIL): T
  RAISES {Error};

Return a data type representing an http proxy server.

           http://hostname.blah.blah.blah:8080/
   

noProxyList specifies a set of domains for which the proxy should not be consulted; the format is a comma-separated list of domain names, with optional port. If noProxyList is NIL, it defaults to the environment variable no_proxy. If no_proxy is empty or undefined, noProxyList defaults to DefaultNoProxyList. If DefaultNoProxyList is the empty string, the proxy will be consulted for every URL.

Details about proxies are at:

           http://info.cern.ch/hypertext/WWW/Daemon/User/Proxies/ProxyClients.html

CONST
  DefaultRequestFields = ARRAY [0 .. 0] OF TEXT{"Accept: */*"};

TYPE
  MIMEType = {Application, Audio, Image, Message, Multipart, Text, Video,
              Xperimental};

  HTMLDate = TEXT;

  Header = RECORD
             httpVersion   : TEXT;
             statusCode    : INTEGER;
             reason        : TEXT;
             contentType   : MIMEType;
             contentSubType: TEXT;
             (* optional fields: *)
             allowed      : TEXT     := NIL;
             public       : TEXT     := NIL;
             contentLength: INTEGER  := 0;
             encoding     : TEXT     := NIL;
             date         : HTMLDate := NIL;
             expires      : HTMLDate := NIL;
             lastModified : HTMLDate := NIL;
             server       : TEXT     := NIL;
             MIMEVersion  : TEXT     := NIL;
             title        : TEXT     := NIL;
             location     : TEXT     := NIL;
           END;

  Page = OBJECT
           header  : Header;
           contents: TEXT;
         END;

PROCEDURE Get (    url   : TEXT;
               VAR header: Header;
               READONLY requestFields: ARRAY OF TEXT := DefaultRequestFields;
               forceCache: BOOLEAN := FALSE;
               debug     : BOOLEAN := FALSE;
               server    : T       := NIL    ): Rd.T
  RAISES {Error, Thread.Alerted, IP.Error};

Do a GET request, passing in the requestFields. By default, the proxy server will grab pages from a local cache, if one is available and if the url is in the cache. When forceCache is TRUE, the proxy server will explicitly not use any cache. The Error exception is raised if the header returned by the request is invalid in any way.

PROCEDURE GetHead (url: TEXT;
                   READONLY requestFields: ARRAY OF TEXT := DefaultRequestFields;
                   forceCache: BOOLEAN := FALSE;
                   server    : T       := NIL    ): Rd.T
  RAISES {Error, Thread.Alerted, IP.Error};

Do a HEAD request, passing in the requestFields. By default, the proxy server will grab pages from a local cache, if one is available and if the url is in the cache. When forceCache is TRUE, the proxy server will explicitly not use any cache. Mostly for debugging use.

PROCEDURE Post (    url   : TEXT;
                    argString  : TEXT;
                VAR header: Header;
                READONLY requestFields: ARRAY OF TEXT := DefaultRequestFields;
                server    : T       := NIL    ): Rd.T
  RAISES {Error, Thread.Alerted, IP.Error};

Do a POST request. Like GET, except for extra argument

PROCEDURE ParseHead (rd: Rd.T): Header RAISES {Error, Thread.Alerted};

Parses the information returned by GetHead.

PROCEDURE ToDate (t: HTMLDate): Date.T RAISES {Error, Thread.Alerted};

Takes an HTML format date, such as that in the Date or Last-modified field, and parses it into a Date.T

PROCEDURE AbsoluteURL (url, base: TEXT): TEXT;

Returns an absolute URL constructed from url and base, the URL of the document containing url.

PROCEDURE EncodeURL (t: TEXT): TEXT RAISES {Thread.Alerted};

Encodes special characters in a text string, such as the argument of an ISINDEX query

END Web.