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Sun Feb 16 18:42:29 1997 UTC (27 years, 3 months ago) by frystyk
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CVS tags: Release-5-1l, Release-5-1k, Release-5-1j, Release-5-1g, Release-5-1e, Release-5-1d, Release-5-1b, Release-5-1a, Release-5-1, HEAD
Changed name of sample coed library

<HTML>
<HEAD>
  <!-- Changed by: Henrik Frystyk Nielsen, 30-Jun-1996 -->
  <TITLE>W3C Sample Code Library libwww Link Class</TITLE>
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<H1>
  The Link Class
</H1>
<PRE>
/*
**	(c) COPYRIGHT MIT 1995.
**	Please first read the full copyright statement in the file COPYRIGH.
*/
</PRE>
<P>
A <A HREF="HTLink.html">Link</A> represents the link between anchor objects.
By keeping the link as a object and not as part of the anchor we are capable
of handling link semantics in a much more organized way. For example, we
can then search for link types among all the link objects that we have created.
<A HREF="HTAnchor.html">Anchor objects</A> are bound together using Link
objects. Each anchor can be the source or destination of zero, one, or more
links from and to other anchors.
<P>
This module is implemented by <A HREF="HTLink.c">HTLink.c</A>, and it is
a part of the <A HREF="http://www.w3.org/pub/WWW/Library/"> W3C Sample Code
Library</A>.
<PRE>
#ifndef HTLINK_H
#define HTLINK_H

typedef struct _HTLink	HTLink;

#include "WWWUtil.h"
#include "HTMethod.h"
#include "HTAnchor.h"
</PRE>
<H2>
  Creation and Deletion Methods
</H2>
<P>
These are the methods for crating and deleting new link objects
<H3>
  Create a new Link Object
</H3>
<PRE>typedef HTAtom * 	HTLinkType;

typedef enum _HTLinkResult {
    HT_LINK_INVALID = -1,
    HT_LINK_NONE = 0,
    HT_LINK_ERROR,
    HT_LINK_OK
} HTLinkResult;

struct _HTLink {
    HTAnchor *		dest;		   /* The anchor to which this leads */
    HTLinkType		type;		           /* Semantics of this link */
    HTMethod		method;		   /* Method for this link, e.g. PUT */
    HTLinkResult	result;    /* Result of any attempt to get this link */
};

HTLink * HTLink_new (void);
</PRE>
<H3>
  Delete a Link Object
</H3>
<P>
A link can be removed as any other object
<PRE>BOOL HTLink_delete (HTLink * link);
</PRE>
<H3>
  Remove All Link Information from an Anchor
</H3>
<P>
This is normally a part of deleting anchor objects.
<PRE>extern BOOL HTLink_removeAll (HTAnchor * me);
</PRE>
<H2>
  Handle Link Between Anchors
</H2>
<P>
As mentioned, link objects are the ones that bind anchor objects together
in a Web like structure
<H3>
  Add a Link between two Anchors
</H3>
<P>
This method creates a new link between two <A HREF="HTAnchor.html">anchor
objects</A>.
<PRE>extern BOOL HTLink_add (HTAnchor *	source,
			     HTAnchor * destination, 
			     HTLinkType	type,
			     HTMethod	method);
</PRE>
<H3>
  Remove All Links Between two Anchors
</H3>
<P>
Removes link information from one anchor to another.
<PRE>extern BOOL HTLink_remove (HTAnchor * source, HTAnchor * destination);
</PRE>
<H3>
  Find a Link
</H3>
<P>
Find the anchor object between a destination and a source ancher. Return
link object if any, else NULL
<PRE>extern HTLink * HTLink_find (HTAnchor * source, HTAnchor * destination);
</PRE>
<H2>
  Link Information
</H2>
<P>
This is the set of methods for accessing the information carried by a link
object
<H3>
  Link Destination
</H3>
<P>
The link destination is the destination anchor pointed to by the link.
<PRE>extern BOOL HTLink_setDestination (HTLink * link, HTAnchor * dest);
extern HTAnchor * HTLink_destination (HTLink * link);
</PRE>
<H3>
  Link Types and Semantic Links
</H3>
<P>
Each link has a sematic representation associated with it. This means that
the application can distinguish between pages based on the semantics of the
link. This is very similar to the <CODE>LINK</CODE> tag in HTML pages which
indicates the meaning if this pages to other pages.
<PRE>extern BOOL HTLink_setType (HTLink * link, HTLinkType type);
extern HTLinkType HTLink_type (HTLink * link);
</PRE>
<H3>
  Link Method
</H3>
<P>
The link method is the HTTP method we have performed between the two links.
For example, it can be a POST operation, or a PUT operation where the operation
on the first anchor created a new anchor.
<PRE>extern BOOL HTLink_setMethod (HTLink * link, HTMethod method);
extern HTMethod HTLink_method (HTLink * link);
</PRE>
<H3>
  Link Result
</H3>
<P>
When a link has been used for posting an object from a source to a destination
link, the result of the operation is stored as part of the link information.
This means that we can keep track of which operations we have performed on
a link and hence the application can ask the user whether he or she wants
to do a re-post, for example.
<PRE>
extern BOOL HTLink_setResult (HTLink * link, HTLinkResult result);
extern HTLinkResult HTLink_result (HTLink * link);
</PRE>
<PRE>
#endif /* HTLINK_H */
</PRE>
<P>
  <HR>
<ADDRESS>
  @(#) $Id: HTLink.html,v 2.2 1997/02/16 18:42:29 frystyk Exp $
</ADDRESS>
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