# Public Anchor Object

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

An anchor represents a region of a hypertext document which is linked to another anchor in the same or a different document. As always we must emulate the fancy features of C++ by hand :-(. In this module you find:

- Creation and deletion methods
- Manipulation of Links
- Access Methods for information

This module is implemented by HTAnchor.c, and it is a part of the W3C Reference Library.

    #ifndef HTANCHOR_H
    #define HTANCHOR_H

    #include "HTList.h"
    #include "HTAtom.h"
    #include "HTMethod.h"

## Types defined by the Anchor Object

This is a set of videly used type definitions used through out the Library:

    typedef struct _HTLink		HTLink;

    typedef HTAtom * HTFormat;
    typedef HTAtom * HTLevel;		       /* Used to specify HTML level */
    typedef HTAtom * HTEncoding;				 /* Content Encoding */
    typedef HTAtom * HTCte;				/* Content transfer encoding */
    typedef HTAtom * HTCharset;
    typedef HTAtom * HTLanguage;

    typedef struct _HTAnchor	HTAnchor;
    typedef struct _HTParentAnchor	HTParentAnchor;
    typedef struct _HTChildAnchor	HTChildAnchor;

## The Link Object

Anchors 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.

### Link Destination

    extern BOOL HTLink_setDestination (HTLink * link, HTAnchor * dest);
    extern HTAnchor * HTLink_destination (HTLink * link);

### Link Result

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.

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

    extern BOOL HTLink_setResult (HTLink * link, HTLinkResult result);
    extern HTLinkResult HTLink_result (HTLink * link);

### Link Method

The method used in a link can be PUT, or POST, for example

    extern BOOL HTLink_setMethod (HTLink * link, HTMethod method);
    extern HTMethod HTLink_method (HTLink * link);

### Link Type

This is used for typed links.

    typedef HTAtom * HTLinkType;

    extern BOOL HTLink_setType (HTLink * link, HTLinkType type);
    extern HTLinkType HTLink_type (HTLink * link);

## Relations between Links and Anchors

### Link this Anchor to another given one

A single anchor may have many outgoing links of which the default is the main link. If one already exists then this new link is simply added to the list.

    extern BOOL HTAnchor_link	(HTAnchor *	source,
    				 HTAnchor *	destination,
    				 HTLinkType	type,
    				 HTMethod	method);

### Find the Link Object that Binds two Anchors

If the destination anchor is a target of a link from the source anchor then return the link object, else NULL.

    extern HTLink * HTAnchor_findLink (HTAnchor *src, HTAnchor *dest);

### Find destination with given relationship

Return the anchor with a given typed link.

    extern HTAnchor * HTAnchor_followTypedLink (HTAnchor *me, HTLinkType type);

### Handling the Main Link

Any outgoing link can at any time be the main destination.

    extern BOOL HTAnchor_setMainLink	(HTAnchor * anchor, HTLink * link);
    extern HTLink * HTAnchor_mainLink	(HTAnchor * anchor);

    extern HTAnchor * HTAnchor_followMainLink (HTAnchor * anchor);

### Handling the Sub Links

    extern BOOL HTAnchor_setSubLinks	(HTAnchor * anchor, HTList * list);
    extern HTList * HTAnchor_subLinks	(HTAnchor * anchor);

### Move Link Information

Move all link information form one anchor to another. This is useful when we get a redirection on a request and want to inherit the link information to the new anchor and change the link information in the old one to "redirect".

    extern BOOL HTAnchor_moveAllLinks	(HTAnchor *src, HTAnchor *dest);

### Remove Link Information

Delete link information between two or more anchors

    extern BOOL HTAnchor_removeLink		(HTAnchor *src, HTAnchor *dest);
    extern BOOL HTAnchor_removeAllLinks	(HTAnchor * me);

### Move a child anchor to the head of the list of its siblings

This is to ensure that an anchor which might have already existed is put in the correct order as we load the document.

    extern void HTAnchor_makeLastChild	(HTChildAnchor *me);

## Anchor Objects

We have three variants of the Anchor object - I guess some would call them superclass and subclasses ;-)

### Generic Anchor type

This is the super class of anchors. We often use this as an argument to the functions that both accept parent anchors and child anchors. We separate the first link from the others to avoid too many small mallocs involved by a list creation. Most anchors only point to one place.

### Anchor for a Parent Object

These anchors points to the whole contents of a graphic object (document). The parent anchor of a parent anchor is itself. The parent anchor now contains all meta information about the object. This is largely the entity headers in the HTTP specification.

### Anchor for a Child Object

A child anchor is a anchor object that points to a subpart of a graphic object (document)

## Creation and Deletion Methods

After we have defined the data structures we must define the methods that can be used on them. All anchors are kept in an internal hash table so that they are easier to find again.

### Find/Create a Parent Anchor

This one is for a reference (link) which is found in a document, and might not be already loaded. The parent anchor returned can either be created on the spot or is already in the hash table.

    extern HTAnchor * HTAnchor_findAddress		(CONST char * address);

### Find/Create a Child Anchor

This one is for a new child anchor being edited into an existing document. The parent anchor must already exist but the child returned can either be created on the spot or is already in the hash table. The tag is the part that's after the '#' sign in a URI.

    extern HTChildAnchor * HTAnchor_findChild	(HTParentAnchor *parent,
    						 CONST char *	tag);

### Find/Create a Child Anchor and Link to Another Parent

Find a child anchor anchor with a given parent and possibly a tag, and (if passed) link this child to the URI given in the href. As we really want typed links to the caller should also indicate what the type of the link is (see HTTP spec for more information). The link is relative to the address of the parent anchor.

    extern HTChildAnchor * HTAnchor_findChildAndLink
    		(HTParentAnchor * parent,		/* May not be 0 */
    		CONST char * tag,			/* May be "" or 0 */
    		CONST char * href,			/* May be "" or 0 */
    		HTLinkType ltype);			/* May be 0 */

### Delete an Anchor

All outgoing links from parent and children are deleted, and this anchor is removed from the sources list of all its targets. We also delete the targets. If this anchor's source list is empty, we delete it and its children.

    extern BOOL HTAnchor_delete	(HTParentAnchor *me);

### Delete all Anchors

Deletes all anchors and return a list of all the objects (hyperdoc) hanging of the parent anchors found while doing it. The application may keep its own list of `HyperDoc`s, but this function returns it anyway. It is always for the application to delete any `HyperDoc`s. If NULL then no hyperdocs are returned. Return YES if OK, else NO.

Note: This function is different from cleaning up the history list!

    extern BOOL HTAnchor_deleteAll	(HTList * objects);

## Access Methods of an Anchor

These functions should be used to access information within the anchor structures.

### Relations to Other Anchors

#### Who is Parent?

For parent anchors this returns the anchor itself

    extern HTParentAnchor * HTAnchor_parent	(HTAnchor *me);

#### Does it have any Anchors within it?

    extern BOOL HTAnchor_hasChildren	(HTParentAnchor *me);

### Binding a Data Object to an Anchor

A parent anchor can have a data object bound to it. This data object does can for example be a parsed version of a HTML that knows how to present itself to the user, or it can be an unparsed data object. It's completely free for the application to use this possibility, but a typical usage would to manage the data object as part of a memory cache.

    extern void HTAnchor_setDocument	(HTParentAnchor *me, void * doc);
    extern void * HTAnchor_document		(HTParentAnchor *me);

### URI Information of Anchors

There are two addresses of an anchor. The URI that was passed when the anchor was crated and the physical address that's used when the URI is going to be requested. The two addresses may be different if the request is going through a proxy or a gateway.

#### Get URI Address

Returns the full URI of the anchor, child or parent as a malloc'd string to be freed by the caller as when the anchor was created.

    extern char * HTAnchor_address		(HTAnchor *me);

### Cache Information

If the cache manager finds a cached object, it is registered in the anchor object. This way the file loader knows that it is a MIME data object. The cache manager does not know whether the data object is out of date (for example if a Expires: header is in the MIME header. This is for the MIME parser to find out.

    extern BOOL HTAnchor_cacheHit		(HTParentAnchor	*me);
    extern void HTAnchor_setCacheHit	(HTParentAnchor	*me, BOOL cacheHit);

### Physical address

Contains the physical address after we haved looked for proxies etc.

    extern char * HTAnchor_physical		(HTParentAnchor * me);

    extern void HTAnchor_setPhysical	(HTParentAnchor * me, char * protocol);

### Is the Anchor searchable?

    extern void HTAnchor_clearIndex		(HTParentAnchor *me);
    extern void HTAnchor_setIndex		(HTParentAnchor *me);
    extern BOOL HTAnchor_isIndex		(HTParentAnchor *me);

### Title handling

We keep the title in the anchor as we then can refer to it later in the history list etc. We can also obtain the title element if it is passed as a HTTP header in the response. Any title element found in an HTML document will overwrite a title given in a HTTP header.

    extern CONST char * HTAnchor_title	(HTParentAnchor *me);

    extern void HTAnchor_setTitle		(HTParentAnchor *me,
    					 CONST char *	title);

    extern void HTAnchor_appendTitle	(HTParentAnchor *me,
    					 CONST char *	title);

### Media Types (Content-Type)

    extern HTFormat HTAnchor_format		(HTParentAnchor *me);
    extern void HTAnchor_setFormat		(HTParentAnchor *me,
    					 HTFormat	form);

### Charset parameter to Content-Type

    extern HTCharset HTAnchor_charset	(HTParentAnchor *me);
    extern void HTAnchor_setCharset		(HTParentAnchor *me,
    					 HTCharset	charset);

### Level parameter to Content-Type

    extern HTLevel HTAnchor_level		(HTParentAnchor * me);
    extern void HTAnchor_setLevel		(HTParentAnchor * me,
    					 HTLevel	level);

### Content Language

    extern HTLanguage HTAnchor_language	(HTParentAnchor *me);
    extern void HTAnchor_setLanguage	(HTParentAnchor *me,
    					 HTLanguage	language);

### Content Encoding

    extern HTEncoding HTAnchor_encoding	(HTParentAnchor *me);
    extern void HTAnchor_setEncoding	(HTParentAnchor *me,
    					 HTEncoding	encoding);

### Content Transfer Encoding

    extern HTCte HTAnchor_cte		(HTParentAnchor *me);
    extern void HTAnchor_setCte		(HTParentAnchor *me,
    					 HTCte		cte);

### Content Length

    extern long int HTAnchor_length		(HTParentAnchor *me);
    extern void HTAnchor_setLength		(HTParentAnchor *me,
    					 long int	length);

### Allowed methods (Allow)

    extern int HTAnchor_methods		(HTParentAnchor *me);
    extern void HTAnchor_setMethods		(HTParentAnchor *me,
    					 int		methodset);
    extern void HTAnchor_appendMethods	(HTParentAnchor *me,
    					 int		methodset);

### Version

    extern char * HTAnchor_version	(HTParentAnchor * me);
    extern void HTAnchor_setVersion	(HTParentAnchor * me, CONST char * version);

### Date

Returns the date that was registered in the RFC822 header "Date"

    extern time_t HTAnchor_date		(HTParentAnchor * me);
    extern void HTAnchor_setDate		(HTParentAnchor	* me, CONST time_t date);

### Last Modified Date

Returns the date that was registered in the RFC822 header "Last-Modified"

    extern time_t HTAnchor_lastModified	(HTParentAnchor * me);
    extern void HTAnchor_setLastModified	(HTParentAnchor	* me, CONST time_t lm);

### Expires Date

    extern time_t HTAnchor_expires		(HTParentAnchor * me);
    extern void HTAnchor_setExpires		(HTParentAnchor	* me, CONST time_t exp);

### Derived from

    extern char * HTAnchor_derived	(HTParentAnchor *me);
    extern void HTAnchor_setDerived	(HTParentAnchor *me, CONST char *derived_from);

### Extra Headers

List of unknown headers coming in from the network. Do not use the `HTAnchor_addExtra()` function to extra headers here, but use the field in the request structure for sending test headers.

    extern HTList * HTAnchor_Extra		(HTParentAnchor *me);
    extern void HTAnchor_addExtra		(HTParentAnchor *me,
    					 CONST char *	header);

### Status of Header Parsing

These are primarily for internal use

    extern BOOL HTAnchor_headerParsed	(HTParentAnchor *me);
    extern void HTAnchor_setHeaderParsed	(HTParentAnchor *me);

### We want to clear the header information...

    extern void HTAnchor_clearHeader	(HTParentAnchor *me);

    #endif /* HTANCHOR_H */