# History Manager

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

This is a simple history module for a WWW client. It keeps a linear history, with a destructive or non-destructive backtrack, and list sequencing (previous, next) operations.

If you are building a client, you don't have to use this: just don't call it. This module is not used by any other modules in the libwww, so if you don't refer to it you don't get it in your linked application.

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

    #ifndef HTHISTORY_H
    #define HTHISTORY_H

    #include "HTAnchor.h"

    #ifdef __cplusplus
    extern "C" {
    #endif

## Creation and Deletion Methods

The history module can handle multiple history lists which can be useful in a multithreaded environment with several open windows in the client application. A new histrory lidt is referenced by the handle returned from the creation method.

    typedef struct _HTHistory HTHistory;

    extern HTHistory *HTHistory_new		(void);
    extern BOOL HTHistory_delete		(HTHistory *old);

## Add and delete History Elements

### Record an entry in a list

Registers the object in the linear list. The first entry is the home page. No check is done for duplicates. Returns YES if ok, else NO

    extern BOOL HTHistory_record		(HTHistory *hist, HTAnchor *cur);

### Replace list with new element

Iserts the new element at the current position and removes all any old list from current position. For example if c is cur pos

- before: a b c d e
- after : a b f

Returns YES if ok, else NO

    extern BOOL HTHistory_replace		(HTHistory *hist, HTAnchor *cur);

### Delete last entry in a list

Deletes the last object from the list Returns YES if OK, else NO

    extern BOOL HTHistory_removeLast 	(HTHistory *hist);

### Remove the History list from position

Deletes the history list FROM the entry at position 'cur' (excluded). Home page has position 1. Returns YES if OK, else NO

    extern BOOL HTHistory_removeFrom 	(HTHistory *hist, int pos);

### Number of elements stored

Returns the size of the history list or -1 if none.

    extern int HTHistory_count		(HTHistory *hist);

### Current Position

Returns the current position or -1 on error

    extern int HTHistory_position		(HTHistory *hist);

### Find and re-register visited anchor

Finds already registered anchor at given position and registers it again EXCEPT if last entry. This allows for `circular' history lists with duplicate entries. Position 1 is the home anchor. The current position is updated.

    extern HTAnchor * HTHistory_recall 	(HTHistory *hist, int pos);

### Find Entry at position

Entry with the given index in the list (1 is the home page). Like `HTHistory_recall` but without re-registration. Un success, the current position is updated to the value 'pos' value.

    extern HTAnchor * HTHistory_find 	(HTHistory *hist, int pos);

### List the History List

This function is like `HTHistory_find()` but does not update the current position

    extern HTAnchor * HTHistory_list	(HTHistory *hist, int pos);

## Navigation

### Can we back in history

Returns YES if the current anchor is not the first entry (home page)

    extern BOOL HTHistory_canBacktrack 	(HTHistory *hist);

### Backtrack with deletion

Returns the previous object and erases the last object. This does not allow for 'forward' as we are always at the end of the list. If no previous object exists, NULL is returned so that the application knows that no previous object was found. See also HTHistory_back().

    extern HTAnchor * HTHistory_backtrack 	(HTHistory *hist);

### Backtrack without deletion

Returns the previos object but does not erase the last object. This does not allow for 'forward'. If no previous object exists, NULL is returned so that the application knows that no previous object was found. See also HTHistory_backtrack()

    extern HTAnchor * HTHistory_back 	(HTHistory *hist);

### Can we go forward

Returns YES if the current anchor is not the last entry

    extern BOOL HTHistory_canForward 	(HTHistory *hist);

### Forward

Return the next object in the list or NULL if none

    extern HTAnchor * HTHistory_forward 	(HTHistory *hist);

    #ifdef __cplusplus
    }
    #endif

    #endif /* HTHISTORY_H */