115 lines
2.4 KiB
C++
115 lines
2.4 KiB
C++
/*
|
|
* \brief Browser history buffer
|
|
* \date 2005-11-03
|
|
* \author Norman Feske <norman.feske@genode-labs.com>
|
|
*/
|
|
|
|
/*
|
|
* Copyright (C) 2005-2013 Genode Labs GmbH
|
|
*
|
|
* This file is part of the Genode OS framework, which is distributed
|
|
* under the terms of the GNU General Public License version 2.
|
|
*/
|
|
|
|
#ifndef _HISTORY_H_
|
|
#define _HISTORY_H_
|
|
|
|
#include "elements.h"
|
|
|
|
namespace Scout { class History; }
|
|
|
|
|
|
class Scout::History
|
|
{
|
|
private:
|
|
|
|
static const int _size = 128; /* history size */
|
|
|
|
int _idx; /* current position in history */
|
|
Anchor *_history[_size]; /* ring buffer of history references */
|
|
|
|
/**
|
|
* Increment history position
|
|
*
|
|
* \offset The incrementation offset must be higher than -_size
|
|
*/
|
|
inline void _inc(int offset) { _idx = (_idx + _size + offset) % _size; }
|
|
|
|
/**
|
|
* Return next index of current position
|
|
*/
|
|
inline int _next() { return (_idx + 1) % _size; }
|
|
|
|
/**
|
|
* Return previous index of current position
|
|
*/
|
|
inline int _prev() { return (_idx + _size - 1) % _size; }
|
|
|
|
public:
|
|
|
|
/**
|
|
* Constructor
|
|
*/
|
|
History()
|
|
{
|
|
_idx = 0;
|
|
memset(_history, 0, sizeof(_history));
|
|
}
|
|
|
|
/**
|
|
* Request element at current history position
|
|
*/
|
|
Anchor *curr() { return _history[_idx]; }
|
|
|
|
/**
|
|
* Add element to history.
|
|
*
|
|
* We increment the current history position and insert the
|
|
* new element there. If the new element is identical with
|
|
* with the old element at that position, we keep the following
|
|
* history elements. Otherwise, we follow a new link 'branch'
|
|
* and cut off the old one.
|
|
*/
|
|
void add(Anchor *e)
|
|
{
|
|
/* discard invalid history elements */
|
|
if (!e) return;
|
|
|
|
/* increment history position */
|
|
_inc(1);
|
|
|
|
/* do we just follow the forward path? */
|
|
if (curr() == e) return;
|
|
|
|
/* cut off old forward history branch */
|
|
_history[_next()] = 0;
|
|
|
|
/* insert new element */
|
|
_history[_idx] = e;
|
|
}
|
|
|
|
/**
|
|
* Assign new element to current history entry
|
|
*/
|
|
void assign(Anchor *e) { if (e) _history[_idx] = e; }
|
|
|
|
/**
|
|
* Travel forward or backward in history
|
|
*
|
|
* \return 1 on success,
|
|
* 0 if end of history is reached
|
|
*/
|
|
enum direction { FORWARD, BACKWARD };
|
|
int go(direction dir)
|
|
{
|
|
/* stop at the boundaries of the history */
|
|
if (!_history[dir == FORWARD ? _next() : _prev()]) return 0;
|
|
|
|
/* travel in history */
|
|
_inc(dir == FORWARD ? 1 : -1);
|
|
return 1;
|
|
}
|
|
};
|
|
|
|
#endif
|