function strpos (haystack, needle, offset) {
	var i=0;
    // Finds position of first occurrence of a string within another  
    // 
    // version: 909.322
    // discuss at: http://phpjs.org/functions/strpos    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Onno Marsman    
    // +   bugfixed by: Daniel Esteban
    // *     example 1: strpos('Kevin van Zonneveld', 'e', 5);
    // *     returns 1: 14    var i = (haystack+'').indexOf(needle, (offset ? offset : 0));
    return i === -1 ? false : i;
}

jQuery.fn.initScrollBars = function(elem,slider,knopdown,knopup) {
	var hGalerij = document.getElementById(elem).clientHeight;
	var positie = document.getElementById(elem).style.top;	
	if (!positie) {
		positie=0;
	}
	if (isNaN(positie)) {
		positie = positie.replace('px','');	
	}
	var fHeight = document.getElementById(slider).clientHeight;	
	var som = parseInt(positie) + parseInt(hGalerij);	
	var status = document.getElementById('state').value;	
	if (som<(fHeight)) {
		document.getElementById(knopdown).style.display='none';
	} else {
		document.getElementById(knopdown).style.display='block';
	} 
	if (positie>=0) {
		document.getElementById(knopup).style.display='none';
	} else {
		document.getElementById(knopup).style.display='block';
	}
}

jQuery.fn.scrollDown = function(lengte,elem,slider,scrollknopdown,scrollknopup) {	
	var hGalerij = document.getElementById(elem).clientHeight;
	var positie = document.getElementById(elem).style.top;
	positie = positie.replace('px','');
	if (!positie) {
		positie=0;
	}
	var fHeight = document.getElementById(slider).clientHeight;
	var equivalent = (parseInt(hGalerij) + parseInt(positie)-parseInt(lengte));
	var mins = (equivalent-(lengte*2));
	/*
	if (mins < 0) {		
		lengte = Math.abs(mins);
	}
	*/
	
	positie = parseInt(positie);
	hGalerij = parseInt(hGalerij);	
	var som = positie + hGalerij;	
	var status = document.getElementById('state').value;
	if (som>(fHeight) && status==1) {
			newpos = positie - lengte;
			document.getElementById('state').value=0;
			jQuery('#' + elem).animate( { top: newpos + 'px' }, 600 );
			setTimeout("document.getElementById('state').value=1;",700);
	} 
	setTimeout("jQuery(document).initScrollBars('" + elem + "','" + slider + "','" + scrollknopdown + "','" + scrollknopup + "')",700);
}

jQuery.fn.scrollUp = function(lengte,elem,slider,scrollknopdown,scrollknopup) {	
	var hGalerij = document.getElementById(elem).clientHeight;
	var positie = document.getElementById(elem).style.top;
	if (!positie) {
		positie=0;
	}	
	var fHeight = document.getElementById(slider).clientHeight;
	var status = document.getElementById('state').value;
	var equivalent = (parseInt(hGalerij) + parseInt(positie)-parseInt(lengte));
	var mins = (equivalent+(lengte*2));	
	if (mins > hGalerij) {		
		lengte = parseInt(mins)-parseInt(hGalerij);
	}	
	//alert(mins + " - " + hGalerij);
//	alert(positie);
	positie = positie.replace('px','');
//	alert(positie);
	if (positie > -(lengte)) {
		positie = -(parseInt(lengte));
	//	alert(positie);
	} else {
		positie = parseInt(positie);
	}
	if (positie<0 && status==1) {
			newpos = positie + lengte;
			document.getElementById('state').value=0;
			jQuery('#' + elem).animate( { top: newpos + 'px' }, 600 );
			setTimeout("document.getElementById('state').value=1;",700);
	}	
	setTimeout("jQuery(document).initScrollBars('" + elem + "','" + slider + "','" + scrollknopdown + "','" + scrollknopup + "')",700);
}