Refill function

function refill(targetSlot, targetItems, fromSlot, toSlot)
    if turtle.getItemCount( targetSlot )<targetItems then
        for i=fromSlot, toSlot do
            if turtle.getItemCount ( i )~=0 then
                turtle.select( i )
                turtle.transferTo(targetSlot, turtle.getItemCount ( i ))

                if turtle.getItemCount( targetSlot )>=targetItems then
                    turtle.select(targetSlot)
                    return true
                end
            end
        end
    else
        return true
    end

    turtle.select(targetSlot)
    return false --if not enough items in the targetSlot
end