How to search a specific selector through all preceding siblings

Question

When traversing DOM with jQuery, is there an easy way to know how many siblings have a particular class before my selector ?

For example with the following HTML :

<ul>
    <li class="foo">One</li>
    <li>Two</li>
    <li>Three</li>
    <li>Four</li>
    <li class="foo">Five</li>
    <li>Six</li>
    <li class="active">Seven</li>
    <li>Eight</li>  
    <li class="foo">Eight</li>  
</ul>

from li.active i would like to know that i have 2 li (One and Five) with the 'foo' class preceding my active object.

Can i do that without parsing all the siblings and comparing indexes ?

I thought .prevAll() could help me but it wouldn't find more than the first sibling encountered..