Recommend a library for testing the 'closedness' of '.stl' geometries?

Question

Some clarification is necessary, I am not referring to the Standard Template Library. I am referring to the '.stl file format'.

< my eventual goal > A little background, my end goal is to use the Kinect and 'point cloud' type scanning to create .stl files. These .stl representations will be provided to 3D printing services to create 3D models. I have the point cloud scanning working quite nicely as well as simple export to .stl (as it's really not that difficult) < / my eventual goal >

In most 3D cad software packages, you are able to export a model to .stl format. The format is really simple to create by hand and I have no issue with that here. My questions stems from the requirement that most 3D printing services (Ponoko, Shapeways to name 2) will not be accept your model if it isn't 'closed' (aka each side of the 'triangle' is a side of another triangle) which is to be expected of them in order to create the 3D object.

There are some software packages (such as Nettfab) that can 'fix' these problems but using a 3rd party program will not work for me.

Does anyone have any experience or know of a '.stl' library that will be able to do a 'closedness' check? If not, I will be moving forward and creating one... but I do not want to put the time and effort into something that has (probably) already been done and vetted...

I am also open to a python library if one exists.

EDIT

Also looking for this library to 'fix' the stl edges... Just doing a closedness test can be done quite easily but fixing it is the issue...