Vertex index with API

Hello,

i've a problem,
i know the index of a vertex in object-relative, but i'd like to know this index in a specific face (so, the face-relative index)

I've found a function to convert face-relative index to object-relative index .... but not inverse

Does anyone can help me ?

(to be complete, i get these object-relative indexes by the function getTriangle in MItMeshPolygon class.... but i need the face-relative to use function like normalIndex and getUVIndex in the same class)