I see this question is somewhat old - perhaps this has been solved by now?
I just had a look at the DXF specification docs, as found
here[
^]
I downloaded the one for AutoCad 2002, since I understand that there were some
changes made between 2000 and 2002[
^] (though now that I think of it - there must have been changes between each version. Hmm, never-mind)
Um, there's a table in the doc that lists the various control codes used.
I just opened up A9CAD and drew a 6 point polyline. Upon searching the saved DXF file, I find that this polyline is represented (at least in part) by the following text:
AcDbPolyline
90
6
70
0
43
0.0
10
-34.68044809800129
20
-1.29110251450677
10
-27.93802385557705
20
10.47227595099936
10
-16.82019664732431
20
3.156028368794326
10
-9.503949065119278
20
12.55238555770471
10
-12.8034332688588
20
-5.164410058027079
10
-32.88725016118633
20
-4.518858800773694
0
ENDSEC
Key
----
90 - number of vertices marker
70 - Polyline flag (0 is default)
43 - Constant width flag
10 - X value of a vertex
20 - Y value of a vertex
Sooo, we can immediately see that we
(a) have 6 vertices
(b) have a polyline
(c) it is a constant width and finally
(d) It joins the vertices below:
{-34.68,-1.29}, {-27.94, 10.47}, {-16.82,3.16},
{-9.50,12.55}, {-12.80,-5.16}, {-32.89, -4.52}
Hope it's useful. :)