Breaking Eggs And Making Omelettes

Topics On Multimedia Technology and Reverse Engineering


ANSI Code Coverage Followup

March 8th, 2012 by Multimedia Mike

The people behind noticed my code coverage project concerning the ANSI video decoder and asked what they could do to help. I had already downloaded 350 / 4000 of their artpacks but didn’t want to download the remainder if I could avoid it. They offered to run my tool against their local collection of files.

Aside: They have all of the artpacks archived at Github.

The full corpus of nearly 4000 artpacks contains over 146,000 files. Versus my sampling of 350 artpacks and 13,000 files that covered all but 45 lines of the ansi.c source file, the full corpus has files to exercise… 6 more of those lines. Whee. This means that there are files which exercise the reverse and concealed attributes, all 3 “erase in line” modes, and one more error path (which probably wasn’t a valid file anyway).

Missing features mostly cluster around different video modes, including: 320×200 (25 rows), 640×200 (25 rows), 640×350 (43 rows), and 640×480 (60 rows); on the plus side, nothing tripped the “unsupported screen mode” case. There are no files that switch modes during playback.

I guess statistical sampling theory holds out here– a small set of randomly chosen files would do a fine job covering code. But this experiment is about finding the statistical outliers.

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