[userbinator]

Usual ASN.1 caveat: parsing its specifications requires money and a lot of time, implementing many of its encodings (e.g. unaligned PER) is a lifetime's work

...unless you're Fabrice Bellard, who apparently wrote one just because it was one of the minor obstacles on the way to writing a full LTE base station:

http://www.bellard.org/ffasn1/