how to generate c code from asn1?

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hi, I'm a newer to develop wireshark. currently I know the basic process of generating c code from asn1 and .cnf,template.c/.h files. take lte-rrc as example , to generate the latest version. the asn files extracted from latest 3gpp doc is simple. my question is : how to generate(or get) the latest version of .cnf,.temlate.c/.h files ? If these files need to be manually made, where's the guide and examples ? Thanks a lot in advance!