Need information on jni and jnx

[Salila]

Currently, I need to decode the grammer of compiler and generate
output files. The compiler is making use of .jni file as input and
produce output files. It is required to modified the contents of the
output files. I have tried to modified .jni file (input file) but the
file header is barring me to do so as it is mentioned that it is
machine generated file. I have some jnx files also in the same folder
where jni file is lying . Can someone guide me through this confusion
that what are .jnx and .jni files ? How can one generate jni file?

Thanks in advance,