igzip equivalent of zlib inflateInit2(&state, 15+16)

Hello,
i m a newbie , something that i don't know is how to do to decompress gzip (stream)

i used a code that use zlib inflateinit2 instead of inflateinit function because it specify windowbit and zstream structure :
http://blog.cppse.nl/deflate-and-gzip-compress-and-decompress-functions

What is the equivalent with igzip_lib ?

i don't find the solution the code below.

sorry to lost your time.
Thank you.

[decompress_gzip.txt](https://github.com/intel/isa-l/files/4424294/decompress_gzip.txt)