c++ - Using zlib with const data

To compress/decompress data with zlib , first I need to set up a struct called z_stream. z_stream has two non-const pointers called next_in and next_out.

If I want to do a function like this:

void ungzip(std::vector<unsigned char>& dst,const std::vector<unsigned char>& src)
{
  z_stream strm;
  // more code
}

and other like,

void gzip  (std::vector<unsigned char>& dst,const std::vector<unsigned char>& src);

What I should do?

Copy src in a local std::vector<unsigned char>

std::vector<unsigned char> tmp(src);

and use it as source or setting pointer like this , strm.next_in = const_cast<char*>(&src[0])?

Does zlib keep input data?