You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: zstream.m
    path of file: ./repos/CBIG/external_packages/matlab/non_default_packages/cifti-matlab-WashU-gradient/@gifti/private
    
    the code of the file until where you have to start completion: function Z = zstream(action,D)
% Compress/decompress stream of bytes using Deflate/Inflate
% FORMAT Z = zstream('C',D)
% D        - data stream to compress (converted to uint8 if needed)
% Z        - compressed data stream (uint8 vector)
% FORMAT D = zstream('D',Z)

    
function Z = zstream(action,D)
% Compress/decompress stream of bytes using Deflate/Inflate
% FORMAT Z = zstream('C',D)
% D        - data stream to compress (converted to uint8 if needed)
% Z        - compressed data stream (uint8 vector)
% FORMAT D = zstream('D',Z)
% Z        - data stream to decompress (uint8 vector)
% D        - decompressed data stream (uint8 vector)
%__________________________________________________________________________
%
% This C-MEX file relies on:
% * miniz, by Rich Geldreich
%   http://code.google.com/p/miniz/
% Fallback Java implementation is adapted from:
% * dzip/dunzip, by Michael Kleder
%   http://www.mathworks.com/matlabcentral/fileexchange/8899
%__________________________________________________________________________
% Copyright (C) 2015 Wellcome Trust Centre for Neuroimaging

% Guillaume Flandin
% $Id: zstream.m 6417 2015-04-21 16:03:44Z guillaume $


if exist('OCTAVE_VERSION','builtin')
    error('zstream.c not compiled - see Makefile');
end