How to generate c code for filtfilt for low pass fir filter

Hi, i used a low pass fir filter using the following function

 d1=designfilt('lowpassfir','PassbandFrequency',0.45,'StopbandFrequency',0.5,'PassbandRipple',3,'StopbandAttenuation',6
  0,'DesignMethod','equiripple');
  a = filtfilt(d1,deriv1);

I want to generate c code for this but when i look in matlab fileexchange i found thishttps://www.mathworks.com/matlabcentral/fileexchange/32261-filterm

And i don't know how to define the b and a used in this code. Can anyone help me please?