%-------------------------------------
function y=cirshift(x,m,N)
%y=output
%x=input with length < N
%m=sample shift
%N=size of circular buffer
%Method y[n]=x[n-m]mod N
if length(x)>N
   error('N must be >= length(x)');
end
x=[x zeros(1,N-length(x))]; %zero padding
n=[0:1:N-1];
n=mod(n-m,N);
y=x(n+1);
%--------------------------------------