function xt=fwhtrv(x,blksiz)

% xt = FWHTRV (x,blksiz) recursively calculates the Walsh-Hadamard transform
% with results in bit-reversed order
%
% x:  data to transform, as a row vector
% blksiz: block size for x (defaults to 1)
%
% length(x)/blksiz is 2^(order of the transform)
% elements x(1), x(2),..., x(blksiz) taken as first block
% elements x(blksiz+1), ..., x(2*blksiz) taken as second block
%
% output explained (xb(j)=jth block of xb):
% first block of xt:   xb(1)+xb(2)+xb(3)+xb(4)...
% second block of xt:  xb(1)-xb(2)+xb(3)-xb(4)...
% third block of xt:   xb(1)+xb(2)-xb(3)-xb(4)...
% fourth block of xt:  xb(1)-xb(2)-xb(3)+xb(4)...
%
error(nargchk(1,2,nargin));
if (nargin == 1)
   blksiz=1;
end
lenx=length(x);
blocks=lenx/blksiz;
curord=floor(log2(blocks));
if (curord <= 0)
   xt=x;
   return
else
   half=lenx/2;
   x1=x(1:half);
   x2=x((half+1):lenx);
   xt1=fwhtrv(x1,blksiz);
   xt2=fwhtrv(x2,blksiz);
   xt=[xt1+xt2 xt1-xt2];
   return
end