samer@4: % gatherer - API for autoexpanding arrays for accumulating data
samer@7: %
samer@7: % gatherer ::
samer@7: %    [N,M]:[[1,2]]  ~'size of elements to gather',
samer@7: %    options {
samer@7: %       init :: natural/512  ~'initial size of buffer';
samer@7: %       grow :: natural/2    ~'factor by which to auto-expand buffer';
samer@7: %       max  :: natural/1e9  ~'maximum size of buffer'
samer@7: %    }
samer@7: % -> struct {
samer@7: %    remove  :: natural => void ~'action to remove last n elements';
samer@7: %    length  :: void => natural ~'action to return current buffer length';
samer@7: %    append  :: [[N,M]] => void ~'action to append data to buffer';
samer@7: %    collect :: void =>[[N,L]]  ~'action to return buffer contents and reset';
samer@7: % }.
samer@4: function api=gatherer(size_in,varargin)
samer@37: 	opts=options('chunk',256,'init',512,'grow',2,'max',1e9,varargin{:});
samer@4: 	n=uint32(0); 
samer@4: 	cap=opts.init; % initial capacity of buffer
samer@4: 	buf=zeros(size_in(1),cap); % buffer
samer@4: 
samer@4: 	api.remove=@remove;
samer@4: 	api.collect=@collect;
samer@4: 	api.length=@curlen;
samer@4: 
samer@4: 	if isnan(size_in(2)),
samer@4: 		api.append=@append;
samer@4: 	elseif size_in(2)>1,
samer@4: 		m=uint32(size_in(2)); M=1:m;
samer@4: 		api.append=@append_m;
samer@4: 	else
samer@4: 		api.append=@append_1;
samer@4: 	end
samer@4: 
samer@4: 	function l=curlen, l=n; end
samer@4: 	function remove(rem), n=n-rem;  end
samer@4: 	function x=collect, x=buf(:,1:n); buf=[]; end 
samer@4: 	function append_1(x)
samer@4: 		if n+1>cap, grow; end % need more room
samer@4: 		n=n+1; buf(:,n)=x;
samer@4: 	end
samer@4: 
samer@4: 	function grow
samer@4: 		if n>opts.max, error('maximum capacity exceeded'); end
samer@4: 		cap=opts.grow*cap; 
samer@4: 		buf=repmat(buf,1,opts.grow); 
samer@4: 	end
samer@4: 
samer@4: 	function append_var(x)
samer@4: 		chunk=size(x,2);
samer@4: 		if n+chunk>cap, grow; end % need more room
samer@4: 		buf(:,n+(1:chunk))=x;
samer@4: 		n=n+chunk;
samer@4: 	end
samer@4: 
samer@4: 	function append_m(x)
samer@4: 		if n+m>cap, grow; end % need more room
samer@4: 		buf(:,n+M)=x;
samer@4: 		n=n+m;
samer@4: 	end
samer@4: end