cobssi.m

classdef cobssi < handle
    %COBSSI Consistent Overhead Byte Stuffing Streaming decoder
    % Byte-wise (streaming) COBS decode - see
    % http://www.stuartcheshire.org/papers/cobsforton.pdf for algorithm
    % details
    
    properties (Access = private)
        data = uint8.empty;
        code = 0; % used to decide whether to add '0' following EOB
        count = 0; % number of values before EOB
    end
    
    methods        
        function obj = push(obj, data)
            if obj.count == 0 % read a new stuffing code
                obj.code = data;
                obj.count = obj.code - 1; % code, n, indicates n-1 values before EOB
            else
                obj.data(end+1) = data;
                obj.count = obj.count - 1; % one less value before EOB
            end
            
            if obj.count == 0 && obj.code ~= 255 % 254 = n-1 = maximum block length.
                obj.data(end+1) = 0; % no '0' after 254 block length
            end
        end
        
        function data = peek(obj)
            data = obj.data;
        end
        
        function data = get(obj)
            if obj.count ~= 0 % if count not zero then current message would be invalid
                error('Decoded message is invalid or incomplete.');
            else
                data = obj.data(1:end-1); % remove the trailing zero
            end
        end
    end  
end