docs: function (left_obj, right_obj, given_spec) {
  
  		// console.log("here is left_obj ", left_obj);
  		// console.log("here is right_obj ", right_obj);
  
  
  		var extent = "entire";	// default - diff which portions of buffers
  		var master = "left";	// default - determines which buffer determines buffer length
  
  		var spec;
  
  	    if (typeof given_spec === "undefined") {
  
  	        console.log("seeing NO input spec so populating with defaults");
  
  	    	spec = { 
  						extent : extent,	// diff which portions of buffers
  						master : master,	// determines which buffer determines buffer length
  					};
  		} else {
  	        spec = given_spec;
  	        console.log("seeing input spec ", spec);
  	    };
  
  	    if (typeof spec.extent !== "undefined") {
  	        extent = spec.extent;
  	        console.log("seeing input spec with spec.extent ", spec.extent);
  	    };
  	    if (typeof spec.master !== "undefined") {
  	        master = spec.master;
  	        console.log("seeing input spec with spec.master ", spec.master);
  	    };
  
  	    given_spec.extent = extent;
  	    given_spec.master = master;
  
  	    console.log("here is spec ", given_spec);
  	    console.log("here is extent ", extent);
  	    console.log("here is master ", master);
  
  	    var size_buffer;
  
          switch (master) {
  
              case "left" : {
  
                  size_buffer = left_obj.buffer.length;
                  break;
              }
  
              case "right" : {
  
                  size_buffer = right_obj.buffer.length;
                  break;
              }
  
              // --- default - catch all if not identifed above
  
              default :
  
              console.error("ERROR - failed to find spec.master in diff_buffers");
              process.exit(8);
  
              break;
          };
  
  	    console.log("size_buffer ", size_buffer);
  	    console.log("size left   ", left_obj.buffer.length);
  	    console.log("size right  ", right_obj.buffer.length);
  
  	    if (size_buffer > left_obj.buffer.length || size_buffer > right_obj.buffer.length) {
  
              console.error("ERROR - you defined master as : ", master, 
              			  " yet buffer size is larger than other buffer");
              process.exit(8);
  	    };
  
  	    spec.size_buffer = size_buffer;
  
  	    // ---
  
          switch (extent) {
  
              case "entire" : {
  
  	            console.log("OK extent is ", extent)    ;
  
  	    		diff_entire_buffers(left_obj, right_obj, size_buffer, given_spec);
  
  	    		break;
              }
  
              // --- default - catch all if not identifed above
  
              default :
  
              console.error("ERROR - failed to find recognized value of spec.extent : ", extent);
              process.exit(8);
  
              break;
          };
  
  	    console.log("extent ", extent);
  
  	}