Let nsedebug.tostr support other datatypes with tostring

Instead of erroring, just use tostring to handle functions, userdata,
etc. This works for booleans and numbers, too, so no need for special
handling there.

Also switched from a string-concatenation model to a table-building one,
with a final concatenation. This could prevent catastrophic slowness
with representing large tables due to continuous reallocation of
strings.

nselib/nsedebug.lua

@@ -12,6 +12,7 @@ local io = require "io"
 local math = require "math"
 local stdnse = require "stdnse"
 local string = require "string"
+local table = require "table"
 _ENV = stdnse.module("nsedebug", stdnse.seeall)
 
 local EMPTY = {}; -- Empty constant table
@@ -25,41 +26,38 @@ local EMPTY = {}; -- Empty constant table
 --              is 0. 
 --@return A string representation of a data, will be one or more full lines. 
 function tostr(data, indent)
-	local str = ""
+	local str
 
 	if(indent == nil) then
 		indent = 0
 	end
 
 	-- Check the type
-	if(type(data) == "nil") then
+	local typ = type(data)
-		str = str .. (" "):rep(indent) .. "nil\n"
+	if(typ == "nil" or typ == "number" or typ == "boolean" or typ == "function" or typ == "thread" or typ == "userdata") then
+		str = {(" "):rep(indent), tostring(data), "\n"}
 	elseif(type(data) == "string") then
-		str = str .. (" "):rep(indent) .. string.format("%q", data) .. "\n"
+		str = {(" "):rep(indent), string.format("%q", data), "\n"}
-	elseif(type(data) == "number") then
-		str = str .. (" "):rep(indent) .. data .. "\n"
-	elseif(type(data) == "boolean") then
-		if(data == true) then
-			str = str .. "true\n"
-		else
-			str = str .. "false\n"
-		end
 	elseif(type(data) == "table") then
 		local i, v
+		str = {}
 		for i, v in pairs(data) do
 			-- Check for a table in a table
+			str[#str+1] = (" "):rep(indent)
+			str[#str+1] = tostring(i)
 			if(type(v) == "table") then
-				str = str .. (" "):rep(indent) .. tostring(i) .. ":\n"
+				str[#str+1] = ":\n"
-				str = str .. tostr(v, indent + 2)
+				str[#str+1] = tostr(v, indent + 2)
 			else
-				str = str .. (" "):rep(indent) .. tostring(i) .. ": " .. tostr(v, 0)
+				str[#str+1] = ": "
+				str[#str+1] = tostr(v, 0)
 			end
 		end
 	else
 		stdnse.print_debug(1, "Error: unknown data type: %s", type(data))
 	end
 
-	return str
+	return table.concat(str)
 end
 
 --- Print out a string in hex, for debugging.