--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/debug.lua	Thu Nov 03 12:41:21 2011 +0000
@@ -0,0 +1,135 @@
+-- Variables ending with these names will not
+-- have their values printed ('password' includes
+-- 'new_password', etc.)
+local censored_names = {
+	password = true;
+	passwd = true;
+	pass = true;
+	pwd = true;
+};
+
+local function get_locals_table(level)
+	local locals = {};
+	for local_num = 1, math.huge do
+		local name, value = debug.getlocal(level, local_num);
+		if not name then break; end
+		table.insert(locals, { name = name, value = value });
+	end
+	return locals;
+end
+
+local function get_upvalues_table(func)
+	local upvalues = {};
+	for upvalue_num = 1, math.huge do
+		local name, value = debug.getupvalue(func, upvalue_num);
+		if not name then break; end
+		table.insert(upvalues, { name = name, value = value });
+	end
+	return upvalues;
+end
+
+local function string_from_var_table(var_table, max_line_len, indent_str)
+	local var_string = {};
+	local col_pos = 0;
+	max_line_len = max_line_len or math.huge;
+	indent_str = "\n"..(indent_str or "");
+	for _, var in ipairs(var_table) do
+		local name, value = var.name, var.value;
+		if name:sub(1,1) ~= "(" then
+			if type(value) == "string" then
+				if censored_names[name:match("%a+$")] then
+					value = "<hidden>";
+				else
+					value = ("%q"):format(value);
+				end
+			else
+				value = tostring(value);
+			end
+			if #value > max_line_len then
+				value = value:sub(1, max_line_len-3).."…";
+			end
+			local str = ("%s = %s"):format(name, tostring(value));
+			col_pos = col_pos + #str;
+			if col_pos > max_line_len then
+				table.insert(var_string, indent_str);
+				col_pos = 0;
+			end
+			table.insert(var_string, str);
+		end
+	end
+	if #var_string == 0 then
+		return nil;
+	else
+		return "{ "..table.concat(var_string, ", "):gsub(indent_str..", ", indent_str).." }";
+	end
+end
+
+function get_traceback_table(thread, start_level)
+	local levels = {};
+	for level = start_level, math.huge do
+		local info;
+		if thread then
+			info = debug.getinfo(thread, level);
+		else
+			info = debug.getinfo(level);
+		end
+		if not info then break; end
+		
+		levels[(level-start_level)+1] = {
+			level = level;
+			info = info;
+			locals = get_locals_table(level);
+			upvalues = get_upvalues_table(info.func);
+		};
+	end	
+	return levels;
+end
+
+function debug.traceback(thread, message, level)
+	if type(thread) ~= "thread" then
+		thread, message, level = coroutine.running(), thread, message;
+	end
+	if level and type(message) ~= "string" then
+		return nil, "invalid message";
+	elseif not level then
+		level = message or 2;
+	end
+	
+	message = message and (message.."\n") or "";
+	
+	local levels = get_traceback_table(thread, level+2);
+	
+	local lines = {};
+	for nlevel, level in ipairs(levels) do
+		local info = level.info;
+		local line = "...";
+		local func_type = info.namewhat.." ";
+		if func_type == " " then func_type = ""; end;
+		if info.short_src == "[C]" then
+			line = "[ C ] "..func_type.."C function "..(info.name and ("%q"):format(info.name) or "(unknown name)")
+		elseif info.what == "main" then
+			line = "[Lua] "..info.short_src.." line "..info.currentline;
+		else
+			local name = info.name or " ";
+			if name ~= " " then
+				name = ("%q"):format(name);
+			end
+			if func_type == "global " or func_type == "local " then
+				func_type = func_type.."function ";
+			end
+			line = "[Lua] "..info.short_src.." line "..info.currentline.." in "..func_type..name.." defined on line "..info.linedefined;
+		end
+		nlevel = nlevel-1;
+		table.insert(lines, "\t"..(nlevel==0 and ">" or " ").."("..nlevel..") "..line);
+		local npadding = (" "):rep(#tostring(nlevel));
+		local locals_str = string_from_var_table(level.locals, 65, "\t            "..npadding);
+		if locals_str then
+			table.insert(lines, "\t    "..npadding.."Locals: "..locals_str);
+		end
+		local upvalues_str = string_from_var_table(level.upvalues, 65, "\t            "..npadding);
+		if upvalues_str then
+			table.insert(lines, "\t    "..npadding.."Upvals: "..upvalues_str);
+		end
+	end
+	return message.."stack traceback:\n"..table.concat(lines, "\n");
+end