lua -- temp loader

fix a few bugs, improve memory usage

Change-Id: I6ceefd033000a6178eab0dd513679b5d72cec81c

apps/plugins/lua/include_lua/temploader.lua

@@ -1,30 +1,63 @@
 --[[
-temp loader allows some lua requires to be loaded and later garbage collected
-unfortunately the module needs to be formatted in such a way to pass back a 
-call table in order to keep the functions within from being garbage collected 
-too early
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2021 William Wilgus
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+--
+temp_loader allows some (pure) lua requires to be loaded and later garbage collected
+unfortunately the 'required' module needs to be formatted in such a way to
+pass back a reference to a function or call table in order to keep the functions
+within from being garbage collected too early
 
-BE AWARE this bypasses the module loader which would allow code reuse
-so if you aren't careful this memory saving tool could spell disaster
-for free RAM if you load the same code multiple times
+modules that add things to _G table are unaffected by using this function
+except if later you use require or temp_loader those tables will again
+be reloaded with fresh data since nothing was recorded about the module being loaded
+
+modulename - same as require()
+newinstance == true -- get a new copy (from disk) of the module
+... other args for the module
+
+BE AWARE this bypasses the module loader
+which would allow code reuse so if you aren't careful this memory saving tool
+could spell disaster for free RAM if you load the same code multiple times
 --]]
 
-
-local function tempload(modulename)
+local function tempload(modulename, newinstance, ...)
   --http://lua-users.org/wiki/LuaModulesLoader
   local errmsg = ""
+  -- Is there current a loaded module by this name?
+  if package.loaded[modulename] ~= nil and not newinstance then
+    return require(modulename)
+  end
   -- Find source
   local modulepath = string.gsub(modulename, "%.", "/")
   for path in string.gmatch(package.path, "([^;]+)") do
     local filename = string.gsub(path, "%?", modulepath)
-    local file = io.open(filename, "r")
+    --attempt to open and compile module
+    local file, err = loadfile(filename)
     if file then
-      -- Compile and return the module
-      return assert(loadstring(assert(file:read("*a")), filename))()
+      -- execute the compiled chunk
+      return file(... or modulename)
     end
-    errmsg = errmsg.."\n\tno file '"..filename.."' (temp loader)"
+    errmsg = table.concat({errmsg, "\n\tno file '", filename, "' (temp loader)"})
   end
-  return errmsg
+  return nil, errmsg
 end
 
 return tempload