lua add better memory stats

lua gives you a memory used number that only reflects the current allocations
if fact it doesn't even give you a way to get the amount of ram free

rb.mem_stats() seeks to fill this gap by marking the memory allocated for lua
with a sentinel value which can later be checked to get a high water mark
of the ram used by lua and a pretty good idea of how much ram is available

Also includes an example script
usage:
used, allocd, free = rb.mem_stats()

Change-Id: Ia282869f989848324d7d88c7df4827fdbce4fb4e

apps/plugins/lua/rocklib.c

@@ -53,6 +53,8 @@
  *
  * -----------------------------
  */
+extern size_t rock_get_allocated_bytes(void); /* tlsf_helper.c */
+extern size_t rock_get_unused_bytes(void);
 
 #define RB_WRAP(func) static int rock_##func(lua_State UNUSED_ATTR *L)
 #define SIMPLE_VOID_WRAPPER(func) RB_WRAP(func) { (void)L; func(); return 0; }
@@ -931,6 +933,19 @@ RB_WRAP(show_logo)
     return 0;
 }
 
+RB_WRAP(mem_stats)
+{
+    /* used, allocd, free = rb.mem_stats() */
+    /* note free is the high watermark */
+    size_t allocd = rock_get_allocated_bytes();
+    size_t free = rock_get_unused_bytes();
+
+    lua_pushinteger(L, allocd - free);
+    lua_pushinteger(L, allocd);
+    lua_pushinteger(L, free);
+    return 3;
+}
+
 #define RB_FUNC(func) {#func, rock_##func}
 #define RB_ALIAS(name, func) {name, rock_##func}
 static const luaL_Reg rocklib[] =
@@ -1015,6 +1030,7 @@ static const luaL_Reg rocklib[] =
     /* MISC */
     RB_FUNC(restart_lua),
     RB_FUNC(show_logo),
+    RB_FUNC(mem_stats),
 
     {NULL, NULL}
 };

apps/plugins/lua/tlsf_helper.c

@@ -21,16 +21,62 @@
 #include "plugin.h"
 #include <tlsf.h>
 #include "lua.h"
+static const unsigned int sentinel = 0xBA5EFAC7;
+#define SENTINEL(n) (sentinel ^ (n))
+
+static char *pluginbuf_ptr = NULL;
+static size_t pluginbuf_size = 0;
+static char *audiobuf_ptr = NULL;
+static size_t audiobuf_size = 0;
+
+static void set_sentinel(void* buf, size_t size)
+{
+    size_t i;
+    unsigned int *b = (int*) buf;
+    for(i = 0; i < size / sizeof(sentinel); i++)
+        *b++ = SENTINEL(i);
+}
+
+static size_t check_sentinel(void* buf, size_t size)
+{
+    const size_t sz = size / sizeof(sentinel);
+    size_t unused = 0;
+    size_t i;
+    unsigned int *b = (int*) buf;
+    for(i = 0; i < sz; i++)
+        if (b[i] == SENTINEL(i))
+        {
+            unused++;
+            while(++i < sz && b[i] == SENTINEL(i) && ++unused)
+                ;;
+        }
+    return unused * sizeof(sentinel);
+}
+
+size_t rock_get_allocated_bytes(void)
+{
+    return pluginbuf_size + audiobuf_size;
+}
+
+size_t rock_get_unused_bytes(void)
+{
+    size_t unused = 0;
+    if (pluginbuf_size)
+        unused += check_sentinel(pluginbuf_ptr, pluginbuf_size);
+    if (audiobuf_size)
+        unused += check_sentinel(audiobuf_ptr, audiobuf_size);
+    return unused;
+}
 
 void *get_new_area(size_t *size)
 {
-    static char *pluginbuf_ptr = NULL;
-    static char *audiobuf_ptr = NULL;
-
     if (pluginbuf_ptr == NULL)
     {
         pluginbuf_ptr = rb->plugin_get_buffer(size);
 
+        pluginbuf_size = *size;
+        set_sentinel(pluginbuf_ptr, pluginbuf_size);
+
         /* kill tlsf signature if any */
         memset(pluginbuf_ptr, 0, 4);
 
@@ -43,6 +89,9 @@ void *get_new_area(size_t *size)
         /* grab audiobuffer */
         audiobuf_ptr = rb->plugin_get_audio_buffer(size);
 
+        audiobuf_size = *size;
+        set_sentinel(audiobuf_ptr, audiobuf_size);
+
         return audiobuf_ptr;
     }
 

apps/plugins/lua_scripts/memchk.lua

@@ -0,0 +1,32 @@
+--[[
+             __________               __   ___.
+   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+                     \/            \/     \/    \/            \/
+ $Id$
+ Example Lua Memory Use
+ Copyright (C) 2020 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.
+]]--
+
+local used, allocd, free = rb.mem_stats()
+local lu = collectgarbage("count")
+local fmt = function(t, v) return string.format("%s: %d Kb\n", t, v /1024) end
+
+-- this is how lua recommends to concat strings rather than ..
+local s_t = {}
+s_t[1] = "rockbox:\n"
+s_t[2] = fmt("Used  ", used)
+s_t[3] = fmt("Allocd ", allocd)
+s_t[4] = fmt("Free  ", free)
+s_t[5] = "\nlua:\n"
+s_t[6] = fmt("Used", lu * 1024)
+s_t[7] = "\n\nNote that the rockbox used count is a high watermark"
+rb.splash_scroller(10 * rb.HZ, table.concat(s_t))