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

1 files changed, 52 insertions, 3 deletions

diff --git a/apps/plugins/lua/tlsf_helper.c b/apps/plugins/lua/tlsf_helper.c
index 097d39c8e4..52ef269bcd 100644
--- a/apps/plugins/lua/tlsf_helper.c
+++ b/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))
 
-void *get_new_area(size_t *size)
+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)
 {
-    static char *pluginbuf_ptr = NULL;
-    static char *audiobuf_ptr = NULL;
+    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)
+{
     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;
     }