Lua Add Emergency Garbage Collector

Derivative of work by RobertGabrielJakabosky
 http://lua-users.org/wiki/EmergencyGarbageCollector

I've only implemented the not enough memory part and
 expanded this idea to adding a mechanism to signal
 the OOM condition of the plugin buffer which allows us to only
 grab the playback buffer after garbage collection fails
 (SO THE MUSIC KEEPS PLAYING AS LONG AS POSSIBLE)

Change-Id: I684fb98b540ffc01f7ba324ab5b761ceb59b9f9b

1 files changed, 24 insertions, 6 deletions

diff --git a/apps/plugins/lua/lauxlib.c b/apps/plugins/lua/lauxlib.c
index 2e4b3b1e3c..acd7e0e636 100644
--- a/apps/plugins/lua/lauxlib.c
+++ b/apps/plugins/lua/lauxlib.c
@@ -13,7 +13,6 @@
 #include <string.h>
 #include "lstring.h" /* ROCKLUA ADDED */
 
-
 /* This file uses only the official API of Lua.
 ** Any function declared here could be written as an application function.
 ** Note ** luaS_newlloc breaks this guarantee ROCKLUA ADDED
@@ -34,7 +33,9 @@
 #define abs_index(L, i)         ((i) > 0 || (i) <= LUA_REGISTRYINDEX ? (i) : \
                                         lua_gettop(L) + (i) + 1)
 
-
+#ifndef LUA_OOM
+  #define LUA_OOM(L) {}
+#endif
 /*
 ** {======================================================
 ** Error-report functions
@@ -756,14 +757,30 @@ LUALIB_API int (luaL_loadstring) (lua_State *L, const char *s) {
 
 
 static void *l_alloc (void *ud, void *ptr, size_t osize, size_t nsize) {
-  (void)ud;
-  (void)osize;
+  (void) osize;
+  lua_State *L = (lua_State *)ud;
+  void *nptr;
+
   if (nsize == 0) {
     free(ptr);
     return NULL;
   }
-  else
-    return realloc(ptr, nsize);
+
+  nptr = realloc(ptr, nsize);
+  if (nptr == NULL) {
+    if(L != NULL)
+    {
+      luaC_fullgc(L); /* emergency full collection. */
+      nptr = realloc(ptr, nsize); /* try allocation again */
+    }
+
+    if (nptr == NULL) {
+      LUA_OOM(L); /* if defined.. signal OOM condition */
+      nptr = realloc(ptr, nsize); /* try allocation again */
+    }
+  }
+
+  return nptr;
 }
 
 
@@ -779,6 +796,7 @@ static int panic (lua_State *L) {
 
 LUALIB_API lua_State *luaL_newstate (void) {
   lua_State *L = lua_newstate(l_alloc, NULL);
+  lua_setallocf(L, l_alloc, L); /* allocator needs lua_State. */
   if (L) lua_atpanic(L, &panic);
   return L;
 }