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, 16 insertions, 12 deletions

diff --git a/apps/plugins/lua/lstring.c b/apps/plugins/lua/lstring.c
index bf0536e311..6d73f1e9ea 100644
--- a/apps/plugins/lua/lstring.c
+++ b/apps/plugins/lua/lstring.c
@@ -22,30 +22,34 @@
 
 
 void luaS_resize (lua_State *L, int newsize) {
-  GCObject **newhash;
   stringtable *tb;
   int i;
-  if (G(L)->gcstate == GCSsweepstring)
-    return;  /* cannot resize during GC traverse */
-  newhash = luaM_newvector(L, newsize, GCObject *);
   tb = &G(L)->strt;
-  for (i=0; i<newsize; i++) newhash[i] = NULL;
+  if (luaC_sweepstrgc(L) || newsize == tb->size || is_resizing_strings_gc(L))
+    return;  /* cannot resize during GC traverse or doesn't need to be resized */
+  set_resizing_strings_gc(L);
+  if (newsize > tb->size) {
+    luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
+    for (i=tb->size; i<newsize; i++) tb->hash[i] = NULL;
+  }
   /* rehash */
   for (i=0; i<tb->size; i++) {
     GCObject *p = tb->hash[i];
+    tb->hash[i] = NULL;
     while (p) {  /* for each node in the list */
       GCObject *next = p->gch.next;  /* save next */
       unsigned int h = gco2ts(p)->hash;
       int h1 = lmod(h, newsize);  /* new position */
       lua_assert(cast_int(h%newsize) == lmod(h, newsize));
-      p->gch.next = newhash[h1];  /* chain it */
-      newhash[h1] = p;
+      p->gch.next = tb->hash[h1];  /* chain it */
+      tb->hash[h1] = p;
       p = next;
     }
   }
-  luaM_freearray(L, tb->hash, tb->size, TString *);
+  if (newsize < tb->size)
+    luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
   tb->size = newsize;
-  tb->hash = newhash;
+  unset_resizing_strings_gc(L);
 }
 
 
@@ -55,6 +59,9 @@ static TString *newlstr (lua_State *L, const char *str, size_t l,
   stringtable *tb;
   if (l > ((MAX_SIZET - sizeof(TString))/sizeof(char)) - sizeof(""))
     luaM_toobig(L);
+  tb = &G(L)->strt;
+  if ((tb->nuse + 1) > cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
+    luaS_resize(L, tb->size*2);  /* too crowded */
   ts = cast(TString *, luaM_malloc(L, sizetstring(type, l)));
   ts->tsv.len = l;
   ts->tsv.hash = h;
@@ -70,13 +77,10 @@ static TString *newlstr (lua_State *L, const char *str, size_t l,
     memcpy(ts+1, str, l*sizeof(char));
     ((char *)(ts+1))[l] = '\0';  /* ending 0 */
   }
-  tb = &G(L)->strt;
   h = lmod(h, tb->size);
   ts->tsv.next = tb->hash[h];  /* chain new entry */
   tb->hash[h] = obj2gco(ts);
   tb->nuse++;
-  if (tb->nuse > cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
-    luaS_resize(L, tb->size*2);  /* too crowded */
   return ts;
 }