pgraph: Use BamAuxData for RenderState overrides reading

Saves a bit of memory.  Fast path for empty RenderState.

Author: rdb

panda/src/pgraph/renderState.cxx

@@ -74,7 +74,6 @@ RenderState() :
   _saved_entry = -1;
   _last_mi = -1;
   _cache_stats.add_num_states(1);
-  _read_overrides = nullptr;
   _generated_shader = nullptr;
 
 #ifdef DO_MEMORY_USAGE
@@ -99,7 +98,6 @@ RenderState(const RenderState &copy) :
   _saved_entry = -1;
   _last_mi = -1;
   _cache_stats.add_num_states(1);
-  _read_overrides = nullptr;
   _generated_shader = nullptr;
 
 #ifdef DO_MEMORY_USAGE
@@ -1899,23 +1897,21 @@ int RenderState::
 complete_pointers(TypedWritable **p_list, BamReader *manager) {
   int pi = TypedWritable::complete_pointers(p_list, manager);
 
-  if (_read_overrides != nullptr) {
-    RenderAttribRegistry *reg = RenderAttribRegistry::quick_get_global_ptr();
-    for (size_t i = 0; i < (*_read_overrides).size(); ++i) {
-      int override = (*_read_overrides)[i];
-
-      RenderAttrib *attrib = DCAST(RenderAttrib, p_list[pi++]);
-      if (attrib != nullptr) {
-        int slot = attrib->get_slot();
-        if (slot > 0 && slot < reg->get_max_slots()) {
-          _attributes[slot].set(attrib, override);
-          _filled_slots.set_bit(slot);
-        }
+  BamAuxData *aux = (BamAuxData *)manager->get_aux_data(this, "overrides");
+  nassertr(aux != nullptr, pi);
+
+  RenderAttribRegistry *reg = RenderAttribRegistry::quick_get_global_ptr();
+  for (size_t i = 0; i < aux->_overrides.size(); ++i) {
+    int override = aux->_overrides[i];
+
+    RenderAttrib *attrib = DCAST(RenderAttrib, p_list[pi++]);
+    if (attrib != nullptr) {
+      int slot = attrib->get_slot();
+      if (slot > 0 && slot < reg->get_max_slots()) {
+        _attributes[slot].set(attrib, override);
+        _filled_slots.set_bit(slot);
       }
     }
-
-    delete _read_overrides;
-    _read_overrides = nullptr;
   }
 
   return pi;
@@ -1974,15 +1970,19 @@ finalize(BamReader *) {
  */
 TypedWritable *RenderState::
 make_from_bam(const FactoryParams &params) {
-  RenderState *state = new RenderState;
   DatagramIterator scan;
   BamReader *manager;
 
   parse_params(params, scan, manager);
-  state->fillin(scan, manager);
-  manager->register_change_this(change_this, state);
 
-  return state;
+  if (scan.peek_uint16() != 0) {
+    RenderState *state = new RenderState;
+    state->fillin(scan, manager);
+    manager->register_change_this(change_this, state);
+    return state;
+  } else {
+    return (TypedWritable *)_empty_state;
+  }
 }
 
 /**
@@ -1994,16 +1994,15 @@ fillin(DatagramIterator &scan, BamReader *manager) {
   TypedWritable::fillin(scan, manager);
 
   int num_attribs = scan.get_uint16();
-  if (num_attribs == 0) {
-    _read_overrides = nullptr;
-  } else {
-    _read_overrides = new vector_int;
-    (*_read_overrides).reserve(num_attribs);
 
-    for (int i = 0; i < num_attribs; ++i) {
-      manager->read_pointer(scan);
-      int override = scan.get_int32();
-      (*_read_overrides).push_back(override);
-    }
+  BamAuxData *aux_data = new BamAuxData;
+  aux_data->_overrides.reserve(num_attribs);
+
+  for (int i = 0; i < num_attribs; ++i) {
+    manager->read_pointer(scan);
+    int override = scan.get_int32();
+    aux_data->_overrides.push_back(override);
   }
+
+  manager->set_aux_data(this, "overrides", aux_data);
 }

panda/src/pgraph/renderState.h

@@ -338,7 +338,11 @@ class EXPCL_PANDA_PGRAPH RenderState : public NodeCachedReferenceCount {
   };
   unsigned int _flags;
 
-  vector_int *_read_overrides;  // Only used during bam reading.
+  // This data is only needed when reading from a bam file.
+  class BamAuxData : public BamReader::AuxData {
+  public:
+    vector_int _overrides;
+  };
 
   // This mutex protects _flags, and all of the above computed values.
   LightMutex _lock;