Add signature to mjSpec and mjModel and use it to perform safe bind to mjModel and mjData.

PiperOrigin-RevId: 740378879
Change-Id: If14b326942529494f172e7aedcae30195798b458

src/engine/engine_io.c

@@ -2014,6 +2014,9 @@ static void _resetData(const mjModel* m, mjData* d, unsigned char debug_value) {
       }
     }
   }
+
+  // copy signature from model
+  d->signature = m->signature;
 }
 
 

src/user/user_flexcomp.cc

@@ -403,12 +403,14 @@ bool mjCFlexcomp::Make(mjsBody* body, char* error, int error_sz) {
   mjCFlex* flex = model->AddFlex();
   mjsFlex* pf = &flex->spec;
   int id = flex->id;
+  int uid = flex->uid;
 
   *flex = def.Flex();
   flex->PointToLocal();
 
   flex->model = model;
   flex->id = id;
+  flex->uid = uid;
   mjs_setString(pf->name, name.c_str());
   mjs_setInt(pf->elem, element.data(), element.size());
   mjs_setFloat(pf->texcoord, texcoord.data(), texcoord.size());

src/user/user_model.cc

@@ -201,6 +201,7 @@ mjCModel::mjCModel() {
   world->mass = 0;
   mjuu_zerovec(world->inertia, 3);
   world->id = 0;
+  world->uid = GetUid();
   world->parent = nullptr;
   world->weldid = 0;
   world->name = "world";
@@ -213,6 +214,9 @@ mjCModel::mjCModel() {
 
   // the source spec is the model itself, overwritten in the copy constructor
   source_spec_ = &spec;
+
+  // set the signature
+  spec.element->signature = 0;
 }
 
 
@@ -289,6 +293,7 @@ void mjCModel::CopyList(std::vector<T*>& dest,
     // copy the element from the other model to this model
     if (deepcopy_) {
       source[i]->ForgetKeyframes();
+      candidate->uid = GetUid();
     } else {
       candidate->AddRef();
     }
@@ -499,6 +504,9 @@ mjCModel& mjCModel::operator+=(const mjCModel& other) {
     nq = nv = na = nu = nmocap = 0;
   }
 
+  // update signature before we reset the tree lists
+  spec.element->signature = Signature();
+
   PointToLocal();
   return *this;
 }
@@ -633,6 +641,9 @@ mjCModel& mjCModel::operator-=(const mjCBody& subtree) {
   RemoveFromList(sensors_, oldmodel);
   RemovePlugins();
 
+  // update signature before we reset the tree lists
+  spec.element->signature = Signature();
+
   return *this;
 }
 
@@ -803,6 +814,9 @@ void mjCModel::DeleteElement(mjsElement* el) {
       break;
   }
 
+  // update signature before we reset the tree lists
+  spec.element->signature = Signature();
+
   ResetTreeLists();  // in case of a nested delete
   MakeTreeLists();
   ProcessLists(/*checkrepeat=*/false);
@@ -1019,7 +1033,9 @@ template <class T>
 T* mjCModel::AddObject(vector<T*>& list, string type) {
   T* obj = new T(this);
   obj->id = (int)list.size();
+  obj->uid = GetUid();
   list.push_back(obj);
+  spec.element->signature = Signature();
   return obj;
 }
 
@@ -1030,7 +1046,9 @@ T* mjCModel::AddObjectDefault(vector<T*>& list, string type, mjCDef* def) {
   T* obj = new T(this, def ? def : defaults_[0]);
   obj->id = (int)list.size();
   obj->classname = def ? def->name : "main";
+  obj->uid = GetUid();
   list.push_back(obj);
+  spec.element->signature = Signature();
   return obj;
 }
 
@@ -4572,6 +4590,28 @@ void mjCModel::TryCompile(mjModel*& m, mjData*& d, const mjVFS* vfs) {
     mju::strcpy_arr(errInfo.message, warningtext);
     errInfo.warning = true;
   }
+
+  // save signature
+  m->signature = Signature();
+}
+
+
+
+uint64_t mjCModel::Signature() {
+  std::string uid_str;
+  for (int i = 0; i < mjNOBJECT; ++i) {
+    if (i == mjOBJ_XBODY || i == mjOBJ_UNKNOWN || i == mjOBJ_DOF) {
+      continue;
+    }
+    if (object_lists_[i] == nullptr) {
+      throw mjCError(0, "object list %s is null", std::to_string(i).c_str());
+    }
+    uid_str += '|';
+    for (mjCBase* object : *object_lists_[i]) {
+      uid_str += std::to_string(object->uid) + " ";
+    }
+  }
+  return mj_hashString(uid_str.c_str(), UINT64_MAX);
 }
 
 

src/user/user_model.h

@@ -16,6 +16,7 @@
 #define MUJOCO_SRC_USER_USER_MODEL_H_
 
 #include <array>
+#include <cstdint>
 #include <functional>
 #include <map>
 #include <string>
@@ -324,6 +325,9 @@ class mjCModel : public mjCModel_, private mjSpec {
   // set attached flag
   void SetAttached(bool deepcopy) { attached_ |= !deepcopy; }
 
+  // get new uid
+  int GetUid() { return uid_count_++; }
+
  private:
   // settings for each defaults class
   std::vector<mjCDef*> defaults_;
@@ -440,11 +444,14 @@ class mjCModel : public mjCModel_, private mjSpec {
   void MarkPluginInstance(std::unordered_map<std::string, bool>& instances,
                           const std::vector<T*>& list);
 
+  // generate a signature for the model
+  uint64_t Signature();
 
   mjListKeyMap ids;   // map from object names to ids
   mjCError errInfo;   // last error info
   std::vector<mjKeyInfo> key_pending_;  // attached keyframes
   bool deepcopy_;     // copy objects when attaching
   bool attached_ = false;  // true if model is attached to a parent model
+  int uid_count_ = 0;  // unique id count for all objects
 };
 #endif  // MUJOCO_SRC_USER_USER_MODEL_H_

src/user/user_objects.cc

@@ -837,6 +837,7 @@ mjCBody::mjCBody(mjCModel* _model) {
 
 mjCBody::mjCBody(const mjCBody& other, mjCModel* _model) {
   model = _model;
+  uid = model->GetUid();
   mjSpec* origin = model->FindSpec(other.compiler);
   compiler = origin ? &origin->compiler : &model->spec.compiler;
   *this = other;
@@ -930,6 +931,7 @@ mjCBody& mjCBody::operator+=(const mjCFrame& other) {
   frames.back()->frame = other.frame;
   if (model->deepcopy_) {
     frames.back()->NameSpace(other_model);
+    frames.back()->uid = model->GetUid();
   } else {
     frames.back()->AddRef();
   }
@@ -1022,6 +1024,8 @@ void mjCBody::CopyList(std::vector<T*>& dst, const std::vector<T*>& src,
     // increment refcount if shallow copy is made
     if (!model->deepcopy_) {
       dst.back()->AddRef();
+    } else {
+      dst.back()->uid = model->GetUid();
     }
 
     // set namespace
@@ -1237,6 +1241,10 @@ mjCBody* mjCBody::AddBody(mjCDef* _def) {
   model->MakeTreeLists();
 
   obj->parent = this;
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1248,6 +1256,10 @@ mjCFrame* mjCBody::AddFrame(mjCFrame* _frame) {
   frames.push_back(obj);
   model->ResetTreeLists();
   model->MakeTreeLists();
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1268,6 +1280,10 @@ mjCJoint* mjCBody::AddFreeJoint() {
   model->ResetTreeLists();
   model->MakeTreeLists();
 
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1287,6 +1303,10 @@ mjCJoint* mjCBody::AddJoint(mjCDef* _def) {
   model->ResetTreeLists();
   model->MakeTreeLists();
 
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1306,6 +1326,10 @@ mjCGeom* mjCBody::AddGeom(mjCDef* _def) {
   model->ResetTreeLists();
   model->MakeTreeLists();
 
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1325,6 +1349,10 @@ mjCSite* mjCBody::AddSite(mjCDef* _def) {
   model->ResetTreeLists();
   model->MakeTreeLists();
 
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1344,6 +1372,10 @@ mjCCamera* mjCBody::AddCamera(mjCDef* _def) {
   model->ResetTreeLists();
   model->MakeTreeLists();
 
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 
@@ -1363,6 +1395,10 @@ mjCLight* mjCBody::AddLight(mjCDef* _def) {
   model->ResetTreeLists();
   model->MakeTreeLists();
 
+
+  // update signature
+  obj->uid = model->GetUid();
+  model->spec.element->signature = model->Signature();
   return obj;
 }
 

src/user/user_objects.h

@@ -219,6 +219,7 @@ class mjCBoundingVolumeHierarchy : public mjCBoundingVolumeHierarchy_ {
 class mjCBase_ : public mjsElement {
  public:
   int id;                 // object id
+  int uid;                // unique identifier
   std::string name;       // object name
   std::string classname;  // defaults class name
   std::string info;       // error message info set by the user