Added functionality for user payload data in mjSpec.

PiperOrigin-RevId: 738343134
Change-Id: I6217362ced9993afcd5a2914c78718ffe3bf753a

src/user/user_objects.h

@@ -23,11 +23,14 @@
 #include <map>
 #include <string>
 #include <string_view>
+#include <unordered_map>
 #include <utility>
 #include <vector>
 
+#include <mujoco/mjmodel.h>
+#include <mujoco/mjplugin.h>
 #include <mujoco/mjspec.h>
-#include <mujoco/mujoco.h>
+#include <mujoco/mjtnum.h>
 #include "user/user_cache.h"
 #include "user/user_util.h"
 #include <tiny_obj_loader.h>
@@ -274,12 +277,20 @@ class mjCBase : public mjCBase_ {
     }
   }
 
+  // Set and get user payload
+  void SetUserValue(std::string_view key, const void* data);
+  const void* GetUserValue(std::string_view key);
+  void DeleteUserValue(std::string_view key);
+
  protected:
   mjCBase();                                 // constructor
   mjCBase(const mjCBase& other);             // copy constructor
 
   // reference count for allowing deleting an attached object
   int refcount = 1;
+
+  // user payload
+  std::unordered_map<std::string, const void*> user_payload_;
 };
 
 
@@ -781,7 +792,7 @@ class mjCLight : public mjCLight_, private mjsLight {
 
 class mjCFlex_ : public mjCBase {
  protected:
-  int nvert;                              // number of verices
+  int nvert;                              // number of vertices
   int nnode;                              // number of nodes
   int nedge;                              // number of edges
   int nelem;                              // number of elements