Implement plugin mechanism for actuators and sensors.

PiperOrigin-RevId: 474874088
Change-Id: I65a8ffdf845f4fa0f8266c165883a747ab5812d8

include/mujoco/mujoco.h

@@ -34,6 +34,7 @@ extern "C" {
 // type definitions
 #include <mujoco/mjdata.h>
 #include <mujoco/mjmodel.h>
+#include <mujoco/mjplugin.h>
 #include <mujoco/mjrender.h>
 #include <mujoco/mjtnum.h>
 #include <mujoco/mjui.h>
@@ -453,6 +454,10 @@ MJAPI mjtNum mj_getTotalmass(const mjModel* m);
 // Scale body masses and inertias to achieve specified total mass.
 MJAPI void mj_setTotalmass(mjModel* m, mjtNum newmass);
 
+// Return a config attribute value of a plugin instance;
+// NULL: invalid plugin instance ID or attribute name
+MJAPI const char* mj_getPluginConfig(const mjModel* m, int plugin_id, const char* attrib);
+
 // Return version number: 1.0.2 is encoded as 102.
 MJAPI int mj_version(void);
 
@@ -1135,6 +1140,29 @@ MJAPI void mjd_transitionFD(const mjModel* m, mjData* d, mjtNum eps, mjtByte cen
 
 
 
+//---------------------- Plugins -------------------------------------------------------------------
+
+// Set default plugin definition.
+MJAPI void mjp_defaultPlugin(mjpPlugin* plugin);
+
+// Globally register a plugin. This function is thread-safe.
+// If an identical mjpPlugin is already registered, this function does nothing.
+// If a non-identical mjpPlugin with the same name is already registered, an mju_error is raised.
+// Two mjpPlugins are considered identical if all member function pointers and numbers are equal,
+// and the name and attribute strings are all identical, however the char pointers to the strings
+// need not be the same.
+MJAPI int mjp_registerPlugin(const mjpPlugin* plugin);
+
+// Return the number of globally registered plugins.
+MJAPI int mjp_pluginCount();
+
+// Look up a plugin by name. If slot is not NULL, also write its registered slot number into it.
+MJAPI const mjpPlugin* mjp_getPlugin(const char* name, int* slot);
+
+// Look up a plugin by the registered slot number that was returned by mjp_registerPlugin.
+MJAPI const mjpPlugin* mjp_getPluginAtSlot(int slot);
+
+
 #if defined(__cplusplus)
 }
 #endif