Add compiler C API for mjmSite.

PiperOrigin-RevId: 604573450
Change-Id: I6ba7fcece0942ddc0d109413ba5684b2df3fab96

src/user/user_api.h

@@ -0,0 +1,92 @@
+// Copyright 2021 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef MUJOCO_SRC_USER_USER_API_H_
+#define MUJOCO_SRC_USER_USER_API_H_
+
+#include <mujoco/mjexport.h>
+#include <mujoco/mjmodel.h>
+
+typedef struct _mjString* mjString;
+typedef struct _mjDouble* mjDouble;
+typedef struct _mjElement* mjElement;
+
+
+
+//---------------------------------- Public structs ------------------------------------------------
+typedef struct _mjmOrientation {
+  double axisangle[4];            // rotation axis and angle
+  double xyaxes[6];               // x and y axes
+  double zaxis[3];                // z axis (use minimal rotation)
+  double euler[3];                // euler rotations
+  double fullinertia[6];          // non-axis-aligned inertia matrix
+} mjmOrientation;
+
+typedef struct _mjmSite {
+  mjElement element;              // only used internally, do not modify
+  mjString name;                  // name
+  mjString classname;             // class name
+  mjString info;                  // message appended to errors
+  mjtGeom type;                   // geom type for rendering
+  int group;                      // group id, used for visualization
+  double size[3];                 // geom size for rendering
+  double pos[3];                  // position
+  double quat[4];                 // orientation
+  mjString material;              // name of material for rendering
+  mjDouble userdata;              // user data
+  float rgba[4];                  // rgba when material is omitted
+  double fromto[6];               // alternative for capsule, cylinder, box, ellipsoid
+  mjmOrientation alt;             // alternative orientation specification
+} mjmSite;
+
+//---------------------------------- Public API ----------------------------------------------------
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Create model.
+MJAPI void* mjm_createModel();
+
+// Delete model.
+MJAPI void mjm_deleteModel(void* model);
+
+// Add body to body.
+MJAPI void* mjm_addBody(void* body, void* def);
+
+// Add site to body.
+MJAPI mjmSite* mjm_addSite(void* body, void* def);
+
+// Find object of given type.
+MJAPI void* mjm_findObject(void* model, mjtObj type, const char* name);
+
+// Copy input text to destination string.
+MJAPI void mjm_setString(mjString dest, const char* text);
+
+// Copy input array to destination vector.
+MJAPI void mjm_setDouble(mjDouble dest, const double* array, int size);
+
+// Get const pointer to mjString data.
+MJAPI const char* mjm_getString(mjString source);
+
+// Get const pointer to mjDouble data and its size.
+MJAPI const double* mjm_getDouble(mjDouble source, int* size);
+
+// Set frame.
+MJAPI void mjm_setFrame(void* dest, void* frame);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // MUJOCO_SRC_USER_USER_API_H_