Add compiler C API for mjmSite.

PiperOrigin-RevId: 604573450
Change-Id: I6ba7fcece0942ddc0d109413ba5684b2df3fab96

test/user/user_api_test.cc

@@ -0,0 +1,58 @@
+// 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.
+
+// Tests for user/user_api.cc.
+
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include "src/user/user_api.h"
+#include <mujoco/mjmodel.h>
+#include "test/fixture.h"
+
+namespace mujoco {
+namespace {
+
+using ::testing::HasSubstr;
+
+
+// ----------------------------- test set/get  --------------------------------
+
+TEST_F(MujocoTest, ReadWriteData) {
+  void* model = mjm_createModel();
+  void* world = mjm_findObject(model, mjOBJ_BODY, "world");
+  void* body = mjm_addBody(world, 0);
+  mjmSite* site = mjm_addSite(body, 0);
+
+  {
+    double vec[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+    const char* str = "sitename";
+
+    mjm_setString(site->name, str);
+    mjm_setDouble(site->userdata, vec, 10);
+  }
+
+  EXPECT_THAT(mjm_getString(site->name), HasSubstr("sitename"));
+
+  int nsize;
+  const double* vec = mjm_getDouble(site->userdata, &nsize);
+  for (int i = 0; i < nsize; ++i) {
+    EXPECT_EQ(vec[i], i);
+  }
+
+  mjm_deleteModel(model);
+}
+
+}  // namespace
+}  // namespace mujoco