Split name2id and id2name into a separate source file.

PiperOrigin-RevId: 647373431
Change-Id: I3bab0ea7157750b79826739e3d739e4114fa0af7

src/engine/engine_name.h

@@ -0,0 +1,41 @@
+// 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_ENGINE_ENGINE_NAME_H_
+#define MUJOCO_SRC_ENGINE_ENGINE_NAME_H_
+
+#include <stdint.h>
+
+#include <mujoco/mjexport.h>
+#include <mujoco/mjmodel.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+//-------------------------- name functions --------------------------------------------------------
+
+// get string hash, see http://www.cse.yorku.ca/~oz/hash.html
+uint64_t mj_hashString(const char* s, uint64_t n);
+
+// get id of object with the specified mjtObj type and name, returns -1 if id not found
+MJAPI int mj_name2id(const mjModel* m, int type, const char* name);
+
+// get name of object with the specified mjtObj type and id, returns NULL if name not found
+MJAPI const char* mj_id2name(const mjModel* m, int type, int id);
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // MUJOCO_SRC_ENGINE_ENGINE_NAME_H_