Move engine/engine_vfs.{c,h} to user/user_vfs.{c,h}.

PiperOrigin-RevId: 636219666
Change-Id: I820de511948e82256784edb0893f209a73b221e6

src/user/user_vfs.h

@@ -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.
+// IWYU pragma: private, include "third_party/mujoco/include/mujoco.h"
+// IWYU pragma: friend "third_party/mujoco/src/.*"
+
+#ifndef MUJOCO_SRC_USER_USER_VFS_H_
+#define MUJOCO_SRC_USER_USER_VFS_H_
+
+#include <stddef.h>
+
+#include <mujoco/mjexport.h>
+#include <mujoco/mjmodel.h>
+#include <mujoco/mjplugin.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// initialize to empty (no deallocation)
+MJAPI void mj_defaultVFS(mjVFS* vfs);
+
+// add file to VFS, return 0: success, 1: full, 2: repeated name, -1: not found on disk
+MJAPI int mj_addFileVFS(mjVFS* vfs, const char* directory, const char* filename);
+
+// deprecated: use mj_copyBufferVFS
+MJAPI int mj_makeEmptyFileVFS(mjVFS* vfs, const char* filename, int filesize);
+
+// add file from buffer into VFS, return 0: success, 1: full, 2: repeated name, -1: failed to load
+MJAPI int mj_copyBufferVFS(mjVFS* vfs, const char* filename, const void* buffer, int nbuffer);
+
+// return file index in VFS, or -1 if not found in VFS
+MJAPI int mj_findFileVFS(const mjVFS* vfs, const char* filename);
+
+// delete file from VFS, return 0: success, -1: not found in VFS
+MJAPI int mj_deleteFileVFS(mjVFS* vfs, const char* filename);
+
+// delete all files from VFS
+MJAPI void mj_deleteVFS(mjVFS* vfs);
+
+// open VFS resource
+MJAPI mjResource* mju_openVfsResource(const char* name, const mjVFS* vfs);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // MUJOCO_SRC_USER_USER_VFS_H_