Initial release of the Unity plugin.

PiperOrigin-RevId: 425947505

unity/Runtime/Tools/MjVfs.cs

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+// Copyright 2019 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.
+
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using UnityEngine;
+
+namespace Mujoco {
+
+using static MujocoLib;
+
+// A wrapper around Mujoco's native _mjVFS that simplifies the process of creating memory files.
+public sealed class MjVfs : IDisposable {
+
+  private _mjVFS _managedVfs;
+  private IntPtr _unmanagedVfs;
+
+  // Managed version of the underlying _mjVFS structure.
+  public _mjVFS Data {
+    get {
+      _managedVfs = (_mjVFS)Marshal.PtrToStructure(_unmanagedVfs, typeof(_mjVFS));
+      return _managedVfs;
+    }
+    set {
+      _managedVfs = value;
+      Marshal.StructureToPtr(_managedVfs, _unmanagedVfs, fDeleteOld: false);
+    }
+  }
+
+  // Number of files added to the filesystem.
+  public int FilesCount {
+    get { return Data.nfile; }
+  }
+
+  // Adds a new file to the virtual filesystem.
+  public unsafe void AddFile(string filename, string contents) {
+    var result = mj_makeEmptyFileVFS(_unmanagedVfs.ToPointer(), filename, contents.Length);
+    if (result != 0) {
+      throw new Exception(
+          "VFS error (" + result + ") encountered while creating an empty file");
+    }
+    var fileIndex = mj_findFileVFS(_unmanagedVfs.ToPointer(), filename);
+    if (fileIndex < 0) {
+      throw new IndexOutOfRangeException("VFS didn't properly create the empty file.");
+    }
+    SetFileContents(fileIndex, contents);
+  }
+
+  // Searches the VFS for the specified file and returns its index.
+  // The index then can be used to retrieve the file contents from Data.filedata array.
+  public unsafe int FindFile(string filename) {
+    return mj_findFileVFS(_unmanagedVfs.ToPointer(), filename);
+  }
+
+  // Loads a model from the specified file.
+  // The file is assumed to be located in the filesystem. If it's not found, the method will throw
+  // an ArgumentException.
+  public unsafe MujocoLib.mjModel_* LoadXML(string filename) {
+    if (FindFile(filename) < 0) {
+      throw new ArgumentException($"File {filename} was not added to the VFS.");
+    }
+
+    var errorBuf = new StringBuilder(1024);
+    MujocoLib.mjModel_* model = MujocoLib.mj_loadXML(
+      filename, _unmanagedVfs.ToPointer(), errorBuf, errorBuf.Capacity);
+    if (model == null || errorBuf.Length > 0) {
+      throw new IOException($"Error loading the model: {errorBuf}");
+    }
+    return model;
+  }
+
+  private unsafe void SetFileContents(int fileIndex, string contents) {
+    var data = Data;
+    Marshal.FreeHGlobal(data.filedata[fileIndex]);
+    data.filedata[fileIndex] = Marshal.StringToHGlobalAnsi(contents);
+    Data = data;
+  }
+
+  public MjVfs() {
+    _managedVfs = new _mjVFS();
+    _unmanagedVfs = Marshal.AllocHGlobal(Marshal.SizeOf(_managedVfs));
+    Marshal.StructureToPtr(_managedVfs, _unmanagedVfs, true);
+  }
+
+  ~MjVfs() {
+    ReleaseUnmanagedMemory();
+  }
+
+  public void Dispose() {
+    GC.SuppressFinalize(this);
+    ReleaseUnmanagedMemory();
+  }
+
+  private void ReleaseUnmanagedMemory() {
+    if (_unmanagedVfs != IntPtr.Zero) {
+      var data = Data;
+      for (var fileIndex = 0; fileIndex < data.nfile; ++fileIndex) {
+        Marshal.FreeHGlobal(data.filedata[fileIndex]);
+      }
+
+      Marshal.FreeHGlobal(_unmanagedVfs);
+      _unmanagedVfs = IntPtr.Zero;
+    }
+  }
+}
+}