Class MountableFileSystem

src/backend/MountableFileSystem.ts:60–345

 * With no mounted file systems, `MountableFileSystem` acts as a simple `InMemory` filesystem.
 */
export default class MountableFileSystem extends BaseFileSystem implements FileSystem {
  public static readonly Name = "MountableFileSystem";

  public static readonly Options: FileSystemOptions = {};

  /**
   * Creates a MountableFileSystem instance with the given options.
   */
  public static Create(opts: MountableFileSystemOptions, cb: BFSCallback<MountableFileSystem>): void {
    const fs = new MountableFileSystem();
    Object.keys(opts).forEach((mountPoint) => {
      fs.mount(mountPoint, opts[mountPoint]);
    });
    cb(null, fs);
  }
  public static isAvailable(): boolean {
    return true;
  }

  private mntMap: {[path: string]: FileSystem};
  // Contains the list of mount points in mntMap, sorted by string length in decreasing order.
  // Ensures that we scan the most specific mount points for a match first, which lets us
  // nest mount points.
  private mountList: string[] = [];
  private rootFs: FileSystem;

  /**
   * Creates a new, empty MountableFileSystem.
   */
  constructor() {
    super();
    this.mntMap = {};
    // The InMemory file system serves purely to provide directory listings for
    // mounted file systems.
    this.rootFs = new InMemoryFileSystem();
  }

  /**
   * Mounts the file system at the given mount point.
   */
  public mount(mountPoint: string, fs: FileSystem): void {
    if (mountPoint[0] !== '/') {
      mountPoint = `/${mountPoint}`;
    }
    mountPoint = path.resolve(mountPoint);
    if (this.mntMap[mountPoint]) {
      throw new ApiError(ErrorCode.EINVAL, "Mount point " + mountPoint + " is already taken.");
    }
    mkdirpSync(mountPoint, 0x1ff, this.rootFs);
    this.mntMap[mountPoint] = fs;
    this.mountList.push(mountPoint);
    this.mountList = this.mountList.sort((a, b) => b.length - a.length);
  }

  public umount(mountPoint: string): void {
    if (mountPoint[0] !== '/') {
      mountPoint = `/${mountPoint}`;
    }