getStreamWrapperManager example

  public function buildUri($uri) {
    $source_scheme = $scheme = StreamWrapperManager::getScheme($uri);
    $default_scheme = $this->fileDefaultScheme();

    if ($source_scheme) {
      $path = StreamWrapperManager::getTarget($uri);
      // The scheme of derivative image files only needs to be computed for       // source files not stored in the default scheme.       if ($source_scheme != $default_scheme) {
        $class = $this->getStreamWrapperManager()->getClass($source_scheme);
        $is_writable = NULL;
        if ($class) {
          $is_writable = $class::getType() & StreamWrapperInterface::WRITE;
        }

        // Compute the derivative URI scheme. Derivatives created from writable         // source stream wrappers will inherit the scheme. Derivatives created         // from read-only stream wrappers will fall-back to the default scheme.         $scheme = $is_writable ? $source_scheme : $default_scheme;
      }
    }