# File lib/rubygems/remote_fetcher.rb, line 255
  def open_uri_or_path(uri, last_modified = nil, head = false, depth = 0)
    raise "block is dead" if block_given?

    uri = URI.parse uri unless URI::Generic === uri

    # This check is redundant unless Gem::RemoteFetcher is likely
    # to be used directly, since the scheme is checked elsewhere.
    # - Daniel Berger
    unless ['http', 'https', 'file'].include?(uri.scheme)
     raise ArgumentError, 'uri scheme is invalid'
    end

    if uri.scheme == 'file'
      path = uri.path

      # Deal with leading slash on Windows paths
      if path[0].chr == '/' && path[1].chr =~ /[a-zA-Z]/ && path[2].chr == ':'
         path = path[1..-1]
      end

      return Gem.read_binary(path)
    end

    fetch_type = head ? Net::HTTP::Head : Net::HTTP::Get
    response   = request uri, fetch_type, last_modified

    case response
    when Net::HTTPOK, Net::HTTPNotModified then
      head ? response : response.body
    when Net::HTTPMovedPermanently, Net::HTTPFound, Net::HTTPSeeOther,
         Net::HTTPTemporaryRedirect then
      raise FetchError.new('too many redirects', uri) if depth > 10

      open_uri_or_path(response['Location'], last_modified, head, depth + 1)
    else
      raise FetchError.new("bad response #{response.message} #{response.code}", uri)
    end
  end