module Google::Cloud::Storage::File::Verifier

def self.md5_for local_file
  if local_file.respond_to? :to_path
    ::File.open Pathname(local_file).to_path, "rb" do |f|
      ::Digest::MD5.file(f).base64digest
    end
  else # StringIO
    local_file.rewind
    md5 = ::Digest::MD5.base64digest local_file.read
    local_file.rewind
    md5
  end
end