class Aws::S3::Plugins::Md5s::Handler

def call(context)
  body = context.http_request.body
  if body.size > 0
    context.http_request.headers['Content-Md5'] ||= md5(body)
  end
  @handler.call(context)
end

def md5(value)
  if (File === value || Tempfile === value) && !value.path.nil? && File.exist?(value.path)
    Base64.encode64(OpenSSL::Digest::MD5.file(value).digest).strip
  elsif value.respond_to?(:read)
    md5 = OpenSSL::Digest::MD5.new
    update_in_chunks(md5, value)
    Base64.encode64(md5.digest).strip
  else
    Base64.encode64(OpenSSL::Digest::MD5.digest(value)).strip
  end
end

def update_in_chunks(digest, io)
  while chunk = io.read(CHUNK_SIZE)
    digest.update(chunk)
  end
  io.rewind
end