class Aws::Plugins::HttpChecksum::Handler

def call(context)
  if context.operation.http_checksum_required &&
     !context[:http_checksum][:request_algorithm] && # skip in favor of flexible checksum
     !context[:s3_express_endpoint] # s3 express endpoints do not support md5
    body = context.http_request.body
    context.http_request.headers['Content-Md5'] ||= md5(body)
  end
  @handler.call(context)
end

def md5(value)
  if (value.is_a?(File) || value.is_a?(Tempfile)) &&
     !value.path.nil? && File.exist?(value.path)
    OpenSSL::Digest::MD5.file(value).base64digest
  elsif value.respond_to?(:read)
    md5 = OpenSSL::Digest::MD5.new
    update_in_chunks(md5, value)
    md5.base64digest
  else
    OpenSSL::Digest::MD5.digest(value).base64digest
  end
end

def update_in_chunks(digest, io)
  loop do
    chunk = io.read(CHUNK_SIZE)
    break unless chunk
    digest.update(chunk)
  end
  io.rewind
end