class Aws::Signers::V4

def hexdigest(value)
  digest = OpenSSL::Digest::SHA256.new
  if value.respond_to?(:read)
    chunk = nil
    chunk_size = 1024 * 1024 # 1 megabyte
    digest.update(chunk) while chunk = value.read(chunk_size)
    value.rewind
  else
    digest.update(value)
  end
  digest.hexdigest
end