whole_func_string: function sha256x2 (buffer) {
    var tmp = createHash('sha256').update(buffer).digest()
    return createHash('sha256').update(tmp).digest()
  }
func_code_string: function sha256x2 (buffer) {
    var tmp = createHash('sha256').update(buffer).digest()
    return createHash('sha256').update(tmp).digest()
  }
func_documentation_string: SHA256(SHA256(buffer))