struct CURLMsg {
    CURLMSG msg;       /* what this message means */
    CURL *easy_handle; /* the handle it concerns */
    union {
      void *whatever;    /* message-specific data */
      CURLcode result;   /* return code for transfer */
    } data;
  };

Structure CURLMsg
  *CURLMSG.s
  *CURL
EndStructure