Function build_real 

pub fn build_real(
    acc_id: u64,
    cipher: Option<Vec<u8>>,
    security_type: Option<u32>,
    input_source: Option<u32>,
) -> MsgHeader

构造 real-account odr_sys_cmn::MsgHeader.

Args

• acc_id: 账户 id (填 account_id 字段; 同时作为 create_backend_req_id 的派生种子).
• cipher: trade cipher.
  • Some(vec![]) = cache-only query (wire 上 field-present 但为空 bytes).
  • 非空 Some = 持 unlock token 的写路径 (PlaceOrder / ModifyOrder / CancelOrder / OrderFillInfoReq w/ security_type).
  • None = 无 trade 上下文 (如 sim_acc_list / login-time queries).
• security_type: PlaceOrder / ModifyOrder / OrderFillInfoReq 等需要; 纯 list / asset 查询填 None.
• input_source: 仅 PlaceOrder 填 (C++ 行为, see crates/futu-gateway-trd/src/handlers/trd/translate.rs 的 PLACE_ORDER_MSG_INPUT_SOURCE); modify / cancel / query 都 None.