帮我写一个期货 通过CTP 接收合约行情的多线程c++ demo代码

好的，我会尽力帮您写一个符合要求的代码，以下是代码示例：

#include <stdio.h>
#include <stdlib.h>
#include "ThostFtdcMdApi.h"

class CtpMdSpi : public CThostFtdcMdSpi
{
public:
  CtpMdSpi(CThostFtdcMdApi* pMdApi)
    : m_pMdApi(pMdApi)
  {}

  virtual void OnFrontConnected()
  {
    printf("CTP Front connected.\n");
    m_pMdApi->ReqUserLogin(&m_loginReq, 0);
  }

  virtual void OnFrontDisconnected(int nReason)
  {
    printf("CTP Front disconnected.\n");
  }

  virtual void OnRspUserLogin(CThostFtdcRspUserLoginField *pRspUserLogin,
    CThostFtdcRspInfoField *pRspInfo, int nRequestID, bool bIsLast)
  {
    if (pRspInfo->ErrorID == 0)
    {
      printf("CTP User logged in. Trading day: %s\n", pRspUserLogin->TradingDay);
      m_pMdApi->SubscribeMarketData(m_instruList, 1);
    }
    else
    {
      printf("CTP User login failed. Error ID: %d\n", pRspInfo->ErrorID);
    }
  }

  virtual void OnRtnDepthMarketData(CThostFtdcDepthMarketDataField *pDepthMarketData)
  {
    printf("CTP New tick received. Instrument ID: %s, Last price: %f\n",
      pDepthMarketData->InstrumentID, pDepthMarketData->LastPrice);
  }

private:
  CThostFtdcMdApi* m_pMdApi;
  char m_instruList[10] = "cu1907.SHF"; // 监听的合约代码
  CThostFtdcReqUserLoginField m_loginReq = {
    "your_broker_id",
    "your_user_id",
    "your_password"
  };
};

int main()
{
  CThostFtdcMdApi* pMdApi = CThostFtdcMdApi::CreateFtdcMdApi("");
  CtpMdSpi spi(pMdApi);

  pMdApi->RegisterSpi(&spi);
  pMdApi->RegisterFront("tcp://ctp_md_address:port");
  pMdApi->Init();

  while (true)
  {
    // 等待消息处理
    Sleep(1000);
  }

  pMdApi->Release();
  return 0;
}

请注意将代码中的变量值替换为您自己的实际值，然后编译运行即可。当有新的行情到达时，会输出相应的消息。