www.kanpian.com:Step 7. Multithreading support and canceling queries

//  Cancel - Creates a new thread with long running query when the letter 'a' is typed.//  Cancels a query when letter 'C' is typed.//  All threads are terminated when the letter 'Q' is entered.////  This program requires the multithread library.#include #include #include #include #include #include #include #include void main(void);/* Thread 1: main */void KbdFunc(void );/* Keyboard input, thread dispatch */void LongQuery(void *addl);/* Threads 2: Long running query */void LongQueryCancel();void ShutDown(void);/* Program shutdown */void WriteTitle();/* Display title bar information */HANDLE  hConsoleOut;                   /* Handle to the console */HANDLE  hQueryMutex;                   /* "Query Running" mutex */HANDLE  hScreenMutex;                  /* "Screen update" mutex  */SAConnectiong_Conn;SACommandg_Cmd(&g_Conn);// connection and query information// modify here to provide your real informationconst char *LONG_RUNNING_QUERY ="select * from test_bulk "" where fvarchar20 like '%hj' or fvarchar20 like '%dfds'"" or fvarchar20 in (select fvarchar20 from test_bulk)"" order by fvarchar20 desc, finteger desc";const char *DATABASE = "test";const char *USER = "tester";const char *PASSWORD = "tester";SAClient_t CLIENT = SA_DB2_Client;void main()                            /* Thread One */{    /* Get display screen information & clear the screen.*/    hConsoleOut = GetStdHandle(STD_OUTPUT_HANDLE);    WriteTitle();    /* Create the mutexes and reset thread count. */    hScreenMutex = CreateMutex(NULL, FALSE, NULL);   /* Cleared */    hQueryMutex = CreateMutex(NULL, FALSE, NULL);     /* Cleared */try{// connectg_Conn.Connect(DATABASE, USER, PASSWORD, CLIENT);/* Start waiting for keyboard input to dispatch threads or exit. */KbdFunc();}catch(SAException &x){std::cout << (const char*)x.ErrText() << std::endl;try{g_Conn.Rollback();}catch(SAException &){}}    /* All threads done. Clean up handles. */    CloseHandle(hScreenMutex);    CloseHandle(hQueryMutex);    CloseHandle(hConsoleOut);}void ShutDown(void){// try to cancel the query if still runningif(WaitForSingleObject(hQueryMutex, 75L) == WAIT_TIMEOUT)LongQueryCancel();elseReleaseMutex(hQueryMutex);}void KbdFunc(void){    int         KeyInfo;    do    {        KeyInfo = _getch();        if(tolower(KeyInfo) == 'a')_beginthread(LongQuery, 0, NULL);        if(tolower(KeyInfo) == 'c')            LongQueryCancel();    }while(tolower(KeyInfo) != 'q');    ShutDown();}void LongQuery(void *addl){if(WaitForSingleObject(hQueryMutex, 75L) == WAIT_TIMEOUT){WaitForSingleObject(hScreenMutex, INFINITE);std::cout << "query still running, use 'C' to cancel it." << std::endl;ReleaseMutex(hScreenMutex);return;}try{g_Cmd.setCommandText(LONG_RUNNING_QUERY);WaitForSingleObject(hScreenMutex, INFINITE);std::cout << "executing " << (const char*)g_Cmd.CommandText() << std::endl;ReleaseMutex(hScreenMutex);g_Cmd.Execute();WaitForSingleObject(hScreenMutex, INFINITE);std::cout << "executed" << std::endl;ReleaseMutex(hScreenMutex);}catch(SAException &x){WaitForSingleObject(hScreenMutex, INFINITE);std::cout << (const char*)x.ErrText() << std::endl;ReleaseMutex(hScreenMutex);}ReleaseMutex(hQueryMutex);}void LongQueryCancel(){try{WaitForSingleObject(hScreenMutex, INFINITE);std::cout << "CANCELLING..." << std::endl;ReleaseMutex(hScreenMutex);g_Cmd.Cancel();WaitForSingleObject(hScreenMutex, INFINITE);std::cout << "CANCELLED" << std::endl;ReleaseMutex(hScreenMutex);}catch(SAException &x){WaitForSingleObject(hScreenMutex, INFINITE);std::cout << (const char*)x.ErrText() << std::endl;ReleaseMutex(hScreenMutex);}}void WriteTitle(){    char    NThreadMsg[1024];    sprintf(NThreadMsg, "Press 'A' to start a long running query in a thread, 'C' to cancel it, 'Q' to quit.");    SetConsoleTitle(NThreadMsg);}