Multitasking in VC++ 6(threads by AfxBeginThread())

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  12 years ago

  by russbude

  Russell Brown

  Cornwall, United Kingdom

  Joined 13 years ago

   Hello guys

  I am learning VC++ 6.0 which is not an easy language at all.  I have just learnt how to create threads using AfxBeginThread( ).  I have listed here my own example program (multitask.cpp) to show the use of threads.  Hopefully the program is simple and self explannary to eveybody.  I would like to share what I have learnt!!  I would be grateful if anybody can comment on my program and may suggest a way to improve it.

  All the best

  Chong

  P.C.

  If anybody wants another version of this program which uses _beginthread() instead of AfxBeginThread(), let me know.

  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 

  // multitask.cpp

  // Note : Before building for an executable file, do the following (after compiling):
  //   (1) Choose the [Project] menu
  //   (2) Choose [Settings]
  //   (3) Choose [General] and select [Use MFC in a Static Library]
  //       for [Microsoft Foundation Classes].

  // Note that, when the main application exits/terminates, it kills all its
  // threads.

  // the test.txt file contains "abcdefghi" 

  #include <stdio.h>
  #include <stdlib.h>
  #include <fcntl.h>
  #include <io.h>

  #include <Afxwin.h> // for CWinThread

  #include <windows.h> // for Sleep()
  #include <winbase.h> // for Sleep()

  
  UINT ThreadFunc(LPVOID pParam);

  
  class MsgFromFile {
  private:
   int fp; char buf[100];
  public:
   BOOL OpenDataFile() {
    if ((fp=open("test.txt",O_RDONLY))<0) return FALSE;
     else return TRUE;
   }
   BOOL ReadDataFile(){
    int nbytes, k =0;
    while (TRUE){
     if ((nbytes=read(fp,buf,3-k))<0) return FALSE;
     else if (nbytes == 0) {buf[k]=NULL;return TRUE;}
     else if ((k=k+nbytes)<3) continue;
     break;
    }
    buf[k]=NULL;
    return TRUE;
   }
   void WriteMsg(){ printf("Thread:%s\n",buf);}
  };

  
  char gMsg[100]; // global to the threads too!

  
  main()
  {
   MsgFromFile a;
   int iPriority = 0;
   CWinThread* ThreadID[2];

   a.OpenDataFile();
   a.ReadDataFile();
   printf("The main application: ");
   a.WriteMsg();

   strcpy(gMsg,"This works");

   //Start the independent threads
   ThreadID[0] = AfxBeginThread(ThreadFunc,(LPVOID)&a,iPriority);
   ThreadID[1] = AfxBeginThread(ThreadFunc,(LPVOID)&a,iPriority);
   
   //ThreadID[0]->SuspendThread(); //This suspends the thread ThreadID[0].It does not kill
           //the thread.
   //ThreadID[0]->ResumeThread(); //This resumes the thread ThreadID[0].

   //Wait until the threads have died.
   HANDLE hthread;
   hthread= ThreadID[0]->m_hThread;
   WaitForSingleObject(hthread,INFINITE);
   hthread = ThreadID[1]->m_hThread;
   WaitForSingleObject(hthread,INFINITE);

   printf("The main application: "); a.WriteMsg();
   printf("The main application(parent) exits\n");
   Sleep(10000); //Sleep for 10 seconds

  } // main

  
  UINT ThreadFunc(LPVOID pParam)
  {

   MsgFromFile* myfile = (MsgFromFile*)pParam;

   if (!(myfile->ReadDataFile())) {
    printf("Thread: failed to read the data file\n");
    //exit(-1); //This kills the main application too!
    return 0;
   } // if

   myfile->WriteMsg();
   printf("Thread: %s \n", gMsg);

   Sleep(5000);
   printf("Thread: exits\n");

   return 0;
  } // ThreadFunc
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