[C++]Programming in general with multiple threads.

Code:

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.:[Smith's guide to Multi-Threaded Programming in C++]:.

.:I make programming FUN!!:.

.:[Part 1]:.
OK, before we jump into this all unprepared we need to go over a few things first!

What you need:
1. Compiler ( I use Microsoft Visual Compiler 6.0 )
2. Win32 API Reference ( Don't have it? use google )
3. A Brain ( Preferably in working order  )

Ok lets begin with a basic C++ layout for Win32, it should look like this:

       

Code:

       

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#include <stdio.h>
#include <windows.h>

int APIENTRY WinMain(HINSTANCE hInstance,
             HINSTANCE hPrevInstance,
             LPSTR lpCmdLine,
             int nShowCmd)
{

return(0);
}

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Now if we look at our Win32 API Ref and look up CreateThread we get this:

       

Quote:

       

               

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HANDLE CreateThread(

  LPSECURITY_ATTRIBUTES lpThreadAttributes, // pointer to thread security attributes 
  DWORD dwStackSize, // initial thread stack size, in bytes
  LPTHREAD_START_ROUTINE lpStartAddress, // pointer to thread function
  LPVOID lpParameter, // argument for new thread
  DWORD dwCreationFlags, // creation flags
  LPDWORD lpThreadId // pointer to returned thread identifier
  );
                       
               

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This will get explained later. I just have it here for reference. Ok onto the code now we need
to add a few things first:

       

Code:

       

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#include <stdio.h>
#include <windows.h>

ULONG WINAPI OurFirstThread(LPVOID);

ULONG WINAPI OurFirstThread(LPVOID p)
{
MessageBox(NULL,"Yay our thread was excuted","Smith's Multi-Thread Example",MB_OK);

return(0);
}

int APIENTRY WinMain(HINSTANCE hInstance,
             HINSTANCE hPrevInstance,
             LPSTR lpCmdLine,
             int nShowCmd)
{
unsigned long ThreadId;
CreateThread(NULL,0,OurFirstThread,0,0,&ThreadId);

Sleep(5000) \\ Sleep for 5 seconds so the MB can be
         \\ displayed.
return(0);
}

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Ok, time to explain how this all works.  Ok this line here:

ULONG WINAPI OurFirstThread(LPVOID);

Sets the thread up. Kinda like Dim <value> in VB. I wont go into a huge explaination you just
need it ok? This part here:

ULONG WINAPI OurFirstThread(LPVOID p)
{
MessageBox(NULL,"Yay our thread was excuted","Smith's Multi-Thread Example",MB_OK);

return(0);
}

This is the part of the program that gets turned into a thread. Whatever code is between the
"{" and "}" will be executed seperatly from the rest of the program.

And finally we get to the actual creation of
the thread:

CreateThread(NULL,0,OurFirstThread,0,0,&ThreadId);

This creates the thread the functions are explained in order.

1. Do we want a child processes to be able to inherit this thread? No
2. How big in bytes will this thread be? 0 = Autosize
3. Thread Name
4. Useless Parameter leave as 0
5. Creation flag, we can have different values in here, say you want make a thread but have it
  paused to run at another time. You would use the CREATE_SUSPENDED flag.
6. Finally the pointer to hold the data ThreadId, yes it is needed.

*Just remember this is a basic tutorial.

Finally after all this you may be wondering, this is all good and well WHY? Would i need this?
Well threads are mainly used when a program needs to do 2 things at the same time. Because your
program can't do to things at once can it? Not unless you use threads. Example: Looping and
Creating a socket.

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