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Switching threads

, 16 Sep 2007 CPOL
How to switch the thread that a routine is running on.
// ThreadSwitch.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include "ThreadSwitch.h"
#include "tswitch.h"

#define MAX_LOADSTRING		100

//
// Global Variables:
//
HINSTANCE hInst;								// current instance
TCHAR szTitle[MAX_LOADSTRING];					// The title bar text
TCHAR szWindowClass[MAX_LOADSTRING];			// the main window class name

//
// Forward declarations of functions included in this code module:
//
ATOM				MyRegisterClass(HINSTANCE hInstance);
BOOL				InitInstance(HINSTANCE, int);
LRESULT CALLBACK	WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK	About(HWND, UINT, WPARAM, LPARAM);
void				RunThread( void *pv );
int __stdcall		StdcallFunction( HWND hwnd, char ch, int a );
int	__cdecl			CdeclFunction( HWND hwnd, short a, short b );

int APIENTRY _tWinMain( HINSTANCE hInstance,
                        HINSTANCE hPrevInstance,
						LPTSTR    lpCmdLine,
						int       nCmdShow)
{
	UNREFERENCED_PARAMETER(hPrevInstance);
	UNREFERENCED_PARAMETER(lpCmdLine);

	MSG msg;
	HACCEL hAccelTable;

	//
	// Initialize global strings
	//
	LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
	LoadString(hInstance, IDC_THREADSWITCH, szWindowClass, MAX_LOADSTRING);
	MyRegisterClass(hInstance);

	//
	// Perform application initialization:
	//
	if (!InitInstance (hInstance, nCmdShow))
	{
		return FALSE;
	}

	hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_THREADSWITCH));

	//
	// Main message loop:
	//
	while (GetMessage(&msg, NULL, 0, 0))
	{
		if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
	}

	return (int) msg.wParam;
}



//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
//  COMMENTS:
//
//    This function and its usage are only necessary if you want this code
//    to be compatible with Win32 systems prior to the 'RegisterClassEx'
//    function that was added to Windows 95. It is important to call this function
//    so that the application will get 'well formed' small icons associated
//    with it.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
	WNDCLASSEX wcex;

	wcex.cbSize = sizeof(WNDCLASSEX);

	wcex.style			= CS_HREDRAW | CS_VREDRAW;
	wcex.lpfnWndProc	= WndProc;
	wcex.cbClsExtra		= 0;
	wcex.cbWndExtra		= 0;
	wcex.hInstance		= hInstance;
	wcex.hIcon			= LoadIcon(hInstance, MAKEINTRESOURCE(IDI_THREADSWITCH));
	wcex.hCursor		= LoadCursor(NULL, IDC_ARROW);
	wcex.hbrBackground	= (HBRUSH)CreateSolidBrush( RGB( 240, 240, 240 ) );
	wcex.lpszMenuName	= MAKEINTRESOURCE(IDC_THREADSWITCH);
	wcex.lpszClassName	= szWindowClass;
	wcex.hIconSm		= LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

	return RegisterClassEx(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   HWND hWnd;

   //
   // Store instance handle in our global variable
   //
   hInst = hInstance; 

   SIZE sizeScreen = { GetSystemMetrics( SM_CXSCREEN ),
	   GetSystemMetrics( SM_CYSCREEN ) };
   SIZE sizeWin = { 320, 240 };

   hWnd = CreateWindow( szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      ( sizeScreen.cx - sizeWin.cx ) / 2,
	  ( sizeScreen.cy - sizeWin.cy ) / 2,
	  sizeWin.cx,
	  sizeWin.cy,
	  NULL, NULL, hInstance, NULL);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE:  Processes messages for the main window.
//
//  WM_COMMAND	- process the application menu
//  WM_PAINT	- Paint the main window
//  WM_DESTROY	- post a quit message and return
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	int					wmId, wmEvent;
	PAINTSTRUCT			ps;
	HDC					hdc;
	RECT				rcClient;
	static const TCHAR	szText[] = _T( "Click anywhere in the window to exercise thread switching." );

	//
	// process WM_INVOKE; this cannot be a case statement because
	// WM_INVOKE is not a constant
	//
	if( message == WM_INVOKE )
	{
		THREAD_SWITCH_INVOKE(wParam);
	}

	switch (message)
	{
	case WM_COMMAND:
		wmId    = LOWORD(wParam);
		wmEvent = HIWORD(wParam);

		//
		// Parse the menu selections:
		//
		switch (wmId)
		{
		case IDM_ABOUT:
			DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
			break;
		case IDM_EXIT:
			DestroyWindow(hWnd);
			break;
		default:
			return DefWindowProc(hWnd, message, wParam, lParam);
		}
		break;

	case WM_PAINT:
		hdc = BeginPaint(hWnd, &ps);

		GetClientRect( hWnd, &rcClient );
		SetBkMode( ps.hdc, TRANSPARENT );

		DrawText( ps.hdc, szText, ( sizeof( szText ) / sizeof( TCHAR ) ) - 1,
				  &rcClient,
				  DT_CENTER | DT_WORDBREAK );

		EndPaint(hWnd, &ps);
		break;

	case WM_LBUTTONDOWN:
		{
			_beginthread( RunThread, 0, hWnd );
			break;
		};

	case WM_DESTROY:
		PostQuitMessage(0);
		break;

	default:
		return DefWindowProc(hWnd, message, wParam, lParam);
	}

	return 0;
}

int __stdcall StdcallFunction( HWND hwnd, char ch, int a )
{
	THREAD_SWITCH_WITH_RETURN(hwnd, StdcallFunction, 3, ccStdcall, int)

	TCHAR szBuf[1024];
	wsprintf( szBuf, _T( "Thread ID = %d, hwnd = 0x%X, ch = %c, a = %d\n" ),
		GetCurrentThreadId(), (DWORD_PTR)hwnd, ch, a );
	MessageBox( hwnd, szBuf, _T( "ThreadSwitch - STDCALL" ), MB_OK | MB_ICONINFORMATION );

	return 5;
}

int __cdecl CdeclFunction( HWND hwnd, short a, short b )
{
	THREAD_SWITCH_WITH_RETURN(hwnd, CdeclFunction, 3, ccCdecl, int)

	TCHAR szBuf[1024];
	wsprintf( szBuf, _T( "Thread ID = %d, hwnd = 0x%X, a = %d, b = %d\n" ),
		GetCurrentThreadId(), (DWORD_PTR)hwnd, a, b );
	MessageBox( hwnd, szBuf, _T( "ThreadSwitch - CDECL" ), MB_OK | MB_ICONINFORMATION );

	return 10;
}

void RunThread( void *pv )
{
	int result;

	result = StdcallFunction( (HWND)pv, 'c', 20 );
	_ASSERT( result == 5 );

	result = CdeclFunction( (HWND)pv, 10, 20 );
	_ASSERT( result == 10 );
}

//
// Message handler for about box.
//
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
	UNREFERENCED_PARAMETER(lParam);
	switch (message)
	{
	case WM_INITDIALOG:
		return (INT_PTR)TRUE;

	case WM_COMMAND:
		if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
		{
			EndDialog(hDlg, LOWORD(wParam));
			return (INT_PTR)TRUE;
		}
		break;
	}
	return (INT_PTR)FALSE;
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Rajasekharan Vengalil
Microsoft
United States United States
No Biography provided

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Article Copyright 2007 by Rajasekharan Vengalil
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