#include
// This is a child thread procedure that waits for a semaphore,
// holds the semaphore for five seconds, and releases the semaphore.
// Threads that cannot get semaphores will wait until other threads exit.
DWORD WINAPI ChildThreadProc( HWND hWnd )
{
TCHAR szBuffer[256]; // buffer
DWORD dwSemCount = 0; // printing semaphore count
HANDLE hSemaphore = OpenSemaphore( SYNCHRONIZE, FALSE, "TEST_SEMAPHORE" );
wsprintf( szBuffer,"Thread %x waiting for semaphore %x",
GetCurrentThreadId( ), hSemaphore );
SendMessage( hWnd, WM_USER, 0, (LPARAM) szBuffer );
// Check for signaled semaphore.
WaitForSingleObject( hSemaphore, INFINITE );
wsprintf( szBuffer,"Thread %x got semaphore", GetCurrentThreadId( ) );
SendMessage( hWnd, WM_USER, 0, (LPARAM) szBuffer );
Sleep( 5000 );
// Release semaphore.
ReleaseSemaphore( hSemaphore, 1, &dwSemCount );
wsprintf( szBuffer,"Thread %x is done with semaphore. Its count was %ld.",
GetCurrentThreadId( ), dwSemCount );
SendMessage( hWnd, WM_USER, 0, (LPARAM) szBuffer );
CloseHandle( hSemaphore );
ExitThread( TRUE );
}
// Windows message procedure.
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
static HANDLE hSemaphore = 0;
switch (uMsg)
{
case WM_CREATE:
hSemaphore = CreateSemaphore( NULL, 4, 4, "TEST_SEMAPHORE" );
return DefWindowProc( hWnd, uMsg, wParam, lParam );
case WM_COMMAND: // process menu items
switch ( LOWORD( wParam ) )
{
case IDM_TEST: // start up a thread.
{
DWORD dwChildId;
CreateThread( NULL, 0, ChildThreadProc, hWnd, 0, &dwChildId );
}
break;
case IDM_EXIT:
DestroyWindow( hWnd );
break;
}
break;
case WM_USER:
{ // Message to show synchronization actions.
TCHAR szBuffer[101];
static int row = 0;
static int msg_num = 1;
HDC hDC = GetDC( hWnd );
FillMemory( szBuffer, 100, 32 );
TextOut( hDC, 0, row, szBuffer, 100 );
wsprintf( szBuffer, "%3d: %s", msg_num++, (LPTSTR)lParam );
TextOut( hDC, 0, row, szBuffer, lstrlen( szBuffer ) );
if ( row > 200 )
row = 0;
else
row += 20;
ReleaseDC( hWnd, hDC );
}
break;
case WM_DESTROY:
if ( hSemaphore )
CloseHandle( hSemaphore );
PostQuitMessage( 0 );
break;
default:
return DefWindowProc( hWnd, uMsg, wParam, lParam );
}
return NULL;
}
