thread_msg.c

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#include <windows.h>
#include <stdio.h>
#include <assert.h>
 
HANDLE hWaitForFailure;
HANDLE hOkToPostThreadMessage;
HANDLE hOkToTerminate;
 
DWORD WINAPI thread( LPVOID crap )
{
    MSG msg;
 
    /* Failure case ... Wait for the parent to try to post a message
       before queue creation */
    printf( "Waiting to create the message queue.\n" );
 
        WaitForSingleObject(hWaitForFailure,INFINITE);
 
    printf( "Creating message queue.\n" );
 
    /* "Create" a message queue */
    PeekMessage( &msg, NULL, 0, 0, PM_NOREMOVE );
 
    printf( "Signalling the parent that we're ready.\n" );
 
    /* Signal that it's ok to post */
    SetEvent( hOkToPostThreadMessage );
 
    printf( "Listening messages.\n" );
 
    /* Now read some messages */
    while( GetMessage( &msg, 0,0,0 ) ) {
        printf( "Received message: %04x %04x %08lx\n",
                (msg.message & 0xffff),
            (msg.wParam & 0xffff),
            msg.lParam );
        assert( !msg.hwnd );
    }
 
    printf( "Finished receiving messages.\n" );
    SetEvent( hOkToTerminate );
 
    return 0;
}
 
int main( int argc, char **argv )
{
    DWORD id;
 
    printf( "Creating events\n" );
 
    hOkToPostThreadMessage = CreateEvent( NULL, FALSE, FALSE, NULL );
    hOkToTerminate = CreateEvent( NULL, FALSE, FALSE, NULL );
        hWaitForFailure = CreateEvent( NULL, FALSE, FALSE, NULL );
 
    printf( "Created events\n" );
 
    if( CreateThread( 0, 0, thread, 0, 0, &id ) == NULL ) {
        printf( "Couldn't create one thread.\n" );
        return 0;
        }
 
        printf( "Posting to non-existent queue\n" );
 
    /* Check failure case */
    assert( PostThreadMessage( id, WM_USER + 0, 1, 2 ) == FALSE );
 
    printf( "Signalling thread to advance.\n" );
 
        SetEvent( hWaitForFailure );
 
    printf( "Waiting for signal from thread.\n" );
    WaitForSingleObject( hOkToPostThreadMessage, INFINITE );
 
    printf( "Sending three messages, then quit.\n" );
    assert( PostThreadMessage( id, WM_USER + 0, 1, 2 ) );
    assert( PostThreadMessage( id, WM_USER + 1, 3, 4 ) );
    Sleep( 500 ); /* Sleep a bit, so that the queue is empty for a bit. */
    assert( PostThreadMessage( id, WM_USER + 2, 5, 6 ) );
    assert( PostThreadMessage( id, WM_QUIT, 0,0 ) );
 
    WaitForSingleObject( hOkToTerminate, INFINITE );
    printf( "Test complete.\n" );
 
    return 0;
}