Listing 3: Worker thread routine

/*
   The main gist of this routine comes from the MSDN DBMON
   example.
*/
void EventThreadRoutine(void *pvParam)
{
    HANDLE AckEvent;
    HANDLE ReadyEvent;
    HANDLE SharedFile;
    LPVOID SharedMem;
    LPSTR  String;
    LPSTR  lpszDebugText;
    DWORD  ret;
    DWORD  LastPid;
    LPDWORD pThisPid;
    BOOL   fDidCR = TRUE;

    AckEvent = CreateEvent(NULL, FALSE, FALSE,
                           "DBWIN_BUFFER_READY");
    if (!AckEvent)
    {
        MessageBox(NULL, 
            "DBWIN32: Unable to create obj DBWIN_BUFFER_READY", 
            "Error", MB_OK);
        return;
    }

    if (GetLastError() == ERROR_ALREADY_EXISTS)
    {
        MessageBox(NULL, 
                   "DBWIN32: already running",
                   "Error", MB_OK);
        return;
    }

    ReadyEvent = CreateEvent(NULL, FALSE, FALSE,
                             "DBWIN_DATA_READY");
    if (!ReadyEvent)
    {
        MessageBox(NULL, 
            "DBWIN32: Unable to create object DBWIN_DATA_READY",
            "Error", MB_OK);
        return;
    }

    SharedFile = CreateFileMapping((HANDLE)-1, NULL, 
        PAGE_READWRITE, 0, 4096, "DBWIN_BUFFER");
    if (!SharedFile)
    {
        MessageBox(NULL, 
            "DBWIN32: Unable to create file object DBWIN_BUFFER",
            "Error", MB_OK);
        return;
    }

    SharedMem = MapViewOfFile(SharedFile, FILE_MAP_READ,
                              0, 0, 512);
    if (!SharedMem)
    {
        MessageBox(NULL, "DBWIN32: Unable to map shared memory",
            "Error", MB_OK);
        return;
    }

    String = (LPSTR)SharedMem + sizeof(DWORD);
    pThisPid = SharedMem;
    LastPid = 0xffffffff;
    SetEvent(AckEvent);

    for (;;) {

        ret = WaitForSingleObject(ReadyEvent, INFINITE);

        if (ret != WAIT_OBJECT_0)
        {
            MessageBox(NULL, "DBWIN32: wait failed",
                       "Error", MB_OK);
            return;
        }
        else
        {
            // only output if it is requested
            if ( fOutput )
            {
                LPSTR lpszScratch;
                BOOL fWantNewLine = FALSE;
                if (LastPid != *pThisPid)
                {
                    LastPid = *pThisPid;
                    if ( !fDidCR )
                    {
                        fWantNewLine = TRUE;
                        fDidCR = TRUE;
                    }
                }

                // fix up the newlines
                lpszScratch = FixNewLines(String);

                // allocate display buffer
                lpszDebugText = malloc(strlen(lpszScratch) + 20);
                if ( !lpszDebugText )
                {
                    MessageBox(NULL, 
                       "DBWIN32: malloc failed", "Error", MB_OK);
                    continue;
                }

                // make it empty or a newline
                if ( fWantNewLine )
                    strcpy(lpszDebugText, "\r\n");
                else
                    *lpszDebugText = 0;

                // prepend the PID necessary
                if ( fDisplayPID && fDidCR )
                {
                    // avoid overwriting the \r\n if it exists
                    int iLen = strlen(lpszDebugText);
                    wsprintf(&lpszDebugText[iLen], "%3lu: ",
                             LastPid);
                }

                // build display buffer
                strcat(lpszDebugText, lpszScratch);

                // record newline status
                fDidCR =
                    (*lpszScratch &&
                     (lpszScratch[strlen(lpszScratch)-1]=='\n'));

                // cleanup from FixNewLines
                free(lpszScratch);

                // send the display string to the window
                PostMessage(hwndDBWin, WM_DEBUGTEXT,
                            (WPARAM)lpszDebugText, 0);
            }

            // ready for new event
            SetEvent(AckEvent);
        }
    }

    return;
}
/* End of File */