Sharing variables between programs?

[Alan Clarke]

I have a PB/CC program that I end it's process when a file exists as shown below.

DO
...
IF Exist("file.txt") THEN EXIT LOOP

LOOP

I dislike having to create "file.txt" to accomplish the termination for various reasons: I must create/delete the file or I may want to run the program in an environment that has no writeable disk.

Is there anyway to accomplish this with some kind variable that exists in memory? Am I correct in my thinking that most variables are confined to the executable in which they reside? One method that succeeded for me was to write a certain string to the Windows clipboard. The looping program reads the clipboard then exits if the string is found. This proves to me that what I want can be accomplished totally in memory without writing to a drive, but my clipboard is jeophardized for other applications. Can I do this with REGISTER variables (i.e. #REGISTER statement) or an ENVIRONMENT variable? I want to use the least amount of code as possible.

[Michael Mattias]

Win32: Memory Mapped Files/Control User Count April 26, 2001

[Michael Mattias]

Above is but one method of performing Interprocess Communication..

However, a better question might be ....

>IF Exist("file.txt") THEN EXIT LOOP

.... "What causes 'file.txt' to exist?"

Window provides numerous synchronization objects which are designed to transfer the load of "waiting for something to happen" to the operating system and to tell your program it is time to "do something."

MCM

[Alan Clarke]

My goal is to stop/kill the exe, MyProg.exe, which contains the DO LOOP. I simply create a zero-byte file.txt file using batch commands, then MyProg.exe terminates when file.txt is discovered. I used Mark Russinovich's process utility to kill MyProg.exe but this like blunt trauma to the head. Your suggestion of using mutex's was helpful but I keep thinking something simpler exists like a single-bit register tucked away somewhere that both programs can share. I'm not ruling out assembler code. Is there nothing like this?

[Michael Mattias]

If they are both your programs (which we would call "cooperating programs") then the solution I would recommend would be a user-named Windows Event.

Demo here:
Terminate Worker Threads Using Windows Events (and Using Thread Local Storage) Demo Dec 23 2005

That demo uses a named event; different functions obtain handles to that event as needed; as long as the "Cancel" event is non-signalled, the processing loop continues. When you signal the cancel event (from any program), the loop terminates.

But different processes (programs) can obtain handles to a named event, too.

Study up on Windows synchronization objects and you'll see what I am thinking.

You could also create a (non-visible) Window in the program to be stopped, and send a message to it telling it to end.

You have many options short of 'blunt force trauma' as long as you are talking about cooperating applications.

MCM

[Michael Mattias]

Windows' events, memory mapped files and other 'system' objects (eg atoms, mutexes, semaphores, etc. ) really are 'shared variables' when you think about it.

At least you can use 'em that way.

If you want to stick with creating 'file.txt' in a batch file to signal your program that's it's time to quit, you can use a directory change notification object as demo'd here:

Win32(SDK): Internet Cookie Monitor April 25, 2001

If 'file.txt' is the new file in the monitored folder (it wasn't there last time the event triggered) it's showtime.

[Chris Holbrook]

...I keep thinking something simpler exists like a single-bit register tucked away somewhere that both programs can share. I'm not ruling out assembler code. Is there nothing like this?

There must be something on a port somewhere which you could use but that approach would be deprecated by Windows enthusiasts, and in any event (pun inteneded) you would have to write code to do it, so why not "just" write code which does what your utility program does. Which is to identify the process by name* and send it a polite but firm request to terminate. There are at least two code examples in the forums. Here's a recent thread - note especially posts #9 and #11*.

[Michael Mattias]

One of the founding design principles of 32-bit Windows was the isolation of memory, to make it IMPOSSIBLE for one process do something silly which would affect other processes. Anyone who ever worked on Win/16 (= Windows 3.x) understands why that feature was important. (Heck, USERS know... remember how if one Win/3 program crashed, it generally took a couple of other programs with it?)

However, the designers recognized the need for interprocess communication, and included a ton of ways to accomplish that ... but only when it was done intentionally.

So I wouldn't even bother looking for a 'back door' because even if you find one, there's a good chance it would be closed in a 'security update' since such a back door is virtually the definition of a security flaw.

Instead, learn and use the interprocess communications facilities provided by Windows/32.

Or, contact my office for a quotation.

[Mike Doty]

Private clipboard

Private clipboard (for running on same machine, not network)

http://www.powerbasic.com/support/pbforums/showthread.php?t=23335

[Mike Doty]

You've got to love this routine

Original code by: Pierre Bellisle

Orignal source automatically opens 4 programs at http://www.powerbasic.com/support/pb...ad.php?t=23335

Most of the code is for the LISTBOX and the compiled program should be run several times to see results.
Sprinkled in a few remarks where files could be sent.

Thanks again, Pierre!

#COMPILE EXE "Private.exe"
#DIM ALL
#INCLUDE "Win32Api.Inc"
%Listbox1    = 100
%SendButton  = 101
%ClearButton = 102
%ExitButton  = 103
GLOBAL AppTitle    AS STRING
GLOBAL hDlg        AS DWORD
GLOBAL ClipNoRead  AS LONG
GLOBAL gWorthlessCounter AS DWORD
'_________________________________________________________________________________________________
FUNCTION WriteToClipBoard (BYVAL Txt AS STRING, MyFormat AS LONG) AS LONG
 LOCAL lpMem AS ASCIIZ PTR
 LOCAL hMem  AS DWORD
 ClipNoRead = 1 'No need to read what we send
 hMem       = GlobalAlloc(%GHND, LEN(Txt) + 1)
 lpMem      = GlobalLock(hMem)
 @lpMem     = Txt
 GlobalUnlock hMem
 OpenClipboard 0
 'EmptyClipboard
 SetClipboardData MyFormat, hMem
 CloseClipboard
 FUNCTION = 1
END FUNCTION
'_________________________________________________________________________________________________
CALLBACK FUNCTION DlgProc
 STATIC szMyFormat      AS ASCIIZ * 20
 STATIC MyFormat        AS LONG
 LOCAL  ClipDataPtr     AS ASCIIZ PTR
 LOCAL  ClipData        AS STRING
 STATIC hClipboardChain AS LONG
 LOCAL  Retval          AS LONG
 LOCAL OneLost          AS STRING
 SELECT CASE CBMSG
   CASE %WM_INITDIALOG
     szMyFormat      = "MyOwnClipboardFormat"
     hClipboardChain = SetClipboardViewer(CBHNDL) 'Add ourselve to clipboard chain
     MyFormat        = RegisterClipboardFormat(szMyFormat)
     IF MyFormat = 0 THEN MSGBOX "Error registering clipboard format"
   CASE %WM_DESTROY
     WriteToClipBoard AppTitle & " just past the way!!!" , MyFormat 'Tell everybody that we are ending
     ChangeClipboardChain CBHNDL, hClipboardChain 'Remove ourselve from clipboard chain
     PostQuitMessage 0
   CASE %WM_DRAWCLIPBOARD   'Here we know the clipboard content is beeing updated
     IF IsClipboardFormatAvailable(MyFormat) THEN
       IF ClipNoRead THEN
         ClipNoRead = 0
       ELSE
         OpenClipboard 0
         ClipDataPtr = GetClipboardData(MyFormat)
         ClipData = @ClipDataPtr
         CloseClipboard
         'MSGBOX "Bytes received" + STR$(LEN(ClipData))
         CONTROL SEND hDlg, %Listbox1, %LB_INSERTSTRING, -1, STRPTR(ClipData)
         CONTROL SEND hDlg, %Listbox1, %LB_GETCOUNT, 0, 0 TO Retval
         CONTROL SEND hDlg, %Listbox1, %LB_SETCURSEL, Retval - 1, 0
       END IF
     END IF
     SendMessage hClipboardChain, CBMSG, CBWPARAM, CBLPARAM 'Forward data to next clipboard chain
  CASE %WM_CHANGECBCHAIN
    OneLost = "Some previous clipboard app just ended"
    CONTROL SEND hDlg, %Listbox1, %LB_INSERTSTRING, -1, STRPTR(OneLost)
    CONTROL SEND hDlg, %Listbox1, %LB_GETCOUNT, 0, 0 TO Retval
    CONTROL SEND hDlg, %Listbox1, %LB_SETCURSEL, Retval - 1, 0
    IF CBWPARAM = hClipboardChain THEN
      hClipboardChain = CBLPARAM
    ELSE
      IF hClipboardChain <> 0 THEN SendMessage hClipboardChain, CBMSG, CBWPARAM, CBLPARAM
    END IF
  CASE %WM_COMMAND
      SELECT CASE LOWRD(CBWPARAM)
 
        CASE %SendButton
          'Send data here
          IF CBCTLMSG = %BN_CLICKED THEN
             LOCAL s AS STRING, h AS LONG  'I know, shouldn't go here
             INCR gWorthLessCounter
             s = "#" + FORMAT$(gWorthLessCounter) + " from " + AppTitle + " at " + TIME$
 
             '---  send file ---
             'h = freefile
             'open s for binary As #h
             'Get$ #h, lof(h), s
             'Close #h
 
             WriteToClipBoard s, MyFormat
          END IF
 
        CASE %ClearButton
          IF CBCTLMSG = %BN_CLICKED THEN LISTBOX RESET hDlg, %Listbox1
 
        CASE %ExitButton
          IF CBCTLMSG = %BN_CLICKED THEN DIALOG END CBHNDL, 0
      END SELECT
 END SELECT
END FUNCTION
'_________________________________________________________________________________________________
FUNCTION PBMAIN
 AppTitle = "user" + STR$(INT(TIMER))
 DIALOG NEW 0, AppTitle, 10, 10, 160, 210, _
  %WS_POPUP OR %DS_MODALFRAME OR %WS_CAPTION OR %WS_MINIMIZEBOX OR %WS_SYSMENU, _
  0 TO hDlg
  CONTROL ADD LISTBOX, hdlg, %Listbox1, , 5, 5, 150, 190, _
  %WS_CHILD OR %WS_VISIBLE  OR %WS_VSCROLL OR %WS_TABSTOP, 0
  CONTROL ADD BUTTON, hDlg, %SendButton, "SEND", 20, 192, 35, 15, _
    %WS_CHILD OR %WS_VISIBLE OR %BS_PUSHBUTTON OR %WS_TABSTOP
  CONTROL ADD BUTTON, hdlg, %ClearButton, "CLEAR", 60, 192, 35, 15, _
    %WS_CHILD OR %WS_VISIBLE OR %BS_PUSHBUTTON OR %WS_TABSTOP
  CONTROL ADD BUTTON, hDlg, %ExitButton, "EXIT", 100, 192, 35, 15, _
    %WS_CHILD OR %WS_VISIBLE OR %BS_PUSHBUTTON OR %WS_TABSTOP
  DIALOG SHOW MODAL hDlg CALL DlgProc
END FUNCTION

[Mike Doty]

Just noticed this was PB/CC so I'll post something for that in a few minutes.

[Mike Doty]

Uses CreateWindow with PB/CC

#COMPILE EXE
#DIM ALL  'Private Clipboard with PBCC
%CCWIN=1  'CreateWindow is needed
#INCLUDE "WIN32API.INC"
DECLARE FUNCTION WriteToClipBoard (BYVAL Txt AS STRING, MyFormat AS LONG) AS LONG
DECLARE SUB ShutDown(BYVAL dwEvent AS DWORD)
%ClipBoardSend            = 101
%ClipBoardInit            = 102
GLOBAL hwndTCP  AS LONG
GLOBAL hThread  AS LONG
GLOBAL hDlg               AS DWORD
GLOBAL ClipNoRead         AS LONG
GLOBAL gWorthlessCounter  AS DWORD
GLOBAL gMyFormat          AS LONG
GLOBAL gsSendThis         AS STRING
GLOBAL gsYourName         AS STRING
'Original code is by Pierre Bellisle, modified for use with PB/CC Mike Doty 8/19/08
FUNCTION PBMAIN
  COLOR 7,1,1
  CLS
  ? "PB/CC Private Clipboard"
  LINE INPUT "Your name? ";gsYourName
  IF LEN(gsYourName) = 0 THEN ? "Bye":SLEEP 1000:EXIT FUNCTION
 
  CONSOLE NAME gsYourName
  CLS
  SetConsoleCtrlHandler CODEPTR(ShutDown), 1  'user might click X to terminate
  THREAD CREATE WindowThread(%NULL) TO hThread
  SLEEP 250
 
  SendMessage hwndTCP,%WM_COMMAND,%ClipBoardInit,0
  gsSendThis =  gsYourName + " is now here"
  SendMessage hwndTCP, %WM_COMMAND,%ClipboardSend,0
  DO
    LINE INPUT "<Me> " gsSendThis                       'data to send to everybody
    LOCATE CURSORY-1,1: ? "<Me> " + gsSendThis
    gsSendThis = "<" + gsYourName + "> " + gsSendThis
    SendMessage hwndTCP,%WM_COMMAND,%ClipBoardSend,0
 
   'click X to end programp
  LOOP
 
  '-----------------------------------------------------------------------
EXIT FUNCTION 'line below will never execute.  This line isn't needed
  '-----------------------------------------------------------------------
  SetConsoleCtrlHandler CODEPTR(ShutDown), 0 'uninstall user might click X
END FUNCTION
FUNCTION WriteToClipBoard (BYVAL Txt AS STRING, MyFormat AS LONG) AS LONG
LOCAL lpMem AS ASCIIZ PTR
LOCAL hMem  AS DWORD
ClipNoRead = 1 'No need to read what we send
hMem       = GlobalAlloc(%GHND, LEN(Txt) + 1)
lpMem      = GlobalLock(hMem)
@lpMem     = Txt
GlobalUnlock hMem
OpenClipboard 0
'EmptyClipboard
SetClipboardData MyFormat, hMem
CloseClipboard
FUNCTION = 1
END FUNCTION
'_________________________________________________________________________________________________
FUNCTION HelloWindows (BYVAL hWnd AS LONG, BYVAL wMsg AS LONG, _
                  BYVAL wParam AS LONG, BYVAL lParam AS LONG) AS LONG
STATIC szMyFormat      AS ASCIIZ * 21
STATIC MyFormat        AS LONG              'made a global
LOCAL  ClipDataPtr     AS ASCIIZ PTR
LOCAL  ClipData        AS STRING
STATIC hClipboardChain AS LONG
LOCAL  Retval          AS LONG
LOCAL OneLost          AS STRING
SELECT CASE wMsg
  CASE %WM_COMMAND
    SELECT CASE LOWRD(WParam)
      CASE %ClipboardSend
        WriteToClipBoard gsSendThis, gMyFormat
      CASE  %ClipBoardInit
        szMyFormat = "MyOwnClipboardFormat"
        hClipboardChain = SetClipboardViewer(hWnd)    'PBCC Add ourselve to clipboard chain
        gMyFormat        = RegisterClipboardFormat(szMyFormat)     'was MyFormat made a global
        IF gMyFormat = 0 THEN ? "Clipboard not registered"
    END SELECT
  CASE %WM_DESTROY
     WriteToClipBoard gsYourName + " left clipboard" , gMyFormat 'Tell everybody that we are ending
     'ChangeClipboardChain CBHNDL, hClipboardChain 'Remove ourselve from clipboard chain
     ChangeClipboardChain hWnd, hClipboardChain 'PB/CC Remove ourselve from clipboard chain
     ChangeClipboardChain hWnd, hClipboardChain
     PostQuitMessage 0
  CASE %WM_DRAWCLIPBOARD   'Here we know the clipboard content is being updated
     IF IsClipboardFormatAvailable(gMyFormat) THEN
       IF ClipNoRead THEN
         ClipNoRead = 0
       ELSE                                        'read the clipboard
         OpenClipboard 0
         ClipDataPtr = GetClipboardData(gMyFormat)
         ClipData = @ClipDataPtr
         CloseClipboard
         LOCATE ,1                                 'display inbound message
         ? ClipData                                 'display contents
       END IF
     END IF
     'SendMessage hClipboardChain, CBMSG, CBWPARAM, CBLPARAM 'Forward data to next clipboard chain
     SendMessage hClipboardChain, wMsg,WParam, LParam
  CASE %WM_CHANGECBCHAIN
      OneLost = "Somebody exited"
      IF wParam   = hClipBoardChain THEN
        hClipBoardChain = lParam
      ELSE
        IF hClipBoardChain <> 0 THEN SendMessage hClipBoardChain, wMsg, WParam, LParam
      END IF
  END SELECT
 FUNCTION = DefWindowProc(hWnd, wMsg, wParam, lParam)   'don't forget to add this
END FUNCTION
FUNCTION MakeWindow () AS LONG
LOCAL wce         AS WndClassEx
LOCAL szClassName AS ASCIIZ * 64
LOCAL hWnd        AS LONG
LOCAL hInst       AS LONG
STATIC registered AS LONG
hInst = GetModuleHandle(BYVAL %NULL)
IF ISFALSE registered THEN
  szClassName          = "PRIVATECLIPBOARDTEST"
  wce.cbSize           = SIZEOF(wce)
  wce.style            = %CS_HREDRAW OR %CS_VREDRAW
  wce.lpfnWndProc      = CODEPTR(HelloWindows)
  wce.cbClsExtra       = 0
  wce.cbWndExtra       = 0
  wce.hInstance        = hInst
  wce.hIcon            = %NULL
  wce.hCursor          = %NULL
  wce.hbrBackground    = %NULL
  wce.lpszMenuName     = %NULL
  wce.lpszClassName    = VARPTR(szClassName)
  wce.hIconSm          = %NULL
  RegisterClassEx wce
  registered = %TRUE
END IF
hWnd = CreateWindow(szClassName, "Cool Beans Private Clipboard",  _
                    %WS_OVERLAPPEDWINDOW, 5, 5, 10, 10, %NULL,%NULL, hInst, BYVAL %NULL)
    IF ISFALSE hWnd THEN
        hWnd = GetLastError
    ELSE
        ShowWindow hWnd, %SW_HIDE
        UpdateWindow hWnd
    END IF
    FUNCTION = hWnd
END FUNCTION
FUNCTION WindowThread (BYVAL nIgnored AS LONG) AS LONG
LOCAL Msg AS tagMsg
hwndTCP = MakeWindow
DO WHILE IsWindow(hwndTCP) AND GetMessage(Msg, %NULL, 0, 0)
  TranslateMessage Msg
  DispatchMessage Msg
LOOP
END FUNCTION
 
SUB ShutDown(BYVAL dwEvent AS DWORD)
  'in case user clicks X to terminate
  'SELECT CASE dwEvent
    'CASE %CTRL_C_EVENT
    '  'Do whatever needed...
    '  PRINT "Ctrl-C pressed"
    'CASE %CTRL_BREAK_EVENT
    '  'Do whatever needed...
    '  PRINT "Ctrl-Break pressed"
    'CASE %CTRL_CLOSE_EVENT
    '  'Do whatever needed...
    '  PRINT "[x] Close pressed"
    'CASE %CTRL_LOGOFF_EVENT
    '  PRINT "User logging off or restarting"
    'CASE %CTRL_SHUTDOWN_EVENT
    ' PRINT "System shutting down"
  'END SELECT
  SendMessage hwndTCP, %WM_CLOSE,0,0
END SUB

[Alan Clarke]

Thanks so much for the varied responses. All were helpful in bringing me to the realizaton that a deep chasm exists between each application's memory space. I was hoping for a one-liner. But as you said, if it was that easy, every Tom, Dick & Harry would be corrupting someone else's address space.

[Mike Doty]

One-liner, okay: lResult& = WriteToPrivateClipBoard("Anything")
Anthing can be a block of memory, file, etc ...
Getting closer?

Probably wont work unless the clipboard is left open.

'WriteToPrivateClipboard.bas
'
#INCLUDE "Win32Api.Inc"
'
FUNCTION WriteToPrivateClipBoard (BYVAL Txt AS STRING) AS LONG
 
 STATIC MyFormat&
 IF MyFormat& = 0 THEN
   MyFormat& = RegisterClipBoardFormat("MyOwnClipBoardformat") 'case-insensitive
   'IF MyFormat& = 0 then ? "Error Registering":EXIT FUNCTION
 END IF
 LOCAL lpMem AS ASCIIZ PTR
 LOCAL hMem  AS DWORD
 LOCAL lResult AS LONG
 hMem       = GlobalAlloc(%GHND, LEN(Txt) + 1)
 lpMem      = GlobalLock(hMem)
 @lpMem     = Txt
 GlobalUnlock hMem
 OpenClipboard 0
 lresult = SetClipboardData(MyFormat, hMem)
 CloseClipboard
 FUNCTION = lResult
END FUNCTION
'
FUNCTION PBMAIN
    lResult& = WriteToPrivateClipBoard("Anything")
END FUNCTION

[Michael Mattias]

>Anthing can be a block of memory, file, etc

No, it must be a string, as specified in function header.

>Probably wont work unless the clipboard is left open.

Probably will.

[Mike Doty]

I have it work being closed.

[Mike Doty]

It was here all the time:
Note: The length of the format should be 1-byte longer (for the NUL.)

http://www.powerbasic.com/support/pbforums/showthread.php?t=25044&highlight=registerclipboardformat

Anyone know how to put binary data into a private clipboard?

[Marco Pontello]

Eventually you can always UUE or MIME64 encode them (you pay it with some overhead, say about 30%).
It depends on what you are after, off course.

Bye!

[Michael Mattias]

> Eventually you can always UUE or MIME64 encode them

???

Why bother? It's a private clipboard format, a pedestrian block of memory.

[Marco Pontello]

"eventually" and "it depends" should give enough space options...