whats new ¦  programming tips ¦  indy articles ¦  intraweb articles ¦  informations ¦  links ¦  interviews
 misc ¦  tutorials ¦  Add&Win Game

Tips (1548)

Database (90)
Files (137)
Forms (107)
Graphic (116)
IDE (21)
Indy (5)
Internet / LAN (131)
IntraWeb (0)
Math (76)
Misc (127)
Multimedia (45)
Objects/
ActiveX (51)

OpenTools API (3)
Printing (35)
Strings (83)
System (268)
VCL (243)

Top15

Tips sort by
component


Search Tip

Add new Tip

Add&Win Game

Advertising

36 Visitors Online


 
...hook a function (in your own application) ?
Autor: Thomas Stutz
[ Print tip ]  

Tip Rating (12):  
     



type
  
TSaveRedir = packed record
    
Addr: Pointer;
    Bytes: array[0..4] of Byte;
  end;
  PSaveRedir = ^TSaveRedir;

procedure RedirectCall(FromAddr, ToAddr: Pointer; SaveRedir: PSaveRedir);
var
  
OldProtect: Cardinal;
  NewCode: packed record
    
JMP: Byte;
    Distance: Integer;
  end;
begin
  if not 
VirtualProtect(FromAddr, 5, PAGE_EXECUTE_READWRITE, OldProtect) then
    
RaiseLastWin32Error;
  if Assigned(SaveRedir) then
  begin
    
SaveRedir^.Addr := FromAddr;
    Move(FromAddr^, SaveRedir^.Bytes, 5);
  end;
  NewCode.JMP := $E9;
  NewCode.Distance := PChar(ToAddr) - PChar(FromAddr) - 5;
  Move(NewCode, FromAddr^, 5);
  if not VirtualProtect(FromAddr, 5, OldProtect, OldProtect) then
    
RaiseLastWin32Error;
end;

procedure UndoRedirectCall(const SaveRedir: TSaveRedir);
var
  
OldProtect: Cardinal;
begin
  if not 
VirtualProtect(SaveRedir.Addr, 5, PAGE_EXECUTE_READWRITE, OldProtect) then
    
RaiseLastWin32Error;
  Move(SaveRedir.Bytes, SaveRedir.Addr^, 5);
  if not VirtualProtect(SaveRedir.Addr, 5, OldProtect, OldProtect) then
    
RaiseLastWin32Error;
end;


// Example: Replace Application.MessageBox with your own.

function MyNewMessageBox(Self: TApplication; const Text, Caption: PChar;
  Flags: Longint): Integer;
begin
  
ShowMessage('New Messagebox');
  //....
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  
Application.MessageBox('You'll never see this Text /
    Diesen Text wirst du nie sehen', '...', MB_OK);
end;

var
  
S: TSaveRedir;

initialization
  
RedirectCall(@TApplication.MessageBox, @MyNewMessageBox, @S);

finalization
  
UndoRedirectCall(S);

 

Rate this tip:

poor
very good


Copyright © by SwissDelphiCenter.ch
All trademarks are the sole property of their respective owners