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library Hook;

uses
  windows,
  uallhook;

var
old_CompareStringA:  function(Locale:LCID; dwCmpFlags:DWORD; lpString1:PAnsiChar; cchCount1:Integer; lpString2:PAnsiChar; cchCount2:Integer): Integer; stdcall;
next_CompareStringA: function(Locale:LCID; dwCmpFlags:DWORD; lpString1:PAnsiChar; cchCount1:Integer; lpString2:PAnsiChar; cchCount2:Integer): Integer; stdcall;

function my_CompareStringA(Locale:LCID; dwCmpFlags:DWORD; lpString1:PAnsiChar; cchCount1:Integer; lpString2:PAnsiChar; cchCount2:Integer): Integer;
begin
   MessageBox(0, PChar(lpString1+' with '+lpString2), 'Compare', $00000040);
   Result := next_CompareStringA(Locale, dwCmpFlags, lpString1, cchCount1 ,lpString2, cchCount2);
end;

procedure injectmain;
var p:pointer;
begin
  p := GetProcAddress(GetModuleHandle('kernel32.dll'),'CompareStringA');
  if p <> nil then begin
    @old_CompareStringA := p;
    uallHook.HookCode(@old_CompareStringA,@my_CompareStringA,@next_CompareStringA);
  end;
end;

procedure uninjectmain;
begin
  uallHook.UnhookCode(@next_CompareStringA);
end;

procedure dllmain(dwReason: integer);
begin
  case dwreason of
    DLL_PROCESS_ATTACH:
      injectmain;
    DLL_PROCESS_DETACH:
      uninjectmain;
  end;
end;

begin
  DLLProc := @DLLMain;
  DLLMain(1);
end.