SetConsoleCtrlHandler Verständnisfrage(n)

[turboPASCAL]

Ach, ich musste mich erst einmal mit CreateFile rumschlagen
damit das Loggen nicht gepuffert wird.

Delphi-Quellcode:

program Test;

{$APPTYPE CONSOLE}

uses
  Windows;

var
  AppTerminated: Boolean;
  f: cardinal;

procedure Log(txt: string);
var
  b: cardinal;
  a: array [0..255] of char;
begin
  if not(f<>0) then exit; // no file no write
  zeromemory(@a, sizeof(a));
  lstrcpy(a, PCHAR(txt + #13#10));
  writefile(f, a, lstrlen(a), b, nil);
end;

function ConCtrlHandler(dwCtrlType: DWORD): Bool; stdcall;
begin
  Result := True;

  case dwCtrlType of
    // CTRL+C signal was received, either from keyboard input
    CTRL_C_EVENT: log('App-Event: CTRL_C_EVENT');

    // CTRL+BREAK signal was received, either from keyboard input
    CTRL_BREAK_EVENT: log('App-Event: CTRL_BREAK_EVENT');

    // --> system sends to all processes attached to a console when the user closes the console
    CTRL_CLOSE_EVENT: log('App-Event: CTRL_CLOSE_EVENT');

    // system sends to all console processes when a user is logging off.
    CTRL_LOGOFF_EVENT: log('App-Event: CTRL_LOGOFF_EVENT');

    // system sends to all console processes when the system is shutting down
    CTRL_SHUTDOWN_EVENT: log('App-Event: CTRL_SHUTDOWN_EVENT');
  end;
  AppTerminated := True;
end;

begin

  //////////////////// VERY BAD CODE ////////////////////

  f := CreateFile('log.txt', GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ,
       nil, TRUNCATE_EXISTING, FILE_FLAG_WRITE_THROUGH, 0);

  if f = ERROR_FILE_NOT_FOUND then
  f := CreateFile('log.txt', GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ,
       nil, CREATE_NEW, FILE_FLAG_WRITE_THROUGH, 0);

  //////////////////// ------------- ////////////////////


  log('--------------------------'#13#10'App: Start');

  AppTerminated := False;

  if SetConsoleCtrlHandler(@ConCtrlHandler, True) then log('App: Set CtrlHandler true')
    else log('App: Set CtrlHandler false');


  log('App: Working...');
  while not AppTerminated do
  begin
    Write('Working...'#32);
    sleep(100);
  end;

  writeln(#10#13);
  writeln('...und Tschuess!');
  sleep(500);

  log('App: End');
  closehandle(f);
end.

Die Loggdatei:

Code:

--------------------------
App: Start
App: Set CtrlHandler true
App: Working...
App-Event: CTRL_CLOSE_EVENT

Also wird das Ding mit dem X-Button regelrecht "abgeschossen".