بررسی این یونیت Hook

[_alish_]

با سلام
من می خواهم ببینم این یونیت هوک چطور کار می کند و این دستورات چی هستند؟
دوستانی که دوست دارند مطالعه ای داشته باشند و می توانند در این زمینه راهنمایی کند ، خواهش می کنم یک نیم نگاهی به این کد بندازند.
ممنون


library HookLib;

uses
madExcept,
Windows,
Messages,
SysUtils;

type
PHookRec = ^THookRec;
THookRec = record
AppHnd: Integer;
MemoHnd: Integer;
end;

var
Hooked: Boolean;
hKeyHook, hMemo, hMemFile, hApp: HWND;
PHookRec1: PHookRec;

function KeyHookFunc(Code, VirtualKey, KeyStroke: Integer): LRESULT; stdcall;
var
KeyState1: TKeyBoardState;
AryChar: array[0..1] of Char;
Count: Integer;
begin
Result := 0;
if Code = HC_NOREMOVE then Exit;
Result := CallNextHookEx(hKeyHook, Code, VirtualKey, KeyStroke);
{I moved the CallNextHookEx up here but if you want to block
or change any keys then move it back down}
if Code < 0 then
Exit;

if Code = HC_ACTION then
begin
if ((KeyStroke and (1 shl 30)) <> 0) then
if not IsWindow(hMemo) then
begin
{I moved the OpenFileMapping up here so it would not be opened
unless the app the DLL is attatched to gets some Key messages}
hMemFile := OpenFileMapping(FILE_MAP_WRITE, False, 'Global7v9k');
PHookRec1 := MapViewOfFile(hMemFile, FILE_MAP_WRITE, 0, 0, 0);
if PHookRec1 <> nil then
begin
hMemo := PHookRec1.MemoHnd;
hApp := PHookRec1.AppHnd;
end;
end;
if ((KeyStroke and (1 shl 30)) <> 0) then
begin
GetKeyboardState(KeyState1);
Count := ToAscii(VirtualKey, KeyStroke, KeyState1, AryChar, 0);
if Count = 1 then
begin
SendMessage(hMemo, WM_CHAR, Ord(AryChar[0]), 0);
{I included 2 ways to get the Charaters, a Memo Hnadle and
a WM_USER+1678 message to the program}
PostMessage(hApp, WM_USER + 1678, Ord(AryChar[0]), 0);
end;
end;
end;
end;


function StartHook(MemoHandle, AppHandle: HWND): Byte; export;
begin
Result := 0;
if Hooked then
begin
Result := 1;
Exit;
end;
if not IsWindow(MemoHandle) then
begin
Result := 4;
Exit;
end;
hKeyHook := SetWindowsHookEx(WH_KEYBOARD, KeyHookFunc, hInstance, 0);
if hKeyHook > 0 then
begin
{you need to use a mapped file because this DLL attatches to every app
that gets windows messages when it's hooked, and you can't get info except
through a Globally avaiable Mapped file}
hMemFile := CreateFileMapping($FFFFFFFF, // $FFFFFFFF gets a page memory file
nil, // no security attributes
PAGE_READWRITE, // read/write access
0, // size: high 32-bits
SizeOf(THookRec), // size: low 32-bits
//SizeOf(Integer),
'Global7v9k'); // name of map object
PHookRec1 := MapViewOfFile(hMemFile, FILE_MAP_WRITE, 0, 0, 0);
hMemo := MemoHandle;
PHookRec1.MemoHnd := MemoHandle;
hApp := AppHandle;
PHookRec1.AppHnd := AppHandle;
{set the Memo and App handles to the mapped file}
Hooked := True;
end
else
Result := 2;
end;

function StopHook: Boolean; export;
begin
if PHookRec1 <> nil then
begin
UnmapViewOfFile(PHookRec1);
CloseHandle(hMemFile);
PHookRec1 := nil;
end;
if Hooked then
Result := UnhookWindowsHookEx(hKeyHook)
else
Result := True;
Hooked := False;
end;

procedure EntryProc(dwReason: DWORD);
begin
if (dwReason = Dll_Process_Detach) then
begin
if PHookRec1 <> nil then
begin
UnmapViewOfFile(PHookRec1);
CloseHandle(hMemFile);
end;
UnhookWindowsHookEx(hKeyHook);
end;
end;

exports
StartHook,
StopHook;

begin
PHookRec1 := nil;
Hooked := False;
hKeyHook := 0;
hMemo := 0;
DLLProc := @EntryProc;
EntryProc(Dll_Process_Attach);
end.