import time
import threading
import winsound
from ctypes import *
from ctypes.wintypes import *

LRESULT=c_long

HOOKPROC=WINFUNCTYPE(LRESULT,c_int,WPARAM,LPARAM)

VK_RETURN=13
WM_QUIT=18
WH_KEYBOARD_LL=13
HC_ACTION=0
LLKHF_UP=128

class KBDLLHOOKSTRUCT(Structure):
	_fields_=[
		('vkCode',DWORD),
		('scanCode',DWORD),
		('flags',DWORD),
		('time',DWORD),
		('dwExtraInfo',DWORD),
	]

@HOOKPROC
def keyHookFunc(code,wParam,lParam):
	if code!=HC_ACTION:
		return windll.user32.CallNextHookEx(0,code,wParam,lParam)
	kbd=KBDLLHOOKSTRUCT.from_address(lParam)
	if not (kbd.flags&LLKHF_UP) and kbd.vkCode!=VK_RETURN:
		winsound.Beep(770,70)
		return 1
	return windll.user32.CallNextHookEx(0,code,wParam,lParam)

def hookThreadFunc():
	keyHookID=windll.user32.SetWindowsHookExW(WH_KEYBOARD_LL,keyHookFunc,windll.kernel32.GetModuleHandleW(None),0)
	if keyHookID==0:
		raise OSError("Could not register keyboard hook")
	msg=MSG()
	while windll.user32.GetMessageW(byref(msg),None,0,0):
		pass
	if windll.user32.UnhookWindowsHookEx(keyHookID)==0:
		raise OSError("could not unregister key hook %s"%keyHookID)

if __name__=='__main__':
	print "Starting hook thread"
	hookThread=threading.Thread(target=hookThreadFunc)
	hookThread.start()
	print "The keyboard is hooked, characters except for enter should be blocked"
	buf=raw_input("Type some characters and press enter: ")
	if len(buf)==0:
		print "blocking was successful"
	else:
		print "Keys were not blocked"
	print "Sending quit message to hook thread"
	windll.user32.PostThreadMessageW(hookThread.ident,WM_QUIT,0,0)
	hookThread.join()
	print "done"