InternalGetWindowText函数为我们提供了获取Windows NT/2000系统中窗口标题的最快速的方法。它位于User32.dll。这个函数的功能类似于 GetWindowText，但是比GetWindowText快多了，因为它使用INT 2E 中断。InternalGetWindowText 是一个未公开的函数，它只能在Windows NT/2000 系统中使用，Windows 95/98系统中虽然也有这个函数，但只是摆摆样子而已，每次调用都返回错误代码 ERROR_CALL_NOT_IMPLEMENTED。

// fastgetwndtext.cpp (Windows NT/2000)
//
// This example will show you the most faster method how you can obtain
// the text of the specified window's title bar under Windows NT/2000 system.

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

// User32!InternalGetWindowText (NT specific!)
//
// The function copies the text of the specified window's title bar
// (if it has one) into a buffer. The InternalGetWindowText function is
// much faster then documented GetWindowText because it uses INT 2E interrupt
//
// int InternalGetWindowText(
//   HWND hWnd,        // handle to window or control with text
//   LPWSTR lpString, // pointer to buffer for text (UNICODE!!!)
//   int nMaxCount     // maximum number of characters to copy
// );
typedef int (WINAPI *PROCINTERNALGETWINDOWTEXT)(HWND,LPWSTR,int);

PROCINTERNALGETWINDOWTEXT InternalGetWindowText;

void main(int argc, char* argv[])
{
    if (argc<2)
    {
        printf("Usage:\n\nfastgetwndtext.exe hWnd\n");
        return;
    }

    HWND hWnd;
    sscanf(argv[1],"%lx",&hWnd);

    if (!IsWindow(hWnd))
    {
        printf("Incorrect window handle\n");
        return;
    }

    HMODULE hUser32 = GetModuleHandle("user32");
    if (!hUser32)
        return;

    InternalGetWindowText = (PROCINTERNALGETWINDOWTEXT)
                             GetProcAddress(hUser32,"InternalGetWindowText");

    if (!InternalGetWindowText)
        return;

    WCHAR wCaption[280];

    // retrieves the window's caption by using INT 2E interruption
    if (InternalGetWindowText(hWnd,wCaption,sizeof(wCaption)))
        printf("%S",wCaption);

}