该函数经常被用来处理UTF-8和ANSI格式的字符串，将它们转换为宽字节(UTF-16)

#include <iostream>
#include <Windows.h>
#include <string>

#define MAXBUFFERSIZE 1024

using namespace std;

int main()
{
    DWORD windowStart = 0; DWORD windowEnd = 15; DWORD windowSize = 15; // buffer window containing tag candidate
    wstring windowCopy;
    DWORD bufferSize = MAXBUFFERSIZE;
    _int64 fileRemaining;

    HANDLE hFile;
    DWORD  dwBytesRead = 0;
    OVERLAPPED ol = { 0 };
    LARGE_INTEGER dwPosition;

    TCHAR* buffer = new TCHAR[MAXBUFFERSIZE];;

    hFile = CreateFileW(
        L"test.txt",         // file to open  其中包含UTF-8格式或者ANSI格式的文本
        GENERIC_READ,          // open for reading
        FILE_SHARE_READ | FILE_SHARE_WRITE,       // share for reading and writing
        NULL,                  // default security
        OPEN_EXISTING,         // existing file only
        FILE_ATTRIBUTE_NORMAL, // normal file    | FILE_FLAG_OVERLAPPED
        NULL);                 // no attr. template

    if (hFile == INVALID_HANDLE_VALUE)
    {
        wprintf(L"CreateFile");
        return 0;
    }

    LARGE_INTEGER size;
    GetFileSizeEx(hFile, &size);

    _int64 fileSize = (__int64)size.QuadPart;
    double gigabytes = fileSize * 9.3132e-10;
    wprintf(L"file size: %lld bytes \(%.1f gigabytes\)\n", fileSize, gigabytes);

    fileRemaining = fileSize;

    wprintf(L"file remaining: %lld bytes\n", fileRemaining);

    while (fileRemaining)                                       
    {

        if (bufferSize > fileRemaining)                       
            bufferSize = fileRemaining;
        memset(buffer, 0, fileSize);
        if (FALSE == ReadFile(hFile, buffer, bufferSize, &dwBytesRead, NULL))
        {
            wprintf(L"file read failed\n");
            CloseHandle(hFile);
            return 0;
        }

        fileRemaining -= bufferSize;                            
        wprintf(L"outer loop\n");
   
        while (windowEnd < bufferSize)            
        {
            windowSize = windowEnd - windowStart;
         
            wstring str(buffer);
            wstring sub = str.substr(windowStart, windowSize);
            TCHAR converted[60] = { 0 };
            MultiByteToWideChar(CP_ACP, MB_COMPOSITE, (LPCCH)sub.c_str(), -1, converted, 60);
            wprintf(L"windowStart:%d windowEnd:%d char:%s\n", windowStart, windowEnd, converted);
            windowStart = windowEnd;
            windowEnd+=windowSize;

        }
    }  

    delete buffer;
}