MFC/C++用Char*（Byte*）读取文件utf-8的文件乱码—-解码

//utf8Str：以字节（char*或者Byte*）读取中文的字符串（乱码）
CString UTF8toUnicode(const char* utf8Str)
{
    UINT theLength=strlen(utf8Str);
    return UTF8toUnicode(utf8Str,theLength);
}

CString UTF8toUnicode(const char* utf8Str,UINT length)
{
    CString unicodeStr;
    unicodeStr=_T("");

    if (!utf8Str)
        return unicodeStr;

    if (length==0)
        return unicodeStr;


    WCHAR chr=0;//一个中文字符
    for (UINT i=0;i<length;)
    {
        //UTF8的三种中文格式
        if ((0x80&utf8Str[i])==0) //只占用一个字节
        {
            chr=utf8Str[i];
            i++;
        }
        else if((0xE0&utf8Str[i])==0xC0) //占用两个字节
        {
            chr =(utf8Str[i+0]&0x3F)<<6;
            chr|=(utf8Str[i+1]&0x3F);
            i+=2;
        }
        else if((0xF0&utf8Str[i])==0xE0)//占用三个字节
        {
            chr =(utf8Str[i+0]&0x1F)<<12;
            chr|=(utf8Str[i+1]&0x3F)<<6;
            chr|=(utf8Str[i+2]&0x3F);
            i+=3;
        }

        else 
        {
            return unicodeStr;
        }
        unicodeStr.AppendChar(chr);
    }

    return unicodeStr;
}