GBK(GB2312) 转换 UTF-8 (Windows下)

char *gbk2utf8( const char *strGBK )
{
    int len;
    wchar_t *strUnicode;
    char *strUTF8;
    if ( !strGBK )
    {
        return NULL;
    }

    len = MultiByteToWideChar( CP_ACP, 0,strGBK, -1, NULL,0 );
    if ( len < 1 )
    {
        return NULL;
    }
    strUnicode = (wchar_t *) malloc( sizeof(wchar_t) * len );
    if ( !strUnicode )
    {
        return NULL;
    }
    len = MultiByteToWideChar( CP_ACP, 0, strGBK, -1, strUnicode, len );
    if ( len < 1 )
    {
        free(strUnicode);
        return NULL;
    }

    len = WideCharToMultiByte( CP_UTF8, 0, strUnicode, -1, NULL, 0, NULL, NULL );
    if ( len < 1 )
    {
        free(strUnicode);
        return NULL;
    }
    strUTF8 = (char *) malloc( sizeof(char) * len );
    if ( !strUTF8 )
    {
        free(strUnicode);
        return NULL;
    }
    len = WideCharToMultiByte( CP_UTF8, 0, strUnicode, -1, strUTF8, len, NULL, NULL );
    free(strUnicode);
    if ( len < 1 )
    {
        free(strUTF8);
        return NULL;
    }
    return strUTF8;
}