_WIN32_CLIENT_RELEASES = {
    (6, 0): "Vista",
    (6, 1): "7",
    (6, 2): "8",
    (6, 3): "8.1",
    (6, None): "post8.1",
    
    (10, 0): "10",
    (10, None): "post10",
}

# Server release name lookup will default to client names if necessary
_WIN32_SERVER_RELEASES = {
    (6, 0): "2008Server",
    (6, 1): "2008ServerR2",
    (6, 2): "2012Server",
    (6, 3): "2012ServerR2",
    (6, None): "post2012ServerR2",
}

def win32_ver(release='', version='', csd='', ptype=''):
    from ctypes import byref, cast, POINTER, Structure, WinDLL
    from ctypes import create_unicode_buffer, c_buffer
    from ctypes.wintypes import DWORD
    from sys import getwindowsversion
    from winreg import QueryValueEx, OpenKeyEx, CloseKey, HKEY_LOCAL_MACHINE
    
    class VS_FIXEDFILEINFO(Structure):
        _fields_ = [
            ("dwSignature", DWORD),
            ("dwStrucVersion", DWORD),
            ("dwFileVersionMS", DWORD),
            ("dwFileVersionLS", DWORD),
            ("dwProductVersionMS", DWORD),
            ("dwProductVersionLS", DWORD),
            ("dwFileFlagsMask", DWORD),
            ("dwFileFlags", DWORD),
            ("dwFileOS", DWORD),
            ("dwFileType", DWORD),
            ("dwFileSubtype", DWORD),
            ("dwFileDateMS", DWORD),
            ("dwFileDateLS", DWORD),
        ]

    kernel32 = WinDLL('kernel32')
    version = WinDLL('version')

    # We will immediately double the length up to MAX_PATH, but the
    # path may be longer, so we retry until the returned string is
    # shorter than our buffer.
    name_len = actual_len = 130
    while actual_len == name_len:
        name_len *= 2
        name = create_unicode_buffer(name_len)
        actual_len = kernel32.GetModuleFileNameW(kernel32._handle, name, len(name))
        if not actual_len:
            return release, version, csd, ptype

    size = version.GetFileVersionInfoSizeW(name, None)
    if not size:
        return release, version, csd, ptype

    ver_block = byref(c_buffer(size))
    if not version.GetFileVersionInfoW(name, None, size, ver_block) or not ver_block:
        return release, version, csd, ptype

    pvi = POINTER(VS_FIXEDFILEINFO)()
    if not version.VerQueryValueW(ver_block, "\\", byref(pvi), byref(DWORD())):
        return release, version, csd, ptype

    maj = int(pvi.contents.dwProductVersionMS >> 16)
    min = int(pvi.contents.dwProductVersionMS & 0xFFFF)
    build = int(pvi.contents.dwProductVersionLS >> 16)
    
    version = '{0}.{1}.{2}'.format(maj, min, build)
    
    release = (_WIN32_CLIENT_RELEASES.get((maj, min)) or
               _WIN32_CLIENT_RELEASES.get((maj, None)) or
               release)
    
    winver = getwindowsversion()
    
    # getwindowsversion() reflect the compatibility mode Python is
    # running under, and so the service pack value is only going to be
    # valid if the versions match.
    if winver[:2] == (maj, min):
        try:
            csd = 'SP{}'.format(winver.service_pack_major)
        except AttributeError:
            if csd[:13] == 'Service Pack ':
                csd = 'SP' + csd[13:]
    
    # VER_NT_SERVER = 3
    if getattr(winver, 'product_type', None) == 3:
        release = (_WIN32_SERVER_RELEASES.get((maj, min)) or
                   _WIN32_SERVER_RELEASES.get((maj, None)) or
                   release)

    key = None
    try:
        key = OpenKeyEx(HKEY_LOCAL_MACHINE,
                        r'SOFTWARE\Microsoft\Windows NT\CurrentVersion')
        ptype = QueryValueEx(key, 'CurrentType')[0]
    except:
        pass
    finally:
        if key:
            CloseKey(key)

    return release, version, csd, ptype