Escaping <\> in HTTP Digest (RFC 2617)

Hi,
I would like to get some feedback on what HTTP Digest implementations do
with '\' in username/realm/password. For example, if I have a username
'example.com\user1', do implementations hash 'example.com\\user1' (i.e.
the \ is escaped with another \), or just 'example.com\user1' (single
slash).

Thanks,
Alexey