# Cyrus IMAP Server: Replication Protocol v2.4+

## DList 1.0

The DList protocol is based closely on the IMAP wire protocol, using atoms and literals as the basis, but with two extended types of data:

- kvlist
- rfc822-object

A wart of the protocol is the rfc822-object, which contains an explicit cyrus backend partition. This will be removed in future versions of Cyrus.

### types

#### atom

An atom is actually a sequence of any character other than '\0', the NULL byte. Character encoding is not specified, but it can contain 8 bit characters, and is probably utf8

#### flag

Flag is a horrible special case of atom to allow \word to be represented as an IMAP atom on the wire. This is one of many special cases in the IMAP protocol, and is duplicated into dlist just to make it easier to read

#### num32/num

Both stored as 64 bit integers internally, and sent as decimal numbers over the wire, this type exists only in the API, it just looks like a string on the wire.

#### hex32/hex

Stored like num internally, but sent as an 8 or 16 character hexadecimal string on the wire

#### map

Like atom, but can contain NULL. All values are parsed off the wire as 'map' type and then converted on demand into the requested type

#### list

Encoded in parentheses like so (item item item) a list type can be nested inside other lists: (item (sub sub) item)

#### kvlist

A kvlist allows named parameters, and is indicated with a leading % character. % is invalid in atoms, so parsing is unambiguous, e.g:

%(key1 value1 key2 (list of values) key3 value3)

#### rfc822-object/file

Finally the ugly one. These look like a literal, but with a leading % and two more fields:

    %{partition sha1 size}\r\n
    data