Libdmapsharing Server Internals

I will use DAAPShare to document the libdmapsharing internals. DAAPShare provides an example appropriate for any implmentation of the abstract class DMAPShare, including DPAPShare. DAAPShare calls _dmap_share_server_start() and _dmap_share_publish_start() when an object is created. The latter function starts a new web server by calling soup_server_new() and adds callbacks to the SoupServer object to handle the various paths required by the DMAP specification (/server-info, /content-codes, /login, etc). These callbacks are implemented in DAAPShare and provided to the SoupServer object after being wrapped in adapter functions (note that some callbacks are common to all DMAP protocols and are implemented in DMAPShare; e.g., the login callback). The latter function, _dmap_share_publish_start, starts the mDNS subsystem. It does this by using the mDNS implmentation option choosen at compile-time (e.g., Avahi, Howl or DNS-SD).

The DMAPStructure class is used to build a representation of the data that makes up a DMAP request or response. The array cc_defs defines all possible valid entries in a DMAPStructure representation. Likewise, the numeric content code used by each node is defined by the enum DMAPContentCode. Both the cc_defs array and the DMAPContentCode enum must be in the same order. That is, if you add an entry to cc_defs, then you must add its corresponding content code to DMAPContentCode in the same order.

Assuming DMAPStructure defines all the entries you require, the actual protocol-specific structures are built in DAAPShare. Note the use of the function dmap_structure_add(). Often, the data dmap_structure_add() adds is provided by a DAAPRecord object that exists in a DMAPDb object (both interfaces are implemented by the application). Eventually, the DAAPShare provides the DMAPStructure to the SoupServer object using the _dmap_share_message_set_from_dmap_structure() function.