Architecture of libmmplaylist

The libmmplaylist library uses a plugin architecture in which each plugin can manage a particular playlist format. When a client opens a session on a playlist, the library determines which plugin is most suited to manage the playlist and uses that selected plugin to carry out subsequent playlist operations.

The library is implemented in three layers:

Playlist management

This layer:

• initializes the library by loading the character-converter service and determining the path of the configuration file
• opens playlist sessions and returns session handles
• loads and validates playlist entries and performs character encoding
• reports the number of playlist entries and the position (index) of the currently playing entry
• updates the playlist position after validating the new position requested by the client

Plugin management

This layer:

• reads the configuration file to learn the plugin filenames and configuration settings
• loads, validates, and unloads plugins
• determines which plugins support a given playlist and ranks those plugins
• provides configuration settings to the playlist management layer to help it perform character encoding

Plugins

This layer consists of many playlist plugins that:

• rate themselves on their ability to support a particular playlist
• open and close playlist sessions when requested by the playlist management layer
• provide basic operations for navigating and retrieving information from playlists
• may provide more efficient methods for some navigation and seek operations