Retired Document

Important: This sample code may not represent best practices for current development. The project may use deprecated symbols and illustrate technologies and techniques that are no longer recommended.

SampleHardwarePlugIn

Last Revision:	Version 1.0, 2009-04-15 Project that uses the API for the CFPlugIn that implements an audio driver for the HAL from user space
Build Requirements:	Mac OS X v10.6 or later
Runtime Requirements:	Mac OS X v10.6 or later

This is the CFPlugIn interface presented by a HAL plug-in. The HAL will create only one instance of each interface. This instance is responsible for providing all required services on behalf of as many devices of the kind it implements.

The Initialize method is called to allow the plug-in to set itself up. At this time any devices of it's kind and their streams can be presented to the system using AudioHardwareDevicesCreated() and AudioHardwareStreamsCreated(). The plug-in is also responsible for managing it's own notifications, and may install any CFRunLoopSources it needs using AudioHardwareAddRunLoopSource() at this time as well. Teardown() is called when the HAL is unloading itself and the plug-in should dispose of any devices and streams it has created using AudioHardwareDevicesDied() and AudioHardareStreamsDied().

The rest of the methods in this interface correspond to the semantics of their similarly named counterparts in <CoreAudio/AudioHardware.h>. The HAL basically passes these calls directly to the plug-in in this fashion. Plug-ins do not have to manage device or stream property listener procs. Instead, a plug-in can call AudioHardwareDevicePropertyChanged() or AudioHardwareStreamPropertyChanged() and the HAL will take care of calling all the appropriate listeners.

Note that only version 4 or later plug-ins will be loaded into 64 bit processes.