Interface of pa_core

From pulsecore/core.h: "The core structure of PulseAudio. Every PulseAudio daemon contains exactly one of these. It is used for storing kind of global variables for the daemon."

pa_core doesn't have any interesting functions associated with it, it is just a central collection of all the components and globally relevant variables. You're not supposed to modify the fields, at least not directly.

Actually, in addition to being a variable collection, there is two interesting enumerations too.

The most important field is perhaps mainloop. That can be used for communicating with the daemon mainloop, see DaemonMainloop.

struct pa_core

parent

pa_core is a subclass of pa_msgobject, which implies that the first field of pa_core is of type pa_msgobject. It means also that pa_core can receive messages, see "The unnamed enumeration" later on this page. At some point in the future I may write a page about the ObjectSystem? used inside PulseAudio. I think MsgobjectAPI? would be useful too.

cookie

A random value which may be used to identify this instance of PulseAudio. Not cryptographically secure in any way.

mainloop

Pointer to the mainloop API.

clients

Currently connected clients. If you're not familiar with the pa_idxset type, see the header.

sinks, sources

Currently existing sinks and sources.

sink_inputs, source_outputs

Currently existing sink inputs and source outputs.

modules

Loaded modules.

scache

The sample cache. The contained items are of type pa_scache_entry.

autoload_idxset

The contained items are of type pa_autoload_entry, and specify what modules should be loaded on demand.

namereg

All sink, source and sample names are stored in this hashmap. The hashmap ensures the uniqueness of the names. This is accessed through the namereg interface.

autoload_hashmap

Same as autoload_idxset, but indexable with the module name, also ensures module name uniqueness.

properties

Modules can share variables through the property system, and this is the data store for those variables. See the property system interface.

default_source_name, default_sink_name

Pretty self-explanatory, but do not access these directly, but through pa_namereg_set_default, pa_namereg_get_default_sink_name and pa_namereg_get_default_source_name that are defined in pulsecore/namereg.h.

default_sample_spec

When in need of a default format for an audio stream, you'll find it here.

default_n_fragments, default_fragment_size_msec

The default buffering settings that should be used by sinks and sources when opening a hardware device.

module_auto_unload_event

The module system uses this to poll for modules that should be unloaded. Not for you.

module_defer_unload_event

The module system uses this to make mainloop unload modules. Not for you.

subscription_defer_event

The subscription system uses this to make mainloop inform the subscribers about an event. Not for you. (What subscription system? See CatchingEvents?.)

subscriptions

Head of the list of existing subscriptions. Not for you.

subscription_event_queue

Head of the list of unprocessed events. Not for you.

subsrciption_event_last

Last item of the list of unprocessed events. Not for you.

mempool

The memory pool. You may need this as an argument to some functions.

exit_idle_time

The time in seconds between the moment the last client has left and the moment pulseaudio exits, if automatic exiting is used.

module_idle_time

The time in seconds between the moment the last client has stopped using a module and the moment the module gets unloaded, if the module is set to be automatically unloaded.

scache_idle_time

The time in seconds between the moment a sample has been fired last time and the moment the that the sample gets unloaded, if the sample is loaded as "lazy".

quit_event

If the daemon is told to exit after a period of idleness, it uses this to track the idle time. Not for you.

scache_auto_unload_event

The sample cache uses this to track the time that the lazy samples have been unused. Not for you.

disallow_module_loading

Controls whether modules can be loaded (and unloaded) or not.

running_as_daemon

If pulseaudio is daemonized, this is one, otherwise zero.

resample_method

The resample method that the user has chosen.

is_system_instance

This indicates whether pulseaudio is running as a per-user or a system-wide daemon.

high_priority

One, if pulseaudio has made itself a high-priority process (i.e. is running with the SCHED_FIFO scheduling class), zero otherwise.

hooks

The hooks that can be used to catch events in core, see CatchingEvents?.

enum pa_core_hook

The enumeration contains all the events that can be catched synchronously, see CatchingEvents?.

The unnamed enumeration

There's this enumeration, that has only two elements: PA_CORE_MESSAGE_UNLOAD_MODULE and PA_CORE_MESSAGE_MAX. It contains all the messages that can be sent from outside the daemon mainloop thread to the core, and currently there is only one such message.

PA_CORE_MESSAGE_UNLOAD_MODULE causes a module (give the pointer as userdata to pa_asyncmsgq_post) to get unloaded. The difference between using this message and calling pa_module_unload_request() is that the latter may only be called using the daemon mainloop, the message can be sent from other threads.

For information on how to use the inter-thread message passing system, see MessagingSystem?, or while waiting for that to materialize, try ThreadingModel.

Functions and macros

As mentioned earlier, the functions pa_core has associated with it, are not interesting for module writers. I'll list them here anyway for completeness's sake.

pa_core_new

Creates a new core that will use the given mainloop. The parameter shared is a boolean indicating whether the created mempool should be shared or not.

pa_core_check_quit

Updates the quit_event field, called by the client system when clients come and leave.

PA_DECLARE_CLASS(pa_core) in the header causes the following functions to become available (they are explained in the ObjectSystem? page):

pa_core_isinstance

pa_core_cast

pa_core_ref

pa_core_unref

pa_core_refcnt

pa_core_assert_ref

And then there is the PA_CORE macro, that is just an alias for pa_core_cast.