mirror of
https://gitlab.freedesktop.org/pulseaudio/pulseaudio.git
synced 2025-11-12 13:30:10 -05:00
99 lines
3 KiB
C
99 lines
3 KiB
C
|
#ifndef foopulsecoreaupdatehfoo
|
||
|
|
#define foopulsecoreaupdatehfoo
|
||
|
|
|
||
|
|
/***
|
||
|
|
This file is part of PulseAudio.
|
||
|
|
|
||
|
|
Copyright 2009 Lennart Poettering
|
||
|
|
|
||
|
|
PulseAudio is free software; you can redistribute it and/or modify
|
||
|
|
it under the terms of the GNU Lesser General Public License as
|
||
|
|
published by the Free Software Foundation; either version 2.1 of the
|
||
|
|
License, or (at your option) any later version.
|
||
|
|
|
||
|
|
PulseAudio is distributed in the hope that it will be useful, but
|
||
|
|
WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
|
|
General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU Lesser General Public
|
||
|
|
License along with PulseAudio; if not, write to the Free Software
|
||
|
|
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
|
||
|
|
USA.
|
||
|
|
***/
|
||
|
|
|
||
|
|
typedef struct pa_aupdate pa_aupdate;
|
||
|
|
|
||
|
|
pa_aupdate *pa_aupdate_new(void);
|
||
|
|
void pa_aupdate_free(pa_aupdate *a);
|
||
|
|
|
||
|
|
/* Will return 0, or 1, depending on which copy of the data the caller
|
||
|
|
* should look at */
|
||
|
|
unsigned pa_aupdate_read_begin(pa_aupdate *a);
|
||
|
|
void pa_aupdate_read_end(pa_aupdate *a);
|
||
|
|
|
||
|
|
/* Will return 0, or 1, depending which copy of the data the caller
|
||
|
|
* should modify */
|
||
|
|
unsigned pa_aupdate_write_begin(pa_aupdate *a);
|
||
|
|
void pa_aupdate_write_end(pa_aupdate *a);
|
||
|
|
|
||
|
|
/* Will return 0, or 1, depending which copy of the data the caller
|
||
|
|
* should modify. Each time called this will return the opposite of
|
||
|
|
* the previous pa_aupdate_write_begin()/pa_aupdate_write_swap()
|
||
|
|
* call. Should only be called between pa_aupdate_write_begin() and
|
||
|
|
* pa_aupdate_write_end() */
|
||
|
|
unsigned pa_aupdate_write_swap(pa_aupdate *a);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* This infrastructure allows lock-free updates of arbitrary data
|
||
|
|
* structures in an rcu'ish way: two copies of the data structure
|
||
|
|
* should be exisiting. One side ('the reader') has read access to one
|
||
|
|
* of the two data structure at a time. It does not have to lock it,
|
||
|
|
* however it needs to signal that it is using it/stopped using
|
||
|
|
* it. The other side ('the writer') modifes the second data structure,
|
||
|
|
* and then atomically swaps the two data structures, followed by a
|
||
|
|
* modification of the other one.
|
||
|
|
*
|
||
|
|
* This is intended to be used for cases where the reader side needs
|
||
|
|
* to be fast while the writer side can be slow.
|
||
|
|
*
|
||
|
|
* The reader side is signal handler safe.
|
||
|
|
*
|
||
|
|
* The writer side lock is not recursive. The reader side is.
|
||
|
|
*
|
||
|
|
* There may be multiple readers and multiple writers at the same
|
||
|
|
* time.
|
||
|
|
*
|
||
|
|
* Usage is like this:
|
||
|
|
*
|
||
|
|
* static struct foo bar[2];
|
||
|
|
* static pa_aupdate *a;
|
||
|
|
*
|
||
|
|
* reader() {
|
||
|
|
* unsigned j;
|
||
|
|
*
|
||
|
|
* j = pa_update_read_begin(a);
|
||
|
|
*
|
||
|
|
* ... read the data structure bar[j] ...
|
||
|
|
*
|
||
|
|
* pa_update_read_end(a);
|
||
|
|
* }
|
||
|
|
*
|
||
|
|
* writer() {
|
||
|
|
* unsigned j;
|
||
|
|
*
|
||
|
|
* j = pa_update_write_begin(a);
|
||
|
|
*
|
||
|
|
* ... update the data structure bar[j] ...
|
||
|
|
*
|
||
|
|
* j = pa_update_write_swap(a);
|
||
|
|
*
|
||
|
|
* ... update the data structure bar[j], the same way as above ...
|
||
|
|
*
|
||
|
|
* pa_update_write_end(a)
|
||
|
|
* }
|
||
|
|
*
|
||
|
|
*/
|
||
|
|
|
||
|
|
#endif
|