From a774694be0e64179cf6c193430d57d31b5658ff9 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 23 Oct 2023 22:01:05 -0400
Subject: [PATCH] pulseaudio: Simplified default device change detection code.
This reduces allocations, simplifies some code, and makes it quick to decide
from the hotplug thread if there was _actually_ a device change.
---
src/audio/pulseaudio/SDL_pulseaudio.c | 86 +++++++++++++++------------
1 file changed, 48 insertions(+), 38 deletions(-)
diff --git a/src/audio/pulseaudio/SDL_pulseaudio.c b/src/audio/pulseaudio/SDL_pulseaudio.c
index 6aef52928b93..6dab00028630 100644
--- a/src/audio/pulseaudio/SDL_pulseaudio.c
+++ b/src/audio/pulseaudio/SDL_pulseaudio.c
@@ -54,10 +54,12 @@ static SDL_Thread *pulseaudio_hotplug_thread = NULL;
static SDL_AtomicInt pulseaudio_hotplug_thread_active;
// These are the OS identifiers (i.e. ALSA strings)...these are allocated in a callback
-// when the default changes, and claimed/free'd by the hotplug thread when it alerts SDL
+// when the default changes, and noticed by the hotplug thread when it alerts SDL
// to the change.
static char *default_sink_path = NULL;
static char *default_source_path = NULL;
+static Uint32 default_sink_hash = 0;
+static Uint32 default_source_hash = 0;
static const char *(*PULSEAUDIO_pa_get_library_version)(void);
@@ -804,11 +806,28 @@ static void SourceInfoCallback(pa_context *c, const pa_source_info *i, int is_la
static void ServerInfoCallback(pa_context *c, const pa_server_info *i, void *data)
{
//SDL_Log("PULSEAUDIO ServerInfoCallback!");
- SDL_free(default_sink_path);
- default_sink_path = SDL_strdup(i->default_sink_name);
- SDL_free(default_source_path);
- default_source_path = SDL_strdup(i->default_source_name);
+ Uint32 hash; // just hash the strings so we can decide if this is different without having to manage a string copy.
+
+ hash = SDL_HashString(i->default_sink_name, NULL);
+ if (hash != default_sink_hash) {
+ char *str = SDL_strdup(i->default_sink_name);
+ if (str) {
+ SDL_free(default_sink_path);
+ default_sink_path = str;
+ default_sink_hash = hash;
+ }
+ }
+
+ hash = SDL_HashString(i->default_source_name, NULL);
+ if (hash != default_source_hash) {
+ char *str = SDL_strdup(i->default_source_name);
+ if (str) {
+ SDL_free(default_source_path);
+ default_source_path = str;
+ default_source_hash = hash;
+ }
+ }
PULSEAUDIO_pa_threaded_mainloop_signal(pulseaudio_threaded_mainloop, 0);
}
@@ -857,14 +876,12 @@ static void HotplugCallback(pa_context *c, pa_subscription_event_type_t t, uint3
PULSEAUDIO_pa_threaded_mainloop_signal(pulseaudio_threaded_mainloop, 0);
}
-static void CheckDefaultDevice(char **pnew_device)
+static void CheckDefaultDevice(char *new_device_path, Uint32 *prev_hash, Uint32 new_hash)
{
- char *new_device = *pnew_device;
- if (new_device) {
- SDL_AudioDevice *device = SDL_FindPhysicalAudioDeviceByCallback(FindAudioDeviceByPath, new_device);
+ if (new_device_path && (*prev_hash != new_hash)) {
+ SDL_AudioDevice *device = SDL_FindPhysicalAudioDeviceByCallback(FindAudioDeviceByPath, new_device_path);
if (device) { // if NULL, we might still be waiting for a SinkInfoCallback or something, we'll try later.
- SDL_free(new_device); // done with this, free it.
- *pnew_device = NULL;
+ *prev_hash = new_hash;
SDL_DefaultAudioDeviceChanged(device);
}
}
@@ -873,6 +890,8 @@ static void CheckDefaultDevice(char **pnew_device)
// this runs as a thread while the Pulse target is initialized to catch hotplug events.
static int SDLCALL HotplugThread(void *data)
{
+ Uint32 prev_default_sink_hash = default_sink_hash;
+ Uint32 prev_default_source_hash = default_source_hash;
pa_operation *op;
SDL_SetThreadPriority(SDL_THREAD_PRIORITY_LOW);
@@ -892,28 +911,26 @@ static int SDLCALL HotplugThread(void *data)
}
// Update default devices; don't hold the pulse lock during this, since it could deadlock vs a playing device that we're about to lock here.
- char *new_default_sink = default_sink_path;
- char *new_default_source = default_source_path;
+ char *current_default_sink = default_sink_path;
+ char *current_default_source = default_source_path;
default_sink_path = default_source_path = NULL; // make sure we own these before releasing the lock.
+ const Uint32 current_default_sink_hash = default_sink_hash;
+ const Uint32 current_default_source_hash = default_source_hash;
PULSEAUDIO_pa_threaded_mainloop_unlock(pulseaudio_threaded_mainloop);
- CheckDefaultDevice(&new_default_sink);
- CheckDefaultDevice(&new_default_source);
+ CheckDefaultDevice(current_default_sink, &prev_default_sink_hash, current_default_sink_hash);
+ CheckDefaultDevice(current_default_source, &prev_default_source_hash, current_default_source_hash);
PULSEAUDIO_pa_threaded_mainloop_lock(pulseaudio_threaded_mainloop);
- if (new_default_sink) { // couldn't find this device, try again later.
- if (default_sink_path) {
- SDL_free(new_default_sink); // uhoh, something else became default while we were unlocked. Dump ours.
- } else {
- default_sink_path = new_default_sink; // put string back to try again later.
- }
+ if (default_sink_path) {
+ SDL_free(current_default_sink); // uhoh, something else became default while we were unlocked. Dump ours.
+ } else {
+ default_sink_path = current_default_sink; // put string back for later.
}
- if (new_default_source) { // couldn't find this device, try again later.
- if (default_source_path) {
- SDL_free(new_default_source); // uhoh, something else became default while we were unlocked. Dump ours.
- } else {
- default_source_path = new_default_source; // put string back to try again later.
- }
+ if (default_source_path) {
+ SDL_free(current_default_source); // uhoh, something else became default while we were unlocked. Dump ours.
+ } else {
+ default_source_path = current_default_source; // put string back for later.
}
}
@@ -936,17 +953,8 @@ static void PULSEAUDIO_DetectDevices(SDL_AudioDevice **default_output, SDL_Audio
WaitForPulseOperation(PULSEAUDIO_pa_context_get_source_info_list(pulseaudio_context, SourceInfoCallback, NULL));
PULSEAUDIO_pa_threaded_mainloop_unlock(pulseaudio_threaded_mainloop);
- if (default_sink_path) {
- *default_output = SDL_FindPhysicalAudioDeviceByCallback(FindAudioDeviceByPath, default_sink_path);
- SDL_free(default_sink_path);
- default_sink_path = NULL;
- }
-
- if (default_source_path) {
- *default_capture = SDL_FindPhysicalAudioDeviceByCallback(FindAudioDeviceByPath, default_source_path);
- SDL_free(default_source_path);
- default_source_path = NULL;
- }
+ *default_output = SDL_FindPhysicalAudioDeviceByCallback(FindAudioDeviceByPath, default_sink_path);
+ *default_capture = SDL_FindPhysicalAudioDeviceByCallback(FindAudioDeviceByPath, default_source_path);
// ok, we have a sane list, let's set up hotplug notifications now...
SDL_AtomicSet(&pulseaudio_hotplug_thread_active, 1);
@@ -980,8 +988,10 @@ static void PULSEAUDIO_Deinitialize(void)
SDL_free(default_sink_path);
default_sink_path = NULL;
+ default_sink_hash = 0;
SDL_free(default_source_path);
default_source_path = NULL;
+ default_source_hash = 0;
UnloadPulseAudioLibrary();
}