Remove allocations during bass device sync polling operation

osu.Framework.Tests/Audio/AudioManagerWithDeviceLoss.cs

@@ -1,7 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using ManagedBass;
 using osu.Framework.Audio;
@@ -40,12 +40,20 @@ protected override bool InitBass(int device)
             }
         }
 
-        protected override IEnumerable<DeviceInfo> EnumerateAllDevices()
+        protected override bool CheckForDeviceChanges(ImmutableArray<DeviceInfo> previousDevices)
         {
-            var devices = base.EnumerateAllDevices();
+            if (simulateLoss)
+                return true;
+
+            return base.CheckForDeviceChanges(previousDevices);
+        }
+
+        protected override ImmutableArray<DeviceInfo> GetAllDevices()
+        {
+            var devices = base.GetAllDevices();
 
             if (simulateLoss)
-                devices = devices.Take(BASS_INTERNAL_DEVICE_COUNT);
+                devices = devices.Take(BASS_INTERNAL_DEVICE_COUNT).ToImmutableArray();
 
             return devices;
         }

osu.Framework/Audio/AudioManager.cs

@@ -137,15 +137,14 @@ public class AudioManager : AudioCollectionManager<AudioComponent>
                                          Bass.CurrentDevice != Bass.DefaultDevice;
 
         // Mutated by multiple threads, must be thread safe.
-        private ImmutableList<DeviceInfo> audioDevices = ImmutableList<DeviceInfo>.Empty;
+        private ImmutableArray<DeviceInfo> audioDevices = ImmutableArray<DeviceInfo>.Empty;
         private ImmutableList<string> audioDeviceNames = ImmutableList<string>.Empty;
 
         private Scheduler scheduler => thread.Scheduler;
 
         private Scheduler eventScheduler => EventScheduler ?? scheduler;
 
         private readonly CancellationTokenSource cancelSource = new CancellationTokenSource();
-        private readonly DeviceInfoUpdateComparer updateComparer = new DeviceInfoUpdateComparer();
 
         /// <summary>
         /// The scheduler used for invoking publicly exposed delegate events.
@@ -208,7 +207,8 @@ public AudioManager(AudioThread audioThread, ResourceStore<byte[]> trackStore, R
                     {
                         try
                         {
-                            syncAudioDevices();
+                            if (CheckForDeviceChanges(audioDevices))
+                                syncAudioDevices();
                             Thread.Sleep(1000);
                         }
                         catch
@@ -427,17 +427,10 @@ protected virtual bool InitBass(int device)
 
         private void syncAudioDevices()
         {
-            // audioDevices are updated if:
-            // - A new device is added
-            // - An existing device is Enabled/Disabled or set as Default
-            var updatedAudioDevices = EnumerateAllDevices().ToImmutableList();
-            if (audioDevices.SequenceEqual(updatedAudioDevices, updateComparer))
-                return;
-
-            audioDevices = updatedAudioDevices;
+            audioDevices = GetAllDevices();
 
             // Bass should always be providing "No sound" and "Default" device.
-            Trace.Assert(audioDevices.Count >= BASS_INTERNAL_DEVICE_COUNT, "Bass did not provide any audio devices.");
+            Trace.Assert(audioDevices.Length >= BASS_INTERNAL_DEVICE_COUNT, "Bass did not provide any audio devices.");
 
             var oldDeviceNames = audioDeviceNames;
             var newDeviceNames = audioDeviceNames = audioDevices.Skip(BASS_INTERNAL_DEVICE_COUNT).Where(d => d.IsEnabled).Select(d => d.Name).ToImmutableList();
@@ -459,11 +452,50 @@ private void syncAudioDevices()
             }
         }
 
-        protected virtual IEnumerable<DeviceInfo> EnumerateAllDevices()
+        /// <summary>
+        /// Check whether any audio device changes have occurred.
+        ///
+        /// Changes supported are:
+        /// - A new device is added
+        /// - An existing device is Enabled/Disabled or set as Default
+        /// </summary>
+        /// <remarks>
+        /// This method is optimised to incur the lowest overhead possible.
+        /// </remarks>
+        /// <param name="previousDevices">The previous audio devices array.</param>
+        /// <returns>Whether a change was detected.</returns>
+        protected virtual bool CheckForDeviceChanges(ImmutableArray<DeviceInfo> previousDevices)
         {
             int deviceCount = Bass.DeviceCount;
+
+            if (previousDevices.Length != deviceCount)
+                return true;
+
             for (int i = 0; i < deviceCount; i++)
-                yield return Bass.GetDeviceInfo(i);
+            {
+                var prevInfo = previousDevices[i];
+
+                Bass.GetDeviceInfo(i, out var info);
+
+                if (info.IsEnabled != prevInfo.IsEnabled)
+                    return true;
+
+                if (info.IsDefault != prevInfo.IsDefault)
+                    return true;
+            }
+
+            return false;
+        }
+
+        protected virtual ImmutableArray<DeviceInfo> GetAllDevices()
+        {
+            int deviceCount = Bass.DeviceCount;
+
+            var devices = ImmutableArray.CreateBuilder<DeviceInfo>(deviceCount);
+            for (int i = 0; i < deviceCount; i++)
+                devices.Add(Bass.GetDeviceInfo(i));
+
+            return devices.MoveToImmutable();
         }
 
         // The current device is considered valid if it is enabled, initialized, and not a fallback device.
@@ -479,12 +511,5 @@ public override string ToString()
             string deviceName = audioDevices.ElementAtOrDefault(Bass.CurrentDevice).Name;
             return $@"{GetType().ReadableName()} ({deviceName ?? "Unknown"})";
         }
-
-        private class DeviceInfoUpdateComparer : IEqualityComparer<DeviceInfo>
-        {
-            public bool Equals(DeviceInfo x, DeviceInfo y) => x.IsEnabled == y.IsEnabled && x.IsDefault == y.IsDefault;
-
-            public int GetHashCode(DeviceInfo obj) => obj.Name.GetHashCode();
-        }
     }
 }

osu.Framework/Input/Bindings/KeyCombination.cs

@@ -644,7 +644,9 @@ public static KeyCombination FromInputState(InputState state, Vector2? scrollDel
 
             Debug.Assert(!keys.Contains(InputKey.None)); // Having None in pressed keys will break IsPressed
             keys.Sort();
-            return new KeyCombination(keys.ToImmutable());
+
+            // Can't use `MoveToImmutable` here as we don't provide accurate capacity.
+            return new KeyCombination(keys.ToImmutableList());
         }
     }
 

osu.Framework/Platform/SDL2Window_Windowing.cs

@@ -341,7 +341,7 @@ private static ImmutableArray<Display> getSDLDisplays()
                     Logger.Log($"Failed to retrieve SDL display at index ({i})", level: LogLevel.Error);
             }
 
-            return builder.ToImmutable();
+            return builder.MoveToImmutable();
         }
 
         private static bool tryGetDisplayFromSDL(int displayIndex, [NotNullWhen(true)] out Display? display)