1 files changed, 228 insertions, 0 deletions
diff --git a/src/Ryujinx.Common/PreciseSleep/NanosleepPool.cs b/src/Ryujinx.Common/PreciseSleep/NanosleepPool.cs
new file mode 100644
index 00000000..c0973dcb
--- /dev/null
+++ b/src/Ryujinx.Common/PreciseSleep/NanosleepPool.cs
@@ -0,0 +1,228 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.Versioning;
+using System.Threading;
+
+namespace Ryujinx.Common.PreciseSleep
+{
+    /// <summary>
+    /// A pool of threads used to allow "interruptable" nanosleep for a single target event.
+    /// </summary>
+    [SupportedOSPlatform("macos")]
+    [SupportedOSPlatform("linux")]
+    [SupportedOSPlatform("android")]
+    [SupportedOSPlatform("ios")]
+    internal class NanosleepPool : IDisposable
+    {
+        public const int MaxThreads = 8;
+
+        /// <summary>
+        /// A thread that nanosleeps and may signal an event on wake.
+        /// When a thread is assigned a nanosleep to perform, it also gets a signal ID.
+        /// The pool's target event is only signalled if this ID matches the latest dispatched one.
+        /// </summary>
+        private class NanosleepThread : IDisposable
+        {
+            private static readonly long _timePointEpsilon;
+
+            static NanosleepThread()
+            {
+                _timePointEpsilon = PerformanceCounter.TicksPerMillisecond / 100; // 0.01ms
+            }
+
+            private readonly Thread _thread;
+            private readonly NanosleepPool _parent;
+            private readonly AutoResetEvent _newWaitEvent;
+            private bool _running = true;
+
+            private long _signalId;
+            private long _nanoseconds;
+            private long _timePoint;
+
+            public long SignalId => _signalId;
+
+            /// <summary>
+            /// Creates a new NanosleepThread for a parent pool, with a specified thread ID.
+            /// </summary>
+            /// <param name="parent">Parent NanosleepPool</param>
+            /// <param name="id">Thread ID</param>
+            public NanosleepThread(NanosleepPool parent, int id)
+            {
+                _parent = parent;
+                _newWaitEvent = new(false);
+
+                _thread = new Thread(Loop)
+                {
+                    Name = $"Common.Nanosleep.{id}",
+                    Priority = ThreadPriority.AboveNormal,
+                    IsBackground = true
+                };
+
+                _thread.Start();
+            }
+
+            /// <summary>
+            /// Service requests to perform a nanosleep, signal parent pool when complete.
+            /// </summary>
+            private void Loop()
+            {
+                _newWaitEvent.WaitOne();
+
+                while (_running)
+                {
+                    Nanosleep.Sleep(_nanoseconds);
+
+                    _parent.Signal(this);
+                    _newWaitEvent.WaitOne();
+                }
+
+                _newWaitEvent.Dispose();
+            }
+
+            /// <summary>
+            /// Assign a nanosleep for this thread to perform, then signal at the end.
+            /// </summary>
+            /// <param name="nanoseconds">Nanoseconds to sleep</param>
+            /// <param name="signalId">Signal ID</param>
+            /// <param name="timePoint">Target timepoint</param>
+            public void SleepAndSignal(long nanoseconds, long signalId, long timePoint)
+            {
+                _signalId = signalId;
+                _nanoseconds = nanoseconds;
+                _timePoint = timePoint;
+                _newWaitEvent.Set();
+            }
+
+            /// <summary>
+            /// Resurrect an active nanosleep's signal if its target timepoint is a close enough match.
+            /// </summary>
+            /// <param name="signalId">New signal id to assign the nanosleep</param>
+            /// <param name="timePoint">Target timepoint</param>
+            /// <returns>True if resurrected, false otherwise</returns>
+            public bool Resurrect(long signalId, long timePoint)
+            {
+                if (Math.Abs(timePoint - _timePoint) < _timePointEpsilon)
+                {
+                    _signalId = signalId;
+
+                    return true;
+                }
+
+                return false;
+            }
+
+            /// <summary>
+            /// Dispose the NanosleepThread, interrupting its worker loop.
+            /// </summary>
+            public void Dispose()
+            {
+                if (_running)
+                {
+                    _running = false;
+                    _newWaitEvent.Set();
+                }
+            }
+        }
+
+        private readonly object _lock = new();
+        private readonly List<NanosleepThread> _threads = new();
+        private readonly List<NanosleepThread> _active = new();
+        private readonly Stack<NanosleepThread> _free = new();
+        private readonly AutoResetEvent _signalTarget;
+
+        private long _signalId;
+
+        /// <summary>
+        /// Creates a new NanosleepPool with a target event to signal when a nanosleep completes.
+        /// </summary>
+        /// <param name="signalTarget">Event to signal when nanosleeps complete</param>
+        public NanosleepPool(AutoResetEvent signalTarget)
+        {
+            _signalTarget = signalTarget;
+        }
+
+        /// <summary>
+        /// Signal the target event (if the source sleep has not been superseded)
+        /// and free the nanosleep thread.
+        /// </summary>
+        /// <param name="thread">Nanosleep thread that completed</param>
+        private void Signal(NanosleepThread thread)
+        {
+            lock (_lock)
+            {
+                _active.Remove(thread);
+                _free.Push(thread);
+
+                if (thread.SignalId == _signalId)
+                {
+                    _signalTarget.Set();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Sleep for the given number of nanoseconds and signal the target event.
+        /// This does not block the caller thread.
+        /// </summary>
+        /// <param name="nanoseconds">Nanoseconds to sleep</param>
+        /// <param name="timePoint">Target timepoint</param>
+        /// <returns>True if the signal will be set, false otherwise</returns>
+        public bool SleepAndSignal(long nanoseconds, long timePoint)
+        {
+            lock (_lock)
+            {
+                _signalId++;
+
+                // Check active sleeps, if any line up with the requested timepoint then resurrect that nanosleep.
+                foreach (NanosleepThread existing in _active)
+                {
+                    if (existing.Resurrect(_signalId, timePoint))
+                    {
+                        return true;
+                    }
+                }
+
+                if (!_free.TryPop(out NanosleepThread thread))
+                {
+                    if (_threads.Count >= MaxThreads)
+                    {
+                        return false;
+                    }
+
+                    thread = new NanosleepThread(this, _threads.Count);
+
+                    _threads.Add(thread);
+                }
+
+                _active.Add(thread);
+
+                thread.SleepAndSignal(nanoseconds, _signalId, timePoint);
+
+                return true;
+            }
+        }
+
+        /// <summary>
+        /// Ignore the latest nanosleep.
+        /// </summary>
+        public void IgnoreSignal()
+        {
+            _signalId++;
+        }
+
+        /// <summary>
+        /// Dispose the NanosleepPool, disposing all of its active threads.
+        /// </summary>
+        public void Dispose()
+        {
+            GC.SuppressFinalize(this);
+
+            foreach (NanosleepThread thread in _threads)
+            {
+                thread.Dispose();
+            }
+
+            _threads.Clear();
+        }
+    }
+}