1 files changed, 220 insertions, 0 deletions
diff --git a/src/Ryujinx.Common/PreciseSleep/WindowsGranularTimer.cs b/src/Ryujinx.Common/PreciseSleep/WindowsGranularTimer.cs
new file mode 100644
index 00000000..a0de1634
--- /dev/null
+++ b/src/Ryujinx.Common/PreciseSleep/WindowsGranularTimer.cs
@@ -0,0 +1,220 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+using System.Threading;
+
+namespace Ryujinx.Common.SystemInterop
+{
+    /// <summary>
+    /// Timer that attempts to align with the hardware timer interrupt,
+    /// and can alert listeners on ticks.
+    /// </summary>
+    [SupportedOSPlatform("windows")]
+    internal partial class WindowsGranularTimer
+    {
+        private const int MinimumGranularity = 5000;
+
+        private static readonly WindowsGranularTimer _instance = new();
+        public static WindowsGranularTimer Instance => _instance;
+
+        private readonly struct WaitingObject
+        {
+            public readonly long Id;
+            public readonly EventWaitHandle Signal;
+            public readonly long TimePoint;
+
+            public WaitingObject(long id, EventWaitHandle signal, long timePoint)
+            {
+                Id = id;
+                Signal = signal;
+                TimePoint = timePoint;
+            }
+        }
+
+        [LibraryImport("ntdll.dll", SetLastError = true)]
+        private static partial int NtSetTimerResolution(int DesiredResolution, [MarshalAs(UnmanagedType.Bool)] bool SetResolution, out int CurrentResolution);
+
+        [LibraryImport("ntdll.dll", SetLastError = true)]
+        private static partial int NtQueryTimerResolution(out int MaximumResolution, out int MinimumResolution, out int CurrentResolution);
+
+        [LibraryImport("ntdll.dll", SetLastError = true)]
+        private static partial uint NtDelayExecution([MarshalAs(UnmanagedType.Bool)] bool Alertable, ref long DelayInterval);
+
+        public long GranularityNs => _granularityNs;
+        public long GranularityTicks => _granularityTicks;
+
+        private readonly Thread _timerThread;
+        private long _granularityNs = MinimumGranularity * 100L;
+        private long _granularityTicks;
+        private long _lastTicks = PerformanceCounter.ElapsedTicks;
+        private long _lastId;
+
+        private readonly object _lock = new();
+        private readonly List<WaitingObject> _waitingObjects = new();
+
+        private WindowsGranularTimer()
+        {
+            _timerThread = new Thread(Loop)
+            {
+                IsBackground = true,
+                Name = "Common.WindowsTimer",
+                Priority = ThreadPriority.Highest
+            };
+
+            _timerThread.Start();
+        }
+
+        /// <summary>
+        /// Measure and initialize the timer's target granularity.
+        /// </summary>
+        private void Initialize()
+        {
+            NtQueryTimerResolution(out _, out int min, out int curr);
+
+            if (min > 0)
+            {
+                min = Math.Max(min, MinimumGranularity);
+
+                _granularityNs = min * 100L;
+                NtSetTimerResolution(min, true, out _);
+            }
+            else
+            {
+                _granularityNs = curr * 100L;
+            }
+
+            _granularityTicks = (_granularityNs * PerformanceCounter.TicksPerMillisecond) / 1_000_000;
+        }
+
+        /// <summary>
+        /// Main loop for the timer thread. Wakes every clock tick and signals any listeners,
+        /// as well as keeping track of clock alignment.
+        /// </summary>
+        private void Loop()
+        {
+            Initialize();
+            while (true)
+            {
+                long delayInterval = -1; // Next tick
+                NtSetTimerResolution((int)(_granularityNs / 100), true, out _);
+                NtDelayExecution(false, ref delayInterval);
+
+                long newTicks = PerformanceCounter.ElapsedTicks;
+                long nextTicks = newTicks + _granularityTicks;
+
+                lock (_lock)
+                {
+                    for (int i = 0; i < _waitingObjects.Count; i++)
+                    {
+                        if (nextTicks > _waitingObjects[i].TimePoint)
+                        {
+                            // The next clock tick will be after the timepoint, we need to signal now.
+                            _waitingObjects[i].Signal.Set();
+
+                            _waitingObjects.RemoveAt(i--);
+                        }
+                    }
+
+                    _lastTicks = newTicks;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Sleep until a timepoint.
+        /// </summary>
+        /// <param name="evt">Reset event to use to be awoken by the clock tick, or an external signal</param>
+        /// <param name="timePoint">Target timepoint</param>
+        /// <returns>True if waited or signalled, false otherwise</returns>
+        public bool SleepUntilTimePoint(AutoResetEvent evt, long timePoint)
+        {
+            if (evt.WaitOne(0))
+            {
+                return true;
+            }
+
+            long id;
+
+            lock (_lock)
+            {
+                // Return immediately if the next tick is after the requested timepoint.
+                long nextTicks = _lastTicks + _granularityTicks;
+
+                if (nextTicks > timePoint)
+                {
+                    return false;
+                }
+
+                id = ++_lastId;
+
+                _waitingObjects.Add(new WaitingObject(id, evt, timePoint));
+            }
+
+            evt.WaitOne();
+
+            lock (_lock)
+            {
+                for (int i = 0; i < _waitingObjects.Count; i++)
+                {
+                    if (id == _waitingObjects[i].Id)
+                    {
+                        _waitingObjects.RemoveAt(i--);
+                        break;
+                    }
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Sleep until a timepoint, but don't expect any external signals.
+        /// </summary>
+        /// <remarks>
+        /// Saves some effort compared to the sleep that expects to be signalled.
+        /// </remarks>
+        /// <param name="evt">Reset event to use to be awoken by the clock tick</param>
+        /// <param name="timePoint">Target timepoint</param>
+        /// <returns>True if waited, false otherwise</returns>
+        public bool SleepUntilTimePointWithoutExternalSignal(EventWaitHandle evt, long timePoint)
+        {
+            long id;
+
+            lock (_lock)
+            {
+                // Return immediately if the next tick is after the requested timepoint.
+                long nextTicks = _lastTicks + _granularityTicks;
+
+                if (nextTicks > timePoint)
+                {
+                    return false;
+                }
+
+                id = ++_lastId;
+
+                _waitingObjects.Add(new WaitingObject(id, evt, timePoint));
+            }
+
+            evt.WaitOne();
+
+            return true;
+        }
+
+        /// <summary>
+        /// Returns the two nearest clock ticks for a given timepoint.
+        /// </summary>
+        /// <param name="timePoint">Target timepoint</param>
+        /// <returns>The nearest clock ticks before and after the given timepoint</returns>
+        public (long, long) ReturnNearestTicks(long timePoint)
+        {
+            long last = _lastTicks;
+            long delta = timePoint - last;
+
+            long lowTicks = delta / _granularityTicks;
+            long highTicks = (delta + _granularityTicks - 1) / _granularityTicks;
+
+            return (last + lowTicks * _granularityTicks, last + highTicks * _granularityTicks);
+        }
+    }
+}