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Swan/Diagnostics/RealtimeClock.cs

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+namespace Swan.Diagnostics
+{
+    using System;
+    using System.Diagnostics;
+    using Threading;
+
+    /// <summary>
+    /// A time measurement artifact.
+    /// </summary>
+    internal sealed class RealTimeClock : IDisposable
+    {
+        private readonly Stopwatch _chrono = new Stopwatch();
+        private ISyncLocker? _locker = SyncLockerFactory.Create(useSlim: true);
+        private long _offsetTicks;
+        private double _speedRatio = 1.0d;
+        private bool _isDisposed;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RealTimeClock"/> class.
+        /// The clock starts paused and at the 0 position.
+        /// </summary>
+        public RealTimeClock()
+        {
+            Reset();
+        }
+
+        /// <summary>
+        /// Gets or sets the clock position.
+        /// </summary>
+        public TimeSpan Position
+        {
+            get
+            {
+                using (_locker?.AcquireReaderLock())
+                {
+                    return TimeSpan.FromTicks(
+                        _offsetTicks + Convert.ToInt64(_chrono.Elapsed.Ticks * SpeedRatio));
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the clock is running.
+        /// </summary>
+        public bool IsRunning
+        {
+            get
+            {
+                using (_locker?.AcquireReaderLock())
+                {
+                    return _chrono.IsRunning;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the speed ratio at which the clock runs.
+        /// </summary>
+        public double SpeedRatio
+        {
+            get
+            {
+                using (_locker?.AcquireReaderLock())
+                {
+                    return _speedRatio;
+                }
+            }
+            set
+            {
+                using (_locker?.AcquireWriterLock())
+                {
+                    if (value < 0d) value = 0d;
+
+                    // Capture the initial position se we set it even after the Speed Ratio has changed
+                    // this ensures a smooth position transition
+                    var initialPosition = Position;
+                    _speedRatio = value;
+                    Update(initialPosition);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Sets a new position value atomically.
+        /// </summary>
+        /// <param name="value">The new value that the position property will hold.</param>
+        public void Update(TimeSpan value)
+        {
+            using (_locker?.AcquireWriterLock())
+            {
+                var resume = _chrono.IsRunning;
+                _chrono.Reset();
+                _offsetTicks = value.Ticks;
+                if (resume) _chrono.Start();
+            }
+        }
+
+        /// <summary>
+        /// Starts or resumes the clock.
+        /// </summary>
+        public void Play()
+        {
+            using (_locker?.AcquireWriterLock())
+            {
+                if (_chrono.IsRunning) return;
+                _chrono.Start();
+            }
+        }
+
+        /// <summary>
+        /// Pauses the clock.
+        /// </summary>
+        public void Pause()
+        {
+            using (_locker?.AcquireWriterLock())
+            {
+                _chrono.Stop();
+            }
+        }
+
+        /// <summary>
+        /// Sets the clock position to 0 and stops it.
+        /// The speed ratio is not modified.
+        /// </summary>
+        public void Reset()
+        {
+            using (_locker?.AcquireWriterLock())
+            {
+                _offsetTicks = 0;
+                _chrono.Reset();
+            }
+        }
+
+        /// <inheritdoc />
+        public void Dispose()
+        {
+            if (_isDisposed) return;
+            _isDisposed = true;
+            _locker?.Dispose();
+            _locker = null;
+        }
+    }
+}