+ astar project

1 files changed, 28 insertions, 0 deletions

diff --git a/Other/AstarPathfindingDemo/Packages/com.arongranberg.astar/Utilities/SpinLock.cs b/Other/AstarPathfindingDemo/Packages/com.arongranberg.astar/Utilities/SpinLock.cs
new file mode 100644
index 0000000..88b9092
--- /dev/null
+++ b/Other/AstarPathfindingDemo/Packages/com.arongranberg.astar/Utilities/SpinLock.cs
@@ -0,0 +1,28 @@
+using System.Threading;
+
+namespace Pathfinding.Jobs {
+	/// <summary>
+	/// Spin lock which can be used in Burst.
+	/// Good when the lock is generally uncontested.
+	/// Very inefficient when the lock is contested.
+	/// </summary>
+	public struct SpinLock {
+		private volatile int locked;
+
+		public void Lock () {
+			while (Interlocked.CompareExchange(ref locked, 1, 0) != 0)
+				Unity.Burst.Intrinsics.Common.Pause(); // spin
+
+			// We need to ensure that any optimizer does not reorder loads to before we aquire the lock.
+			System.Threading.Thread.MemoryBarrier();
+		}
+
+		public void Unlock () {
+			// We need a memory barrier to ensure that all writes are visible to other threads, before we unlock.
+			// We also need to ensure that any optimizer does not reorder stores to after the unlock.
+			System.Threading.Thread.MemoryBarrier();
+			// Release the lock by writing 0 to it. Use atomics to make it immediately visible to other threads.
+			if (Interlocked.Exchange(ref locked, 0) == 0) throw new System.InvalidOperationException("Trying to unlock a lock which is not locked");
+		}
+	}
+}