Pr/support multi thread

src/Box2D.NET.Samples/Primitives/TaskScheduler.cs

@@ -1,24 +1,81 @@
 // SPDX-FileCopyrightText: 2025 Ikpil Choi([email protected])
 // SPDX-License-Identifier: MIT
 
+using System;
+using System.Collections.Concurrent;
+using System.Threading;
+using System.Threading.Tasks;
+
 namespace Box2D.NET.Samples.Primitives;
 
 public class TaskScheduler
 {
+    private ConcurrentQueue<Task> _runningTasks;
+    private ConcurrentQueue<uint> _workers;
+    private SemaphoreSlim _semaphore;
+
+    private int _workerCount;
+
     public void Initialize(int workerCount)
     {
-        //Debug.Assert(false);
+        _workerCount = workerCount;
+        _semaphore = new SemaphoreSlim(workerCount);
+        _runningTasks = new ConcurrentQueue<Task>();
+        _workers = new ConcurrentQueue<uint>();
+        for (int i = 0; i < _workerCount; ++i)
+        {
+            _workers.Enqueue((uint)i);
+        }
     }
-    
+
     public void AddTaskSetToPipe(SampleTask task)
     {
-        task.m_task.Invoke(0, task.m_SetSize, 0, task.m_taskContext);
-        // !!
-        //Debug.Assert(false);
+        // single thread
+        if (1 >= _workerCount)
+        {
+            task.m_task.Invoke(0, task.m_SetSize, 0, task.m_taskContext);
+            return;
+        }
+
+        uint loop = 0;
+        int index = 0;
+        int remain = task.m_SetSize;
+        int minRange = task.m_MinRange;
+        while (0 < remain)
+        {
+            var stepCount = Math.Min(remain, minRange);
+            remain -= stepCount;
+
+            var startIndex = index;
+            var endIndex = startIndex + stepCount;
+
+            index = endIndex;
+
+            var running = Task.Run(async () =>
+            {
+                await _semaphore.WaitAsync();
+                _workers.TryDequeue(out uint workerIndex);
+                try
+                {
+                    task.m_task.Invoke(startIndex, endIndex, workerIndex, task.m_taskContext);
+                }
+                finally
+                {
+                    _workers.Enqueue(workerIndex);
+                    _semaphore.Release();
+                }
+            });
+
+            _runningTasks.Enqueue(running);
+        }
     }
 
     public void WaitforTask(SampleTask task)
     {
-        //Debug.Assert(false);
+        // wait!
+        while (_runningTasks.TryDequeue(out var runningTask))
+        {
+            runningTask.Wait();
+        }
     }
-}
+}