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Assets/Mirror/Core/Tools/Extensions.cs

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+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using UnityEngine;
+
+namespace Mirror
+{
+    public static class Extensions
+    {
+        public static string ToHexString(this ArraySegment<byte> segment) =>
+            BitConverter.ToString(segment.Array, segment.Offset, segment.Count);
+
+        // string.GetHashCode is not guaranteed to be the same on all
+        // machines, but we need one that is the same on all machines.
+        // Uses fnv1a as hash function for more uniform distribution http://www.isthe.com/chongo/tech/comp/fnv/
+        // Tests: https://softwareengineering.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed
+        // NOTE: Do not call this from hot path because it's slow O(N) for long method names.
+        // - As of 2012-02-16 There are 2 design-time callers (weaver) and 1 runtime caller that caches.
+        public static int GetStableHashCode(this string text)
+        {
+            unchecked
+            {
+                uint hash = 0x811c9dc5;
+                uint prime = 0x1000193;
+
+                for (int i = 0; i < text.Length; ++i)
+                {
+                    byte value = (byte)text[i];
+                    hash = hash ^ value;
+                    hash *= prime;
+                }
+
+                //UnityEngine.Debug.Log($"Created stable hash {(ushort)hash} for {text}");
+                return (int)hash;
+            }
+        }
+
+        // smaller version of our GetStableHashCode.
+        // careful, this significantly increases chance of collisions.
+        public static ushort GetStableHashCode16(this string text)
+        {
+            // deterministic hash
+            int hash = GetStableHashCode(text);
+
+            // Gets the 32bit fnv1a hash
+            // To get it down to 16bit but still reduce hash collisions we cant just cast it to ushort
+            // Instead we take the highest 16bits of the 32bit hash and fold them with xor into the lower 16bits
+            // This will create a more uniform 16bit hash, the method is described in:
+            // http://www.isthe.com/chongo/tech/comp/fnv/ in section "Changing the FNV hash size - xor-folding"
+            return (ushort)((hash >> 16) ^ hash);
+        }
+
+        // previously in DotnetCompatibility.cs
+        // leftover from the UNET days. supposedly for windows store?
+        internal static string GetMethodName(this Delegate func)
+        {
+#if NETFX_CORE
+            return func.GetMethodInfo().Name;
+#else
+            return func.Method.Name;
+#endif
+        }
+
+        // helper function to copy to List<T>
+        // C# only provides CopyTo(T[])
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void CopyTo<T>(this IEnumerable<T> source, List<T> destination)
+        {
+            // foreach allocates. use AddRange.
+            destination.AddRange(source);
+        }
+
+#if !UNITY_2021_OR_NEWER
+        // Unity 2020 and earlier don't have Queue.TryDequeue which we need for batching.
+        public static bool TryDequeue<T>(this Queue<T> source, out T element)
+        {
+            if (source.Count > 0)
+            {
+                element = source.Dequeue();
+                return true;
+            }
+
+            element = default;
+            return false;
+        }
+#endif
+
+#if !UNITY_2021_OR_NEWER
+        // Unity 2020 and earlier don't have ConcurrentQueue.Clear which we need for ThreadedTransport.
+        public static void Clear<T>(this ConcurrentQueue<T> source)
+        {
+            // while count > 0 risks deadlock if other thread write at the same time.
+            // our safest solution is a best-effort approach to clear 'Count' once.
+            int count = source.Count; // get it only once
+            for (int i = 0; i < count; ++i)
+            {
+                source.TryDequeue(out _);
+            }
+        }
+#endif
+
+#if !UNITY_2021_3_OR_NEWER
+        // Unity 2021.2 and earlier don't have transform.GetPositionAndRotation which we use for performance in some places
+        public static void GetPositionAndRotation(this Transform transform, out Vector3 position, out Quaternion rotation)
+        {
+            position = transform.position;
+            rotation = transform.rotation;
+        }
+#endif
+    }
+}