(61d00a474) v0.9.7.1

2020-03-04 13:04:10 +01:00
parent 3c50efa5c9
commit 3c09ebe02f
5086 changed files with 786063 additions and 295871 deletions
@@ -0,0 +1,80 @@
+using System;
+using System.Diagnostics;
+
+namespace Barotrauma.Networking
+{
+    /// <summary>
+    /// Helper class for dealing with 16-bit IDs that wrap around ushort.MaxValue
+    /// </summary>
+    static class NetIdUtils
+    {
+        /// <summary>
+        /// Is newID more recent than oldID
+        /// </summary>
+        public static bool IdMoreRecent(ushort newID, ushort oldID)
+        {
+            uint id1 = newID;
+            uint id2 = oldID;
+
+            return
+                (id1 > id2) && (id1 - id2 <= ushort.MaxValue / 2)
+                   ||
+                (id2 > id1) && (id2 - id1 > ushort.MaxValue / 2);
+        }
+
+        public static ushort Clamp(ushort id, ushort min, ushort max)
+        {
+            if (IdMoreRecent(min, max))
+            {
+                throw new ArgumentException($"Min cannot be larger than max ({min}, {max})");
+            }
+
+            if (!IdMoreRecent(id, min))
+            {
+                return min;
+            }
+            else if (IdMoreRecent(id, max))
+            {
+                return max;
+            }
+
+            return id;
+        }
+
+        /// <summary>
+        /// Is the current ID valid given the previous ID and latest possible ID (not smaller than the previous ID or larger than the latest ID)
+        /// </summary>
+        public static bool IsValidId(ushort currentId, ushort previousId, ushort latestPossibleId)
+        {
+            //cannot be valid if more recent than the latest Id
+            if (IdMoreRecent(currentId, latestPossibleId)) { return false; }
+
+            //normally the id needs to be more recent than the previous id,
+            //but there's a special case when the previous id was 0:
+            //  if a client reconnects mid-round and tries to jump from the unitialized state (0) back to some previous high id (> ushort.MaxValue / 2),
+            //  this would normally get interpreted as trying to jump backwards, but in this case we'll allow it
+            return IdMoreRecent(currentId, previousId) || (previousId == 0 && currentId > ushort.MaxValue / 2);
+        }
+
+#if DEBUG
+        public static void Test()
+        {
+            Debug.Assert(IdMoreRecent((ushort)2, (ushort)1));
+            Debug.Assert(IdMoreRecent((ushort)2, (ushort)(ushort.MaxValue - 5)));
+            Debug.Assert(!IdMoreRecent((ushort)ushort.MaxValue, (ushort)5));
+
+            Debug.Assert(Clamp((ushort)5, (ushort)1, (ushort)10) == 5);
+            Debug.Assert(Clamp((ushort)(ushort.MaxValue - 5), (ushort)(ushort.MaxValue - 2), (ushort)3) == (ushort)(ushort.MaxValue - 2));
+
+            Debug.Assert(IsValidId((ushort)10, (ushort)1, (ushort)10));
+            Debug.Assert(!IsValidId((ushort)11, (ushort)1, (ushort)10));
+
+            Debug.Assert(IsValidId((ushort)1, (ushort)(ushort.MaxValue - 5), (ushort)10));
+            Debug.Assert(!IsValidId((ushort)(ushort.MaxValue - 6), (ushort)(ushort.MaxValue - 5), (ushort)10));
+
+            Debug.Assert(IsValidId((ushort)0, (ushort)ushort.MaxValue - 100, (ushort)ushort.MaxValue));
+            Debug.Assert(!IsValidId((ushort)(ushort.MaxValue - 101), (ushort)ushort.MaxValue - 100, (ushort)ushort.MaxValue));
+        }
+#endif
+    }
+}