Only update RFC 1123 once per second

Text only changes once per second; not fastest and allocates but moves
it out of hot path

Author: benaadams

experimental/ManagedRIOHttpServer/Program.cs

@@ -273,9 +273,8 @@ static async Task ServeSocket(RIOTcpConnection socket)
                         break;
                     }
 
-                    var date = DateTime.UtcNow.ToString("r");
-                    Encoding.UTF8.GetBytes(date, 0, dateBytes.Length, dateBytes, 0);
-
+                    SetDateBytes(dateBytes);
+                    
                     for (var i = 1; i < count; i++)
                     {
                         socket.QueueSend(headerBuffer, false);
@@ -300,28 +299,46 @@ static async Task ServeSocket(RIOTcpConnection socket)
                 socket.Close();
             }
         }
+        
+        // Number of 100ns ticks per time unit
+        private const long TicksPerMillisecond = 10000;
+        private const long TicksPerSecond = TicksPerMillisecond * 1000;
+        private long _lastSeconds = 0L;
+        private void SetDateBytes(byte[] dateBytes)
+        {
+            var now = DateTime.UtcNow;
+            var ticks = now.Ticks / TicksPerSecond;
+            if (_lastSeconds == ticks) return;
+            _lastSeconds = ticks;
 
+            var date = now.ToString("r");
+            Encoding.ASCII.GetBytes(date, 0, dateBytes.Length, dateBytes, 0);
+        }
 
-        public static void LowerCaseSIMD(byte[] data)
-        {
-            var A = new Vector<byte>(65); // A
-            var Z = new Vector<byte>(90); // Z
+        //public static void LowerCaseSIMD(ArraySegment<byte> data)
+        //{
+        //    if (data.Offset + data.Count + Vector<byte>.Count < data.Array.Length)
+        //    {
+        //        throw new ArgumentOutOfRangeException("Nope");
+        //    }
+        //    var A = new Vector<byte>(65); // A
+        //    var Z = new Vector<byte>(90); // Z
 
-            for (var o = 0; o < data.Length - Vector<byte>.Count; o += Vector<byte>.Count)
-            {
-                var v = new Vector<byte>(data, o);
-
-                v = Vector.ConditionalSelect(
-                    Vector.BitwiseAnd(
-                        Vector.GreaterThanOrEqual(v, A),
-                        Vector.LessThanOrEqual(v, Z)
-                    ),
-                    Vector.BitwiseOr(new Vector<byte>(0x20), v), // 0010 0000
-                    v
-                );
-                v.CopyTo(data, o);
-            }
-        }
+        //    for (var o = data.Offset; o < data.Count - Vector<byte>.Count; o += Vector<byte>.Count)
+        //    {
+        //        var v = new Vector<byte>(data.Array, o);
+
+        //        v = Vector.ConditionalSelect(
+        //            Vector.BitwiseAnd(
+        //                Vector.GreaterThanOrEqual(v, A),
+        //                Vector.LessThanOrEqual(v, Z)
+        //            ),
+        //            Vector.BitwiseOr(new Vector<byte>(0x20), v), // 0010 0000
+        //            v
+        //        );
+        //        v.CopyTo(data.Array, o);
+        //    }
+        //}
     }
 
 }