UTC时间读写简化

src/JT809.Protocol/MessagePack/JT809MessagePackReader.cs

@@ -391,14 +391,7 @@ namespace JT809.Protocol.MessagePack
             DateTime d;
             try
             {
-                ulong result = 0;
-                var readOnlySpan = GetReadOnlySpan(8);
-                for (int i = 0; i < 8; i++)
-                {
-                    ulong currentData = (ulong)readOnlySpan[i] << (8 * (8 - i - 1));
-                    result += currentData;
-                }
-                d = JT809Constants.UTCBaseTime.AddSeconds(result).AddHours(8);
+                d = JT809Constants.UTCBaseTime.AddSeconds(ReadUInt64()).AddHours(8);
             }
             catch (Exception)
             {

src/JT809.Protocol/MessagePack/JT809MessagePackWriter.cs

@@ -229,18 +229,7 @@ namespace JT809.Protocol.MessagePack
             span[4] = (byte)(value.Millisecond);
             writer.Advance(5);
         }
-        public void WriteUTCDateTime(DateTime value)
-        {
-            ulong totalSecends = (ulong)(value.AddHours(-8) - JT809Constants.UTCBaseTime).TotalSeconds;
-            var span = writer.Free;
-            //高位在前
-            for (int i = 7; i >= 0; i--)
-            {
-                span[i] = (byte)(totalSecends & 0xFF);  //取低8位
-                totalSecends >>= 8;
-            }
-            writer.Advance(8);
-        }
+        public void WriteUTCDateTime(DateTime value)=>WriteUInt64((ulong)(value.AddHours(-8) - JT809Constants.UTCBaseTime).TotalSeconds);
         /// <summary>
         /// YYYYMMDD
         /// </summary>