2014-08-01 update 6 Add comment

NA200H/ModBus.Net/ProtocalLinkerBytesExtend.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ModBus.Net
+{
+    /// <summary>
+    /// 协议字节伸缩
+    /// </summary>
+    public abstract class ProtocalLinkerBytesExtend
+    {
+        /// <summary>
+        /// 协议扩展，协议内容发送前调用
+        /// </summary>
+        /// <param name="content">扩展前的原始协议内容</param>
+        /// <returns>扩展后的协议内容</returns>
+        public abstract byte[] BytesExtend(byte[] content);
+
+        /// <summary>
+        /// 协议收缩，协议内容接收后调用
+        /// </summary>
+        /// <param name="content">收缩前的完整协议内容</param>
+        /// <returns>收缩后的协议内容</returns>
+        public abstract byte[] BytesDecact(byte[] content);
+    }
+    
+    /// <summary>
+    /// Tcp协议字节伸缩
+    /// </summary>
+    public class ModbusTcpProtocalLinkerBytesExtend : ProtocalLinkerBytesExtend
+    {
+        public override byte[] BytesExtend(byte[] content)
+        {
+            //Modbus/Tcp协议扩张，前面加6个字节，前面4个为0，后面两个为协议整体内容的长度
+            byte[] newFormat = new byte[6 + content.Length];
+            int tag = 0;
+            ushort leng = (ushort)content.Length;
+            Array.Copy(ValueHelper.Instance.GetBytes(tag), 0, newFormat, 0, 4);
+            Array.Copy(ValueHelper.Instance.GetBytes(leng), 0, newFormat, 4, 2);
+            Array.Copy(content, 0, newFormat, 6, content.Length);
+            return newFormat;
+        }
+
+        public override byte[] BytesDecact(byte[] content)
+        {
+            //Modbus/Tcp协议收缩，抛弃前面6个字节的内容
+            byte[] newContent = new byte[content.Length - 6];
+            Array.Copy(content, 6, newContent, 0, newContent.Length);
+            return newContent;
+        }
+    }
+}