From d530f1e4226faa22330c8ff34cec51c5c14e038b Mon Sep 17 00:00:00 2001
From: Serge Camille <sergecamille@gmail.com>
Date: Tue, 18 Aug 2020 20:38:11 +0200
Subject: [PATCH] COTP TPDU: change byte array copy.

This removes the binary reader, and fixes too things:

1. Properly set the data length (previous implementation requested too much, but that did not matter with BinaryReader)
2. Start reading Data after HeaderLength+1 offset, not always at 3.
---
 S7.Net/COTP.cs | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/S7.Net/COTP.cs b/S7.Net/COTP.cs
index 79d60fb..c4af73a 100644
--- a/S7.Net/COTP.cs
+++ b/S7.Net/COTP.cs
@@ -1,7 +1,6 @@
 using System;
 using System.IO;
 using System.Threading.Tasks;
-using System.Linq;
 
 namespace S7.Net
 {
@@ -27,17 +26,17 @@ namespace S7.Net
             {
                 TPkt = tPKT;
 
-                var br = new BinaryReader(new MemoryStream(tPKT.Data));
-                HeaderLength = br.ReadByte();
+                HeaderLength = tPKT.Data[0]; // Header length excluding this length byte
                 if (HeaderLength >= 2)
                 {
-                    PDUType = br.ReadByte();
+                    PDUType = tPKT.Data[1];
                     if (PDUType == 0xf0) //DT Data
                     {
-                        var flags = br.ReadByte();
+                        var flags = tPKT.Data[2];
                         TPDUNumber = flags & 0x7F;
                         LastDataUnit = (flags & 0x80) > 0;
-                        Data = br.ReadBytes(tPKT.Length - HeaderLength - 4); //4 = TPKT Size
+                        Data = new byte[tPKT.Data.Length - HeaderLength - 1]; // substract header length byte + header length.
+                        Array.Copy(tPKT.Data, HeaderLength + 1, Data, 0, Data.Length);
                         return;
                     }
                     //TODO: Handle other PDUTypes