From e2a0ed548d64a0b2bd32bf0fdc847b7a91411313 Mon Sep 17 00:00:00 2001
From: Serge Camille <sergecamille@gmail.com>
Date: Sat, 12 Sep 2020 21:33:53 +0200
Subject: [PATCH] Unify async read request header building.

Add concept of DataRequestItem which contains the necessary data to build the request.
---
 S7.Net/DataRequestItem.cs | 42 +++++++++++++++++++++++++++++++++++++++
 S7.Net/PLCHelpers.cs      |  6 +++---
 S7.Net/PlcAsynchronous.cs | 37 ++++++++++++++++------------------
 3 files changed, 62 insertions(+), 23 deletions(-)
 create mode 100644 S7.Net/DataRequestItem.cs

diff --git a/S7.Net/DataRequestItem.cs b/S7.Net/DataRequestItem.cs
new file mode 100644
index 0000000..6b27c85
--- /dev/null
+++ b/S7.Net/DataRequestItem.cs
@@ -0,0 +1,42 @@
+
+using S7.Net.Types;
+
+namespace S7.Net
+{
+    internal class DataRequestItem
+    {
+        public DataRequestItem(DataType dataType, int db, int startByteAddress, int byteLength)
+        {
+            DataType = dataType;
+            DB = db;
+            StartByteAddress = startByteAddress;
+            ByteLength = byteLength;
+        }
+
+        public DataRequestItem(DataItem dataItem)
+            : this(dataItem.DataType, dataItem.DB, dataItem.StartByteAdr, Plc.VarTypeToByteLength(dataItem.VarType, dataItem.Count))
+        {
+
+        }
+
+        /// <summary>
+        /// Memory area to read 
+        /// </summary>
+        public DataType DataType { get; }
+
+        /// <summary>
+        /// Address of memory area to read (example: for DB1 this value is 1, for T45 this value is 45)
+        /// </summary>
+        public int DB { get; }
+
+        /// <summary>
+        /// Address of the first byte to read
+        /// </summary>
+        public int StartByteAddress { get; }
+
+        /// <summary>
+        /// Length of data to read
+        /// </summary>
+        public int ByteLength { get; }
+    }
+}
diff --git a/S7.Net/PLCHelpers.cs b/S7.Net/PLCHelpers.cs
index f2c757d..949fcd3 100644
--- a/S7.Net/PLCHelpers.cs
+++ b/S7.Net/PLCHelpers.cs
@@ -14,7 +14,7 @@ namespace S7.Net
         /// </summary>
         /// <param name="amount"></param>
         /// <returns></returns>
-        private void BuildHeaderPackage(System.IO.MemoryStream stream, int amount = 1)
+        private static void BuildHeaderPackage(System.IO.MemoryStream stream, int amount = 1)
         {
             //header size = 19 bytes
             stream.WriteByteArray(new byte[] { 0x03, 0x00 });
@@ -37,7 +37,7 @@ namespace S7.Net
         /// <param name="startByteAdr">Start address of the byte</param>
         /// <param name="count">Number of bytes to be read</param>
         /// <returns></returns>
-        private void BuildReadDataRequestPackage(System.IO.MemoryStream stream, DataType dataType, int db, int startByteAdr, int count = 1)
+        private static void BuildReadDataRequestPackage(System.IO.MemoryStream stream, DataType dataType, int db, int startByteAdr, int count = 1)
         {
             //single data req = 12
             stream.WriteByteArray(new byte[] { 0x12, 0x0a, 0x10 });
@@ -176,7 +176,7 @@ namespace S7.Net
         /// <param name="varType"></param>
         /// <param name="varCount"></param>
         /// <returns>Byte lenght of variable</returns>
-        private int VarTypeToByteLength(VarType varType, int varCount = 1)
+        internal static int VarTypeToByteLength(VarType varType, int varCount = 1)
         {
             switch (varType)
             {
diff --git a/S7.Net/PlcAsynchronous.cs b/S7.Net/PlcAsynchronous.cs
index fd3e6fd..8f33940 100644
--- a/S7.Net/PlcAsynchronous.cs
+++ b/S7.Net/PlcAsynchronous.cs
@@ -262,20 +262,10 @@ namespace S7.Net
 
             try
             {
-                // first create the header
-                int packageSize = 19 + (dataItems.Count * 12);
-                var package = new System.IO.MemoryStream(packageSize);
-                BuildHeaderPackage(package, dataItems.Count);
-                // package.Add(0x02);  // datenart
-                foreach (var dataItem in dataItems)
-                {
-                    BuildReadDataRequestPackage(package, dataItem.DataType, dataItem.DB, dataItem.StartByteAdr, VarTypeToByteLength(dataItem.VarType, dataItem.Count));
-                }
-
-                var dataToSend = package.ToArray();
+                var dataToSend = BuildReadRequestPackage(dataItems.Select(d=> new DataRequestItem(d)).ToList());
                 await stream.WriteAsync(dataToSend, 0, dataToSend.Length);
 
-                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken); //TODO use Async
+                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
 
                 ParseDataIntoDataItems(s7data, dataItems);
@@ -295,6 +285,20 @@ namespace S7.Net
             return dataItems;
         }
 
+        private static byte[] BuildReadRequestPackage(IList<DataRequestItem> dataItems)
+        {                
+            // first create the header
+            int packageSize = 19 + (dataItems.Count * 12);
+            var package = new System.IO.MemoryStream(packageSize);
+            BuildHeaderPackage(package, dataItems.Count);
+            // package.Add(0x02);  // datenart
+            foreach (var dataItem in dataItems)
+            {
+                BuildReadDataRequestPackage(package, dataItem.DataType, dataItem.DB, dataItem.StartByteAddress, dataItem.ByteLength);
+            }
+            return package.ToArray();
+        }
+
         /// <summary>
         /// Write a number of bytes from a DB starting from a specified index. This handles more than 200 bytes with multiple requests.
         /// If the write was not successful, check LastErrorCode or LastErrorString.
@@ -444,14 +448,7 @@ namespace S7.Net
         {
             var stream = GetStreamIfAvailable();
 
-            // first create the header
-            int packageSize = 31; 
-            var package = new System.IO.MemoryStream(packageSize);
-            BuildHeaderPackage(package);
-            // package.Add(0x02);  // datenart
-            BuildReadDataRequestPackage(package, dataType, db, startByteAdr, count);
-
-            var dataToSend = package.ToArray();
+            var dataToSend = BuildReadRequestPackage(new [] { new DataRequestItem(dataType, db, startByteAdr, count)});
             await stream.WriteAsync(dataToSend, 0, dataToSend.Length, cancellationToken);
 
             var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken);