Merge pull request #485 from dylandrush/484_Public_PLCExceptions

Made all exceptions public

GitVersion.yml

@@ -1,21 +0,0 @@
-assembly-informational-format: '{NuGetVersion}'
-mode: ContinuousDeployment
-branches:
-  master:
-    tag: rc
-    increment: Minor
-  feature:
-    regex: features?[/-]
-    tag: rc-{BranchName}
-    increment: Minor
-  pull-request:
-    regex: (pull|pull\-requests|pr)[/-]
-    tag: rc-pr-{BranchName}
-    increment: Minor
-  hotfix:
-    regex: hotfix(es)?[/-]
-    tag: rc
-    increment: Patch
-  develop:
-    regex: dev(elop)?(ment)?$
-    tag: b

S7.Net.UnitTest/S7NetTestsAsync.cs

@@ -9,6 +9,11 @@ using System.Threading.Tasks;
 using System.Threading;
 using System.Security.Cryptography;
 
+
+#if NET5_0_OR_GREATER
+using System.Buffers;
+#endif
+
 #endregion
 
 /**
@@ -139,6 +144,33 @@ namespace S7.Net.UnitTest
             CollectionAssert.AreEqual(data, readData);
         }
 
+#if NET5_0_OR_GREATER
+
+        /// <summary>
+        /// Write/Read a large amount of data to test PDU max
+        /// </summary>
+        [TestMethod]
+        public async Task Test_Async_WriteLargeByteArrayWithMemory()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            var randomEngine = new Random();
+            using var dataOwner = MemoryPool<byte>.Shared.Rent(8192);
+            var data = dataOwner.Memory.Slice(0, 8192);
+            var db = 2;
+            randomEngine.NextBytes(data.Span);
+
+            await plc.WriteBytesAsync(DataType.DataBlock, db, 0, data);
+
+            using var readDataOwner = MemoryPool<byte>.Shared.Rent(data.Length);
+            var readData = readDataOwner.Memory.Slice(0, data.Length);
+            await plc.ReadBytesAsync(readData, DataType.DataBlock, db, 0);
+
+            CollectionAssert.AreEqual(data.ToArray(), readData.ToArray());
+        }
+
+#endif
+
         /// <summary>
         /// Read/Write a class that has the same properties of a DB with the same field in the same order
         /// </summary>
@@ -933,6 +965,31 @@ namespace S7.Net.UnitTest
             }
         }
 
+#if NET5_0_OR_GREATER
+
+        [TestMethod]
+        public async Task Test_Async_ReadWriteBytesManyWithMemory()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            using var data = MemoryPool<byte>.Shared.Rent(2000);
+            for (int i = 0; i < data.Memory.Length; i++)
+                data.Memory.Span[i] = (byte)(i % 256);
+
+            await plc.WriteBytesAsync(DataType.DataBlock, 2, 0, data.Memory);
+
+            using var readData = MemoryPool<byte>.Shared.Rent(data.Memory.Length);
+
+            await plc.ReadBytesAsync(readData.Memory.Slice(0, data.Memory.Length), DataType.DataBlock, 2, 0);
+
+            for (int x = 0; x < data.Memory.Length; x++)
+            {
+                Assert.AreEqual(x % 256, readData.Memory.Span[x], string.Format("Bit {0} failed", x));
+            }
+        }
+
+#endif
+
         /// <summary>
         /// Write a large amount of data and test cancellation
         /// </summary>
@@ -969,6 +1026,47 @@ namespace S7.Net.UnitTest
             Console.WriteLine("Task was not cancelled as expected.");
         }
 
+#if NET5_0_OR_GREATER
+
+        /// <summary>
+        /// Write a large amount of data and test cancellation
+        /// </summary>
+        [TestMethod]
+        public async Task Test_Async_WriteLargeByteArrayWithCancellationWithMemory()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            var cancellationSource = new CancellationTokenSource();
+            var cancellationToken = cancellationSource.Token;
+
+            using var dataOwner = MemoryPool<byte>.Shared.Rent(8192);
+            var data = dataOwner.Memory.Slice(0, 8192);
+            var randomEngine = new Random();
+            var db = 2;
+            randomEngine.NextBytes(data.Span);
+
+            cancellationSource.CancelAfter(TimeSpan.FromMilliseconds(5));
+            try
+            {
+                await plc.WriteBytesAsync(DataType.DataBlock, db, 0, data, cancellationToken);
+            }
+            catch (OperationCanceledException)
+            {
+                // everything is good, that is the exception we expect
+                Console.WriteLine("Operation was cancelled as expected.");
+                return;
+            }
+            catch (Exception e)
+            {
+                Assert.Fail($"Wrong exception type received. Expected {typeof(OperationCanceledException)}, received {e.GetType()}.");
+            }
+
+            // Depending on how tests run, this can also just succeed without getting cancelled at all. Do nothing in this case.
+            Console.WriteLine("Task was not cancelled as expected.");
+        }
+
+#endif
+
         /// <summary>
         /// Write a large amount of data and test cancellation
         /// </summary>
@@ -1001,6 +1099,7 @@ namespace S7.Net.UnitTest
             };
             await plc.ReadMultipleVarsAsync(dataItems, CancellationToken.None);
         }
+
         #endregion
     }
 }

S7.Net.UnitTest/S7NetTestsSync.cs

@@ -7,6 +7,10 @@ using S7.Net.Types;
 using S7.UnitTest.Helpers;
 using System.Security.Cryptography;
 
+#if NET5_0_OR_GREATER
+using System.Buffers;
+#endif
+
 #endregion
 
 /**
@@ -778,6 +782,33 @@ namespace S7.Net.UnitTest
             CollectionAssert.AreEqual(data, readData);
         }
 
+#if NET5_0_OR_GREATER
+
+        /// <summary>
+        /// Write/Read a large amount of data to test PDU max
+        /// </summary>
+        [TestMethod]
+        public void T33_WriteLargeByteArrayWithSpan()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            var randomEngine = new Random();
+            using var dataOwner = MemoryPool<byte>.Shared.Rent(8192);
+            var data = dataOwner.Memory.Span.Slice(0, 8192);
+            var db = 2;
+            randomEngine.NextBytes(data);
+
+            plc.WriteBytes(DataType.DataBlock, db, 0, data);
+
+            using var readDataOwner = MemoryPool<byte>.Shared.Rent(data.Length);
+            var readData = readDataOwner.Memory.Span.Slice(0, data.Length);
+            plc.ReadBytes(readData, DataType.DataBlock, db, 0);
+
+            CollectionAssert.AreEqual(data.ToArray(), readData.ToArray());
+        }
+
+#endif
+
         [TestMethod, ExpectedException(typeof(PlcException))]
         public void T18_ReadStructThrowsIfPlcIsNotConnected()
         {
@@ -1006,6 +1037,32 @@ namespace S7.Net.UnitTest
             }
         }
 
+#if NET5_0_OR_GREATER
+
+        [TestMethod]
+        public void T27_ReadWriteBytesManyWithSpan()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            using var dataOwner = MemoryPool<byte>.Shared.Rent(2000);
+            var data = dataOwner.Memory.Span;
+            for (int i = 0; i < data.Length; i++)
+                data[i] = (byte)(i % 256);
+
+            plc.WriteBytes(DataType.DataBlock, 2, 0, data);
+
+            using var readDataOwner = MemoryPool<byte>.Shared.Rent(data.Length);
+            var readData = readDataOwner.Memory.Span.Slice(0, data.Length);
+            plc.ReadBytes(readData, DataType.DataBlock, 2, 0);
+
+            for (int x = 0; x < data.Length; x++)
+            {
+                Assert.AreEqual(x % 256, readData[x], $"Mismatch at offset {x}, expected {x % 256}, actual {readData[x]}.");
+            }
+        }
+
+#endif
+
         [TestMethod]
         public void T28_ReadClass_DoesntCrash_When_ReadingLessThan1Byte()
         {
@@ -1060,7 +1117,7 @@ namespace S7.Net.UnitTest
             Assert.AreEqual(test_value, test_value2, "Compare DateTimeLong Write/Read");
         }
 
-        #endregion
+#endregion
 
         #region Private methods
 

S7.Net/Helper/MemoryStreamExtension.cs

@@ -1,6 +1,10 @@
-
+using System;
+using System.Buffers;
+using System.IO;
+
 namespace S7.Net.Helper
 {
+#if !NET5_0_OR_GREATER
     internal static class MemoryStreamExtension
     {
         /// <summary>
@@ -10,9 +14,25 @@ namespace S7.Net.Helper
         /// </summary>
         /// <param name="stream"></param>
         /// <param name="value"></param>
-        public static void WriteByteArray(this System.IO.MemoryStream stream, byte[] value)
+        public static void Write(this MemoryStream stream, byte[] value)
         {
             stream.Write(value, 0, value.Length);
         }
+
+        /// <summary>
+        /// Helper function to write the whole content of the given byte span to a memory stream.
+        /// </summary>
+        /// <param name="stream"></param>
+        /// <param name="value"></param>
+        public static void Write(this MemoryStream stream, ReadOnlySpan<byte> value)
+        {
+            byte[] buffer = ArrayPool<byte>.Shared.Rent(value.Length);
+
+            value.CopyTo(buffer);
+            stream.Write(buffer, 0, value.Length);
+
+            ArrayPool<byte>.Shared.Return(buffer);
+        }
     }
+#endif
 }

S7.Net/PLCExceptions.cs

@@ -6,7 +6,7 @@ using System.Runtime.Serialization;
 
 namespace S7.Net
 {
-    internal class WrongNumberOfBytesException : Exception
+    public class WrongNumberOfBytesException : Exception
     {
         public WrongNumberOfBytesException() : base()
         {
@@ -27,7 +27,7 @@ namespace S7.Net
         #endif
     }
 
-    internal class InvalidAddressException : Exception
+    public class InvalidAddressException : Exception
     {
         public InvalidAddressException() : base ()
         {
@@ -48,7 +48,7 @@ namespace S7.Net
         #endif
     }
 
-    internal class InvalidVariableTypeException : Exception
+    public class InvalidVariableTypeException : Exception
     {
         public InvalidVariableTypeException() : base()
         {
@@ -69,7 +69,7 @@ namespace S7.Net
         #endif
     }
 
-    internal class TPKTInvalidException : Exception
+    public class TPKTInvalidException : Exception
     {
         public TPKTInvalidException() : base()
         {
@@ -90,7 +90,7 @@ namespace S7.Net
         #endif
     }
 
-    internal class TPDUInvalidException : Exception
+    public class TPDUInvalidException : Exception
     {
         public TPDUInvalidException() : base()
         {

S7.Net/PLCHelpers.cs

@@ -1,7 +1,6 @@
 using S7.Net.Helper;
 using S7.Net.Protocol.S7;
 using S7.Net.Types;
-using System;
 using System.Collections.Generic;
 using System.Linq;
 using DateTime = S7.Net.Types.DateTime;
@@ -18,13 +17,13 @@ namespace S7.Net
         private static void BuildHeaderPackage(System.IO.MemoryStream stream, int amount = 1)
         {
             //header size = 19 bytes
-            stream.WriteByteArray(new byte[] { 0x03, 0x00 });
+            stream.Write(new byte[] { 0x03, 0x00 });
             //complete package size
-            stream.WriteByteArray(Types.Int.ToByteArray((short)(19 + (12 * amount))));
-            stream.WriteByteArray(new byte[] { 0x02, 0xf0, 0x80, 0x32, 0x01, 0x00, 0x00, 0x00, 0x00 });
+            stream.Write(Int.ToByteArray((short)(19 + (12 * amount))));
+            stream.Write(new byte[] { 0x02, 0xf0, 0x80, 0x32, 0x01, 0x00, 0x00, 0x00, 0x00 });
             //data part size
-            stream.WriteByteArray(Types.Word.ToByteArray((ushort)(2 + (amount * 12))));
-            stream.WriteByteArray(new byte[] { 0x00, 0x00, 0x04 });
+            stream.Write(Word.ToByteArray((ushort)(2 + (amount * 12))));
+            stream.Write(new byte[] { 0x00, 0x00, 0x04 });
             //amount of requests
             stream.WriteByte((byte)amount);
         }
@@ -41,7 +40,7 @@ namespace S7.Net
         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 });
+            stream.Write(new byte[] { 0x12, 0x0a, 0x10 });
             switch (dataType)
             {
                 case DataType.Timer:
@@ -53,8 +52,8 @@ namespace S7.Net
                     break;
             }
 
-            stream.WriteByteArray(Word.ToByteArray((ushort)(count)));
-            stream.WriteByteArray(Word.ToByteArray((ushort)(db)));
+            stream.Write(Word.ToByteArray((ushort)(count)));
+            stream.Write(Word.ToByteArray((ushort)(db)));
             stream.WriteByte((byte)dataType);
             var overflow = (int)(startByteAdr * 8 / 0xffffU); // handles words with address bigger than 8191
             stream.WriteByte((byte)overflow);
@@ -62,10 +61,10 @@ namespace S7.Net
             {
                 case DataType.Timer:
                 case DataType.Counter:
-                    stream.WriteByteArray(Types.Word.ToByteArray((ushort)(startByteAdr)));
+                    stream.Write(Word.ToByteArray((ushort)(startByteAdr)));
                     break;
                 default:
-                    stream.WriteByteArray(Types.Word.ToByteArray((ushort)((startByteAdr) * 8)));
+                    stream.Write(Word.ToByteArray((ushort)((startByteAdr) * 8)));
                     break;
             }
         }

S7.Net/PlcAsynchronous.cs

@@ -95,7 +95,6 @@ namespace S7.Net
             MaxPDUSize = s7data[18] * 256 + s7data[19];
         }
 
-
         /// <summary>
         /// Reads a number of bytes from a DB starting from a specified index. This handles more than 200 bytes with multiple requests.
         /// If the read was not successful, check LastErrorCode or LastErrorString.
@@ -110,16 +109,34 @@ namespace S7.Net
         public async Task<byte[]> ReadBytesAsync(DataType dataType, int db, int startByteAdr, int count, CancellationToken cancellationToken = default)
         {
             var resultBytes = new byte[count];
+
+            await ReadBytesAsync(resultBytes, dataType, db, startByteAdr, cancellationToken).ConfigureAwait(false);
+
+            return resultBytes;
+        }
+
+        /// <summary>
+        /// Reads a number of bytes from a DB starting from a specified index. This handles more than 200 bytes with multiple requests.
+        /// If the read was not successful, check LastErrorCode or LastErrorString.
+        /// </summary>
+        /// <param name="buffer">Buffer to receive the read bytes. The <see cref="Memory{T}.Length"/> determines the number of bytes to read.</param>
+        /// <param name="dataType">Data type of the memory area, can be DB, Timer, Counter, Merker(Memory), Input, Output.</param>
+        /// <param name="db">Address of the memory area (if you want to read DB1, this is set to 1). This must be set also for other memory area types: counters, timers,etc.</param>
+        /// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is None.
+        /// Please note that cancellation is advisory/cooperative and will not lead to immediate cancellation in all cases.</param>
+        /// <returns>Returns the bytes in an array</returns>
+        public async Task ReadBytesAsync(Memory<byte> buffer, DataType dataType, int db, int startByteAdr, CancellationToken cancellationToken = default)
+        {
             int index = 0;
-            while (count > 0)
+            while (buffer.Length > 0)
             {
                 //This works up to MaxPDUSize-1 on SNAP7. But not MaxPDUSize-0.
-                var maxToRead = Math.Min(count, MaxPDUSize - 18);
-                await ReadBytesWithSingleRequestAsync(dataType, db, startByteAdr + index, resultBytes, index, maxToRead, cancellationToken).ConfigureAwait(false);
-                count -= maxToRead;
+                var maxToRead = Math.Min(buffer.Length, MaxPDUSize - 18);
+                await ReadBytesWithSingleRequestAsync(dataType, db, startByteAdr + index, buffer.Slice(0, maxToRead), cancellationToken).ConfigureAwait(false);
+                buffer = buffer.Slice(maxToRead);
                 index += maxToRead;
             }
-            return resultBytes;
         }
 
         /// <summary>
@@ -295,6 +312,21 @@ namespace S7.Net
             return dataItems;
         }
 
+        /// <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.
+        /// </summary>
+        /// <param name="dataType">Data type of the memory area, can be DB, Timer, Counter, Merker(Memory), Input, Output.</param>
+        /// <param name="db">Address of the memory area (if you want to read DB1, this is set to 1). This must be set also for other memory area types: counters, timers,etc.</param>
+        /// <param name="startByteAdr">Start byte address. If you want to write DB1.DBW200, this is 200.</param>
+        /// <param name="value">Bytes to write. If more than 200, multiple requests will be made.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is None.
+        /// Please note that cancellation is advisory/cooperative and will not lead to immediate cancellation in all cases.</param>
+        /// <returns>A task that represents the asynchronous write operation.</returns>
+        public Task WriteBytesAsync(DataType dataType, int db, int startByteAdr, byte[] value, CancellationToken cancellationToken = default)
+        {
+            return WriteBytesAsync(dataType, db, startByteAdr, value.AsMemory(), cancellationToken);
+        }
 
         /// <summary>
         /// Write a number of bytes from a DB starting from a specified index. This handles more than 200 bytes with multiple requests.
@@ -307,15 +339,14 @@ namespace S7.Net
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is None.
         /// Please note that cancellation is advisory/cooperative and will not lead to immediate cancellation in all cases.</param>
         /// <returns>A task that represents the asynchronous write operation.</returns>
-        public async Task WriteBytesAsync(DataType dataType, int db, int startByteAdr, byte[] value, CancellationToken cancellationToken = default)
+        public async Task WriteBytesAsync(DataType dataType, int db, int startByteAdr, ReadOnlyMemory<byte> value, CancellationToken cancellationToken = default)
         {
             int localIndex = 0;
-            int count = value.Length;
-            while (count > 0)
+            while (value.Length > 0)
             {
-                var maxToWrite = (int)Math.Min(count, MaxPDUSize - 35);
-                await WriteBytesWithASingleRequestAsync(dataType, db, startByteAdr + localIndex, value, localIndex, maxToWrite, cancellationToken).ConfigureAwait(false);
-                count -= maxToWrite;
+                var maxToWrite = (int)Math.Min(value.Length, MaxPDUSize - 35);
+                await WriteBytesWithASingleRequestAsync(dataType, db, startByteAdr + localIndex, value.Slice(0, maxToWrite), cancellationToken).ConfigureAwait(false);
+                value = value.Slice(maxToWrite);
                 localIndex += maxToWrite;
             }
         }
@@ -441,14 +472,14 @@ namespace S7.Net
             await WriteBytesAsync(DataType.DataBlock, db, startByteAdr, bytes, cancellationToken).ConfigureAwait(false);
         }
 
-        private async Task ReadBytesWithSingleRequestAsync(DataType dataType, int db, int startByteAdr, byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+        private async Task ReadBytesWithSingleRequestAsync(DataType dataType, int db, int startByteAdr, Memory<byte> buffer, CancellationToken cancellationToken)
         {
-            var dataToSend = BuildReadRequestPackage(new[] { new DataItemAddress(dataType, db, startByteAdr, count) });
+            var dataToSend = BuildReadRequestPackage(new[] { new DataItemAddress(dataType, db, startByteAdr, buffer.Length) });
 
             var s7data = await RequestTsduAsync(dataToSend, cancellationToken);
-            AssertReadResponse(s7data, count);
+            AssertReadResponse(s7data, buffer.Length);
 
-            Array.Copy(s7data, 18, buffer, offset, count);
+            s7data.AsSpan(18, buffer.Length).CopyTo(buffer.Span);
         }
 
         /// <summary>
@@ -477,11 +508,11 @@ namespace S7.Net
         /// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
         /// <param name="value">Bytes to write. The lenght of this parameter can't be higher than 200. If you need more, use recursion.</param>
         /// <returns>A task that represents the asynchronous write operation.</returns>
-        private async Task WriteBytesWithASingleRequestAsync(DataType dataType, int db, int startByteAdr, byte[] value, int dataOffset, int count, CancellationToken cancellationToken)
+        private async Task WriteBytesWithASingleRequestAsync(DataType dataType, int db, int startByteAdr, ReadOnlyMemory<byte> value, CancellationToken cancellationToken)
         {
             try
             {
-                var dataToSend = BuildWriteBytesPackage(dataType, db, startByteAdr, value, dataOffset, count);
+                var dataToSend = BuildWriteBytesPackage(dataType, db, startByteAdr, value.Span);
                 var s7data = await RequestTsduAsync(dataToSend, cancellationToken).ConfigureAwait(false);
 
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);

S7.Net/PlcSynchronous.cs

@@ -39,16 +39,32 @@ namespace S7.Net
         public byte[] ReadBytes(DataType dataType, int db, int startByteAdr, int count)
         {
             var result = new byte[count];
+
+            ReadBytes(result, dataType, db, startByteAdr);
+
+            return result;
+        }
+
+        /// <summary>
+        /// Reads a number of bytes from a DB starting from a specified index. This handles more than 200 bytes with multiple requests.
+        /// If the read was not successful, check LastErrorCode or LastErrorString.
+        /// </summary>
+        /// <param name="buffer">Buffer to receive the read bytes. The <see cref="Span{T}.Length"/> determines the number of bytes to read.</param>
+        /// <param name="dataType">Data type of the memory area, can be DB, Timer, Counter, Merker(Memory), Input, Output.</param>
+        /// <param name="db">Address of the memory area (if you want to read DB1, this is set to 1). This must be set also for other memory area types: counters, timers,etc.</param>
+        /// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
+        /// <returns>Returns the bytes in an array</returns>
+        public void ReadBytes(Span<byte> buffer, DataType dataType, int db, int startByteAdr)
+        {
             int index = 0;
-            while (count > 0)
+            while (buffer.Length > 0)
             {
                 //This works up to MaxPDUSize-1 on SNAP7. But not MaxPDUSize-0.
-                var maxToRead = Math.Min(count, MaxPDUSize - 18);
-                ReadBytesWithSingleRequest(dataType, db, startByteAdr + index, result, index, maxToRead);
-                count -= maxToRead;
+                var maxToRead = Math.Min(buffer.Length, MaxPDUSize - 18);
+                ReadBytesWithSingleRequest(dataType, db, startByteAdr + index, buffer.Slice(0, maxToRead));
+                buffer = buffer.Slice(maxToRead);
                 index += maxToRead;
             }
-            return result;
         }
 
         /// <summary>
@@ -111,7 +127,6 @@ namespace S7.Net
             return ReadStruct(typeof(T), db, startByteAdr) as T?;
         }
 
-
         /// <summary>
         /// Reads all the bytes needed to fill a class in C#, starting from a certain address, and set all the properties values to the value that are read from the PLC.
         /// This reads only properties, it doesn't read private variable or public variable without {get;set;} specified.
@@ -178,17 +193,29 @@ namespace S7.Net
         /// <param name="startByteAdr">Start byte address. If you want to write DB1.DBW200, this is 200.</param>
         /// <param name="value">Bytes to write. If more than 200, multiple requests will be made.</param>
         public void WriteBytes(DataType dataType, int db, int startByteAdr, byte[] value)
+        {
+            WriteBytes(dataType, db, startByteAdr, value.AsSpan());
+        }
+
+        /// <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.
+        /// </summary>
+        /// <param name="dataType">Data type of the memory area, can be DB, Timer, Counter, Merker(Memory), Input, Output.</param>
+        /// <param name="db">Address of the memory area (if you want to read DB1, this is set to 1). This must be set also for other memory area types: counters, timers,etc.</param>
+        /// <param name="startByteAdr">Start byte address. If you want to write DB1.DBW200, this is 200.</param>
+        /// <param name="value">Bytes to write. If more than 200, multiple requests will be made.</param>
+        public void WriteBytes(DataType dataType, int db, int startByteAdr, ReadOnlySpan<byte> value)
         {
             int localIndex = 0;
-            int count = value.Length;
-            while (count > 0)
+            while (value.Length > 0)
             {
                 //TODO: Figure out how to use MaxPDUSize here
                 //Snap7 seems to choke on PDU sizes above 256 even if snap7
                 //replies with bigger PDU size in connection setup.
-                var maxToWrite = Math.Min(count, MaxPDUSize - 28);//TODO tested only when the MaxPDUSize is 480
-                WriteBytesWithASingleRequest(dataType, db, startByteAdr + localIndex, value, localIndex, maxToWrite);
-                count -= maxToWrite;
+                var maxToWrite = Math.Min(value.Length, MaxPDUSize - 28);//TODO tested only when the MaxPDUSize is 480
+                WriteBytesWithASingleRequest(dataType, db, startByteAdr + localIndex, value.Slice(0, maxToWrite));
+                value = value.Slice(maxToWrite);
                 localIndex += maxToWrite;
             }
         }
@@ -294,22 +321,22 @@ namespace S7.Net
             WriteClassAsync(classValue, db, startByteAdr).GetAwaiter().GetResult();
         }
 
-        private void ReadBytesWithSingleRequest(DataType dataType, int db, int startByteAdr, byte[] buffer, int offset, int count)
+        private void ReadBytesWithSingleRequest(DataType dataType, int db, int startByteAdr, Span<byte> buffer)
         {
             try
             {
                 // first create the header
-                int packageSize = 19 + 12; // 19 header + 12 for 1 request
-                var package = new System.IO.MemoryStream(packageSize);
+                const int packageSize = 19 + 12; // 19 header + 12 for 1 request
+                var dataToSend = new byte[packageSize];
+                var package = new MemoryStream(dataToSend);
                 BuildHeaderPackage(package);
                 // package.Add(0x02);  // datenart
-                BuildReadDataRequestPackage(package, dataType, db, startByteAdr, count);
+                BuildReadDataRequestPackage(package, dataType, db, startByteAdr, buffer.Length);
 
-                var dataToSend = package.ToArray();
                 var s7data = RequestTsdu(dataToSend);
-                AssertReadResponse(s7data, count);
+                AssertReadResponse(s7data, buffer.Length);
 
-                Array.Copy(s7data, 18, buffer, offset, count);
+                s7data.AsSpan(18, buffer.Length).CopyTo(buffer);
             }
             catch (Exception exc)
             {
@@ -326,7 +353,6 @@ namespace S7.Net
         {
             AssertPduSizeForWrite(dataItems);
 
-
             var message = new ByteArray();
             var length = S7WriteMultiple.CreateRequest(message, dataItems);
             var response = RequestTsdu(message.Array, 0, length);
@@ -334,11 +360,11 @@ namespace S7.Net
             S7WriteMultiple.ParseResponse(response, response.Length, dataItems);
         }
 
-        private void WriteBytesWithASingleRequest(DataType dataType, int db, int startByteAdr, byte[] value, int dataOffset, int count)
+        private void WriteBytesWithASingleRequest(DataType dataType, int db, int startByteAdr, ReadOnlySpan<byte> value)
         {
             try
             {
-                var dataToSend = BuildWriteBytesPackage(dataType, db, startByteAdr, value, dataOffset, count);
+                var dataToSend = BuildWriteBytesPackage(dataType, db, startByteAdr, value);
                 var s7data = RequestTsdu(dataToSend);
 
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
@@ -349,35 +375,37 @@ namespace S7.Net
             }
         }
 
-        private byte[] BuildWriteBytesPackage(DataType dataType, int db, int startByteAdr, byte[] value, int dataOffset, int count)
+        private byte[] BuildWriteBytesPackage(DataType dataType, int db, int startByteAdr, ReadOnlySpan<byte> value)
         {
-            int varCount = count;
+            int varCount = value.Length;
             // first create the header
             int packageSize = 35 + varCount;
-            var package = new MemoryStream(new byte[packageSize]);
+            var packageData = new byte[packageSize];
+            var package = new MemoryStream(packageData);
 
             package.WriteByte(3);
             package.WriteByte(0);
             //complete package size
-            package.WriteByteArray(Int.ToByteArray((short)packageSize));
-            package.WriteByteArray(new byte[] { 2, 0xf0, 0x80, 0x32, 1, 0, 0 });
-            package.WriteByteArray(Word.ToByteArray((ushort)(varCount - 1)));
-            package.WriteByteArray(new byte[] { 0, 0x0e });
-            package.WriteByteArray(Word.ToByteArray((ushort)(varCount + 4)));
-            package.WriteByteArray(new byte[] { 0x05, 0x01, 0x12, 0x0a, 0x10, 0x02 });
-            package.WriteByteArray(Word.ToByteArray((ushort)varCount));
-            package.WriteByteArray(Word.ToByteArray((ushort)(db)));
+            package.Write(Int.ToByteArray((short)packageSize));
+            // This overload doesn't allocate the byte array, it refers to assembly's static data segment
+            package.Write(new byte[] { 2, 0xf0, 0x80, 0x32, 1, 0, 0 });
+            package.Write(Word.ToByteArray((ushort)(varCount - 1)));
+            package.Write(new byte[] { 0, 0x0e });
+            package.Write(Word.ToByteArray((ushort)(varCount + 4)));
+            package.Write(new byte[] { 0x05, 0x01, 0x12, 0x0a, 0x10, 0x02 });
+            package.Write(Word.ToByteArray((ushort)varCount));
+            package.Write(Word.ToByteArray((ushort)(db)));
             package.WriteByte((byte)dataType);
             var overflow = (int)(startByteAdr * 8 / 0xffffU); // handles words with address bigger than 8191
             package.WriteByte((byte)overflow);
-            package.WriteByteArray(Word.ToByteArray((ushort)(startByteAdr * 8)));
-            package.WriteByteArray(new byte[] { 0, 4 });
-            package.WriteByteArray(Word.ToByteArray((ushort)(varCount * 8)));
+            package.Write(Word.ToByteArray((ushort)(startByteAdr * 8)));
+            package.Write(new byte[] { 0, 4 });
+            package.Write(Word.ToByteArray((ushort)(varCount * 8)));
 
             // now join the header and the data
-            package.Write(value, dataOffset, count);
+            package.Write(value);
 
-            return package.ToArray();
+            return packageData;
         }
 
         private byte[] BuildWriteBitPackage(DataType dataType, int db, int startByteAdr, bool bitValue, int bitAdr)
@@ -386,33 +414,33 @@ namespace S7.Net
             int varCount = 1;
             // first create the header
             int packageSize = 35 + varCount;
-            var package = new MemoryStream(new byte[packageSize]);
+            var packageData = new byte[packageSize];
+            var package = new MemoryStream(packageData);
 
             package.WriteByte(3);
             package.WriteByte(0);
             //complete package size
-            package.WriteByteArray(Int.ToByteArray((short)packageSize));
-            package.WriteByteArray(new byte[] { 2, 0xf0, 0x80, 0x32, 1, 0, 0 });
-            package.WriteByteArray(Word.ToByteArray((ushort)(varCount - 1)));
-            package.WriteByteArray(new byte[] { 0, 0x0e });
-            package.WriteByteArray(Word.ToByteArray((ushort)(varCount + 4)));
-            package.WriteByteArray(new byte[] { 0x05, 0x01, 0x12, 0x0a, 0x10, 0x01 }); //ending 0x01 is used for writing a sinlge bit
-            package.WriteByteArray(Word.ToByteArray((ushort)varCount));
-            package.WriteByteArray(Word.ToByteArray((ushort)(db)));
+            package.Write(Int.ToByteArray((short)packageSize));
+            package.Write(new byte[] { 2, 0xf0, 0x80, 0x32, 1, 0, 0 });
+            package.Write(Word.ToByteArray((ushort)(varCount - 1)));
+            package.Write(new byte[] { 0, 0x0e });
+            package.Write(Word.ToByteArray((ushort)(varCount + 4)));
+            package.Write(new byte[] { 0x05, 0x01, 0x12, 0x0a, 0x10, 0x01 }); //ending 0x01 is used for writing a sinlge bit
+            package.Write(Word.ToByteArray((ushort)varCount));
+            package.Write(Word.ToByteArray((ushort)(db)));
             package.WriteByte((byte)dataType);
             var overflow = (int)(startByteAdr * 8 / 0xffffU); // handles words with address bigger than 8191
             package.WriteByte((byte)overflow);
-            package.WriteByteArray(Word.ToByteArray((ushort)(startByteAdr * 8 + bitAdr)));
-            package.WriteByteArray(new byte[] { 0, 0x03 }); //ending 0x03 is used for writing a sinlge bit
-            package.WriteByteArray(Word.ToByteArray((ushort)(varCount)));
+            package.Write(Word.ToByteArray((ushort)(startByteAdr * 8 + bitAdr)));
+            package.Write(new byte[] { 0, 0x03 }); //ending 0x03 is used for writing a sinlge bit
+            package.Write(Word.ToByteArray((ushort)(varCount)));
 
             // now join the header and the data
-            package.WriteByteArray(value);
+            package.Write(value);
 
-            return package.ToArray();
+            return packageData;
         }
 
-
         private void WriteBitWithASingleRequest(DataType dataType, int db, int startByteAdr, int bitAdr, bool bitValue)
         {
             try
@@ -444,7 +472,8 @@ namespace S7.Net
             {
                 // first create the header
                 int packageSize = 19 + (dataItems.Count * 12);
-                var package = new System.IO.MemoryStream(packageSize);
+                var dataToSend = new byte[packageSize];
+                var package = new MemoryStream(dataToSend);
                 BuildHeaderPackage(package, dataItems.Count);
                 // package.Add(0x02);  // datenart
                 foreach (var dataItem in dataItems)
@@ -452,8 +481,7 @@ namespace S7.Net
                     BuildReadDataRequestPackage(package, dataItem.DataType, dataItem.DB, dataItem.StartByteAdr, VarTypeToByteLength(dataItem.VarType, dataItem.Count));
                 }
 
-                var dataToSend = package.ToArray();
-                var s7data = RequestTsdu(dataToSend);
+                byte[] s7data = RequestTsdu(dataToSend);
 
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
 

S7.Net/S7.Net.csproj

@@ -27,6 +27,10 @@
     <DefineConstants>NET_FULL</DefineConstants>
   </PropertyGroup>
 
+  <ItemGroup Condition="'$(TargetFramework)' != 'net5.0'">
+    <PackageReference Include="System.Memory" Version="4.5.5" />
+  </ItemGroup>
+  
   <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All" />
   </ItemGroup>