Release S7NetPlus 0.12.0

Release highlights:
- Add synchronization to methods interacting with the PLC

S7.Net.UnitTest/TypeTests/BooleanTests.cs

@@ -0,0 +1,38 @@
+using System;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Boolean = S7.Net.Types.Boolean;
+
+namespace S7.Net.UnitTest.TypeTests
+{
+    [TestClass]
+    public class BooleanTests
+    {
+        [DataTestMethod]
+        [DataRow(0)]
+        [DataRow(1)]
+        [DataRow(2)]
+        [DataRow(3)]
+        [DataRow(4)]
+        [DataRow(5)]
+        [DataRow(6)]
+        [DataRow(7)]
+        public void TestValidSetBitValues(int index)
+        {
+            Assert.AreEqual(Math.Pow(2, index), Boolean.SetBit(0, index));
+        }
+
+        [DataTestMethod]
+        [DataRow(0)]
+        [DataRow(1)]
+        [DataRow(2)]
+        [DataRow(3)]
+        [DataRow(4)]
+        [DataRow(5)]
+        [DataRow(6)]
+        [DataRow(7)]
+        public void TestValidClearBitValues(int index)
+        {
+            Assert.AreEqual((byte) ((uint) Math.Pow(2, index) ^ uint.MaxValue), Boolean.ClearBit(byte.MaxValue, index));
+        }
+    }
+}

S7.Net/Internal/TaskQueue.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace S7.Net.Internal
+{
+    internal class TaskQueue
+    {
+        private static readonly object Sentinel = new object();
+
+        private Task prev = Task.FromResult(Sentinel);
+
+        public async Task<T> Enqueue<T>(Func<Task<T>> action)
+        {
+            var tcs = new TaskCompletionSource<object>();
+            await Interlocked.Exchange(ref prev, tcs.Task).ConfigureAwait(false);
+
+            try
+            {
+                return await action.Invoke().ConfigureAwait(false);
+            }
+            finally
+            {
+                tcs.SetResult(Sentinel);
+            }
+        }
+    }
+}

S7.Net/PLC.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Net.Sockets;
+using S7.Net.Internal;
 using S7.Net.Protocol;
 using S7.Net.Types;
 
@@ -13,8 +15,10 @@ namespace S7.Net
     /// </summary>
     public partial class Plc : IDisposable
     {
+        private readonly TaskQueue queue = new TaskQueue();
+
         private const int CONNECTION_TIMED_OUT_ERROR_CODE = 10060;
-        
+
         //TCP connection to device
         private TcpClient? tcpClient;
         private NetworkStream? _stream;
@@ -242,6 +246,16 @@ namespace S7.Net
             }
         }
 
+        private Stream GetStreamIfAvailable()
+        {
+            if (_stream == null)
+            {
+                throw new PlcException(ErrorCode.ConnectionError, "Plc is not connected");
+            }
+
+            return _stream;
+        }
+
         #region IDisposable Support
         private bool disposedValue = false; // To detect redundant calls
 

S7.Net/PLCHelpers.cs

@@ -30,8 +30,8 @@ namespace S7.Net
         }
 
         /// <summary>
-        /// Create the bytes-package to request data from the PLC. You have to specify the memory type (dataType), 
-        /// the address of the memory, the address of the byte and the bytes count. 
+        /// Create the bytes-package to request data from the PLC. You have to specify the memory type (dataType),
+        /// the address of the memory, the address of the byte and the bytes count.
         /// </summary>
         /// <param name="dataType">MemoryType (DB, Timer, Counter, etc.)</param>
         /// <param name="db">Address of the memory to be read</param>
@@ -184,7 +184,7 @@ namespace S7.Net
             switch (varType)
             {
                 case VarType.Bit:
-                    return varCount + 7 / 8;
+                    return (varCount + 7) / 8;
                 case VarType.Byte:
                     return (varCount < 1) ? 1 : varCount;
                 case VarType.String:

S7.Net/PlcAsynchronous.cs

@@ -1,11 +1,11 @@
 using S7.Net.Types;
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Net.Sockets;
 using System.Threading.Tasks;
 using S7.Net.Protocol;
-using System.IO;
 using System.Threading;
 using S7.Net.Protocol.S7;
 
@@ -28,9 +28,14 @@ namespace S7.Net
             var stream = await ConnectAsync().ConfigureAwait(false);
             try
             {
-                cancellationToken.ThrowIfCancellationRequested();
-                await EstablishConnection(stream, cancellationToken).ConfigureAwait(false);
-                _stream = stream;
+                await queue.Enqueue(async () =>
+                {
+                    cancellationToken.ThrowIfCancellationRequested();
+                    await EstablishConnection(stream, cancellationToken).ConfigureAwait(false);
+                    _stream = stream;
+
+                    return default(object);
+                }).ConfigureAwait(false);
             }
             catch(Exception)
             {
@@ -47,29 +52,30 @@ namespace S7.Net
             return tcpClient.GetStream();
         }
 
-        private async Task EstablishConnection(NetworkStream stream, CancellationToken cancellationToken)
+        private async Task EstablishConnection(Stream stream, CancellationToken cancellationToken)
         {
             await RequestConnection(stream, cancellationToken).ConfigureAwait(false);
             await SetupConnection(stream, cancellationToken).ConfigureAwait(false);
         }
 
-        private async Task RequestConnection(NetworkStream stream, CancellationToken cancellationToken)
+        private async Task RequestConnection(Stream stream, CancellationToken cancellationToken)
         {
             var requestData = ConnectionRequest.GetCOTPConnectionRequest(CPU, Rack, Slot);
-            await stream.WriteAsync(requestData, 0, requestData.Length).ConfigureAwait(false);
-            var response = await COTP.TPDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
+            var response = await NoLockRequestTpduAsync(stream, requestData, cancellationToken).ConfigureAwait(false);
+
             if (response.PDUType != COTP.PduType.ConnectionConfirmed)
             {
                 throw new InvalidDataException("Connection request was denied", response.TPkt.Data, 1, 0x0d);
             }
         }
 
-        private async Task SetupConnection(NetworkStream stream, CancellationToken cancellationToken)
+        private async Task SetupConnection(Stream stream, CancellationToken cancellationToken)
         {
             var setupData = GetS7ConnectionSetup();
-            await stream.WriteAsync(setupData, 0, setupData.Length).ConfigureAwait(false);
 
-            var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
+            var s7data = await NoLockRequestTsduAsync(stream, setupData, 0, setupData.Length, cancellationToken)
+                .ConfigureAwait(false);
+
             if (s7data.Length < 2)
                 throw new WrongNumberOfBytesException("Not enough data received in response to Communication Setup");
 
@@ -112,7 +118,7 @@ namespace S7.Net
         }
 
         /// <summary>
-        /// Read and decode a certain number of bytes of the "VarType" provided. 
+        /// Read and decode a certain number of bytes of the "VarType" provided.
         /// This can be used to read multiple consecutive variables of the same type (Word, DWord, Int, etc).
         /// If the read was not successful, check LastErrorCode or LastErrorString.
         /// </summary>
@@ -179,10 +185,10 @@ namespace S7.Net
         }
 
         /// <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. 
+        /// 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.
         /// </summary>
-        /// <param name="sourceClass">Instance of the class that will store the values</param>       
+        /// <param name="sourceClass">Instance of the class that will store the values</param>
         /// <param name="db">Index of the DB; es.: 1 is for DB1</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.
@@ -205,7 +211,7 @@ namespace S7.Net
         }
 
         /// <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. 
+        /// 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. To instantiate the class defined by the generic
         /// type, the class needs a default constructor.
         /// </summary>
@@ -221,7 +227,7 @@ namespace S7.Net
         }
 
         /// <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. 
+        /// 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.
         /// </summary>
         /// <typeparam name="T">The class that will be instantiated</typeparam>
@@ -245,10 +251,10 @@ namespace S7.Net
         }
 
         /// <summary>
-        /// Reads multiple vars in a single request. 
+        /// Reads multiple vars in a single request.
         /// You have to create and pass a list of DataItems and you obtain in response the same list with the values.
         /// Values are stored in the property "Value" of the dataItem and are already converted.
-        /// If you don't want the conversion, just create a dataItem of bytes. 
+        /// If you don't want the conversion, just create a dataItem of bytes.
         /// The number of DataItems as well as the total size of the requested data can not exceed a certain limit (protocol restriction).
         /// </summary>
         /// <param name="dataItems">List of dataitems that contains the list of variables that must be read.</param>
@@ -256,18 +262,15 @@ namespace S7.Net
         /// Please note that cancellation is advisory/cooperative and will not lead to immediate cancellation in all cases.</param>
         public async Task<List<DataItem>> ReadMultipleVarsAsync(List<DataItem> dataItems, CancellationToken cancellationToken = default)
         {
-            //Snap7 seems to choke on PDU sizes above 256 even if snap7 
+            //Snap7 seems to choke on PDU sizes above 256 even if snap7
             //replies with bigger PDU size in connection setup.
             AssertPduSizeForRead(dataItems);
 
-            var stream = GetStreamIfAvailable();
-
             try
             {
                 var dataToSend = BuildReadRequestPackage(dataItems.Select(d => DataItem.GetDataItemAddress(d)).ToList());
-                await stream.WriteAsync(dataToSend, 0, dataToSend.Length).ConfigureAwait(false);
+                var s7data = await RequestTsduAsync(dataToSend, cancellationToken);
 
-                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
 
                 ParseDataIntoDataItems(s7data, dataItems);
@@ -435,12 +438,9 @@ namespace S7.Net
 
         private async Task ReadBytesWithSingleRequestAsync(DataType dataType, int db, int startByteAdr, byte[] buffer, int offset, int count, CancellationToken cancellationToken)
         {
-            var stream = GetStreamIfAvailable();
-
             var dataToSend = BuildReadRequestPackage(new [] { new DataItemAddress(dataType, db, startByteAdr, count)});
-            await stream.WriteAsync(dataToSend, 0, dataToSend.Length, cancellationToken);
 
-            var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
+            var s7data = await RequestTsduAsync(dataToSend, cancellationToken);
             AssertReadResponse(s7data, count);
 
             Array.Copy(s7data, 18, buffer, offset, count);
@@ -456,13 +456,11 @@ namespace S7.Net
         {
             AssertPduSizeForWrite(dataItems);
 
-            var stream = GetStreamIfAvailable();
-
             var message = new ByteArray();
             var length = S7WriteMultiple.CreateRequest(message, dataItems);
-            await stream.WriteAsync(message.Array, 0, length).ConfigureAwait(false);
 
-            var response = await COTP.TSDU.ReadAsync(stream, CancellationToken.None).ConfigureAwait(false);
+            var response = await RequestTsduAsync(message.Array, 0, length).ConfigureAwait(false);
+
             S7WriteMultiple.ParseResponse(response, response.Length, dataItems);
         }
 
@@ -476,15 +474,11 @@ namespace S7.Net
         /// <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)
         {
-
             try
             {
-                var stream = GetStreamIfAvailable();
                 var dataToSend = BuildWriteBytesPackage(dataType, db, startByteAdr, value, dataOffset, count);
+                var s7data = await RequestTsduAsync(dataToSend, cancellationToken).ConfigureAwait(false);
 
-                await stream.WriteAsync(dataToSend, 0, dataToSend.Length, cancellationToken).ConfigureAwait(false);
-
-                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
             }
             catch (OperationCanceledException)
@@ -499,15 +493,11 @@ namespace S7.Net
 
         private async Task WriteBitWithASingleRequestAsync(DataType dataType, int db, int startByteAdr, int bitAdr, bool bitValue, CancellationToken cancellationToken)
         {
-            var stream = GetStreamIfAvailable();
-
             try
             {
                 var dataToSend = BuildWriteBitPackage(dataType, db, startByteAdr, bitValue, bitAdr);
+                var s7data = await RequestTsduAsync(dataToSend, cancellationToken).ConfigureAwait(false);
 
-                await stream.WriteAsync(dataToSend, 0, dataToSend.Length).ConfigureAwait(false);
-
-                var s7data = await COTP.TSDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
             }
             catch (OperationCanceledException)
@@ -520,13 +510,33 @@ namespace S7.Net
             }
         }
 
-        private Stream GetStreamIfAvailable()
+        private Task<byte[]> RequestTsduAsync(byte[] requestData, CancellationToken cancellationToken = default) =>
+            RequestTsduAsync(requestData, 0, requestData.Length, cancellationToken);
+
+        private Task<byte[]> RequestTsduAsync(byte[] requestData, int offset, int length, CancellationToken cancellationToken = default)
         {
-            if (_stream == null)
-            {
-                throw new PlcException(ErrorCode.ConnectionError, "Plc is not connected");
-            }
-            return _stream;
+            var stream = GetStreamIfAvailable();
+
+            return queue.Enqueue(() =>
+                NoLockRequestTsduAsync(stream, requestData, offset, length, cancellationToken));
+        }
+
+        private static async Task<COTP.TPDU> NoLockRequestTpduAsync(Stream stream, byte[] requestData,
+            CancellationToken cancellationToken = default)
+        {
+            await stream.WriteAsync(requestData, 0, requestData.Length, cancellationToken).ConfigureAwait(false);
+            var response = await COTP.TPDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
+
+            return response;
+        }
+
+        private static async Task<byte[]> NoLockRequestTsduAsync(Stream stream, byte[] requestData, int offset, int length,
+            CancellationToken cancellationToken = default)
+        {
+            await stream.WriteAsync(requestData, offset, length, cancellationToken).ConfigureAwait(false);
+            var response = await COTP.TSDU.ReadAsync(stream, cancellationToken).ConfigureAwait(false);
+
+            return response;
         }
     }
 }

S7.Net/PlcSynchronous.cs

@@ -2,8 +2,6 @@
 using System;
 using System.IO;
 using System.Collections.Generic;
-using System.Linq;
-using System.Net.Sockets;
 using S7.Net.Protocol;
 using S7.Net.Helper;
 
@@ -54,7 +52,7 @@ namespace S7.Net
         }
 
         /// <summary>
-        /// Read and decode a certain number of bytes of the "VarType" provided. 
+        /// Read and decode a certain number of bytes of the "VarType" provided.
         /// This can be used to read multiple consecutive variables of the same type (Word, DWord, Int, etc).
         /// If the read was not successful, check LastErrorCode or LastErrorString.
         /// </summary>
@@ -115,10 +113,10 @@ namespace S7.Net
 
 
         /// <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. 
+        /// 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.
         /// </summary>
-        /// <param name="sourceClass">Instance of the class that will store the values</param>       
+        /// <param name="sourceClass">Instance of the class that will store the values</param>
         /// <param name="db">Index of the DB; es.: 1 is for DB1</param>
         /// <param name="startByteAdr">Start byte address. If you want to read DB1.DBW200, this is 200.</param>
         /// <returns>The number of read bytes</returns>
@@ -138,7 +136,7 @@ namespace S7.Net
         }
 
         /// <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. 
+        /// 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. To instantiate the class defined by the generic
         /// type, the class needs a default constructor.
         /// </summary>
@@ -152,7 +150,7 @@ namespace S7.Net
         }
 
         /// <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. 
+        /// 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.
         /// </summary>
         /// <typeparam name="T">The class that will be instantiated</typeparam>
@@ -186,7 +184,7 @@ namespace S7.Net
             while (count > 0)
             {
                 //TODO: Figure out how to use MaxPDUSize here
-                //Snap7 seems to choke on PDU sizes above 256 even if snap7 
+                //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);
@@ -298,7 +296,6 @@ namespace S7.Net
 
         private void ReadBytesWithSingleRequest(DataType dataType, int db, int startByteAdr, byte[] buffer, int offset, int count)
         {
-            var stream = GetStreamIfAvailable();
             try
             {
                 // first create the header
@@ -309,9 +306,7 @@ namespace S7.Net
                 BuildReadDataRequestPackage(package, dataType, db, startByteAdr, count);
 
                 var dataToSend = package.ToArray();
-                stream.Write(dataToSend, 0, dataToSend.Length);
-
-                var s7data = COTP.TSDU.Read(stream);
+                var s7data = RequestTsdu(dataToSend);
                 AssertReadResponse(s7data, count);
 
                 Array.Copy(s7data, 18, buffer, offset, count);
@@ -331,13 +326,11 @@ namespace S7.Net
         {
             AssertPduSizeForWrite(dataItems);
 
-            var stream = GetStreamIfAvailable();
 
             var message = new ByteArray();
             var length = S7WriteMultiple.CreateRequest(message, dataItems);
-            stream.Write(message.Array, 0, length);
+            var response = RequestTsdu(message.Array, 0, length);
 
-            var response = COTP.TSDU.Read(stream);
             S7WriteMultiple.ParseResponse(response, response.Length, dataItems);
         }
 
@@ -345,12 +338,9 @@ namespace S7.Net
         {
             try
             {
-                var stream = GetStreamIfAvailable();
                 var dataToSend = BuildWriteBytesPackage(dataType, db, startByteAdr, value, dataOffset, count);
+                var s7data = RequestTsdu(dataToSend);
 
-                stream.Write(dataToSend, 0, dataToSend.Length);
-
-                var s7data = COTP.TSDU.Read(stream);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
             }
             catch (Exception exc)
@@ -425,14 +415,11 @@ namespace S7.Net
 
         private void WriteBitWithASingleRequest(DataType dataType, int db, int startByteAdr, int bitAdr, bool bitValue)
         {
-            var stream = GetStreamIfAvailable();
             try
             {
                 var dataToSend = BuildWriteBitPackage(dataType, db, startByteAdr, bitValue, bitAdr);
+                var s7data = RequestTsdu(dataToSend);
 
-                stream.Write(dataToSend, 0, dataToSend.Length);
-
-                var s7data = COTP.TSDU.Read(stream);
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
             }
             catch (Exception exc)
@@ -442,10 +429,10 @@ namespace S7.Net
         }
 
         /// <summary>
-        /// Reads multiple vars in a single request. 
+        /// Reads multiple vars in a single request.
         /// You have to create and pass a list of DataItems and you obtain in response the same list with the values.
         /// Values are stored in the property "Value" of the dataItem and are already converted.
-        /// If you don't want the conversion, just create a dataItem of bytes. 
+        /// If you don't want the conversion, just create a dataItem of bytes.
         /// The number of DataItems as well as the total size of the requested data can not exceed a certain limit (protocol restriction).
         /// </summary>
         /// <param name="dataItems">List of dataitems that contains the list of variables that must be read.</param>
@@ -453,8 +440,6 @@ namespace S7.Net
         {
             AssertPduSizeForRead(dataItems);
 
-            var stream = GetStreamIfAvailable();
-
             try
             {
                 // first create the header
@@ -468,9 +453,7 @@ namespace S7.Net
                 }
 
                 var dataToSend = package.ToArray();
-                stream.Write(dataToSend, 0, dataToSend.Length);
-
-                var s7data = COTP.TSDU.Read(stream); //TODO use Async
+                var s7data = RequestTsdu(dataToSend);
 
                 ValidateResponseCode((ReadWriteErrorCode)s7data[14]);
 
@@ -481,5 +464,12 @@ namespace S7.Net
                 throw new PlcException(ErrorCode.ReadData, exc);
             }
         }
+
+        private byte[] RequestTsdu(byte[] requestData) => RequestTsdu(requestData, 0, requestData.Length);
+
+        private byte[] RequestTsdu(byte[] requestData, int offset, int length)
+        {
+            return RequestTsduAsync(requestData, offset, length).GetAwaiter().GetResult();
+        }
     }
 }

S7.Net/Types/Boolean.cs

@@ -14,20 +14,51 @@
         }
 
         /// <summary>
-        /// Sets the value of a bit to 1 (true), given the address of the bit
+        /// Sets the value of a bit to 1 (true), given the address of the bit. Returns
+        /// a copy of the value with the bit set.
         /// </summary>
+        /// <param name="value">The input value to modify.</param>
+        /// <param name="bit">The index (zero based) of the bit to set.</param>
+        /// <returns>The modified value with the bit at index set.</returns>
         public static byte SetBit(byte value, int bit)
         {
-            return (byte)((value | (1 << bit)) & 0xFF);
+            SetBit(ref value, bit);
+
+            return value;
+        }
+
+        /// <summary>
+        /// Sets the value of a bit to 1 (true), given the address of the bit.
+        /// </summary>
+        /// <param name="value">The value to modify.</param>
+        /// <param name="bit">The index (zero based) of the bit to set.</param>
+        public static void SetBit(ref byte value, int bit)
+        {
+            value = (byte) ((value | (1 << bit)) & 0xFF);
+        }
+
+        /// <summary>
+        /// Resets the value of a bit to 0 (false), given the address of the bit. Returns
+        /// a copy of the value with the bit cleared.
+        /// </summary>
+        /// <param name="value">The input value to modify.</param>
+        /// <param name="bit">The index (zero based) of the bit to clear.</param>
+        /// <returns>The modified value with the bit at index cleared.</returns>
+        public static byte ClearBit(byte value, int bit)
+        {
+            ClearBit(ref value, bit);
+
+            return value;
         }
 
         /// <summary>
         /// Resets the value of a bit to 0 (false), given the address of the bit
         /// </summary>
-        public static byte ClearBit(byte value, int bit)
+        /// <param name="value">The input value to modify.</param>
+        /// <param name="bit">The index (zero based) of the bit to clear.</param>
+        public static void ClearBit(ref byte value, int bit)
         {
-            return (byte)((value | (~(1 << bit))) & 0xFF);
+            value = (byte) (value & ~(1 << bit) & 0xFF);
         }
-
     }
 }