Implemented Modbus Serial Client

AMWD.Protocols.Modbus.Serial/Utils/SafeUnixHandle.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Runtime.InteropServices;
+#if NETSTANDARD
+using System.Runtime.ConstrainedExecution;
+using System.Security.Permissions;
+#endif
+
+namespace AMWD.Protocols.Modbus.Serial.Utils
+{
+	/// <summary>
+	/// Implements a safe handle for unix systems.
+	/// <br/>
+	/// Found on https://stackoverflow.com/a/10388107
+	/// </summary>
+#if NETSTANDARD
+	[SecurityPermission(SecurityAction.InheritanceDemand, UnmanagedCode = true)]
+	[SecurityPermission(SecurityAction.Demand, UnmanagedCode = true)]
+#endif
+	[System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+	internal sealed class SafeUnixHandle : SafeHandle
+	{
+		/// <summary>
+		/// Initializes a new instance of the <see cref="SafeUnixHandle"/> class.
+		/// </summary>
+#if NETSTANDARD
+		[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
+#endif
+		private SafeUnixHandle()
+			: base(new IntPtr(-1), true)
+		{ }
+
+		public override bool IsInvalid
+			=> handle == new IntPtr(-1);
+
+		protected override bool ReleaseHandle()
+			=> UnsafeNativeMethods.Close(handle) != -1;
+	}
+}