Imported Upstream version 5.18.0.142

Former-commit-id: 7467d4b717762eeaf652d77f1486dd11ffb1ff1f

mcs/class/System/corefx/Unix/Interop.Read.cs

@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// This file reiimplements CoreFX source file 'src/Common/src/Interop/Unix/System.Native/Interop.Read.cs'
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+using System;
+
+internal static partial class Interop
+{
+	internal static partial class Sys
+	{
+		static Sys ()
+		{
+			Interop.mono_pal_init ();
+		}
+
+		/// <summary>
+		/// Reads a number of bytes from an open file descriptor into a specified buffer.
+		/// </summary>
+		/// <param name="fd">The open file descriptor to try to read from</param>
+		/// <param name="buffer">The buffer to read info into</param>
+		/// <param name="count">The size of the buffer</param>
+		/// <returns>
+		/// Returns the number of bytes read on success; otherwise, -1 is returned
+		/// Note - on fail. the position of the stream may change depending on the platform; consult man 2 read for more info
+		/// </returns>
+		internal static unsafe int Read (SafeFileHandle fd, byte* buffer, int count)
+		{
+			int bytes_read = -1;
+			bool release = false;
+			try {
+				fd.DangerousAddRef (ref release);
+				do {
+					bytes_read = Read (fd.DangerousGetHandle (), buffer, count);
+				} while (bytes_read < 0 && Marshal.GetLastWin32Error () == (int) Interop.Error.EINTR);
+			}
+			finally {
+				if (release)
+					fd.DangerousRelease ();
+			}
+			return bytes_read;
+		}
+
+		[MethodImplAttribute(MethodImplOptions.InternalCall)]
+		internal static extern unsafe int Read (IntPtr fd, byte* buffer, int count);
+	}
+}