Add nativefilestream and several new methods to File and FileStream (#98)

Author: josesimoes

System.IO.FileSystem.UnitTests/DirectoryUnitTests.cs

@@ -0,0 +1,105 @@
+//
+// Copyright (c) .NET Foundation and Contributors
+// See LICENSE file in the project root for full license information.
+//
+
+using nanoFramework.System.IO.FileSystem;
+using nanoFramework.TestFramework;
+using System.Threading;
+
+namespace System.IO.FileSystem.UnitTests
+{
+    [TestClass]
+    public abstract class FileSystemUnitTestsBase
+    {
+        /////////////////////////////////////////////////////////////////////
+        // The test execution can be configured using the following fields //
+        /////////////////////////////////////////////////////////////////////
+
+        // set to the number of drives available in the target
+        internal const int _numberOfDrives = 1;
+
+        // set to the root of the drive to use for the tests
+        // D: SD card
+        // E: USB mass storage
+        // I: and J: internal flash
+        internal const string Root = @"I:\";
+
+        // set to true to wait for removable drive(s) to be mounted
+        internal const bool _waitForRemovableDrive = false;
+
+        // set to true to have SPI SD card mounted
+        internal const bool _configAndMountSdCard = false;
+
+        //////////////////////////////////////////////////
+
+        private SDCard _mycardBacking;
+
+        internal SDCard MyCard
+        {
+            set
+            {
+                _mycardBacking = value;
+            }
+
+            get
+            {
+                _mycardBacking ??= InitializeSDCard();
+
+                return _mycardBacking;
+            }
+        }
+
+        /// <summary>
+        /// Initializes the SD card. Can be overridden in the derived class to provide specific initialization.
+        /// </summary>
+        /// <returns></returns>
+        protected SDCard InitializeSDCard()
+        {
+            // Example initialization logic
+            SDCard.SDCardMmcParameters parameters = new SDCard.SDCardMmcParameters
+            {
+                dataWidth = SDCard.SDDataWidth._4_bit,
+                enableCardDetectPin = true,
+                cardDetectPin = 21
+            };
+
+            return new SDCard(parameters);
+        }
+
+        /// <summary>
+        /// Helper method to be called from the tests to handle removable drives.
+        /// </summary>
+        internal void RemovableDrivesHelper()
+        {
+            if (_configAndMountSdCard)
+            {
+            TryToMountAgain:
+
+                try
+                {
+                    MyCard.Mount();
+                }
+                catch (Exception ex)
+                {
+                    OutputHelper.WriteLine($"SDCard mount failed: {ex.Message}");
+
+                    Thread.Sleep(TimeSpan.FromSeconds(2));
+
+                    MyCard = null;
+
+                    goto TryToMountAgain;
+                }
+            }
+
+            if (_waitForRemovableDrive)
+            {
+                // wait until all removable drives are mounted
+                while (DriveInfo.GetDrives().Length < _numberOfDrives)
+                {
+                    Thread.Sleep(1000);
+                }
+            }
+        }
+    }
+}