Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Data.Entity.Design/System/Data/EntityModel/LazyTextWriterCreator.cs

@@ -0,0 +1,85 @@
+//---------------------------------------------------------------------
+// <copyright file="LazyTextWriterCreator.cs" company="Microsoft">
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//
+// @owner       [....]
+// @backupOwner [....]
+//---------------------------------------------------------------------
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.IO;
+using System.Diagnostics;
+using System.Runtime.Versioning;
+
+namespace System.Data.Entity.Design
+{
+    /// <summary>
+    /// This class is responsible for abstracting the knowledge
+    /// of whether the user provided a TextWriter or a FilePath.
+    /// 
+    /// If the user gave us a filePath we try not to create the TextWriter
+    /// till we absolutely need it in order to prevent the file from being created
+    /// in error cases.
+    /// </summary>
+    internal class LazyTextWriterCreator : IDisposable
+    {
+        private bool _ownTextWriter;
+        private TextWriter _writer = null;
+        private string _targetFilePath = null;
+
+        internal LazyTextWriterCreator(TextWriter writer)
+        {
+            Debug.Assert(writer != null, "writer parameter is null");
+
+            _ownTextWriter = false;
+            _writer = writer;
+        }
+
+        [ResourceExposure(ResourceScope.Machine)] //The target file path is used to open a stream which is a machine resource.
+        internal LazyTextWriterCreator(string targetFilePath)
+        {
+            Debug.Assert(targetFilePath != null, "targetFilePath parameter is null");
+
+            _ownTextWriter = true;
+            _targetFilePath = targetFilePath;
+        }
+
+        [ResourceExposure(ResourceScope.None)] //The resource( target file path) is not exposed to the callers of this method
+        [ResourceConsumption(ResourceScope.Machine, ResourceScope.Machine)] //For StreamWriter constructor and we pick 
+                                                                            //the target file path from class variable.
+        internal TextWriter GetOrCreateTextWriter()
+        {
+            if (_writer == null)
+            {
+                // lazy creating the writer
+                _writer = new StreamWriter(_targetFilePath);
+            }
+            return _writer;
+        }
+
+        internal string TargetFilePath
+        {
+            get { return _targetFilePath; }
+        }
+
+        internal bool IsUserSuppliedTextWriter
+        {
+            get { return !_ownTextWriter; }
+        }
+
+        public void Dispose()
+        {
+            // Technically, calling GC.SuppressFinalize is not required because the class does not
+            // have a finalizer, but it does no harm, protects against the case where a finalizer is added
+            // in the future, and prevents an FxCop warning.
+            GC.SuppressFinalize(this);
+            if (_ownTextWriter && _writer != null)
+            {
+                _writer.Dispose();
+            }
+        }
+    }
+}