Add a version header to Object-Streams.

src/Compilers/CSharp/Portable/Syntax/CSharpSyntaxNode.cs

@@ -204,8 +204,14 @@ public static SyntaxNode DeserializeFrom(Stream stream, CancellationToken cancel
                 throw new InvalidOperationException(CodeAnalysisResources.TheStreamCannotBeReadFrom);
             }
 
-            using (var reader = new StreamObjectReader(stream, knownObjects: GetDeserializationObjectData(), binder: s_defaultBinder, cancellationToken: cancellationToken))
+
+            using (var reader = StreamObjectReader.TryGetReader(stream, knownObjects: GetDeserializationObjectData(), binder: s_defaultBinder, cancellationToken: cancellationToken))
             {
+                if (reader == null)
+                {
+                    throw new ArgumentException(CodeAnalysisResources.Stream_contains_invalid_data, nameof(stream));
+                }
+
                 var root = (Syntax.InternalSyntax.CSharpSyntaxNode)reader.ReadValue();
                 return root.CreateRed();
             }

src/Compilers/Core/CodeAnalysisTest/ObjectSerializationTests.cs

@@ -12,6 +12,19 @@ namespace Microsoft.CodeAnalysis.UnitTests
 {
     public sealed class ObjectSerializationTests
     {
+        [Fact]
+        private void TestInvalidStreamVersion()
+        {
+            var stream = new MemoryStream();
+            stream.WriteByte(0);
+            stream.WriteByte(0);
+
+            stream.Position = 0;
+
+            var reader = StreamObjectReader.TryGetReader(stream);
+            Assert.Null(reader);
+        }
+
         private void RoundTrip(Action<ObjectWriter> writeAction, Action<ObjectReader> readAction, bool recursive)
         {
             var stream = new MemoryStream();
@@ -25,7 +38,7 @@ private void RoundTrip(Action<ObjectWriter> writeAction, Action<ObjectReader> re
             Assert.Equal(recursive, StreamObjectReader.IsRecursive(stream));
 
             stream.Position = 0;
-            using (var reader = new StreamObjectReader(stream, binder: binder))
+            using (var reader = StreamObjectReader.TryGetReader(stream, binder: binder))
             {
                 readAction(reader);
             }
@@ -50,7 +63,7 @@ private T RoundTrip<T>(T value, Action<ObjectWriter, T> writeAction, Func<Object
             Assert.Equal(recursive, StreamObjectReader.IsRecursive(stream));
 
             stream.Position = 0;
-            using (var reader = new StreamObjectReader(stream, binder: binder))
+            using (var reader = StreamObjectReader.TryGetReader(stream, binder: binder))
             {
                 return (T)readAction(reader);
             }
@@ -978,7 +991,7 @@ public void TestObjectMapLimits()
                 writer.Dispose();
 
                 stream.Position = 0;
-                using (var reader = new StreamObjectReader(stream, binder: binder))
+                using (var reader = StreamObjectReader.TryGetReader(stream, binder: binder))
                 {
                     for (int pass = 0; pass < 2; pass++)
                     {

src/Compilers/Core/Portable/CodeAnalysisResources.resx

@@ -588,4 +588,7 @@
   <data name="Deserialization_reader_for_0_read_incorrect_number_of_values" xml:space="preserve">
     <value>Deserialization reader for '{0}' read incorrect number of values.</value>
   </data>
+  <data name="Stream_contains_invalid_data" xml:space="preserve">
+    <value>Stream contains invalid data</value>
+  </data>
 </root>

src/Compilers/Core/Portable/Serialization/StreamObjectReader.cs

@@ -27,6 +27,14 @@ namespace Roslyn.Utilities
     /// </summary>
     internal sealed partial class StreamObjectReader : ObjectReader, IDisposable
     {
+        /// <summary>
+        /// We start the version at something reasonably random.  That way an older file, with 
+        /// some random start-bytes, has little chance of matching our version.  When incrementing
+        /// this version, just change VersionByte2.
+        /// </summary>
+        internal const byte VersionByte1 = 0b10101010;
+        internal const byte VersionByte2 = 0b00000001;
+
         private readonly BinaryReader _reader;
         private readonly ObjectBinder _binder;
         private readonly bool _recursive;
@@ -67,11 +75,11 @@ internal sealed partial class StreamObjectReader : ObjectReader, IDisposable
         /// <param name="knownObjects">An optional list of objects assumed known by the corresponding <see cref="StreamObjectWriter"/>.</param>
         /// <param name="binder">A binder that provides object and type decoding.</param>
         /// <param name="cancellationToken"></param>
-        public StreamObjectReader(
+        private StreamObjectReader(
             Stream stream,
-            ObjectData knownObjects = null,
-            ObjectBinder binder = null,
-            CancellationToken cancellationToken = default(CancellationToken))
+            ObjectData knownObjects,
+            ObjectBinder binder,
+            CancellationToken cancellationToken)
         {
             // String serialization assumes both reader and writer to be of the same endianness.
             // It can be adjusted for BigEndian if needed.
@@ -93,6 +101,30 @@ internal sealed partial class StreamObjectReader : ObjectReader, IDisposable
             }
         }
 
+        /// <summary>
+        /// Attempts to create a <see cref="StreamObjectReader"/> from the provided <paramref name="stream"/>.
+        /// If the <paramref name="stream"/> does not start with a valid header, then <code>null</code> will
+        /// be returned.
+        /// </summary>
+        public static StreamObjectReader TryGetReader(
+            Stream stream,
+            ObjectData knownObjects = null,
+            ObjectBinder binder = null,
+            CancellationToken cancellationToken = default(CancellationToken))
+        {
+            if (stream == null)
+            {
+                return null;
+            }
+
+            if (stream.ReadByte() != VersionByte1 && stream.ReadByte() != VersionByte2)
+            {
+                return null;
+            }
+
+            return new StreamObjectReader(stream, knownObjects, binder, cancellationToken);
+        }
+
         internal static bool IsRecursive(Stream stream)
         {
             var recursionKind = (EncodingKind)stream.ReadByte(); 

src/Compilers/Core/Portable/Serialization/StreamObjectWriter.cs

@@ -82,6 +82,8 @@ internal sealed partial class StreamObjectWriter : ObjectWriter, IDisposable
             _recursive = recursive;
             _cancellationToken = cancellationToken;
 
+            WriteVersion();
+
             if (_recursive)
             {
                 _writer.Write((byte)EncodingKind.Recursive);
@@ -95,6 +97,12 @@ internal sealed partial class StreamObjectWriter : ObjectWriter, IDisposable
             }
         }
 
+        private void WriteVersion()
+        {
+            _writer.Write(StreamObjectReader.VersionByte1);
+            _writer.Write(StreamObjectReader.VersionByte2);
+        }
+
         public void Dispose()
         {
             _referenceMap.Dispose();

src/Compilers/VisualBasic/Portable/Syntax/VisualBasicSyntaxNode.vb

@@ -140,7 +140,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                 Throw New InvalidOperationException(CodeAnalysisResources.TheStreamCannotBeReadFrom)
             End If
 
-            Using reader = New StreamObjectReader(stream, knownObjects:=GetDeserializationObjectData(), binder:=s_defaultBinder, cancellationToken:=cancellationToken)
+            Using reader = StreamObjectReader.TryGetReader(stream, knownObjects:=GetDeserializationObjectData(), binder:=s_defaultBinder, cancellationToken:=cancellationToken)
+                If reader Is Nothing Then
+                    Throw New ArgumentException(CodeAnalysisResources.Stream_contains_invalid_data, NameOf(stream))
+                End If
+
                 Return DirectCast(reader.ReadValue(), InternalSyntax.VisualBasicSyntaxNode).CreateRed(Nothing, 0)
             End Using
         End Function

src/EditorFeatures/Core/Implementation/TodoComment/TodoCommentState.cs

@@ -1,7 +1,5 @@
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
-using System;
-using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.IO;
 using System.Threading;
@@ -32,33 +30,25 @@ protected override int GetCount(Data data)
 
             protected override Data TryGetExistingData(Stream stream, Document value, CancellationToken cancellationToken)
             {
-                var list = SharedPools.Default<List<TodoItem>>().AllocateAndClear();
-                try
+                using (var reader = StreamObjectReader.TryGetReader(stream))
                 {
-                    using (var reader = new StreamObjectReader(stream))
+                    if (reader != null)
                     {
                         var format = reader.ReadString();
-                        if (!string.Equals(format, FormatVersion))
+                        if (string.Equals(format, FormatVersion))
                         {
-                            return null;
-                        }
-
-                        var textVersion = VersionStamp.ReadFrom(reader);
-                        var dataVersion = VersionStamp.ReadFrom(reader);
+                            var textVersion = VersionStamp.ReadFrom(reader);
+                            var dataVersion = VersionStamp.ReadFrom(reader);
 
-                        AppendItems(reader, value, list, cancellationToken);
+                            var list = ArrayBuilder<TodoItem>.GetInstance();
+                            AppendItems(reader, value, list, cancellationToken);
 
-                        return new Data(textVersion, dataVersion, list.ToImmutableArray<TodoItem>());
+                            return new Data(textVersion, dataVersion, list.ToImmutableAndFree());
+                        }
                     }
                 }
-                catch (Exception)
-                {
-                    return null;
-                }
-                finally
-                {
-                    SharedPools.Default<List<TodoItem>>().ClearAndFree(list);
-                }
+
+                return null;
             }
 
             protected override void WriteTo(Stream stream, Data data, CancellationToken cancellationToken)
@@ -104,7 +94,7 @@ public ImmutableArray<TodoItem> GetItems_TestingOnly(DocumentId documentId)
                 return ImmutableArray<TodoItem>.Empty;
             }
 
-            private void AppendItems(ObjectReader reader, Document document, List<TodoItem> list, CancellationToken cancellationToken)
+            private void AppendItems(ObjectReader reader, Document document, ArrayBuilder<TodoItem> list, CancellationToken cancellationToken)
             {
                 var count = reader.ReadInt32();
                 for (var i = 0; i < count; i++)
@@ -130,4 +120,4 @@ private void AppendItems(ObjectReader reader, Document document, List<TodoItem>
             }
         }
     }
-}
+}

src/Features/Core/Portable/SolutionCrawler/State/AbstractAnalyzerState.cs

@@ -1,10 +1,12 @@
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Concurrent;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Shared.Utilities;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.SolutionCrawler.State
@@ -54,16 +56,22 @@ public async Task<TData> TryGetExistingDataAsync(TValue value, CancellationToken
             var solution = GetSolution(value);
             var persistService = solution.Workspace.Services.GetService<IPersistentStorageService>();
 
-            using (var storage = persistService.GetStorage(solution))
-            using (var stream = await ReadStreamAsync(storage, value, cancellationToken).ConfigureAwait(false))
+            try
             {
-                if (stream == null)
+                using (var storage = persistService.GetStorage(solution))
+                using (var stream = await ReadStreamAsync(storage, value, cancellationToken).ConfigureAwait(false))
                 {
-                    return default(TData);
+                    if (stream != null)
+                    {
+                        return TryGetExistingData(stream, value, cancellationToken);
+                    }
                 }
-
-                return TryGetExistingData(stream, value, cancellationToken);
             }
+            catch (Exception e) when (IOUtilities.IsNormalIOException(e))
+            {
+            }
+
+            return default(TData);
         }
 
         public async Task PersistAsync(TValue value, TData data, CancellationToken cancellationToken)

src/VisualStudio/Core/Def/Implementation/DesignerAttribute/DesignerAttributeState.cs

@@ -31,27 +31,23 @@ protected override int GetCount(Data data)
 
             protected override Data TryGetExistingData(Stream stream, Document value, CancellationToken cancellationToken)
             {
-                try
+                using (var reader = StreamObjectReader.TryGetReader(stream))
                 {
-                    using (var reader = new StreamObjectReader(stream))
+                    if (reader != null)
                     {
                         var format = reader.ReadString();
-                        if (!string.Equals(format, FormatVersion, StringComparison.InvariantCulture))
+                        if (string.Equals(format, FormatVersion, StringComparison.InvariantCulture))
                         {
-                            return null;
-                        }
-
-                        var textVersion = VersionStamp.ReadFrom(reader);
-                        var dataVersion = VersionStamp.ReadFrom(reader);
-                        var designerAttributeArgument = reader.ReadString();
+                            var textVersion = VersionStamp.ReadFrom(reader);
+                            var dataVersion = VersionStamp.ReadFrom(reader);
+                            var designerAttributeArgument = reader.ReadString();
 
-                        return new Data(textVersion, dataVersion, designerAttributeArgument);
+                            return new Data(textVersion, dataVersion, designerAttributeArgument);
+                        }
                     }
                 }
-                catch (Exception)
-                {
-                    return null;
-                }
+
+                return null;
             }
 
             protected override void WriteTo(Stream stream, Data data, CancellationToken cancellationToken)

src/VisualStudio/Core/Def/Implementation/Diagnostics/VisualStudioDiagnosticAnalyzerExecutor.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Composition;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Threading;
@@ -139,8 +140,11 @@ private CompilationWithAnalyzers CreateAnalyzerDriver(CompilationWithAnalyzers a
             // handling of cancellation and exception
             var version = await DiagnosticIncrementalAnalyzer.GetDiagnosticVersionAsync(project, cancellationToken).ConfigureAwait(false);
 
-            using (var reader = new StreamObjectReader(stream))
+            using (var reader = StreamObjectReader.TryGetReader(stream))
             {
+                Debug.Assert(reader != null,
+@"We only ge a reader for data transmitted between live processes.
+This data should always be correct as we're never persisting the data between sessions.");
                 return DiagnosticResultSerializer.Deserialize(reader, analyzerMap, project, version, cancellationToken);
             }
         }