Basic patching support

1 files changed, 71 insertions, 0 deletions

diff --git a/src/WixToolset.Core.WindowsInstaller/Bind/FileSystemManager.cs b/src/WixToolset.Core.WindowsInstaller/Bind/FileSystemManager.cs
new file mode 100644
index 00000000..75477271
--- /dev/null
+++ b/src/WixToolset.Core.WindowsInstaller/Bind/FileSystemManager.cs
@@ -0,0 +1,71 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Core.WindowsInstaller.Bind
+{
+    using System.Collections.Generic;
+    using System.IO;
+    using WixToolset.Extensibility;
+
+    internal class FileSystemManager
+    {
+        public FileSystemManager(IEnumerable<IFileSystemExtension> fileSystemExtensions)
+        {
+            this.Extensions = fileSystemExtensions;
+        }
+
+        private IEnumerable<IFileSystemExtension> Extensions { get; }
+
+        public bool CompareFiles(string firstPath, string secondPath)
+        {
+            foreach (var extension in this.Extensions)
+            {
+                var compared = extension.CompareFiles(firstPath, secondPath);
+                if (compared.HasValue)
+                {
+                    return compared.Value;
+                }
+            }
+
+            return BuiltinCompareFiles(firstPath, secondPath);
+        }
+
+        private static bool BuiltinCompareFiles(string firstPath, string secondPath)
+        {
+            using (var firstStream = File.OpenRead(firstPath))
+            using (var secondStream = File.OpenRead(secondPath))
+            {
+                if (firstStream.Length != secondStream.Length)
+                {
+                    return false;
+                }
+
+                // Using a larger buffer than the default buffer of 4 * 1024 used by FileStream.ReadByte improves performance.
+                // The buffer size is based on user feedback. Based on performance results, a better buffer size may be determined.
+                var firstBuffer = new byte[16 * 1024];
+                var secondBuffer = new byte[16 * 1024];
+
+                var firstReadLength = 0;
+                do
+                {
+                    firstReadLength = firstStream.Read(firstBuffer, 0, firstBuffer.Length);
+                    var secondReadLength = secondStream.Read(secondBuffer, 0, secondBuffer.Length);
+
+                    if (firstReadLength != secondReadLength)
+                    {
+                        return false;
+                    }
+
+                    for (var i = 0; i < firstReadLength; ++i)
+                    {
+                        if (firstBuffer[i] != secondBuffer[i])
+                        {
+                            return false;
+                        }
+                    }
+                } while (0 < firstReadLength);
+            }
+
+            return true;
+        }
+    }
+}