1 files changed, 90 insertions, 0 deletions

diff --git a/src/tools/Dtf/DDiff/VersionedFileDiffEngine.cs b/src/tools/Dtf/DDiff/VersionedFileDiffEngine.cs
new file mode 100644
index 00000000..9a3e399f
--- /dev/null
+++ b/src/tools/Dtf/DDiff/VersionedFileDiffEngine.cs
@@ -0,0 +1,90 @@
+// 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.
+
+using System;
+using System.IO;
+using WixToolset.Dtf.WindowsInstaller;
+
+namespace WixToolset.Dtf.Tools.DDiff
+{
+        public class VersionedFileDiffEngine : IDiffEngine
+        {
+                public VersionedFileDiffEngine()
+                {
+                }
+
+                private bool IsVersionedFile(string file)
+                {
+                        return Installer.GetFileVersion(file) != "";
+                }
+
+                public float GetDiffQuality(string diffInput1, string diffInput2, string[] options, IDiffEngineFactory diffFactory)
+                {
+                        if(diffInput1 != null && File.Exists(diffInput1) &&
+                           diffInput2 != null && File.Exists(diffInput2) &&
+                           (IsVersionedFile(diffInput1) || IsVersionedFile(diffInput2)))
+                        {
+                                return .20f;
+                        }
+                        else
+                        {
+                                return 0;
+                        }
+                }
+
+                public bool GetDiff(string diffInput1, string diffInput2, string[] options, TextWriter diffOutput, string linePrefix, IDiffEngineFactory diffFactory)
+                {
+                        bool difference = false;
+
+                        string ver1 = Installer.GetFileVersion(diffInput1);
+                        string ver2 = Installer.GetFileVersion(diffInput2);
+
+                        if(ver1 != ver2)
+                        {
+                                diffOutput.WriteLine("{0}File version: {1} -> {2}", linePrefix, ver1, ver2);
+                                difference = true;
+                        }
+                        else
+                        {
+                                FileStream stream1 = new FileStream(diffInput1, FileMode.Open, FileAccess.Read, FileShare.Read);
+                                FileStream stream2 = new FileStream(diffInput2, FileMode.Open, FileAccess.Read, FileShare.Read);
+
+                                byte[] buf1 = new byte[512];
+                                byte[] buf2 = new byte[512];
+
+                                while(!difference)
+                                {
+                                        int count1 = stream1.Read(buf1, 0, buf1.Length);
+                                        int count2 = stream2.Read(buf2, 0, buf2.Length);
+
+                                        for(int i = 0; i < count1; i++)
+                                        {
+                                                if(i == count2 || buf1[i] != buf2[i])
+                                                {
+                                                        difference = true;
+                                                        break;
+                                                }
+                                        }
+                                        if(count1 < buf1.Length) // EOF
+                                        {
+                                                break;
+                                        }
+                                }
+
+                                stream1.Close();
+                                stream2.Close();
+
+                                if(difference)
+                                {
+                                        diffOutput.WriteLine("{0}File versions match but bits differ.", linePrefix);
+                                }
+                        }
+
+                        return difference;
+                }
+
+                public IDiffEngine Clone()
+                {
+                        return new VersionedFileDiffEngine();
+                }
+        }
+}