TextFileDiffEngine.cs :  » Installers-Generators » WiX » Microsoft » Deployment » Samples » DDiff » C# / CSharp Open Source

using System;
using System.IO;
using System.Diagnostics;

namespace Microsoft.Deployment.Samples.DDiff{
  public class TextFileDiffEngine : IDiffEngine
  {
    public TextFileDiffEngine()
    {
    }

    private bool IsTextFile(string file)
    {
      // Guess whether this is a text file by reading the first few bytes and checking for non-ascii chars.

      bool isText = true;
      FileStream stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read);
      byte[] buf = new byte[256];
      int count = stream.Read(buf, 0, buf.Length);
      for(int i = 0; i < count; i++)
      {
        if((buf[i] & 0x80) != 0)
        {
          isText = false;
          break;
        }
      }
      stream.Close();
      return isText;
    }

    public float GetDiffQuality(string diffInput1, string diffInput2, string[] options, IDiffEngineFactory diffFactory)
    {
      if(diffInput1 != null && File.Exists(diffInput1) &&
        diffInput2 != null && File.Exists(diffInput2) &&
        (IsTextFile(diffInput1) && IsTextFile(diffInput2)))
      {
        return .70f;
      }
      else
      {
        return 0;
      }
    }

    public bool GetDiff(string diffInput1, string diffInput2, string[] options, TextWriter diffOutput, string linePrefix, IDiffEngineFactory diffFactory)
    {
      try
      {
        bool difference = false;
        ProcessStartInfo psi = new ProcessStartInfo("diff.exe");
        psi.Arguments = String.Format("\"{0}\" \"{1}\"", diffInput1, diffInput2);
        psi.WorkingDirectory = null;
        psi.UseShellExecute = false;
        psi.WindowStyle = ProcessWindowStyle.Hidden;
        psi.RedirectStandardOutput = true;
        Process proc = Process.Start(psi);

        string line;
        while((line = proc.StandardOutput.ReadLine()) != null)
        {
          diffOutput.WriteLine("{0}{1}", linePrefix, line);
          difference = true;
        }

        proc.WaitForExit();
        return difference;
      }
      catch(System.ComponentModel.Win32Exception)  // If diff.exe is not found, just compare the bytes
      {
        return new FileDiffEngine().GetDiff(diffInput1, diffInput2, options, diffOutput, linePrefix, diffFactory);
      }
    }

    public IDiffEngine Clone()
    {
      return new TextFileDiffEngine();
    }
  }
}