Find file duplicates | Optimize

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void FindDuplicateFiles(string directory)
{
  var dirInfo = new DirectoryInfo(directory);
  var fileInfos = dirInfo.EnumerateFiles("*", SearchOption.AllDirectories);

  var skips = 1;
  using var eInner = fileInfos.GetEnumerator();

  while (eInner.MoveNext())
  {
    var fiInner = eInner.Current;

    var skipped = 0;
    using var eOuter = fileInfo.GetEnumerator();

    while (eOuter.MoveNext())
    {
      if (skipped++ < skip)
        continue;

      var fiOuter = eOuter.Current;
  
      if (FileContentsEqual(fiInner, fiOuter))
        Console.WriteLine($"{fiInner.FullName} and {fiOuter.FullName} are equal.");
    }

    i++;
  }
}

bool FileContentsEqual(FileInfo fi1, FileInfo fi2)
{
  if (fi1.Length != fi2.Length)
    return false;

  using var br1 = new BinaryReader(fi1.OpenRead());
  using var br2 = new BinaryReader(fi2.OpenRead());

  while (br1.BaseStream.Position != br1.BaseStream.Length)
  {
    var b1 = br1.ReadByte();
    var b2 = br2.ReadByte();

    if (b1 != b2)
      return false;
  }

  return true;
}

void FindDuplicateFiles(string directory)
{
  var dirInfo = new DirectoryInfo(directory);
  var fileInfos = dirInfo.EnumerateFiles("*", SearchOption.AllDirectories);

  var skips = 1;
  using var eOuter = fileInfos.GetEnumerator();

  while (eOuter.MoveNext())
  {
    var fiOuter = eOuter.Current;

    var skipped = 0;
    using var eInner = fileInfo.GetEnumerator();

    while (eInner.MoveNext())
    {
      if (skipped++ < skip)
        continue;

      var fiInner = eOuter.Current;
  
      if (FileContentsEqual(fiOuter, fiInner))
        Console.WriteLine($"{fiInner.FullName} and {fiOuter.FullName} are equal.");
    }
  }
}

unsafe bool FileContentsEqual(FileInfo fi1, FileInfo fi2)
{
  if (fi1.Length != fi2.Length)
    return false;

  var (s1, s2) = (fi1.OpenRead(), fi2.OpenRead());

  if (ComputeHash(s1) == ComputeHash(s2))
    return true;

  s1.Position = s2.Position = 0;

  using (BinaryReader br1, BinaryReader br2) = (new(s1), new(s2));

  const int CHUNK_SIZE = 256;

  while (br1.BaseStream.Position != br1.BaseStream.Length)
  {
    var b1 = br1.ReadBytes(CHUNK_SIZE);
    var b2 = br2.ReadBytes(CHUNK_SIZE);

    fixed (byte* pB1 = b1, pB2 = b2)
    {
      for (int i = 0; i < b1.Length; i++)
      {
        if (pB1[i] != pB2[i])
          return false;
      }
    }
  }

  return true;
}

string ComputeHash(Stream stream)
{
  using var sha512 = SHA512.Create();

  var hash = sha512.ComputeHash(stream);
  return Convert.ToBase64String(hash);
}