FSO.Files.Formats.PiffEncoder.GeneratePiff C# (CSharp) Method

        public static IffFile GeneratePiff(IffFile iff, HashSet<Type> allowedTypes, HashSet<Type> disallowedTypes)
        {
            var piffFile = new IffFile();

            var piff = new PIFF();
            piff.SourceIff = iff.Filename;
            var entries = new List<PIFFEntry>();
            var chunks = iff.ListAll();

            //write removals first
            foreach (var c in iff.RemovedOriginal)
            {
                lock (c)
                {
                    if ((allowedTypes == null || allowedTypes.Contains(c.GetType()))
                        && (disallowedTypes == null || !disallowedTypes.Contains(c.GetType())))
                    {
                        entries.Add(new PIFFEntry {
                            Type = c.ChunkType, ChunkID = c.OriginalID, Delete = true,
                            ChunkLabel = c.ChunkLabel, ChunkFlags = c.ChunkFlags
                        });
                    }
                }
            }

            foreach (var c in chunks)
            {
                lock (c)
                {
                    if ((allowedTypes == null || allowedTypes.Contains(c.GetType()))
                        && (disallowedTypes == null || !disallowedTypes.Contains(c.GetType())))
                    {
                        if (c.AddedByPatch)
                        {
                            //this chunk has been newly added.
                            var oldParent = c.ChunkParent;
                            piffFile.AddChunk(c);
                            c.ChunkParent = oldParent;
                        }
                        else if ((c.RuntimeInfo == ChunkRuntimeState.Modified || c.RuntimeInfo == ChunkRuntimeState.Patched))
                        {
                            var chunkD = MakeChunkDiff(c);
                            if (chunkD != null && (chunkD.Patches.Length > 0 || c.OriginalLabel != c.ChunkLabel || c.OriginalID != c.ChunkID))
                            {
                                entries.Add(chunkD);
                            }
                            c.RuntimeInfo = ChunkRuntimeState.Patched;
                        }
                    }
                }
            }
            if (entries.Count == 0) return null; //no patch data...
            piff.Entries = entries.ToArray();
            piff.ChunkID = 256;
            piff.ChunkLabel = (piff.SourceIff + " patch");
            piff.ChunkProcessed = true;

            piffFile.AddChunk(piff);
            piffFile.Filename = piff.SourceIff.Substring(0, piff.SourceIff.Length - 4)+".piff";
            return piffFile;
        }