void CopyEntry(ZipFile workFile, ZipUpdate update)
		{
			workFile.WriteLocalEntryHeader(update);

			if ( update.Entry.CompressedSize > 0 ) {
				const int NameLengthOffset = 26;

				long entryDataOffset = update.Entry.Offset + NameLengthOffset;

				// TODO: This wont work for SFX files!
				baseStream_.Seek(entryDataOffset, SeekOrigin.Begin);

				uint nameLength = ReadLEUshort();
				uint extraLength = ReadLEUshort();

				baseStream_.Seek(nameLength + extraLength, SeekOrigin.Current);

				CopyBytes(update, workFile.baseStream_, baseStream_, update.Entry.CompressedSize, false);
			}
			CopyDescriptorBytes(update, workFile.baseStream_, baseStream_);
		}
		void ModifyEntry(ZipFile workFile, ZipUpdate update)
		{
			workFile.WriteLocalEntryHeader(update);
			long dataStart = workFile.baseStream_.Position;

			// TODO: This is slow if the changes don't effect the data!!
			if ( update.Entry.IsFile && (update.Filename != null) ) {
				using ( Stream output = workFile.GetOutputStream(update.OutEntry) ) {
					using ( Stream source = this.GetInputStream(update.Entry) ) {
						CopyBytes(update, output, source, source.Length, true);
					}
				}
			}

			long dataEnd = workFile.baseStream_.Position;
			update.Entry.CompressedSize = dataEnd - dataStart;
		}
		void CopyEntryDirect(ZipFile workFile, ZipUpdate update, ref long destinationPosition)
		{
			bool skipOver = false;
			if ( update.Entry.Offset == destinationPosition ) {
				skipOver = true;
			}

			if ( !skipOver ) {
				baseStream_.Position = destinationPosition;
				workFile.WriteLocalEntryHeader(update);
				destinationPosition = baseStream_.Position;
			}

			long sourcePosition = 0;

			const int NameLengthOffset = 26;

			// TODO: Add base for SFX friendly handling
			long entryDataOffset = update.Entry.Offset + NameLengthOffset;

			baseStream_.Seek(entryDataOffset, SeekOrigin.Begin);

			// Clumsy way of handling retrieving the original name and extra data length for now.
			// TODO: Stop re-reading name and data length in CopyEntryDirect.
			uint nameLength = ReadLEUshort();
			uint extraLength = ReadLEUshort();

			sourcePosition = baseStream_.Position + nameLength + extraLength;

			if ( skipOver ) {
				destinationPosition += 
					(sourcePosition - entryDataOffset) + NameLengthOffset +	// Header size
					update.Entry.CompressedSize + GetDescriptorSize(update);
			}
			else {
				if ( update.Entry.CompressedSize > 0 ) {
					CopyEntryDataDirect(update, baseStream_, false, ref destinationPosition, ref sourcePosition );
				}
				CopyDescriptorBytesDirect(update, baseStream_, ref destinationPosition, sourcePosition);
			}
		}
		void AddEntry(ZipFile workFile, ZipUpdate update)
		{
			Stream source = null;

			if ( update.Entry.IsFile ) {
				source = update.GetSource();
				
				if ( source == null ) {
					source = updateDataSource_.GetSource(update.Entry, update.Filename);
				}
			}

			if ( source != null ) {
				using ( source ) {
					long sourceStreamLength = source.Length;
					if ( update.OutEntry.Size < 0 ) {
						update.OutEntry.Size = sourceStreamLength;
					}
					else {
						// Check for errant entries.
						if ( update.OutEntry.Size != sourceStreamLength ) {
							throw new ZipException("Entry size/stream size mismatch");
						}
					}

					workFile.WriteLocalEntryHeader(update);

					long dataStart = workFile.baseStream_.Position;

					using ( Stream output = workFile.GetOutputStream(update.OutEntry) ) {
						CopyBytes(update, output, source, sourceStreamLength, true);
					}

					long dataEnd = workFile.baseStream_.Position;
					update.OutEntry.CompressedSize = dataEnd - dataStart;

					if ((update.OutEntry.Flags & (int)GeneralBitFlags.Descriptor) == (int)GeneralBitFlags.Descriptor)
					{
						ZipHelperStream helper = new ZipHelperStream(workFile.baseStream_);
						helper.WriteDataDescriptor(update.OutEntry);
					}
				}
			}
			else {
				workFile.WriteLocalEntryHeader(update);
				update.OutEntry.CompressedSize = 0;
			}

		}