ICSharpCode.SharpZipLib.Zip.ZipHelperStream.WriteDataDescriptor C# (CSharp) Method

        public int WriteDataDescriptor(ZipEntry entry)
        {
            if (entry == null) {
                throw new ArgumentNullException(nameof(entry));
            }

            int result = 0;

            // Add data descriptor if flagged as required
            if ((entry.Flags & (int)GeneralBitFlags.Descriptor) != 0) {
                // The signature is not PKZIP originally but is now described as optional
                // in the PKZIP Appnote documenting trhe format.
                WriteLEInt(ZipConstants.DataDescriptorSignature);
                WriteLEInt(unchecked((int)(entry.Crc)));

                result += 8;

                if (entry.LocalHeaderRequiresZip64) {
                    WriteLELong(entry.CompressedSize);
                    WriteLELong(entry.Size);
                    result += 16;
                } else {
                    WriteLEInt((int)entry.CompressedSize);
                    WriteLEInt((int)entry.Size);
                    result += 8;
                }
            }

            return result;
        }

		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;
			}

		}