System.IO.Compression.ZipArchiveEntry.WriteCentralDirectoryFileHeader C# (CSharp) Méthode

        internal void WriteCentralDirectoryFileHeader()
        {
            //This part is simple, because we should definitely know the sizes by this time
            BinaryWriter writer = new BinaryWriter(_archive.ArchiveStream);

            //_entryname only gets set when we read in or call moveTo. MoveTo does a check, and
            //reading in should not be able to produce a entryname longer than ushort.MaxValue
            Debug.Assert(_storedEntryNameBytes.Length <= ushort.MaxValue);

            //decide if we need the Zip64 extra field:
            Zip64ExtraField zip64ExtraField = new Zip64ExtraField();
            uint compressedSizeTruncated, uncompressedSizeTruncated, offsetOfLocalHeaderTruncated;

            bool zip64Needed = false;

            if (SizesTooLarge()
#if DEBUG_FORCE_ZIP64
 || _archive._forceZip64
#endif
)
            {
                zip64Needed = true;
                compressedSizeTruncated = ZipHelper.Mask32Bit;
                uncompressedSizeTruncated = ZipHelper.Mask32Bit;

                //If we have one of the sizes, the other must go in there as speced for LH, but not necessarily for CH, but we do it anyways
                zip64ExtraField.CompressedSize = _compressedSize;
                zip64ExtraField.UncompressedSize = _uncompressedSize;
            }
            else
            {
                compressedSizeTruncated = (uint)_compressedSize;
                uncompressedSizeTruncated = (uint)_uncompressedSize;
            }


            if (_offsetOfLocalHeader > uint.MaxValue
#if DEBUG_FORCE_ZIP64
 || _archive._forceZip64
#endif
)
            {
                zip64Needed = true;
                offsetOfLocalHeaderTruncated = ZipHelper.Mask32Bit;

                //If we have one of the sizes, the other must go in there as speced for LH, but not necessarily for CH, but we do it anyways
                zip64ExtraField.LocalHeaderOffset = _offsetOfLocalHeader;
            }
            else
            {
                offsetOfLocalHeaderTruncated = (uint)_offsetOfLocalHeader;
            }

            if (zip64Needed)
                VersionToExtractAtLeast(ZipVersionNeededValues.Zip64);

            //determine if we can fit zip64 extra field and original extra fields all in
            int bigExtraFieldLength = (zip64Needed ? zip64ExtraField.TotalSize : 0)
                                      + (_cdUnknownExtraFields != null ? ZipGenericExtraField.TotalSize(_cdUnknownExtraFields) : 0);
            ushort extraFieldLength;
            if (bigExtraFieldLength > ushort.MaxValue)
            {
                extraFieldLength = (ushort)(zip64Needed ? zip64ExtraField.TotalSize : 0);
                _cdUnknownExtraFields = null;
            }
            else
            {
                extraFieldLength = (ushort)bigExtraFieldLength;
            }

            writer.Write(ZipCentralDirectoryFileHeader.SignatureConstant);      // Central directory file header signature  (4 bytes)
            writer.Write((byte)_versionMadeBySpecification);                    // Version made by Specification (version)  (1 byte)
            writer.Write((byte)CurrentZipPlatform);                             // Version made by Compatibility (type)     (1 byte)
            writer.Write((ushort)_versionToExtract);                            // Minimum version needed to extract        (2 bytes)
            writer.Write((ushort)_generalPurposeBitFlag);                       // General Purpose bit flag                 (2 bytes)
            writer.Write((ushort)CompressionMethod);                            // The Compression method                   (2 bytes)
            writer.Write(ZipHelper.DateTimeToDosTime(_lastModified.DateTime));  // File last modification time and date     (4 bytes)
            writer.Write(_crc32);                                               // CRC-32                                   (4 bytes)
            writer.Write(compressedSizeTruncated);                              // Compressed Size                          (4 bytes)
            writer.Write(uncompressedSizeTruncated);                            // Uncompressed Size                        (4 bytes)
            writer.Write((ushort)_storedEntryNameBytes.Length);                 // File Name Length                         (2 bytes)
            writer.Write(extraFieldLength);                                     // Extra Field Length                       (2 bytes)

            // This should hold because of how we read it originally in ZipCentralDirectoryFileHeader:
            Debug.Assert((_fileComment == null) || (_fileComment.Length <= ushort.MaxValue));

            writer.Write(_fileComment != null ? (ushort)_fileComment.Length : (ushort)0);    //file comment length
            writer.Write((ushort)0);    //disk number start
            writer.Write((ushort)0);    //internal file attributes
            writer.Write((uint)0);    //external file attributes
            writer.Write(offsetOfLocalHeaderTruncated); //offset of local header

            writer.Write(_storedEntryNameBytes);

            //write extra fields
            if (zip64Needed)
                zip64ExtraField.WriteBlock(_archive.ArchiveStream);
            if (_cdUnknownExtraFields != null)
                ZipGenericExtraField.WriteAllBlocks(_cdUnknownExtraFields, _archive.ArchiveStream);

            if (_fileComment != null)
                writer.Write(_fileComment);
        }