System.IO.Compression.ZipCentralDirectoryFileHeader.TryReadBlock C# (CSharp) Méthode

        static public bool TryReadBlock(BinaryReader reader, bool saveExtraFieldsAndComments, out ZipCentralDirectoryFileHeader header)
        {
            header = new ZipCentralDirectoryFileHeader();

            if (reader.ReadUInt32() != SignatureConstant)
                return false;
            header.VersionMadeBySpecification = reader.ReadByte();
            header.VersionMadeByCompatibility = reader.ReadByte();
            header.VersionNeededToExtract = reader.ReadUInt16();
            header.GeneralPurposeBitFlag = reader.ReadUInt16();
            header.CompressionMethod = reader.ReadUInt16();
            header.LastModified = reader.ReadUInt32();
            header.Crc32 = reader.ReadUInt32();
            uint compressedSizeSmall = reader.ReadUInt32();
            uint uncompressedSizeSmall = reader.ReadUInt32();
            header.FilenameLength = reader.ReadUInt16();
            header.ExtraFieldLength = reader.ReadUInt16();
            header.FileCommentLength = reader.ReadUInt16();
            ushort diskNumberStartSmall = reader.ReadUInt16();
            header.InternalFileAttributes = reader.ReadUInt16();
            header.ExternalFileAttributes = reader.ReadUInt32();
            uint relativeOffsetOfLocalHeaderSmall = reader.ReadUInt32();

            header.Filename = reader.ReadBytes(header.FilenameLength);

            bool uncompressedSizeInZip64 = uncompressedSizeSmall == ZipHelper.Mask32Bit;
            bool compressedSizeInZip64 = compressedSizeSmall == ZipHelper.Mask32Bit;
            bool relativeOffsetInZip64 = relativeOffsetOfLocalHeaderSmall == ZipHelper.Mask32Bit;
            bool diskNumberStartInZip64 = diskNumberStartSmall == ZipHelper.Mask16Bit;

            Zip64ExtraField zip64;

            long endExtraFields = reader.BaseStream.Position + header.ExtraFieldLength;
            using (Stream str = new SubReadStream(reader.BaseStream, reader.BaseStream.Position, header.ExtraFieldLength))
            {
                if (saveExtraFieldsAndComments)
                {
                    header.ExtraFields = ZipGenericExtraField.ParseExtraField(str);
                    zip64 = Zip64ExtraField.GetAndRemoveZip64Block(header.ExtraFields,
                            uncompressedSizeInZip64, compressedSizeInZip64,
                            relativeOffsetInZip64, diskNumberStartInZip64);
                }
                else
                {
                    header.ExtraFields = null;
                    zip64 = Zip64ExtraField.GetJustZip64Block(str,
                            uncompressedSizeInZip64, compressedSizeInZip64,
                            relativeOffsetInZip64, diskNumberStartInZip64);
                }
            }

            // There are zip files that have malformed ExtraField blocks in which GetJustZip64Block() silently bails out without reading all the way to the end
            // of the ExtraField block. Thus we must force the stream's position to the proper place. 
            reader.BaseStream.AdvanceToPosition(endExtraFields);

            if (saveExtraFieldsAndComments)
                header.FileComment = reader.ReadBytes(header.FileCommentLength);
            else
            {
                reader.BaseStream.Position += header.FileCommentLength;
                header.FileComment = null;
            }

            header.UncompressedSize = zip64.UncompressedSize == null
                                                    ? uncompressedSizeSmall
                                                    : zip64.UncompressedSize.Value;
            header.CompressedSize = zip64.CompressedSize == null
                                                    ? compressedSizeSmall
                                                    : zip64.CompressedSize.Value;
            header.RelativeOffsetOfLocalHeader = zip64.LocalHeaderOffset == null
                                                    ? relativeOffsetOfLocalHeaderSmall
                                                    : zip64.LocalHeaderOffset.Value;
            header.DiskNumberStart = zip64.StartDiskNumber == null
                                                    ? diskNumberStartSmall
                                                    : zip64.StartDiskNumber.Value;

            return true;
        }
    }

        private void ReadCentralDirectory()
        {
            try
            {
                //assume ReadEndOfCentralDirectory has been called and has populated _centralDirectoryStart

                _archiveStream.Seek(_centralDirectoryStart, SeekOrigin.Begin);

                long numberOfEntries = 0;

                //read the central directory
                ZipCentralDirectoryFileHeader currentHeader;
                bool saveExtraFieldsAndComments = Mode == ZipArchiveMode.Update;
                while (ZipCentralDirectoryFileHeader.TryReadBlock(_archiveReader,
                                                                  saveExtraFieldsAndComments, out currentHeader))
                {
                    AddEntry(new ZipArchiveEntry(this, currentHeader));
                    numberOfEntries++;
                }

                if (numberOfEntries != _expectedNumberOfEntries)
                {
                    throw new InvalidDataException(SR.NumEntriesWrong);
                }
            }
            catch (EndOfStreamException ex)
            {
                throw new InvalidDataException(SR.Format(SR.CentralDirectoryInvalid, ex));
            }
        }