Crisis.Ionic.Zip.ZipEntry.ReadDirEntry C# (CSharp) Method

        internal static ZipEntry ReadDirEntry(ZipFile zf,
                                              Dictionary<String,Object> previouslySeen)
        {
            System.IO.Stream s = zf.ReadStream;
            System.Text.Encoding expectedEncoding = (zf.AlternateEncodingUsage == ZipOption.Always)
                ? zf.AlternateEncoding
                : ZipFile.DefaultEncoding;

            int signature = Crisis.Ionic.Zip.SharedUtilities.ReadSignature(s);
            // return null if this is not a local file header signature
            if (IsNotValidZipDirEntrySig(signature))
            {
                s.Seek(-4, System.IO.SeekOrigin.Current);
                // workitem 10178
                Crisis.Ionic.Zip.SharedUtilities.Workaround_Ladybug318918(s);

                // Getting "not a ZipDirEntry signature" here is not always wrong or an
                // error.  This can happen when walking through a zipfile.  After the
                // last ZipDirEntry, we expect to read an
                // EndOfCentralDirectorySignature.  When we get this is how we know
                // we've reached the end of the central directory.
                if (signature != ZipConstants.EndOfCentralDirectorySignature &&
                    signature != ZipConstants.Zip64EndOfCentralDirectoryRecordSignature &&
                    signature != ZipConstants.ZipEntrySignature  // workitem 8299
                    )
                {
                    throw new BadReadException(String.Format("  Bad signature (0x{0:X8}) at position 0x{1:X8}", signature, s.Position));
                }
                return null;
            }

            int bytesRead = 42 + 4;
            byte[] block = new byte[42];
            int n = s.Read(block, 0, block.Length);
            if (n != block.Length) return null;

            int i = 0;
            ZipEntry zde = new ZipEntry();
            zde.AlternateEncoding = expectedEncoding;
            zde._Source = ZipEntrySource.ZipFile;
            zde._container = new ZipContainer(zf);

            unchecked
            {
                zde._VersionMadeBy = (short)(block[i++] + block[i++] * 256);
                zde._VersionNeeded = (short)(block[i++] + block[i++] * 256);
                zde._BitField = (short)(block[i++] + block[i++] * 256);
                zde._CompressionMethod = (Int16)(block[i++] + block[i++] * 256);
                zde._TimeBlob = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
                zde._LastModified = Crisis.Ionic.Zip.SharedUtilities.PackedToDateTime(zde._TimeBlob);
                zde._timestamp |= ZipEntryTimestamp.DOS;

                zde._Crc32 = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;
                zde._CompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
                zde._UncompressedSize = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);
            }

            // preserve
            zde._CompressionMethod_FromZipFile = zde._CompressionMethod;

            zde._filenameLength = (short)(block[i++] + block[i++] * 256);
            zde._extraFieldLength = (short)(block[i++] + block[i++] * 256);
            zde._commentLength = (short)(block[i++] + block[i++] * 256);
            zde._diskNumber = (UInt32)(block[i++] + block[i++] * 256);

            zde._InternalFileAttrs = (short)(block[i++] + block[i++] * 256);
            zde._ExternalFileAttrs = block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256;

            zde._RelativeOffsetOfLocalHeader = (uint)(block[i++] + block[i++] * 256 + block[i++] * 256 * 256 + block[i++] * 256 * 256 * 256);

            // workitem 7801
            zde.IsText = ((zde._InternalFileAttrs & 0x01) == 0x01);

            block = new byte[zde._filenameLength];
            n = s.Read(block, 0, block.Length);
            bytesRead += n;
            if ((zde._BitField & 0x0800) == 0x0800)
            {
                // UTF-8 is in use
                zde._FileNameInArchive = Crisis.Ionic.Zip.SharedUtilities.Utf8StringFromBuffer(block);
            }
            else
            {
                zde._FileNameInArchive = Crisis.Ionic.Zip.SharedUtilities.StringFromBuffer(block, expectedEncoding);
            }

            // workitem 10330
            // insure unique entry names
            while (previouslySeen.ContainsKey(zde._FileNameInArchive))
            {
                zde._FileNameInArchive = CopyHelper.AppendCopyToFileName(zde._FileNameInArchive);
                zde._metadataChanged = true;
            }

            if (zde.AttributesIndicateDirectory)
                zde.MarkAsDirectory();  // may append a slash to filename if nec.
            // workitem 6898
            else if (zde._FileNameInArchive.EndsWith("/")) zde.MarkAsDirectory();

            zde._CompressedFileDataSize = zde._CompressedSize;
            if ((zde._BitField & 0x01) == 0x01)
            {
                // this may change after processing the Extra field
                zde._Encryption_FromZipFile = zde._Encryption =
                    EncryptionAlgorithm.PkzipWeak;
                zde._sourceIsEncrypted = true;
            }

            if (zde._extraFieldLength > 0)
            {
                zde._InputUsesZip64 = (zde._CompressedSize == 0xFFFFFFFF ||
                      zde._UncompressedSize == 0xFFFFFFFF ||
                      zde._RelativeOffsetOfLocalHeader == 0xFFFFFFFF);

                // Console.WriteLine("  Input uses Z64?:      {0}", zde._InputUsesZip64);

                bytesRead += zde.ProcessExtraField(s, zde._extraFieldLength);
                zde._CompressedFileDataSize = zde._CompressedSize;
            }

            // we've processed the extra field, so we know the encryption method is set now.
            if (zde._Encryption == EncryptionAlgorithm.PkzipWeak)
            {
                // the "encryption header" of 12 bytes precedes the file data
                zde._CompressedFileDataSize -= 12;
            }
#if AESCRYPTO
            else if (zde.Encryption == EncryptionAlgorithm.WinZipAes128 ||
                        zde.Encryption == EncryptionAlgorithm.WinZipAes256)
            {
                zde._CompressedFileDataSize = zde.CompressedSize -
                    (ZipEntry.GetLengthOfCryptoHeaderBytes(zde.Encryption) + 10);
                zde._LengthOfTrailer = 10;
            }
#endif

            // tally the trailing descriptor
            if ((zde._BitField & 0x0008) == 0x0008)
            {
                // sig, CRC, Comp and Uncomp sizes
                if (zde._InputUsesZip64)
                    zde._LengthOfTrailer += 24;
                else
                    zde._LengthOfTrailer += 16;
            }

            // workitem 12744
            zde.AlternateEncoding = ((zde._BitField & 0x0800) == 0x0800)
                ? System.Text.Encoding.UTF8
                :expectedEncoding;

            zde.AlternateEncodingUsage = ZipOption.Always;

            if (zde._commentLength > 0)
            {
                block = new byte[zde._commentLength];
                n = s.Read(block, 0, block.Length);
                bytesRead += n;
                if ((zde._BitField & 0x0800) == 0x0800)
                {
                    // UTF-8 is in use
                    zde._Comment = Crisis.Ionic.Zip.SharedUtilities.Utf8StringFromBuffer(block);
                }
                else
                {
                    zde._Comment = Crisis.Ionic.Zip.SharedUtilities.StringFromBuffer(block, expectedEncoding);
                }
            }
            //zde._LengthOfDirEntry = bytesRead;
            return zde;
        }

        // build the TOC by reading each entry in the file.
        private static void ReadIntoInstance_Orig(ZipFile zf)
        {
            zf.OnReadStarted();
            //zf._entries = new System.Collections.Generic.List<ZipEntry>();
            zf._entries = new System.Collections.Generic.Dictionary <String, ZipEntry>();

            ZipEntry e;

            if (zf.Verbose)
            {
                if (zf.Name == null)
                {
                    zf.StatusMessageTextWriter.WriteLine("Reading zip from stream...");
                }
                else
                {
                    zf.StatusMessageTextWriter.WriteLine("Reading zip {0}...", zf.Name);
                }
            }

            // work item 6647:  PK00 (packed to removable disk)
            bool         firstEntry = true;
            ZipContainer zc         = new ZipContainer(zf);

            while ((e = ZipEntry.ReadEntry(zc, firstEntry)) != null)
            {
                if (zf.Verbose)
                {
                    zf.StatusMessageTextWriter.WriteLine("  {0}", e.FileName);
                }

                zf._entries.Add(e.FileName, e);
                firstEntry = false;
            }

            // read the zipfile's central directory structure here.
            // workitem 9912
            // But, because it may be corrupted, ignore errors.
            try
            {
                ZipEntry de;
                // in lieu of hashset, use a dictionary
                var previouslySeen = new Dictionary <String, Object>();
                while ((de = ZipEntry.ReadDirEntry(zf, previouslySeen)) != null)
                {
                    // Housekeeping: Since ZipFile exposes ZipEntry elements in the enumerator,
                    // we need to copy the comment that we grab from the ZipDirEntry
                    // into the ZipEntry, so the application can access the comment.
                    // Also since ZipEntry is used to Write zip files, we need to copy the
                    // file attributes to the ZipEntry as appropriate.
                    ZipEntry e1 = zf._entries[de.FileName];
                    if (e1 != null)
                    {
                        e1._Comment = de.Comment;
                        if (de.IsDirectory)
                        {
                            e1.MarkAsDirectory();
                        }
                    }
                    previouslySeen.Add(de.FileName, null); // to prevent dupes
                }

                // workitem 8299
                if (zf._locEndOfCDS > 0)
                {
                    zf.ReadStream.Seek(zf._locEndOfCDS, SeekOrigin.Begin);
                }

                ReadCentralDirectoryFooter(zf);

                if (zf.Verbose && !String.IsNullOrEmpty(zf.Comment))
                {
                    zf.StatusMessageTextWriter.WriteLine("Zip file Comment: {0}", zf.Comment);
                }
            }
            catch (ZipException) { }
            catch (IOException) { }

            zf.OnReadCompleted();
        }