// Reads attributes specific to the GNU format. // Throws if any conversion fails. private void ReadGnuAttributes(Span <byte> buffer) { // Convert byte arrays long aTime = TarHelpers.GetTenBaseLongFromOctalAsciiChars(buffer.Slice(FieldLocations.ATime, FieldLengths.ATime)); _aTime = TarHelpers.GetDateTimeOffsetFromSecondsSinceEpoch(aTime); long cTime = TarHelpers.GetTenBaseLongFromOctalAsciiChars(buffer.Slice(FieldLocations.CTime, FieldLengths.CTime)); _cTime = TarHelpers.GetDateTimeOffsetFromSecondsSinceEpoch(cTime); // TODO: Read the bytes of the currently unsupported GNU fields, in case user wants to write this entry into another GNU archive, they need to be preserved. https://github.com/dotnet/runtime/issues/68230 }
// Attempts to read the fields shared by all formats and stores them in their expected data type. // Throws if any data type conversion fails. // Returns true on success, false if checksum is zero. private static TarHeader?TryReadCommonAttributes(Span <byte> buffer, TarEntryFormat initialFormat) { // Start by collecting fields that need special checks that return early when data is wrong // Empty checksum means this is an invalid (all blank) entry, finish early Span <byte> spanChecksum = buffer.Slice(FieldLocations.Checksum, FieldLengths.Checksum); if (TarHelpers.IsAllNullBytes(spanChecksum)) { return(null); } int checksum = TarHelpers.GetTenBaseNumberFromOctalAsciiChars(spanChecksum); // Zero checksum means the whole header is empty if (checksum == 0) { return(null); } long size = TarHelpers.GetTenBaseNumberFromOctalAsciiChars(buffer.Slice(FieldLocations.Size, FieldLengths.Size)); if (size < 0) { throw new FormatException(string.Format(SR.TarSizeFieldNegative)); } // Continue with the rest of the fields that require no special checks TarHeader header = new(initialFormat, name : TarHelpers.GetTrimmedUtf8String(buffer.Slice(FieldLocations.Name, FieldLengths.Name)), mode : TarHelpers.GetTenBaseNumberFromOctalAsciiChars(buffer.Slice(FieldLocations.Mode, FieldLengths.Mode)), mTime : TarHelpers.GetDateTimeOffsetFromSecondsSinceEpoch(TarHelpers.GetTenBaseLongFromOctalAsciiChars(buffer.Slice(FieldLocations.MTime, FieldLengths.MTime))), typeFlag : (TarEntryType)buffer[FieldLocations.TypeFlag]) { _checksum = checksum, _size = size, _uid = TarHelpers.GetTenBaseNumberFromOctalAsciiChars(buffer.Slice(FieldLocations.Uid, FieldLengths.Uid)), _gid = TarHelpers.GetTenBaseNumberFromOctalAsciiChars(buffer.Slice(FieldLocations.Gid, FieldLengths.Gid)), _linkName = TarHelpers.GetTrimmedUtf8String(buffer.Slice(FieldLocations.LinkName, FieldLengths.LinkName)) }; if (header._format == TarEntryFormat.Unknown) { header._format = header._typeFlag switch { TarEntryType.ExtendedAttributes or TarEntryType.GlobalExtendedAttributes => TarEntryFormat.Pax, TarEntryType.DirectoryList or TarEntryType.LongLink or TarEntryType.LongPath or TarEntryType.MultiVolume or TarEntryType.RenamedOrSymlinked or TarEntryType.SparseFile or TarEntryType.TapeVolume => TarEntryFormat.Gnu, // V7 is the only one that uses 'V7RegularFile'. TarEntryType.V7RegularFile => TarEntryFormat.V7, // We can quickly determine the *minimum* possible format if the entry type // is the POSIX 'RegularFile', although later we could upgrade it to PAX or GNU _ => (header._typeFlag == TarEntryType.RegularFile) ? TarEntryFormat.Ustar : TarEntryFormat.V7 }; } return(header); }