// Determines what kind of stream needs to be saved for the data section.
// - Metadata typeflag entries (Extended Attributes and Global Extended Attributes in PAX, LongLink and LongPath in GNU)
// will get all the data section read and the stream pointer positioned at the beginning of the next header.
// - Block, Character, Directory, Fifo, HardLink and SymbolicLink typeflag entries have no data section so the archive stream pointer will be positioned at the beginning of the next header.
// - All other typeflag entries with a data section will generate a stream wrapping the data section: SeekableSubReadStream for seekable archive streams, and SubReadStream for unseekable archive streams.
private void ProcessDataBlock(Stream archiveStream, bool copyData)
{
bool skipBlockAlignmentPadding = true;
switch (_typeFlag)
{
case TarEntryType.ExtendedAttributes or TarEntryType.GlobalExtendedAttributes:
ReadExtendedAttributesBlock(archiveStream);
break;
case TarEntryType.LongLink or TarEntryType.LongPath:
ReadGnuLongPathDataBlock(archiveStream);
break;
case TarEntryType.BlockDevice:
case TarEntryType.CharacterDevice:
case TarEntryType.Directory:
case TarEntryType.Fifo:
case TarEntryType.HardLink:
case TarEntryType.SymbolicLink:
// No data section
break;
case TarEntryType.RegularFile:
case TarEntryType.V7RegularFile: // Treated as regular file
case TarEntryType.ContiguousFile: // Treated as regular file
case TarEntryType.DirectoryList: // Contains the list of filesystem entries in the data section
case TarEntryType.MultiVolume: // Contains portion of a file
case TarEntryType.RenamedOrSymlinked: // Might contain data
case TarEntryType.SparseFile: // Contains portion of a file
case TarEntryType.TapeVolume: // Might contain data
default: // Unrecognized entry types could potentially have a data section
_dataStream = GetDataStream(archiveStream, copyData);
if (_dataStream is SeekableSubReadStream)
{
TarHelpers.AdvanceStream(archiveStream, _size);
}
else if (_dataStream is SubReadStream)
{
// This stream gives the user the chance to optionally read the data section
// when the underlying archive stream is unseekable
skipBlockAlignmentPadding = false;
}
break;
}
if (skipBlockAlignmentPadding)
{
if (_size > 0)
{
TarHelpers.SkipBlockAlignmentPadding(archiveStream, _size);
}
if (archiveStream.CanSeek)
{
_endOfHeaderAndDataAndBlockAlignment = archiveStream.Position;
}
}
}
// Moves the underlying archive stream position pointer to the beginning of the next header.
internal void AdvanceDataStreamIfNeeded()
{
if (_previouslyReadEntry == null)
{
return;
}
if (_archiveStream.CanSeek)
{
Debug.Assert(_previouslyReadEntry._header._endOfHeaderAndDataAndBlockAlignment > 0);
_archiveStream.Position = _previouslyReadEntry._header._endOfHeaderAndDataAndBlockAlignment;
}
else if (_previouslyReadEntry._header._size > 0)
{
// When working with seekable streams, every time we return an entry, we avoid advancing the pointer beyond the data section
// This is so the user can read the data if desired. But if the data was not read by the user, we need to advance the pointer
// here until it's located at the beginning of the next entry header.
// This should only be done if the previous entry came from a TarReader and it still had its original SubReadStream or SeekableSubReadStream.
if (_previouslyReadEntry._header._dataStream is not SubReadStream dataStream)
{
return;
}
if (!dataStream.HasReachedEnd)
{
// If the user did not advance the position, we need to make sure the position
// pointer is located at the beginning of the next header.
if (dataStream.Position < (_previouslyReadEntry._header._size - 1))
{
long bytesToSkip = _previouslyReadEntry._header._size - dataStream.Position;
TarHelpers.AdvanceStream(_archiveStream, bytesToSkip);
TarHelpers.SkipBlockAlignmentPadding(_archiveStream, _previouslyReadEntry._header._size);
dataStream.HasReachedEnd = true; // Now the pointer is beyond the limit, so any read attempts should throw
}
}
}
}