internal IEnumerable <ZipHeader> ReadSeekableHeader(Stream stream)
{
var reader = new BinaryReader(stream);
SeekBackToHeader(stream, reader, DIRECTORY_END_HEADER_BYTES);
var entry = new DirectoryEndHeader();
entry.Read(reader);
if (entry.IsZip64)
{
_zip64 = true;
SeekBackToHeader(stream, reader, ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR);
var zip64Locator = new Zip64DirectoryEndLocatorHeader();
zip64Locator.Read(reader);
stream.Seek(zip64Locator.RelativeOffsetOfTheEndOfDirectoryRecord, SeekOrigin.Begin);
uint zip64Signature = reader.ReadUInt32();
if (zip64Signature != ZIP64_END_OF_CENTRAL_DIRECTORY)
{
throw new ArchiveException("Failed to locate the Zip64 Header");
}
var zip64Entry = new Zip64DirectoryEndHeader();
zip64Entry.Read(reader);
stream.Seek(zip64Entry.DirectoryStartOffsetRelativeToDisk, SeekOrigin.Begin);
}
else
{
stream.Seek(entry.DirectoryStartOffsetRelativeToDisk, SeekOrigin.Begin);
}
long position = stream.Position;
while (true)
{
stream.Position = position;
uint signature = reader.ReadUInt32();
var nextHeader = ReadHeader(signature, reader, _zip64);
position = stream.Position;
if (nextHeader == null)
{
yield break;
}
if (nextHeader is DirectoryEntryHeader entryHeader)
{
//entry could be zero bytes so we need to know that.
entryHeader.HasData = entryHeader.CompressedSize != 0;
yield return(entryHeader);
}
else if (nextHeader is DirectoryEndHeader endHeader)
{
yield return(endHeader);
}
}
}
protected ZipHeader ReadHeader(uint headerBytes, BinaryReader reader, bool zip64 = false)
{
switch (headerBytes)
{
case ENTRY_HEADER_BYTES:
{
var entryHeader = new LocalEntryHeader(_archiveEncoding);
entryHeader.Read(reader);
LoadHeader(entryHeader, reader.BaseStream);
_lastEntryHeader = entryHeader;
return(entryHeader);
}
case DIRECTORY_START_HEADER_BYTES:
{
var entry = new DirectoryEntryHeader(_archiveEncoding);
entry.Read(reader);
return(entry);
}
case POST_DATA_DESCRIPTOR:
{
if (FlagUtility.HasFlag(_lastEntryHeader.Flags, HeaderFlags.UsePostDataDescriptor))
{
_lastEntryHeader.Crc = reader.ReadUInt32();
_lastEntryHeader.CompressedSize = zip64 ? (long)reader.ReadUInt64() : reader.ReadUInt32();
_lastEntryHeader.UncompressedSize = zip64 ? (long)reader.ReadUInt64() : reader.ReadUInt32();
}
else
{
reader.ReadBytes(zip64 ? 20 : 12);
}
return(null);
}
case DIGITAL_SIGNATURE:
return(null);
case DIRECTORY_END_HEADER_BYTES:
{
var entry = new DirectoryEndHeader();
entry.Read(reader);
return(entry);
}
case SPLIT_ARCHIVE_HEADER_BYTES:
{
return(new SplitHeader());
}
case ZIP64_END_OF_CENTRAL_DIRECTORY:
{
var entry = new Zip64DirectoryEndHeader();
entry.Read(reader);
return(entry);
}
case ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR:
{
var entry = new Zip64DirectoryEndLocatorHeader();
entry.Read(reader);
return(entry);
}
default:
return(null);
}
}
