public void GenerateArchive(byte[] header, byte[] trailer, string outputPath)
{
var headerLength = header.Length;
using (var memory = new FileStream(outputPath, FileMode.Create))
{
using (var writer = new BinaryWriter(memory))
{
writer.Write(header);
foreach (var file in _files)
{
file.LocalHeaderOffset = (uint)(writer.BaseStream.Length - headerLength);
writer.Write(file.LocalFileHeader.FileHeader);
writer.Write(file.File.Span);
}
var localFilesSize = writer.BaseStream.Length - headerLength;
foreach (var file in _files)
{
writer.Write(file.CentralDircetoryFileHeader.FileHeader);
}
var centralDirSize = writer.BaseStream.Length - localFilesSize - headerLength;
var eocdRecord = new EndOfCentralDirectoryRecord((uint)localFilesSize, (uint)centralDirSize, (ushort)_files.Count, _comment);
writer.Write(eocdRecord.FileHeader);
writer.Write(trailer);
}
}
}
public CentralDirectory(Stream reader)
{
_stream = reader;
var sig = EndOfCentralDirectoryRecord.HeaderSignature;
_stream.Seek(-1024, SeekOrigin.End);
var found = false;
var counter = 0;
int currentByte;
while (!found && (currentByte = _stream.ReadByte()) != -1)
{
if (sig[counter] == (byte)currentByte)
{
counter++;
}
else
{
counter = 0;
}
if (counter == sig.Length)
{
found = true;
}
}
if (found)
{
_stream.Seek(-4, SeekOrigin.Current);
Span <byte> buffer = stackalloc byte[(int)(_stream.Length - _stream.Position)];
_stream.Read(buffer);
_eocdHeader = new EndOfCentralDirectoryRecord(buffer);
_stream.Seek(_eocdHeader.CentralDirectoryOffset + 516, SeekOrigin.Begin);
var cdBuffer = new byte[_eocdHeader.CentralDirectorySize].AsSpan();
_stream.Read(cdBuffer);
_cdHeaders = new List <CentralDirectoryFileHeader>(_eocdHeader.TotalEntries);
var offset = 0;
while (_cdHeaders.Count < _eocdHeader.TotalEntries)
{
var header = new CentralDirectoryFileHeader(cdBuffer.Slice(offset));
offset += header.FileHeader.Length;
_cdHeaders.Add(header);
}
}
else
{
throw new ArgumentException("End of Directory Header could not be found!");
}
}
