Read and write compound files

using RecursiveAI.OneArchive;
using System.Text;
 
// Write a Microsoft compound file: storages are directories, streams are files.
byte[] summary = Encoding.UTF8.GetBytes("Quarterly notes");
byte[] chart = new byte[10_000];
Archive.Create("notes.cfb")
    .Add(new ArchiveEntry { Name = "Summary", Kind = ArchiveEntryKind.File, Size = summary.Length }, summary)
    .Add(new ArchiveEntry { Name = "Attachments", Kind = ArchiveEntryKind.Directory }, [])
    .Add(new ArchiveEntry { Name = "Attachments/chart", Kind = ArchiveEntryKind.File, Size = chart.Length }, chart)
    .Save();
 
byte[] head = File.ReadAllBytes("notes.cfb")[..8];
Console.WriteLine($"notes.cfb: {new FileInfo("notes.cfb").Length:N0} bytes, signature {Convert.ToHexString(head)}");
 
// Read it back, the same way as a .doc, .xls, .ppt or .msg file.
using var cfb = Archive.Open("notes.cfb");
foreach (var e in cfb.Entries) Console.WriteLine($"  {e.Kind,-9} {e.Size,6:N0}  {e.Name}");
using var s = cfb.OpenEntry(cfb.Find("Summary")!);
Console.WriteLine($"Summary: {new StreamReader(s).ReadToEnd()}");

notes.cfb: 12,800 bytes, signature D0CF11E0A1B11AE1
  File          15  Summary
  Directory      0  Attachments
  File      10,000  Attachments/chart
Summary: Quarterly notes