sharpcompress/PITCHME.md

SharpCompress - Pure C# Archival and Compression

---

Overview

• History
• Design
• Archival Formats
• Usages (Code!)

---

Why?

• Bored
• Interested in Comics and wanted to make my own cross-platform viewer
• Wrote a viewer in Sliverlight 2 using first versions of SharpCompress.
• Used it on OS X

---

Initial Version

• Started as NUnrar on Codeplex
• Used Visual Studio 2003 to convert JUnrar to C#
• Cleaned up to have a nicer API

---

More Formats

• Integrated DotNetZip
• Created Unified API
• Added Tar
• Contributions: 7Zip, LZip, more!

---

Design

---

Unified APIs

• Random Access
  • Archive API
• Forward-only
  • Reader API
  • Writer API
• Neutral Factories

---

Neural Factories

• Factories
  • ArchiveFactory
  • ReaderFactory
  • WriterFactory
• Strategy
  • Look for Archive Signatures
  • "Rewind" if necessary with RewindableStream

---

Random Access

• Random/Seekable access on a data stream (e.g. a File)
• Strategy
  • Read Header, Skip Data
  • Dictionary

---

Forward-only

• Everything is a stream of data
• Support NetworkStreams
• Very large files
• yield return usage

---

Formats

---

Zip

• Header-Data Format
  • Optional data trailer (forward-only writing support)
  • Trailing dictionary of entries
• pkware spec - APPNOTE.txt
• Supports Reader API, Writer API and Archive API
• Compression algorthims: just about everything
  • Deflate, BZ2, LZMA 1/2, PPMd

---

Rar

• Header-Data Format
  • SOLID is a stream of compressed header-data pairs for small files
  • Multi-file archive
• Unrar open-source, rar is closed-source
• Supports Reader API and Archive API
• Compression looks to be a modification of PPMd

---

7Zip

• Multi-data compressed Format
  • Headers are compressed
  • Multiple compressed "streams"
• Readable Archive API support
• Annoying
• Known for LZMA

---

Tar

• Header-Data Format
• Supports Reader API, Writer API and Archive API
• Uncompressed
• Many additions to out-grow limitations
  • UStar
  • PAX

---

GZip, BZip, LZip, Xz

• Header-Data Format of a single entry
• Supports Reader API, Writer API and Archive API
• Used with Tar
• Compression
  • GZip - Deflate
  • BZip2 - BZip2
  • Xz - LZMA2
  • LZip - LZMA1 (improvement on Xz)

---

Usages

---

Reader

Writing entry to directory

using (Stream stream = new NetworkStream()) // pretend
using (IReader reader = ReaderFactory.Open(stream))
{
    while (reader.MoveToNextEntry())
    {
        if (!reader.Entry.IsDirectory)
        {
            reader.WriteEntryToDirectory(test.SCRATCH_FILES_PATH, new ExtractionOptions()
            {
                ExtractFullPath = true,
                Overwrite = true
            });
        }
    }
}

---

Reader

Writing entry to a stream

using (var reader = RarReader.Open("Rar.rar"))
{
    while (reader.MoveToNextEntry())
    {
        if (!reader.Entry.IsDirectory)
        {
            using (var entryStream = reader.OpenEntryStream())
            {
                string file = Path.GetFileName(reader.Entry.Key);
                string folder = Path.GetDirectoryName(reader.Entry.Key);
                string destdir = Path.Combine(SCRATCH_FILES_PATH, folder);
                if (!Directory.Exists(destdir))
                {
                    Directory.CreateDirectory(destdir);
                }
                string destinationFileName = Path.Combine(destdir, file);
                using (FileStream fs = File.OpenWrite(destinationFileName))
                {
                    entryStream.TransferTo(fs);
                }
            }
        }
    }
}

---

Writer

Creating archive

using (Stream stream = File.OpenWrite("Test.tar.lz"))
using (var writer = WriterFactory.Open(stream, ArchiveType.Tar, CompressionType.LZip))
{
    writer.WriteAll("C:\", "*", SearchOption.AllDirectories);
}

---

Archive

---

Projects

• Mono's Zip implementation
• Nodatime
• Octopus Deploy
• Duplicati
• Large ISO multi-file usage

---

Open-source Notes

• Mostly solo effort
• A few significant contributions
  • Russian friend did RarStream
  • Jon Skeet contributed LZip reading
  • Deflate64 recently added
• Can always use help!
  • Multi-file zip support
  • Encryption in various formats (some support exists)
  • General clean up