oarc is a command-line tool written in Oberon using the Vishap Oberon Compiler (VOC) that allows you to manipulate .Arc archive files originally used in Oberon System 3.

These archives are based on LZ77 compression and were used in the classical Oberon system to bundle and distribute sources. This tool enables modern systems to interact with those .Arc files: listing contents, extracting, adding, or deleting files — all in a native Oberon implementation that runs outside the original OS environment.

This tool was developed to support preservation and access to historical Oberon System 3 archives using modern tooling.

• List archive contents (with optional detail)
• Extract specific files or the entire archive
• Add files to an archive (with optional encryption)
• Delete files from an archive
• Support for several compatible encryption methods

• Faithful reproduction of Oberon S3 archive behavior.
• Minimal dependencies: currently the only dependency outside of libraries distributed with VOC is Unix File System Utils.
• Command-line tool written entirely in Oberon for use on modern systems via VOC.

• Windows is not supported due to reliance on UnixFS.Mod.

• ArcTool.Mod: Core .Arc parsing, compression, and file handling
• FileUtil.Mod: Lists files and abstracts file operations. Depends on standard Files.Mod and UnixFS.Mod
• oarc.Mod: Main command-line interface with argument parsing and dispatch
• Crypt0.Mod: Encryption methods

A GNUmakefile is provided which fetches dependencies (in this case: UnixFS.Mod), builds them, and compiles the tool using VOC.

To build:

make

This will produce the executable oarc in the build directory.

./oarc <command> <archive> [options/files...]

• -d Show detailed listing (for list)
• -c cipher Select encryption cipher (default: mod)
• -e key Use specified key to enable encryption/decryption

• mod: Parks-Miller PRNG with modular arithmetic (default)

  • Uses: ciphertext = (plaintext + keystream) MOD 256

• heidelberg: Voyager project cipher from Crypt0.Mod (has a bug with 1-char keys!)

  • Same as mod but uses Length(key) - 1 as length
  • Warning: crashes with single-character passwords — use only for legacy compatibility

• xor: Simple XOR stream cipher

  • Uses: ciphertext = plaintext XOR keystream

• s3: Cipher from ETH Oberon System 3 CompressCrypt.Mod

  • Uses: ciphertext = plaintext +/- key[i MOD keylen]

# List files
./oarc list WebNavBeta4.Arc

# List with details
./oarc list WebNavBeta4.Arc -d

# Add new files (with encryption)
./oarc add WebNavBeta4.Arc -e mypassword New.Mod More.Text

# Extract files (with cipher and password)
./oarc extract WebNavBeta4.Arc -c heidelberg -e oldkey New.Mod

# Extract all files
./oarc extractall WebNavBeta4.Arc

# Delete files
./oarc delete WebNavBeta4.Arc Old.Mod

• Archives are modified in-place
• Encrypted files are compatible with original Oberon S3 formats (where applicable)

You have to install one of the encryption methods. In Oberon S3 there's CompressCrypt module.

Compress.Add \C CompressCrypt.Install "key" archive.Arc file0.txt file1.txt ~

or

Compress.Extract \C CompressCrypt.Install "key" archive.Arc file0.txt file1.txt ~

Otherwise, if you use compress system from Voyager project then its Crypt0 file encryption should be used.

Compress.Extract \C Crypt0.Install "key" archive.Arc file0.txt file1.txt ~

GPL-3