Interoperability

An archiver is only useful if other tools can open what it writes. interop.sh round-trips contents and compares hashes; it also checks rejection and cleanup. Its final summary reports the count for the selected build and available tools.

What interop.sh checks

• What Arca writes is read by unzip, tar and 7-Zip, at all four levels.
• What zip, tar and 7-Zip write is read by Arca without losing a byte.
• An archive Arca encrypted with AES-256 opens in 7-Zip, and the other way round.
• Adding and removing the password of an existing ZIP archive, Arca’s own or 7-Zip’s.
• An altered ZIP byte is caught by the CRC, or by the AE-2 HMAC when encrypted.
• 7z Copy/LZMA2 at all levels, passwords and hidden headers in both directions.
• External solid LZMA/LZMA2 inputs, Unicode names, empty entries and conflict handling.
• Wrong-password 7z extraction leaves the destination absent or unchanged.
• An entry with ../../ is rejected instead of writing outside the destination.
• The RAR/CBR reader fixtures, also through official UnRAR when UNRAR points at it (ARCA_TEST_RAR=0 skips them).
• .tar.xz at all four levels and with one or four threads opens in xz -t and tar -J, and Arca reads what tar -cJf writes, also named .txz.
• A standalone .xz round-trips with xz, including every --check type and concatenated streams. Two inputs are refused.
• A TAR inside a file named .xz is listed as TAR.XZ; a corrupt .xz fails and publishes nothing, and a truncated .tar.xz fails.

bash interop.sh

RAR archives Arca creates are checked by a separate seeded harness: it builds trees at every level, hashes the source and the trees extracted by Arca, official UnRAR and 7-Zip, and records the result as JSON. Without the two decoders it reports explicit skips; CI downloads pinned copies and fails if they are missing.

cargo build --release -p arca-cliUNRAR=/path/to/unrar SEVENZIP=/path/to/7zz python3 arca-rar/tests/create-stress.py --require-tools

Zstandard in ZIP

Zstandard is ZIP method 93: registered in the specification, but not yet read by classic unzip. That’s why -c auto uses Deflate in a .zip, so that anything can open it. Zstandard is asked for by hand, and will be the default once there is a native format.

Encryption

ZIP AES-256 uses WinZip AE-2. Legacy ZipCrypto archives open with their password and can be upgraded with arca password. 7z uses AES-256-CBC/SHA-256 with CRC, not authenticated encryption; encrypted CRC failure can also mean corruption.

7z t -p"a password" secret.zip        # 7-Zip reads what Arca encrypted

Parser regression checks

cargo test -p arca-7zcargo test -p arca-cli --test sevenzcargo test -p arca-xzcargo test -p arca-cli --test xzcargo test -p arca-7z --test interop -- --ignoredcargo test -p arca-gui -- --ignored

The ignored tests require 7z. The automated suites test every truncated prefix of representative plain, solid, encrypted and hidden-header fixtures and require errors, not panics. They also exercise malformed headers and resource limits. This is regression coverage, not a claim that every malicious archive is covered. No new 7z performance numbers are claimed. Platform/UI validation must be run separately from these shell checks.