Hawkynt

IBM 842

Fixed-block dictionary compression built for IBM POWER hardware accelerators. Encodes data in 8-byte chunks as a template opcode selecting a mix of literal bytes and back-references into 2/4/8-byte ring-buffer dictionaries. This implementation covers the eight core chunk templates plus end-of-stream and padded-tail handling.

Properties

Property	Value
Category	Compression Algorithms
Sub-category	Dictionary-based
Security status	Not classified
Complexity	Advanced
Inventor	IBM Corporation
Year	2010
Origin	🇺🇸 United States
Source	algorithms/compression/ibm842.js

Security

Status: not classified — treat as unverified.

No vulnerabilities are recorded for this implementation.

Documentation

• Wikipedia - 842 (compression algorithm)
• Linux kernel lib/842 reference decoder

References

• plauth/lib842 (userspace/GPU port, format notes)
• Blaner et al., IBM J. Res. Dev. 57(6), 2013

Test vectors

5 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Empty input

Field	Value
input	(empty)
expected	00000000

Vector 2 — Single byte

Field	Value
input	41
expected	010000003a0800000000000007c0

Vector 3 — 256 repeated bytes

Field	Value
input	61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161
expected	000100003b0b0b0b0b0b0b0b08000002 002001801000a006003802001200a005 803001a00e0078040022012009805002 a01600b806003201a00d807003a01ef8

Vector 4 — Text sample repeated 4x

Field	Value
input	74686520717569636b2062726f776e20 666f78206a756d7073206f7665722074 6865206c617a7920646f672e20746865 20717569636b2062726f776e20666f78 206a756d7073206f7665722074686520 6c617a7920646f672e20746865207175 69636b2062726f776e20666f78206a75 6d7073206f76657220746865206c617a 7920646f672e2074686520717569636b 2062726f776e20666f78206a756d7073 206f76657220746865206c617a792064 6f672e20
expected	b40000003ba34329038bab4b19dac818 9c9bdddb880eccdef040d4eadae07732 06f76657220743b432903630bd3c901d 91bd9cb881d1a194e40e2ead2c6d640c 47726f776e20666f78390353ab6b8399 03799d995c88000ed8c2f4f240c8dece 72e20746865207175201820283101c20 2428816181a1c20b11122098a0a9e10f 4606468836383a3c41f2021222119212 9690b8a0a4a8edece5c4000000001f

Vector 5 — All 256 byte values

Field	Value
input	000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f 404142434445464748494a4b4c4d4e4f 505152535455565758595a5b5c5d5e5f 606162636465666768696a6b6c6d6e6f 707172737475767778797a7b7c7d7e7f 808182838485868788898a8b8c8d8e8f 909192939495969798999a9b9c9d9e9f a0a1a2a3a4a5a6a7a8a9aaabacadaeaf b0b1b2b3b4b5b6b7b8b9babbbcbdbebf c0c1c2c3c4c5c6c7c8c9cacbcccdcecf d0d1d2d3d4d5d6d7d8d9dadbdcdddedf e0e1e2e3e4e5e6e7e8e9eaebecedeeef f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff
expected	00010000380008101820283039c20242 82c3034383ce20222426282a2c2e7181 91a1b1c1d1e1f390109111921293139c a0a4a8acb0b4b8bce60626466686a6c6 … (281 bytes; the full value is in the source)

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