Hawkynt

LZWL

LZW whose initial dictionary is seeded with the input’s most frequent byte digrams (found via an up-front frequency analysis), so common byte pairs get single codes from the start. Otherwise a standard trie-based LZW with a decoder-mirrored code-width counter and an explicit stop code.

Properties

Property Value
Category Compression Algorithms
Sub-category Dictionary-based
Security status Not classified
Complexity Intermediate
Inventor Jan Platos, Jiri Dvorsky, Vaclav Snasel
Year 2006
Origin ❓ Unknown
Source algorithms/compression/lzwl.js

Security

Status: not classified — treat as unverified.

No vulnerabilities are recorded for this implementation.

Documentation

References

Test vectors

6 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 01000000000020c000

Vector 3 — Highly repetitive input (256 ‘a’ bytes)

Field Value
input 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161
expected 00010000010061618040a070482c1a0f 0884c2a170c86c3a1f1088c4a27148ac 0e02

Vector 4 — All 256 byte values once each, in order

Field Value
input 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f 404142434445464748494a4b4c4d4e4f 505152535455565758595a5b5c5d5e5f 606162636465666768696a6b6c6d6e6f 707172737475767778797a7b7c7d7e7f 808182838485868788898a8b8c8d8e8f 909192939495969798999a9b9c9d9e9f a0a1a2a3a4a5a6a7a8a9aaabacadaeaf b0b1b2b3b4b5b6b7b8b9babbbcbdbebf c0c1c2c3c4c5c6c7c8c9cacbcccdcecf d0d1d2d3d4d5d6d7d8d9dadbdcdddedf e0e1e2e3e4e5e6e7e8e9eaebecedeeef f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff
expected 000100000000000040403020140c0704 024140b060341c0f0804424130a0542c 170c064341b0e0743c1f100844423120 944c27140a4542b160b45c2f180c4643 … (296 bytes; the full value is in the source)

Vector 5 — Every digram over 0x70..0x73 exactly twice - the frequency sort ties throughout, so the table pins the ascending-digram-value rule

Field Value
input 70707071707270737170717171727173 72707271727272737370737173727373 70707071707270737170717171727173 72707271727272737370737173727373
expected 40000000100070707071707270737170 71717172717372707271727272737371 737273737370804060503824160d0784 426150b87c321b0e88c12110c80c1613 0d8141a15208f47220

Vector 6 — ‘the quick brown fox…’ repeated 4 times (digram-sort tie-break stress test)

Field Value
input 74686520717569636b2062726f776e20 666f78206a756d7073206f7665722074 6865206c617a7920646f672e20746865 20717569636b2062726f776e20666f78 206a756d7073206f7665722074686520 6c617a7920646f672e20746865207175 69636b2062726f776e20666f78206a75 6d7073206f76657220746865206c617a 7920646f672e2074686520717569636b 2062726f776e20666f78206a756d7073 206f76657220746865206c617a792064 6f672e20
expected b4000000290065206865746820742062 20642066206a206c206f20712e20617a 6272636b646f6572666f672e69636a75 6b206c616d706e206f676f766f776f78 707371757220726f73207569756d7665 776e782079207a79814023d138ac3637 1888c9a291790c6a210380c22192787c 4a732b9143a092092c1a390791c76132 48fcaa772882c66174f9650e5f469952 66b4c9c53e2d519f5527556975166348 9a52e6f4e9d5827b53104a40

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