Hawkynt

LZHAM

LZ77 parsing over 32 KB hash chains (matches of 3 to 258 bytes, at most 64 chain probes) with the literal/length and distance alphabets coded by canonical Huffman codes whose code-length table is written verbatim ahead of the token stream. Byte-for-byte identical to CompressionWorkbench’s BB_LZHAM reference block. This is the LZ-plus-Huffman formulation of the design, not the production LZHAM codec’s adaptive binary range coder with rep-match slots.

Properties

Property Value
Category Compression Algorithms
Sub-category Dictionary
Security status 🎓 Educational Only
Complexity Advanced
Inventor Rich Geldreich
Year 2009
Origin 🇺🇸 United States
Source algorithms/compression/lzham.js

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Documentation

References

Test vectors

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

Vector 1 — Empty input - header only

Field Value
input (empty)
expected 00000000

Vector 2 — Single byte 0x41 - one literal, single-symbol table

Field Value
input 41
expected 01000000000000000000000000000000 00000000000000000000000000000000 00000000010000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 000000

Vector 3 — Repeated English pangram (4x) - literals plus long matches

Field Value
input 74686520717569636b2062726f776e20 666f78206a756d7073206f7665722074 6865206c617a7920646f672e20746865 20717569636b2062726f776e20666f78 206a756d7073206f7665722074686520 6c617a7920646f672e20746865207175 69636b2062726f776e20666f78206a75 6d7073206f76657220746865206c617a 7920646f672e2074686520717569636b 2062726f776e20666f78206a756d7073 206f76657220746865206c617a792064 6f672e20
expected b4000000000000000000000000000000 00000000300000000000005000000000 00000000000000000000000000000000 00000000055555555555555455555555 66600000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000006600000000000000000000 06000000000001022000000000000000 0000cb962da7a621172e5030ba10d4eb 805b5dc7b691fcec289a6f8fe0f0

Vector 4 — 256 identical bytes - maximum-length match run

Field Value
input 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161
expected 00010000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000010000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00001010000000000000000000000000 000078

Vector 5 — All 256 byte values in order - uniform 8-bit literal table

Field Value
input 000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f 404142434445464748494a4b4c4d4e4f 505152535455565758595a5b5c5d5e5f 606162636465666768696a6b6c6d6e6f 707172737475767778797a7b7c7d7e7f 808182838485868788898a8b8c8d8e8f 909192939495969798999a9b9c9d9e9f a0a1a2a3a4a5a6a7a8a9aaabacadaeaf b0b1b2b3b4b5b6b7b8b9babbbcbdbebf c0c1c2c3c4c5c6c7c8c9cacbcccdcecf d0d1d2d3d4d5d6d7d8d9dadbdcdddedf e0e1e2e3e4e5e6e7e8e9eaebecedeeef f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff
expected 00010000888888888888888888888888 88888888888888888888888888888888 88888888888888888888888888888888 88888888888888888888888888888888 … (418 bytes; the full value is in the source)

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