Hawkynt

LZRW3

Improved LZ77-based compression using hash table index encoding instead of offsets. Better compression than LZRW1 (50% vs 55%) with persistent phrase storage. Uses group-based hash table updates for compressor/decompressor synchronization.

Properties

Property	Value
Category	Compression Algorithms
Sub-category	Dictionary
Security status	Not classified
Complexity	Intermediate
Inventor	Ross N. Williams
Year	1991
Origin	🇦🇺 Australia
Source	algorithms/compression/lzrw3.js

Security

Status: not classified — treat as unverified.

No vulnerabilities are recorded for this implementation.

Documentation

• LZRW3 Specification
• LZRW3 Release Notes
• Data Compression Conference 1991
• LZRW Wikipedia

References

• Ross Williams Compression
• LZRW Implementation Analysis
• Linux Kernel ftape LZRW3

Test vectors

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

Vector 1 — No repetition - all literals

Source: Round-trip validated

Field	Value
input	41424344
expected	04000000000041424344

Vector 2 — Pattern repetition - ABC repeated 4 times

Source: Round-trip validated

Field	Value
input	414243414243414243414243
expected	0c0000000008414243652c

Vector 3 — Real text compression - English phrase

Source: Round-trip validated

Field	Value
input	54686520717569636b2062726f776e20666f78
expected	13000000000054686520717569636b2062726f776e200000666f78

Vector 4 — High repetition - 16 identical characters

Source: Round-trip validated

Field	Value
input	41414141414141414141414141414141
expected	100000000008414141a27e

Vector 5 — Edge case - empty input

Source: Round-trip validated

Field	Value
input	(empty)
expected	00000000

Vector 6 — Highly repetitive data - 300 bytes

Source: Round-trip validated

Field	Value
input	58585858585858585858585858585858 58585858585858585858585858585858 58585858585858585858585858585858 58585858585858585858585858585858 … (300 bytes; the full value is in the source)
expected	2c010000fff8585858f49bf49bf49bf4 9bf49bf49bf49bf49bf49bf49bf49bf4 9bf49b000ff49bf49bf49b649b

Vector 7 — Alternating pattern - 300 bytes

Source: Round-trip validated

Field	Value
input	5a595a595a595a595a595a595a595a59 5a595a595a595a595a595a595a595a59 5a595a595a595a595a595a595a595a59 5a595a595a595a595a595a595a595a59 … (300 bytes; the full value is in the source)
expected	2c010000fff05a595a59fb10fb10fb10 fb10fb10fb10fb10fb10fb10fb10fb10 fb10001ffb10fb10fb10fb105b10

Vector 8 — English text sample - repeated sentence

Source: Round-trip validated

Field	Value
input	54686520717569636b2062726f776e20 666f78206a756d7073206f7665722074 6865206c617a7920646f672e20546865 20717569636b2062726f776e20666f78 … (450 bytes; the full value is in the source)
expected	c2010000000054686520717569636b20 62726f776e200000666f78206a756d70 73206f7665722074f80105fa6c617a79 20646f672e20f767f7c8fe7af345f016 fffff767f7c8fe7af345f016f767f7c8 fe7af345f016f767f7c8fe7af345f016 f7670003f7c86e7a

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