Lempel-Ziv All Prefixes, a derivative of LZMW: after coding a match the dictionary gains the previous match concatenated with every prefix of the current match rather than a single entry, so far fewer codes are emitted at the cost of a rapidly filling dictionary. Variable-width codes from 9 to 12 bits are packed least-significant-bit first behind a 4-byte little-endian length header, with clear and stop codes.
| Property | Value |
|---|---|
| Category | Compression Algorithms |
| Sub-category | Dictionary |
| Security status | Not classified |
| Complexity | Advanced |
| Inventor | James A. Storer |
| Year | 1988 |
| Origin | 🇺🇸 United States |
| Source | algorithms/compression/lzap.js |
Status: not classified — treat as unverified.
No vulnerabilities are recorded for this implementation.
7 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — Empty input - only the 4-byte little-endian length header
| Field | Value |
|---|---|
input |
(empty) |
expected |
00000000 |
Vector 2 — Single byte 0x41 - one literal code followed by the stop code
| Field | Value |
|---|---|
input |
41 |
expected |
01000000410202 |
Vector 3 — Long repetitive run - 256 copies of 0x61, every prefix widens the dictionary at once
| Field | Value |
|---|---|
input |
61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 |
expected |
0001000061c20824789021c59036b13ece1910 |
Vector 4 — Alternating two-byte pattern - 32 repetitions of ‘ab’
| Field | Value |
|---|---|
input |
61626162616261626162616261626162 61626162616261626162616261626162 61626162616261626162616261626162 61626162616261626162616261626162 |
expected |
4000000061c40814685021448d260302 |
Vector 5 — Pseudo-random binary sample - 16 high-entropy bytes, no reusable matches
| Field | Value |
|---|---|
input |
d3b07a1c8f4e2b6905c1fd3846a70e92 |
expected |
10000000d360e9e1f0c8c98a340582f5c361e49403490101 |
Vector 6 — ASCII text - ‘the quick brown fox jumps over the lazy dog. ‘ repeated four times
| Field | Value |
|---|---|
input |
74686520717569636b2062726f776e20 666f78206a756d7073206f7665722074 6865206c617a7920646f672e20746865 20717569636b2062726f776e20666f78 206a756d7073206f7665722074686520 6c617a7920646f672e20746865207175 69636b2062726f776e20666f78206a75 6d7073206f76657220746865206c617a 7920646f672e2074686520717569636b 2062726f776e20666f78206a756d7073 206f76657220746865206c617a792064 6f672e20 |
expected |
b400000074d0940111a74e9a316b4088 91f3e68e1b1066dee001a1a64e1b3873 40bcb153460e088104d984d193070499 37675c84246810a142860e214aa46811 a3468e1e63963c9972e5cb993777fe1c 7a74a954ab5cc9b2a5fbf77040 |
Vector 7 — All 256 byte values 0x00..0xFF - no repetition, every code is a single byte
| Field | Value |
|---|---|
input |
000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f 404142434445464748494a4b4c4d4e4f 505152535455565758595a5b5c5d5e5f 606162636465666768696a6b6c6d6e6f 707172737475767778797a7b7c7d7e7f 808182838485868788898a8b8c8d8e8f 909192939495969798999a9b9c9d9e9f a0a1a2a3a4a5a6a7a8a9aaabacadaeaf b0b1b2b3b4b5b6b7b8b9babbbcbdbebf c0c1c2c3c4c5c6c7c8c9cacbcccdcecf d0d1d2d3d4d5d6d7d8d9dadbdcdddedf e0e1e2e3e4e5e6e7e8e9eaebecedeeef f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff |
expected |
000100000002081840a0808103081228 58c0a08183071022489840a182850b18 3268d8c0a183870f2042881841a28489 132852a858c1a2858b173062c89841a3 … (294 bytes; the full value is in the source) |