pocketpy/docs/modules/lz4.md

---

icon: package

label: lz4

lz4

Fast compression of byte strings.

!!!info Optional module Enable PK_BUILD_MODULE_LZ4=ON; see build configuration. !!!

Function	Result
compress(data: bytes)	Compressed bytes with a stored uncompressed size.
decompress(data: bytes)	Restored bytes.

import lz4

original = ('tile-data-' * 100).encode()
packed = lz4.compress(original)
assert lz4.decompress(packed) == original

The format is an LZ4 block preceded by a four-byte uncompressed-size field. It is not an LZ4 frame or a .lz4 command-line file. Use matching block-format APIs when exchanging data with another library.

Decompression allocates from the stored size. Keep compressed data within your application's size limits; do not treat the size prefix as trustworthy for untrusted files. Serialize objects before compression, for example using msgpack when its supported types fit.

Implementation: lz4.c.