Skip to content
Pure OCaml implementation of Zlib.
Branch: master
Clone or download
dinosaure Merge pull request #66 from mirage/doc
Pass on documentation
Latest commit b2b7366 Dec 7, 2018
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
bin
fuzz
lib
test
.gitignore
.merlin Add afl fuzz test Sep 23, 2017
.ocamlformat
.travis-cram.sh
.travis.yml gzip - easy.ml correction, travis.yml updated Oct 26, 2018
AUTHORS.md
CHANGES.md
Dockerfile
LICENSE.md
README.md
decompress.opam
dune-project
rfc1951.opam

README.md

Decompress - Pure OCaml implementation of Zlib

Build Status

Decompress is a pure implementation of zlib. The goal is to create an available package for Mirage OS which implements zlib in OCaml (instead a C code).

We respect the interface of zlib and all flush mode is available (experimental):

  1. sync performs the following tasks:
  • if there is some buffered but not yet compressed data, then this data is compressed into one or several blocks
  • a new type 0 block with empty contents is appended
  1. partial is a deprecated flush method
  2. full is a variant of the sync method flush. The difference lies in the LZ77 step. The full flush is a sync flush where the dictionary is emptied: after a full flush, the deflater will refrain from using copy symbols which reference sequences appearing before the flush point.

The interface proposed is a non-blocking interface.

Home page: http://din.osau.re/

Contact: Romain Calascibetta <romain.calascibet ta@gmail.com>

Installation

Decompress can be installed with opam:

opam install decompress

Checkseum & Optint, linking with Decompress

From benchmarks, the biggest bottleneck of decompress seems to be the computation of the ADLER-32. From this acknowledge, we decide to externalize this part of decompress to 2 sub-libraries: checkseum and optint.

checkseum (and, by this way, decompress) uses a trick about linking and let the end-user to choose which implementation he wants. We provide 2 implementations: checkseum.c and checkseum.ocaml. Currently, decompress does not choose an implementation.

When you want to use decompress, you must choose which implementation you want and link with decompress and checkseum.{c,ocaml}.

NOTE: currently the end-user need to put checkseum.{c,ocaml} as the first dependency before decompress in dune file, like:

(executable
 ((name ...)
  (libraries (checkseum.c decompress))))

Otherwise, the end-user should have a linking error (see #47).

RFC 1951

This distribution provides an implementation of zlib and an implementation of RFC 1951 - which is a subset of zlib. You can use both if you link with decompress - or just use the RFC 1951 implementation by the rfc1951 package.

The biggest difference between zlib and rfc1951 is:

  • no header
  • input/output is not aligned on byte
  • no checksum

Sample programs

A good example is provided in bin/easy.ml with the signature:

val compress   : ?level:int -> string -> string
val uncompress : string -> string

And you can compile this program with:

ocamlbuild -use-ocamlfind -package checkseum.c,decompress bin/easy.native

But keep in your mind, it's an easy example and it's not optimized for a productive environment - so, don't copy/paste and think.

Build Requirements

  • OCaml >= 4.03.0
  • base-bytes meta-package
  • Bigarray module (provided by the standard library of OCaml)
  • dune to build the project
  • checkseum & optint to compute ADLER-32 checksum
You can’t perform that action at this time.