nickdichev / huffman-elixir

Implementation of the Huffman algorithm in Elixir

huffman-elixir

This repository contains an implementation of the Huffman algorithm in Elixir.

A blog post series describing the implementation of the algorithm can be found on my blog:

Part 1 (Data Structures)

Part 2 (Compression)

Part 3 (Decompression)

Usage

You can run the program in an iex shell:

iex -S mix

Once you are in an iex shell, you can interact with the program as follows:

iex(1)> gophers = Huffman.compress("go go gophers")
[
  <<0, 0, 0, 53>>,
  <<131, 80, 0, 0, 0, 77, 120, 218, 43, 97, 96, 96, 224, 204, 5, 18, 140, 10,
    137, 76, 96, 58, 53, 145, 17, 76, 167, 39, 50, 131, 233, 12, 40, 63, 31,
    202, 47, 128, 242, 139, 160, 116, 49, 148, 254, 159, 200, 8, ...>>,
  [[[[[], 26], 52], 122], 99],
  <<243, 64>>
]
iex(2)> Huffman.decompress(gophers) |> IO.iodata_to_binary()
"go go gophers"

There are also some sample text files included in test_data/. They can be compressed/decompressed as follows:

iex(1)> Huffman.compress_file("test_data/hamlet")
:ok
iex(2)> Huffman.decompress_file("test_data/hamlet.hf")
:ok

Let's compare the file sizes of the original and compressed files:

ls -lh test_data/hamlet*
-rw-r--r--  1 ndichev  688605420   175K May  1 23:04 test_data/hamlet
-rw-r--r--  1 ndichev  688605420   102K May  4 16:29 test_data/hamlet.hf
-rw-r--r--  1 ndichev  688605420   175K May  4 16:29 test_data/hamlet.hf.orig


diff test_data/hamlet test_data/hamlet.hf.orig
<no  output>

Testing

There are some unit tests in tests/. The unit test suite can be run with mix test. Additionally, excoveralls is configured and can be run with mix coveralls or mix coveralls.html.