HPAX

HPAX is an Elixir implementation of the HPACK header compression algorithm as used in HTTP/2 and defined in RFC 7541. HPAX is used by several Elixir projects, including the Mint HTTP client and bandit HTTP server projects.

Installation

To install HPAX, add it to your mix.exs file.

defp deps do
  [
    {:hpax, "~> 0.1.0"}
  ]
end

Then, run $ mix deps.get.

Usage

HPAX is designed to be used in both encoding and decoding scenarios. In both cases, a context is used to maintain state internal to the HPACK algorithm. In the common use case of using HPAX within HTTP/2, this context is called a table and must be shared between any subsequent encoding/decoding calls within an endpoint. Note that the contexts used for encoding and decoding within HTTP/2 are completely distinct from one another, even though they are structurally identical.

To encode a set of headers into a binary with HPAX:

context = HPAX.new(4096)
headers = [{:store, ":status", "201"}, {:store, "location", "http://example.com"}]
{encoded_headers, context} = HPAX.encode(headers, context)
#=> {iodata, updated_context}

To decode a binary into a set of headers with HPAX:

context = HPAX.new(4096)
encoded_headers = <<...>>
{:ok, headers, context} = HPAX.decode(encoded_headers, context)
#=> {:ok, [{:store, ":status", "201"}, {:store, "location", "http://example.com"}], updated_context}

For complete usage information, please see the HPAX documentation.

Contributing

If you wish to contribute check out the issue list and let us know what you want to work on so we can discuss it and reduce duplicate work.

License

Copyright 2021 Eric Meadows-Jönsson and Andrea Leopardi

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.