Class: Rack::Compress::Deflater

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/compress/deflater.rb

Overview

This middleware enables compression of http responses.

Currently supported compression algorithms:

* br # gem 'brotli'
* zstd # gem 'extlz4'

The middleware automatically detects when compression is supported and allowed. For example no transformation is made when a cache directive of ‘no-transform’ is present, or when the response status code is one that doesn’t allow an entity body.

Defined Under Namespace

Classes: BrotliStream, ZstandardStream

Instance Method Summary collapse

Constructor Details

#initialize(app, options = {}) ⇒ Deflater

Creates Rack::Compress middleware.

app

rack app instance

options

hash of deflater options, i.e. ‘if’ - a lambda enabling / disabling deflation based on returned boolean value

e.g use Rack::Brotli, :if => lambda { |env, status, headers, body| body.map(&:bytesize).reduce(0, :+) > 512 }

‘include’ - a list of content types that should be compressed ‘levels’ - Compression levels



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# File 'lib/rack/compress/deflater.rb', line 29

def initialize(app, options = {})
  @app = app

  @condition = options[:if]
  @compressible_types = options[:include]
  @levels_options = { brotli: 4, zstd: 5 }.merge(options[:levels] || {})
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/rack/compress/deflater.rb', line 37

def call(env)
  status, headers, body = @app.call(env)
  headers = Rack::Utils::HeaderHash.new(headers)

  unless should_deflate?(env, status, headers, body)
    return [status, headers, body]
  end

  request = Rack::Request.new(env)

  encoding = Rack::Utils.select_best_encoding(%w(zstd br), request.accept_encoding)

  return [status, headers, body] unless encoding

  # Set the Vary HTTP header.
  vary = headers["vary"].to_s.split(",").map(&:strip)
  unless vary.include?("*") || vary.include?("accept-encoding")
    headers["vary"] = vary.push("accept-encoding").join(",")
  end

  case encoding
  when "zstd"
    headers['content-encoding'] = "zstd"
    headers.delete(Rack::CONTENT_LENGTH)
    [status, headers, ZstandardStream.new(body, @levels_options[:zstd])]
  when "br"
    headers['content-encoding'] = "br"
    headers.delete(Rack::CONTENT_LENGTH)
    [status, headers, BrotliStream.new(body, @levels_options[:brotli])]
  when nil
    message = "An acceptable encoding for the requested resource #{request.fullpath} could not be found."
    bp = Rack::BodyProxy.new([message]) { body.close if body.respond_to?(:close) }
    [406, {Rack::CONTENT_TYPE => "text/plain", Rack::CONTENT_LENGTH => message.length.to_s}, bp]
  end
end