class Rack::Deflater

This middleware enables content encoding of http responses, usually for purposes of compression.

Currently supported encodings:

gzip
identity (no transformation)

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

Note that despite the name, Deflater does not support the deflate encoding.

Public Class Methods

new (app, options = {})

Creates Rack::Deflater middleware. Options:

:if: a lambda enabling / disabling deflation based on returned boolean value (e.g use Rack::Deflater, :if => lambda { |*, body| sum=0; body.each { |i| sum += i.length }; sum > 512 }). However, be aware that calling ‘body.each` inside the block will break cases where `body.each` is not idempotent, such as when it is an IO instance.
:include: a list of content types that should be compressed. By default, all content types are compressed.
:sync: determines if the stream is going to be flushed after every chunk. Flushing after every chunk reduces latency for time-sensitive streaming applications, but hurts compression and throughput. Defaults to true.

# File lib/rack/deflater.rb, line 39
def initialize(app, options = {})
  @app = app
  @condition = options[:if]
  @compressible_types = options[:include]
  @sync = options.fetch(:sync, true)
end

Public Instance Methods

call (env)

# File lib/rack/deflater.rb, line 46
def call(env)
  status, headers, body = response = @app.call(env)

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

  request = Request.new(env)

  encoding = Utils.select_best_encoding(%w(gzip identity),
                                        request.accept_encoding)

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

  case encoding
  when "gzip"
    headers['content-encoding'] = "gzip"
    headers.delete(CONTENT_LENGTH)
    mtime = headers["last-modified"]
    mtime = Time.httpdate(mtime).to_i if mtime
    response[2] = GzipStream.new(body, mtime, @sync)
    response
  when "identity"
    response
  else # when nil
    # Only possible encoding values here are 'gzip', 'identity', and 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, { CONTENT_TYPE => "text/plain", CONTENT_LENGTH => message.length.to_s }, bp]
  end
end