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Class: Rack::Deflater

Relationships & Source Files
Namespace Children
Classes:
GzipStream
Inherits: Object
Defined in: lib/rack/deflater.rb

Overview

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.

Constant Summary

Class Method Summary

Instance Method Summary

Constructor Details

.new(app, options = {}) ⇒ Deflater

Creates Deflater middleware. Options:

:if

a lambda enabling / disabling deflation based on returned boolean value

(e.g <tt>use Rack::Deflater, :if => lambda { |*, body| sum=0; body.each { |i| sum += i.length }; sum > 512 }</tt>).
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}.
:deflaters

a hash of custom deflaters, where keys are encoding names and values are callables

that take (headers, body) and return a deflated body object. When provided, these
custom deflaters will be used if the client's accept-encoding header matches.
[ GitHub ] 

  


# File 'lib/rack/deflater.rb', line 45



def initialize(app, options = {})
  @app = app
  @condition = options[:if]
  @compressible_types = options[:include]
  @sync = options.fetch(:sync, true)
  @deflaters = options[:deflaters]
  @available_encodings = %w(gzip)
  @deflaters&.each_key { |key| @available_encodings << key }
  @available_encodings << 'identity'
  @available_encodings.freeze
end


  







Instance Method Details



  

    #call(env)  
  

  [ GitHub ]


  

  


# File 'lib/rack/deflater.rb', line 57



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(@available_encodings,
                                        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)
    response[2] = GzipStream.new(body, GZIP_MTIME, @sync)
    response
  when "identity"
    response
  else
    if deflater = @deflaters&.[](encoding)
      headers['content-encoding'] = encoding
      headers.delete(CONTENT_LENGTH)
      response[2] = deflater.call(headers, body)
      response
    else
      # 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
end


  








  

    #should_deflate?(env, status, headers, body)  ⇒ Boolean  (private)
  



  

    

Whether the body should be compressed.


  





  


  [ GitHub ]


  

  


# File 'lib/rack/deflater.rb', line 151



def should_deflate?(env, status, headers, body)
  # Skip compressing empty entity body responses and responses with
  # no-transform set.
  if Utils::STATUS_WITH_NO_ENTITY_BODY.key?(status.to_i) ||
      /\bno-transform\b/.match?(headers[CACHE_CONTROL].to_s) ||
      headers['content-encoding']&.!~(/\bidentity\b/)
    return false
  end

  # Skip if @compressible_types are given and does not include request's content type
  return false if @compressible_types && !(headers.has_key?(CONTENT_TYPE) && @compressible_types.include?(headers[CONTENT_TYPE][/[^;]*/]))

  # Skip if @condition lambda is given and evaluates to false
  return false if @condition && !@condition.call(env, status, headers, body)

  # No point in compressing empty body, also handles usage with
  # Rack::Sendfile.
  return false if headers[CONTENT_LENGTH] == '0'

  true
end