class Rack::Deflater - rack-1.6.2 Documentation

# class Rack::Deflater

This middleware enables compression of http responses.

Currently supported compression algorithms:

    * gzip
    * deflate
    * identity (no transformation)

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.

### Public Class Methods

new(app, options = {}) click to toggle source

Creates Rack::Deflater 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::Deflater, :if => lambda { |env, status, headers, body| body.length > 512 }

  'include' - a list of content types that should be compressed

    # File lib/rack/deflater.rb, line 27
    def initialize(app, options = {})
      @app = app

      @condition = options[:if]
      @compressible_types = options[:include]
    end

### Public Instance Methods

call(env) click to toggle source

    # File lib/rack/deflater.rb, line 34
    def call(env)
      status, headers, body = @app.call(env)
      headers = Utils::HeaderHash.new(headers)

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

      request = Request.new(env)

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

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

      case encoding
      when "gzip"
        headers['Content-Encoding'] = "gzip"
        headers.delete(CONTENT_LENGTH)
        mtime = headers.key?("Last-Modified") ?
          Time.httpdate(headers["Last-Modified"]) : Time.now
        [status, headers, GzipStream.new(body, mtime)]
      when "deflate"
        headers['Content-Encoding'] = "deflate"
        headers.delete(CONTENT_LENGTH)
        [status, headers, DeflateStream.new(body)]
      when "identity"
        [status, headers, body]
      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, {CONTENT_TYPE => "text/plain", CONTENT_LENGTH => message.length.to_s}, bp]
      end
    end

### Private Instance Methods

should_deflate?(env, status, headers, body) click to toggle source

    # File lib/rack/deflater.rb, line 136
    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.include?(status) ||
          headers[CACHE_CONTROL].to_s =~ /\bno-transform\b/ ||
         (headers['Content-Encoding'] && 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)

      true
    end