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# frozen_string_literal: true
require "zlib"
require "time" # for Time.httpdate
require 'rack/utils'
module Rack
# This middleware enables compression of http responses.
#
# Currently supported compression algorithms:
#
# * gzip
# * 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.
class Deflater
##
# 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 { |*, body| sum=0; body.each { |i| sum += i.length }; sum > 512 }
# 'include' - a list of content types that should be compressed
# 'sync' - determines if the stream is going to be flused after every chunk.
# Flushing after every chunk reduces latency for
# time-sensitive streaming applications, but hurts
# compression and throughput. Defaults to `true'.
def initialize(app, options = {})
@app = app
@condition = options[:if]
@compressible_types = options[:include]
@sync = options[:sync] == false ? false : true
end
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 identity),
request.accept_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 "gzip"
headers['Content-Encoding'] = "gzip"
headers.delete('Content-Length')
mtime = headers["Last-Modified"]
mtime = Time.httpdate(mtime).to_i if mtime
[status, headers, GzipStream.new(body, mtime, @sync)]
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
class GzipStream
def initialize(body, mtime, sync)
@sync = sync
@body = body
@mtime = mtime
end
def each(&block)
@writer = block
gzip = ::Zlib::GzipWriter.new(self)
gzip.mtime = @mtime if @mtime
@body.each { |part|
gzip.write(part)
gzip.flush if @sync
}
ensure
gzip.close
@writer = nil
end
def write(data)
@writer.call(data)
end
def close
@body.close if @body.respond_to?(:close)
@body = nil
end
end
private
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.to_i) ||
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
end
end